This report describes the 2014 study by the Science Definition Team SDT of the WideField Infrared Survey Telescope WFIRST mission. It is a space observatory that will address the most compelling scientific problems in dark energy exoplanets and general astrophysics using a 2.4m telescope with a widefield infrared instrument and an optical coronagraph. The Astro2010 Decadal Survey recommended a Wide Field Infrared Survey Telescope as its top priority for a new large space mission. As conceived by the decadal survey WFIRST would carry out a dark energy science program a microlensing program to determine the demographics of exoplanets and a general observing program utilizing its ultra wide field. In October 2012 NASA chartered a Science Definition Team SDT to produce in collaboration with the WFIRST Study Office at GSFC and the Program Office at JPL a Design Reference Mission DRM for an implementation of WFIRST using one of the 2.4m Hubblequality telescope assemblies recently made available to NASA. This DRM builds on the work of the earlier WFIRST SDT reported by Green et al. 2012 and the previous WFIRST2.4 DRM reported by Spergel et. 2013. The 2.4m primary mirror enables a mission with greater sensitivity and higher angular resolution than the 1.3m and 1.1m designs considered previously increasing both the science return of the primary surveys and the capabilities of WFIRST as a Guest Observer facility. The addition of an onaxis coronagraphic instrument to the baseline design enables imaging and spectroscopic studies of planets around nearby stars.
['Astrophysics - Instrumentation and Methods for Astrophysics']
WideField InfrarRed Survey TelescopeAstrophysics Focused Telescope Assets WFIRSTAFTA 2015 Report
{'No Header': '<!-- image -->', 'Science Definition Team (SDT) and WFIRST Study Office': 'D. Spergel 1 , N. Gehrels 2  \nC. Baltay 3 , D. Bennett 4 , J. Breckinridge 5 , M. Donahue 6 , A. Dressler 7 , B. S. Gaudi 8 , T. Greene 9 , O. Guyon 10 C. Hirata 8 , J. Kalirai 11 , N. J. Kasdin 1 , B. Macintosh 12 , W. Moos 13 , S. Perlmutter 14 , M. Postman 11 , B. Rauscher 2 J. Rhodes 15 , Y. Wang 16,17 , D. Weinberg 8 ,  \nEx Officio  \nD. Benford 18 , M. Hudson 19 , W. -S. Jeong 20 , Y. Mellier 21 , W. Traub 15 , T. Yamada 22', 'Consultants': 'P. Capak 17 , J. Colbert 17 , D. Masters 17 , M. Penny 6 , D. Savransky 23 , D. Stern 15 , N. Zimmerman 1', 'Study Team': "R. Barry 2 , L. Bartusek 2 , K. Carpenter 2 , E. Cheng 24 , D. Content 2 , F. Dekens 15 , R. Demers 15 , K. Grady 2 , C. Jackson 25 G. Kuan 15 , J. Kruk 2 , M. Melton 2 , B. Nemati 15 , B. Parvin 15 , I. Poberezhskiy 15 , C. Peddie 2 , J. Ruffa 2 J.K. Wallace 15 , A. Whipple 24 , E. Wollack 2 , F. Zhao 15  \n<!-- image -->  \n<!-- image -->  \n3 / 1 0/15  \n\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_  \n3 / 1 0/15  \n\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_  \nDavid Spergel, SDT-Co-Chair  \nDate  \nNeil Gehrels, SDT Co-Chair  \nDate  \n- 1  Princeton University\n- 2  NASA/Goddard Space Flight Center\n- 3  Yale University\n- 4  University of Notre Dame\n- 5  California Institute of Technology\n- 6  Michigan State University\n- 7  Carnegie Institution for Science\n- 8  Ohio State University\n- 9  NASA/Ames Research Center\n- 10 University of Arizona\n- 11 Space Telescope Science Institute\n- 12 Stanford University\n- 13 Johns Hopkins University\n- 14 University of California Berkeley/Lawrence Berkeley National Laboratory\n- 15 Jet Propulsion Laboratory/California Institute of Technology\n- 16 University of Oklahoma\n- 17 Infrared Processing and Analysis Center/California Institute of Technology\n- 18 NASA Headquarters\n- 19 University of Waterloo (Canadian Space Agency representative)\n- 20 Korea Astronomy and Space Science Institute\n- 21 Institut d'Astrophysique de Paris (European Space Agency representative)\n- 22 Tohoku University Astronomical Institute (Japan Aerospace Exploration Agency representative)\n- 23 Cornell University\n- 24 Conceptual Analytics\n- 25 Stinger Ghaffarian Technologies  \nCover credits: Top image, artist concept of a super-Earth and moon, David A. Aguilar (Harvard-Smithsonian Center for Astrophysics; bottom image, Andromeda galaxy (M31), NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler  \n1  \nEXECUTIVE    SUMMARY    .........................................................................................................................    4  \n1  \n2  \n3  \n3.4  \nCORONAGRAPH    INSTRUMENT    ...........................................................................................................    103", 'EXECUTIVE SUMMARY': "The  transfer  of  the  Astrophysics  Focused  Telescope Assets (AFTA) to NASA enables a truly compelling  version  of  the  Wide  Field  Infrared  Survey  Telescope (WFIRST), the top priority space mission identified in the 2010 National Academy of Sciences' (NAS) decadal  survey,  New  Worlds  New  Horizons  (NWNH). This  report  summarizes  the  science  program  of WFIRST-AFTA,  presents  a  design  reference  mission, overviews  the  mission  concept,  describes  recent  progress  in  advancing  the  technical  readiness  of  the  key components,  and  shows  how  WFIRST-AFTA  complements  other  planned  ground-based  and  space-based telescopes  to  create  an  observing  systems  for  the 2020s that will transform our understanding of the universe.  \nThe mission envisioned in this report uses the repurposed  2.4-m  telescope  equipped  with  a  wide  field instrument (WFI), comprising a wide field camera with a field of view (FoV) 200 times larger than HST's powerful WFC3 and an integral field unit (IFU) that will characterize  supernovae  to  trace  the  evolution  of  the  universe, and a coronagraphic instrument (CGI), which will be the first instrument able to characterize the atmospheres of super-Earth  planets  and  Neptune-like  planets  around nearby Sun-like stars. This mission addresses all three of the questions identified for astrophysics in the NASA 2014 Science Plan 1 :  \n- ∞ How does the universe work?\n- ∞ How did we get here?\n- ∞ Are we alone?  \nThe  WFIRST-AFTA  design  reference  mission (DRM) is a four part observing program comprising (1) a  high-latitude  survey  optimized  to  study  dark  energy but  enabling  an  enormous  variety  of  other  investigations,  (2)  a  galactic  bulge  survey  that  will  use  microlensing observations to complete the planetary census begun  by  Kepler,  (3)  coronagraphic  observations  of nearby planets and proto-planetary systems, and (4) a Guest  Observer  program  that  will  utilize  the  power  of the WFI and the CGI to address a wide-ranging set of open problems in astrophysics.  This  planned  program will  make  major  contributions  towards  all  three  of  the  \n1  \ngoals  identified  for  astrophysics  in  the  NASA  Science Plan:  \n- ∞ Probe the origin  and  destiny  of  our  universe, including the nature of black holes, dark energy, dark matter and gravity.\n- ∞ Explore the origin and evolution of the galaxies,  stars  and  planets  that  make  up  our  universe\n- ∞ Discover and study planets around other stars, and explore whether they could harbor life  \nTogether with JWST, WFIRST is identified as a bedrock near-term mission for all three of these science themes in  the  recent  roadmap report Enduring Quests, Daring Visions: NASA Astrophysics in the Next Three Decades (Kouveliotou et al. 2014).  \nNWNH emphasized that a wide field infrared survey telescope could produce compelling science in areas ranging from the study of dark energy to the search for  exoplanets.  The  2013  Science  Definition  Team  report  concludes:  'If  used  for  the  WFIRST  mission,  the 2.4-meter telescope would be significantly more capable than the smaller versions of WFIRST studied in previous  SDTs.'  The  National  Academy  of  Sciences' 'Evaluation of the Implementation of WFIRST-AFTA in the Context of New Worlds, New Horizons in Astronomy and Astrophysics  (2014)' 2 chaired  by  Fiona  Harrison reinforced this view noting:  \n- '…a configuration  with  a  2.4-m  telescope  utilizing hardware made available to NASA by the National Reconnaissance Office, would enable a mission of the  scientific  scope  envisioned  for  WFIRST.  The larger aperture of WFIRST-AFTA offers the potential  of  substantially  greater  scientific  reach  than  is possible  with  WFIRST/IDRM.  The  large  aperture also  makes  inclusion  of  a  coronagraph  attractive. This addition was not envisioned by NWNH as part of  WFIRST,  but  it  has  the  potential  to  advance NWNH objectives aimed at the eventual realization of  a  future  Earth-like  planet  imaging  mission  that was a high priority of the NWNH survey.'  \nThe  2.4-m  aperture  of  WFIRST-AFTA  collects  almost three  times  as  much  light  as  the  originally  envisioned version of the mission and offers a factor of 1.9 improvement in spatial resolution (point spread function  \neffective area -- PSF), which itself provides another factor-of-two improvement in accomplishing many science programs. In particular, having the greater speed of the  \nProbe  the  origin  and  destiny  of  our  universe,  including the nature of black holes, dark energy, dark  \nBox 1", 'MAPPING ANDROMEDA': "(see http://hubblesite.org/newscenter/archive/releases/2015/02/image/a/format/small\\_web/)  \n<!-- image -->  \nAt the January 2015 AAS meeting, astronomers presented the  largest  NASA  Hubble  Space  Telescope  image  ever assembled,  this  sweeping  bird's-eye  view  of  a  portion  of the Andromeda galaxy (M31)  \n[http://hubblesite.org/newscenter/archive/releases/2015/02 /image/a/].  The  Hubble  telescope  is  powerful  enough  to resolve individual stars in a 61,000-light-year-long  stretch of  the  galaxy's  pancake-shaped  disk.  It's  like  photographing a beach and resolving individual grains of sand. And, there are lots of stars in this sweeping view - over 100 million, with some of them in thousands of star clusters seen embedded in the disk.  \nThe  Panchromatic  Hubble  Andromeda  Treasury  (PHAT)  assembled together  into  a  mosaic  image using 7,398 exposures taken over 411 individual pointings. The panorama is the product of the program.  Images  were  obtained  from  viewing  the  galaxy in near-ultraviolet,  visible,  and  near-infrared wavelengths, using the Advanced Camera for Surveys and the Wide Field Camera 3 (WFC3) about Hubble. With 200 times the field of view of WFC3, WFIRST-AFTA could replicate the WFC3/IR observations with only 2 pointings.  \nlarger  aperture  and  the  sharper  PSF  allows  WFIRSTAFTA to reach a factor-of-two deeper per unit time over an  unprecedentedly  large  field  for  a  large  space  telescope, ~90 times bigger than the HST-ACS FoV, and ~200  times  bigger  than  the  IR  channel  of  WFC3  that has been a tremendously successful scientific tool. Our international  partners  (Canada,  Japan,  South  Korea, UK, France, Germany and Spain) have expressed significant interest in partnering in developing this tremendously powerful telescope. Their potential contributions are described in Appendix I of the report.  \nSection  2  describes  the  WFIRST-AFTA  science program.  Section  3  describes  the  DRM  that  achieves this  science  program.  Section  4  suggests  policies  for maximizing WFIRST-AFTA science through developing well thought out surveys, making its remarkable images available  as  quickly  as  possible  and  selecting  Guest Observer  programs  through  a  competitive  process. Sections 5 and 6 outline the path forward and conclude.  \nThis  science  program  addresses  all  three  of NASA's goals for astrophysics in multiple ways:", 'matter and gravity.': "By  making  precision  measurements  of  both  the growth rate of structure and the expansion history of the universe,  WFIRST-AFTA  will  test  general  relativity  on the largest scales and could reveal the nature of dark energy, the driver of cosmic acceleration, which is one of the great mysteries of modern science. In 2011, the Nobel  Prize  committee  awarded  its  physics  prize  to three American scientists who used observations of supernovae  to  provide  the  first  convincing  evidence  for cosmic acceleration. The use of a 2.4-meter telescope will  enhance  our  ability  to  use  the  three  basic  techniques that were the focus of previous WFIRST mission studies  (baryon  acoustic  oscillations,  supernovae,  and weak  gravitational  lensing)  and  will  also  significantly improve the use of two other important techniques: galaxy cluster counts and redshift space distortions. Specific strengths of WFIRST-AFTA for dark energy studies include:  \n- ∞ In addition to using lines of hydrogen atoms in galaxies to trace the large-scale distribution of matter at redshifts between 1 and 2, WFIRSTAFTA's larger collecting  area  will  enable  it  to also use lines of ionized oxygen in more distant  galaxies.  This  added  capability  enables measurements of  large-scale  structure  out  to nearly redshift 3, just two billion years after the big bang.\n- ∞ WFIRST-AFTA's added sensitivity  will  enable the detection of a 60% higher density of galaxies  in  10%  less  time  at  z=1.5  in  its  spectroscopic survey vs. WFIRST-DRM1 (Green et al. 2012). With this higher density of galaxies, the redshift space distortion measurements (measuring the effects of cosmic acceleration on structure growth) are also improved.\n- ∞ WFIRST-AFTA  will  conduct  a  three  tiered deep supernova survey, a shallow survey over 27.44 deg 2 for  SNe  at  z  <0.4,  a  medium  survey  over  8.96  deg 2 for  SNe  at  z  <0.8,  and  a deep survey over 5.04 deg 2 for  SNe  out  to  z =1.7  and  then  will  use  an  Integral  Field  Unit (IFU)  to  take  spectra  of  ~2700  distant  supernovae discovered in its synoptic imaging survey.  This  enables  more  precise  distance measurements and reduces  uncertainties  associated with cosmic evolution.\n- ∞ WFIRST-AFTA  will  measure  the  shapes  of 380  million  galaxies  over  2200  square  degrees.  By  making  measurements  at  multiple bands  in  an  observing  strategy  designed  to control  for  systematics,  the  DRM  is  designed so that a potential discovery of deviations from general relativity will not be limited by systematic error. The DRM's deeper observations will complement  Euclid's  and  LSST's  wider  and shallower  observations  and  will  enable  precision measurements of non-Gaussian features in the lensing maps, thus, significantly improving  the  dark  energy  measurements.  These deeper  lensing  observations  will  also  enable accurate  determination  of  the  masses  of  galaxy  clusters  whose  abundance  then  provides a complementary method to determine the effects of dark energy on the growth rate of large structure.  \nThe  report  reinforces  the  NAS  Harrison  report's findings that 'WFIRST-AFTA observations will provide a very  strong  complement  to  the  Euclid  and  LSST  data  \nsets'  and  'For  each  of  the  cosmological  probes  described  in  NWNH,  WFIRST-AFTA  exceeds  the  goals set out in NWNH'.", 'Explore  the  origin  and  evolution  of  the  galaxies, stars and planets that make up our universe': "With  the  spatial  resolution  of  HST's  powerful WFC3/IR camera and more than 200 times its field of view,  WFIRST-AFTA will impact a broad range of astrophysics.  \n- ∞ WFIRST-AFTA  will  make  an  accurate  threedimensional  map  of  the  distribution  of  dark matter  across  2200  square  degrees  of  sky. This map will reveal new insights into the relation  between  baryonic  structures  and  dark matter.  When  combined  with  WFIRST-AFTA tracing galaxies across cosmic time through its high-resolution  images,  this  dark  matter  map will  be  a  Rosetta  stone  for  understanding the process of galaxy formation and evolution.\n- ∞ WFIRST-AFTA will be able to make 'DegreeDeep-Fields' almost 100 times larger than the famed Hubble deep fields.  These  samples  of millions  of  galaxies  over  billions  of  years  will make fundamental contributions to our understanding of galaxy evolution.  As  discussed  in Appendix  H,  a  strategy  of  combining  these deep fields with LSST's deep drilling field will significantly  enhance  the  science  return  from both  programs.  Appendix  H  describes  the many  synergies  between  LSST,  Euclid  and WFIRST-AFTA: a synthetic observing program and  data  analysis  system  will  produce  even richer science from the sum of the whole system.\n- ∞ WFIRST-AFTA  will  determine  the  positions and motions of more than 200 million stars in our  Galaxy  to  unprecedented  precision.  With its large collecting area, it will be able to study stars up to 500 times fainter than the European  Gaia  telescope,  a  dedicated  astrometric mission. Its larger aperture will enable WFIRST-AFTA to achieve a given astrometric (positional) precision for a faint star nine times faster than a 1.3-meter unobscured version of WFIRST.  These  measurements  should  be able  to  trace  the  dark  matter  distribution  not only in our Galaxy, but also in our poorly understood  dwarf  companions,  an  important  la-  \nratory for determining the mass and interaction properties of dark matter.  \n- ∞ WFIRST-AFTA's wide field and superb image quality  will  make it  the  ideal  telescope to find counterparts to the gravitational wave merger events  that  will  likely  be  detected  in  large numbers by the upgraded LIGO experiment in Washington  and  Louisiana.  More  generally, WFIRST-AFTA  will  provide  a  newer,  deeper view of the transient universe.\n- ∞ WFIRST-AFTA will enable detailed studies of the  properties  of  stars  not  only  in  our  own Milky Way, but also over the full extent of all neighboring galaxies. These comparative studies  will  greatly  inform  our  understanding  of both stellar evolution and galaxy formation.  \nThe Hubble telescope has been making astounding  contributions  across  a  wide  range  of  astrophysics. WFIRST-AFTA's  Guest  Observer  program  will  extend this  process  of  discovery.  Appendix  D  contains  a  rich set of ~40 potential Guest Investigator (GI) and Guest Observer (GO) science programs that are uniquely enabled by WFIRST-AFTA and address many of the key questions identified in the decadal survey. Appendix E describes some of the conclusions from the Wide-Field InfraRed Surveys: Science and Techniques conference held  in  Pasadena,  CA  on  November  17-20,  2014, where over 200 scientists gathered to discuss the wide range of potential uses of such a powerful survey telescope.  As  has  proven  extremely  successful  on  other NASA  missions,  we  expect  that  the  selection  of  GO science  programs  will  be  made  by  a  peer-reviewed Time  Allocation  Committee  process  and  GI  programs will  be  enabled  through  archival  analysis  of  WFIRSTAFTA's survey data sets and the examples in Appendix D  just  give  a  sense  of  possibilities.  Historical  experience with HST and other great observatories suggests that  our  current  list  and  discussions  do  not  include many of the most important results that will be achieved by WFIRST-AFTA, as many of the visionaries who will use the telescope for novel applications are still in high school!  \nIf  the  two  missions  are  operating  simultaneously, WFIRST-AFTA and the James Webb Space Telescope (JWST) are highly complementary and will be mutually enhancing.  Appendix  B  describes  some  of  the  synergies between the two missions. By surveying thousands of square degrees of the sky, WFIRST-AFTA should be able to detect galaxies forming in the first few hundred million  years  after  the  big  bang  and  could  potentially  \ndetect supernova explosions occurring in the early universe.  JWST's  powerful  spectroscopic  capabilities  will enable  the  detailed  study  of  these  rare  objects. WFIRST-AFTA will discover myriads of strongly lensed quasars  and  galaxies  that  will  be  exciting  objects  for JWST follow-up  observations.  This  powerful  combination of WFIRST-AFTA wide field survey finding rare, but important,  objects  and  JWST  performing  detailed  follow-up study should also yield important results in galactic and extragalactic astronomy.", 'Discover and study planets around other stars, and explore whether they could harbor life': "Over  the  past  five  years,  the  Kepler  mission  has revolutionized  our  understanding  of  the  properties  of extrasolar  planets.  However,  Kepler  tells  only  part  of the story: the transit method used by Kepler is not sensitive to planets in orbits significantly larger than that of the  Earth,  including  analogs  to  all  of  the  outer  giant planets in the Solar System. Kepler is only sensitive to 'hot'  to  'warm'  exoplanets.  WFIRST-AFTA's  gravitational  microlensing  survey  of  the  Galactic  Bulge  will complete  Kepler's  program  through  a  technique  most sensitive to 'cold exoplanets'. It will systematically survey  the  cold,  outer  regions  of  planetary  systems throughout the Galaxy, detecting ~2600 total bound exoplanets in the range of 0.1-10,000 Earth masses, including  ~1000  'Super-Earths'  (roughly  10  times  the mass  of  Earth),  ~370  Earth-mass  planets,  and  ~50 Mars-mass planets. This will enable the measurement of  the  mass  function  of  'cold'  exoplanets  better  than ~10% per decade in mass for masses >0.3 MEarth, and an  estimate  of  the  frequency  of  Mars-mass  embryos accurate  to  ~15%.  When  combined  with  Kepler, WFIRST-AFTA will provide statistical constraints on the characteristic density of rocky planets in the outer habitable zones of Sun-like stars.  \nWFIRST-AFTA will measure the frequency of freefloating planetary-mass objects in the Galaxy over nearly six orders of magnitude in mass, and will detect ~30 free-floating Earth-mass planets if there is one per star in the Galaxy.  \nWFIRST-AFTA will determine the basic properties of  the  microlensing-detected  planetary  systems,  the planetary masses and the separation between star and planets, to better than ~10% for most systems. In addition,  spectroscopic  follow-up  with  JWST  will  allow  for the measurement of host star temperature and metallicities for a subset of the most massive hosts in the disk and bulge.  \nWFIRST-AFTA  will  be  sensitive  to  the  transits  of giant planets around 200 times more stars than Kepler, and  40  times  more  stars  than  TESS.  WFIRST-AFTA will discover about 20,000 transiting planets with orbits less than a few tenths of an AU, with sensitivity down to Neptune-radius  objects.  By  combining  the  transit  and microlensing discoveries, WFIRST-AFTA will determine the  frequency  of  giant  planets  over  all  orbital  separations (from 0 to infinity) from a single survey.  \nAppendix  G  describes  the  needed  precursor  observations  to  maximize  the  science  return  from  the WFIRST-AFTA microlensing program  \nOne  of  NASA's  long-term  goals  is  to  image  and characterize an Earth-like planet around a nearby star. WFIRST-AFTA's coronagraph will be a major step towards this goal and will achieve NWNH's top 'medium scale' priority for NASA by advancing high-contrast imaging in space. The CGI directly responds to this recommendation, providing an unparalleled opportunity for space-flight experience with a very high-contrast coronagraph and wavefront control system. WFIRST-AFTA is  by  no  means  a  coronagraph-optimized  telescope  but it is likely that future coronagraphs will also not have the  luxury  of  designing  to  a  perfect  unobscured  telescope,  since  flagship  missions  will  have  to  satisfy  a range of science goals just as WFIRST does. Thus, the WFIRST-AFTA coronagraph will be the prototype for a future  mission  that  characterizes  Earth-like  planets.  In addition  to  advancing  towards  this  goal,  the  coronagraph will enable an exciting science program:  \n- ∞ The CGI will be the first instrument to characterize  the  atmospheres  of  gaseous  planets around  nearby  Sun-like  stars  using  reflected visible-light  images  and  low-resolution  (R  ~ 70)  spectra.  These  data,  along  with  masses from  existing  radial  velocity  (RV)  measurements, will give us unique information on planetary  compositions,  temperatures,  and  cloud layers  that  are  not  available  via  transmission and emission spectroscopy of transiting planets  that  have  been  observed  by  HST  and Spitzer.  Currently,  only  a  handful  of  planets have  been  directly  imaged  and  spectrally characterized,  all  of  which  are  large,  young, self-luminous  gas  giants  far  from  their  host star.  WFIRST-AFTA  will  characterize  over  a dozen  currently  known  RV  planets  down  to Jupiter size and as close as 1 AU to their parent star. Upcoming RV surveys will likely provide a dozen more candidate targets.  \n- ∞ WFIRST-AFTA can study 'Super-Earths' and 'mini-Neptunes', classes of planets that were unknown until we were able to see planets beyond our solar system. One of the most striking discoveries about extrasolar planets made in  the  past  decade  is  the  large  population  of objects with radius between 1 and 4 times that of  the  Earth.  Based  on  Kepler  observations, these  planets  -  which  have  no  analog  in  our solar system - may be the most common kind of planet in the universe. The exact nature of these planets is poorly known. They could be so-called  'super-Earths'  with  rocky  compositions,  or  'mini-Neptunes' with massive hydrogen envelopes, or even stranger objects, partially or mostly water and ice. In a blind search, WFIRST-AFTA could potentially discover up to 6  mini-Neptunes  and  potentially  4  SuperEarths.  Although  WFIRST-AFTA's  ability  to characterize  the  smallest  planets  will  be  limited,  the  detections  themselves  will  yield  new science  as  well  as  provide  targets  for  future missions  dedicated  to  terrestrial  habitablezone planets.\n- ∞ The  WFIRST-AFTA  CGI  will  deliver  uniquely sensitive images of the planetary disks around nearby stars, resolving much smaller amounts of dust at much closer distances than possible with HST or other observatories. The small inner  working  angle  and  high  contrast  of  the WFIRST-AFTA CGI will allow unique study of several types of circumstellar disks enabling it to  address many of the most important questions  in  planet  formation:  What  are  the  levels of  circumstellar  dust  in,  and  exterior  to,  the habitable zones of exoplanetary systems? Will dust  in  habitable  zones  interfere  with  future planet-finding  space  observatories?  How  do dust  sub-structures  seen  in  disks  trace  the presence  of  seen  or  unseen  planets?  What veneer is  delivered  to  planetary  atmospheres and surfaces by asteroids, comets, and other material? How do disks of protoplanetary materials evolve to make Solar System-like architectures?  The  CGI  imaging  data  collected  in the planet surveys described above will be sufficient for detecting disks around nearby stars down to a level of ~10 times that of our solar system's zodiacal dust. This combined planet and disk dataset will  provide  the  first  full  pic-  \nre of planetary systems around tens of nearby stars.  \nAppendix F describes the basis for estimating the expected CGI science yield for three groups of targets, known RV planets, 'new' as-yet unknown blind-search planets, and debris disks.  \nWhile  adding  a  coronagraph  to  the  WFIRST  mission enables very compelling science and advances our planet-imaging  capabilities,  the  NAS  Harrison  report notes that there are significant risks associated with developing  new  technologies.  The  NAS  Harrison  report recommends:  \n'NASA should move aggressively to mature the coronagraph  design  and  develop  a  credible  cost, schedule, performance, and observing program so that its impact on the WFIRST mission can be determined.'  \nEnabled by the enhanced funding in the 2014 Federal budget, the WFIRST-AFTA team has made significant progress in realizing this recommendation. As described in §3.4, the coronagraph design is based on the highly  successful  High  Contrast  Imaging  Testbed (HCIT),  with  modifications  to  accommodate  the  telescope  design,  serviceability,  volume  constraints,  and the  addition  of  an  Integral  Field  Spectrograph.  Soon after  the  WFIRST-AFTA  CGI  architecture  downselect results  were  announced  in  December  2013,  the  coronagraph  technology  development  plan  (TDP)  was drafted and approved in March 2014. The main objective of the TDP is to mature the WFIRST-AFTA coronagraph to  Technology  Readiness  Level  (TRL)  5  by  the planned Project  Phase  A  start  at  the  beginning  of  FY 2017. §3.4.2 describes nine key milestones in FY 20142016  needed  to  achieve  this  goal.  During  calendar 2014,  the  WFIRST  program  achieved  the  first  three milestones and is on schedule to ensuring that the coronagraph  is  ready  for  integration  into  the  WFIRSTAFTA telescope.  \nThe  NAS  Harrison  report  also  identifies  the  concern that 'The mission may have to compromise some science performance to ensure that issues associated with the low thermal margins do not lead to significant cost  growth  and  schedule  delay'.  The  present  study mitigates the risk of low thermal margins by baselining a telescope operating temperature of 282 K, within the currently  qualified  range  of  the  telescope.  Appendix  A considers  the  impact  of  the  282  K  baseline  and  concludes that the loss in sensitivity is small at Y, J and H  \nbands  and  0.28  mag  at  F184.  The  section  concludes that this sensitivity loss does not have a significant impact on any of the key science programs and that at the new  baseline  operating  temperature  the  mission achieves  its  scientific  objectives  and  now  has  larger thermal margins.  \nTo fully take advantage of this larger telescope, the wide-field instrument uses higher performance infrared detectors (H4RGs) that provide four times as many pixels in about the same size package as the current generation of detectors. With eighteen of these detectors in a single focal plane, the wide field imager covers 0.28 deg 2 of  sky  in  a  single  image  at  a  pixel  scale  of  0.11 arcsec/pix. §3.3.2 details the significant progress made in the past two years in advancing the H4RG-10 detectors, a critical technology for the mission.  \nIn  the  mission  presented  in  this  report,  WFIRSTAFTA  is  deployed  in  a  28.5  degree  inclined  geosynchronous orbit; however, this is not the only option for science  operation.  Appendix  C  discusses  the  relative merits  of  inclined  geosynchronous  and  Sun-Earth  L2 orbits.  \nWFIRST-AFTA will address many of the most profound  questions  in  astrophysics  and  should  be  a  key part of NASA's mission portfolio for launch by 2024. As described in Appendix J, it is an important part of the constellation of tools that astronomers will use to obtain novel insights in the coming decade. With the availability of the 2.4-meter telescope, it is an even more compelling mission than originally envisioned in the decadal survey.", '1 INTRODUCTION': 'This  report  contains  the  findings  of  a  NASAappointed Science Definition Team (SDT) to study the Astrophysics  Focused  Telescope  Assets  (AFTA)  implementation of the Wide-Field Infra-Red Survey Telescope (WFIRST) mission. It follows the study of other implementations  by  the  previous  SDT  as  described  in the  2012  report  (Green  et  al.  2012).  In  July  2013,  the Director of the Astrophysics Division of NASA\'s Science Mission Directorate charged the WFIRST-AFTA SDT to work with the WFIRST Study Office to continue studying  the  design  reference  mission  (DRM)  for  WFIRST, using  an  existing  2.4  meter  telescope  which  was  provided to NASA and baselined a coronagraph instrument for exoplanet imaging in addition to the wide-field infrared imager. The existing telescope significantly reduces the  development  risk  of  the  WFIRST.  This  document fulfills that charge.  \nThe NRC\'s 2010 decadal survey of astronomy and astrophysics, \'New Worlds, New Horizons\' (henceforth NWNH) gave WFIRST the highest  priority  for  a  large space mission. The NWNH science goals for WFIRST are  quite  broad.  They  include:  tiered  infrared  sky  surveys  of  unprecedented  scope  and  depth;  a  census  of exoplanets  using  microlensing;  measurements  of  the history  of  cosmic  acceleration  using  three  distinct  but interlocking  methods  (weak  lensing,  baryon  acoustic oscillations, supernova standard candles); and a guest observer/investigator program. What brought these very different  science  goals  together  was  the  realization, across  the  astronomical  community,  that  recent  advances in  infrared  detector  array  technology  have,  for the first time, made it possible to launch a wide field infrared telescope with a very large number of diffraction limited  "effective  pixels"  in  the  focal  plane.  The  telescope prescribed for WFIRST in the NWNH report had a primary mirror diameter of 1.5 m.  \nIn  addition  to  the  science  and  payload envisioned for WFIRST by NWNH, NASA charged the current SDT with  implementing  the  addition  of  a  coronagraph  instrument to the payload for direct imaging of exoplanets. One rationale for the addition is that the increase in the primary mirror size from 1.5-m to 2.4-m results in a finer  angular  resolution  (smaller  point  spread  function) that enables meaningful coronagraphy.  \nIn October 2011 ESA selected Euclid as one of two Cosmic Vision medium class missions. Euclid is also a wide field telescope (1.2-m primary mirror), with the majority of its detector arrays (36 of 52) working at optical rather than infrared wavelengths. While its optical pixels properly  sample  diffraction-limited  images,  its  infrared  \npixels are eight times coarser in area and do not take advantage  of  the  angular  resolution  that  is  gained  by going into space. The Euclid mission prime science is solely  in  the  area  of  cosmology  with  dark  energy  surveys using the weak lensing and baryon acoustic oscillations techniques. In January 2012 the NRC\'s Committee on the Assessment of a Plan for US Participation in Euclid recommended  a  modest  contribution  to  Euclid, saying "This investment should be made in the context of a strong U.S. commitment to move forward with the full  implementation  of  WFIRST in order to fully realize the decadal science priorities of the NWNH report."  \nIn December 2013 the NRC performed a review of WFIRST as requested by NASA.  The  committee  was chaired  by  Fiona  Harrison  and  co-chaired  by  Marcia Rieke. The charge was to compare the NWNH WFIRST to  WFIRST-AFTA,  with  and  without  the  coronagraph, and, based on the comparison, assess responsiveness of  WFIRST-AFTA to  the  science  objectives  of  NWNH WFIRST and assess responsiveness of WFIRST-AFTA with the coronagraph to the science and technology objectives  of  the  NWNH  technology  development  program. The  conclusion  of  the  report  was  that  WFIRST did  fulfill  the  objectives  of  NWNH,  and  in  some  cases exceeded  the  requirements. The  coronagraph  was found to address some of the NWNH recommendations to  develop  exoplanet  direct  imaging  technology. The report  expressed  concern  about  the  added  risk  of  developing  the  larger  WFIRST-AFTA  mission  compared with  the  simpler  version  described  in  NWNH. It  was  a highly valuable report and we appreciated the committee\'s  efforts. The  Study  Office  and  SDT  have  worked diligently to address the concerns in the report.  \nScience  has  become  even  more  exciting  since NWNH - a growing realization  of  the  importance  and mystery of dark energy and a startling abundance and diversity  of  exoplanet  systems    -  and  the  2.4-m  telescope gives NASA and the community a cost effective way  to  exploit  the  resolution  of  a  Hubble  scale  telescope  which  would  otherwise  have  been  prohibitively expensive if originally proposed back in 2010. In October  2011,  the  Nobel  Prize  in  Physics  was  awarded  to Saul Perlmutter (a member of the SDT), Adam Riess, and Brian Schmidt \'for the discovery of the accelerating expansion of the Universe through observations of distant  supernovae.\' The mechanism of that acceleration is unknown. WFIRST will measure the expansion history of the universe and growth of structure to better than 1% in  narrow  redshift  bins  using  several  independent methods, providing  constraints  that  will  greatly  narrow the range of possible mechanisms.  \nFor exoplanets, we are in the midst of a revolution in  detections  and  understanding.  Five  different  techniques  have  resulted  in  nearly  1500  confirmed  detections  and  an  even  larger  number  of  candidates  to  be confirmed.  The  microlensing  technique  has  detected free-floating planets with an indication that there are as many  unbound  planets  as  there  are  orbiting  stars. When combined with the results from Kepler, WFIRST will produce the first statistically complete census of exoplanets.  The  coronagraph  will  make  the  major  first step in direct imaging of exoplanets and produce results from  exoplanet  images  and  spectra.  In  addition,  although WFIRST-AFTA is by no means a coronagraphoptimized  telescope,  exoplanet  imaging  technology  coronagraphy, wavefront control, and post-processing has  advanced  to  the  point  where  very  high  levels  of performance appear practical with WFIRST-AFTA. This opens up enormous science possibilities, including photometrically and spectroscopically characterizing a large sample of giant planets, mapping of structure in extrasolar zodiacal disks, and potentially characterizing \'super-Earth\' planets around the nearest stars.  \nThe  DRM  studies  by  the  SDT,  called  WFIRSTAFTA DRM has the following characteristics:  \n- ∞ 2.4-m primary mirror\n- ∞ Eighteen  HgCdTe  IR  detector  arrays  in  the  Wide Field Imager (WFI) instrument\n- ∞ Six  imaging  filters  in  the  Wide  Field  Instrument (WFI) from 0.76 to 2.0 microns\n- ∞ Slitless spectroscopy with a grism\n- ∞ Integral Field Unit spectrograph for slit spectroscopy of SNe and other sources\n- ∞ Coronagraph  instrument  for  direct  imaging  of  exoplanets  (along  with  an  additional  year  of  operations)\n- ∞ Integral Field Spectrometer within the coronagraph instrument for exoplanet spectroscopy\n- ∞ 28.5 ϒ inclined geosynchronous orbit  \nThe choice of the more-advanced H4RG detector arrays for WFIRST-AFTA is based on the rapid state of advancement in detector array manufacturing. Ground instruments are being built with 4k x 4k detector arrays and  we  have  judged  that  H4RGs  will  be  the  state-ofthe-art at the time of the WFIRST development. A vigorous program is underway to space qualify the devices in time for WFIRST.  \nThe  detector  array  layout  for  WFIRST-AFTA  is shown in Figure 1-1. The size of the detector arrays is  \nshown  as  a  footprint  on  the  sky  to  illustrate  the  wide field of view (FoV). The FoV is a factor of ~200 larger than  the  instruments  on  HST  (WFC3/IR)  and  JWST (NIRCam), enabling deep sky surveys of unprecedented  size.  This  report  gives  the  science  return  from WFIRST-AFTA and a comparison  to  other  observatories in Section 2 and a detailed description of the mission in Section 3.  \nTo present definite forecasts for the scientific performance  of  WFIRST-AFTA,  we  have  adopted  a  notional observing program for the 6-year prime mission: 3  deg 2 in  the  Galactic  bulge  to  discover  exoplanets through  microlensing,  an  imaging  and  spectroscopic survey  of  2000  deg 2 at  high  Galactic  and  ecliptic  latitude,  a  3-tiered  imaging  and  spectroscopic  survey  for supernovae,  a  year  of  direct  exoplanet  observations with the coronagraph and 1.5 years (i.e., 25% of the 6year mission) devoted to a competed Guest Observer program. The actual allocation of observing time will be decided closer to the launch of WFIRST, based on scientific  and  technical  developments  between  now  and then.  At  the  end  of  its  prime  mission,  WFIRST-AFTA will remain a facility of exceptional scientific power.  \nFigure 1-1: Field of view comparison, to scale, of the WFIRST-AFTA wide field instrument with wide field instruments on the Hubble and James Webb Space Telescopes. Each square is a 4k x 4k HgCdTe sensor array. The field of view is 0.28 degrees 2 . The pixels are mapped to 0.11 arcseconds on the sky.  \n<!-- image -->', '2.1 Science Overview': "The 2010 Decadal Survey, New Worlds, New Horizons (NWNH), recommended that two major programs be accomplished with one telescope: the search to understand  the  acceleration  of  the  universe  and  the search  for  planets  around  other  stars.  The  Decadal Survey  also  made  clear  that  the  same  mission  would provide opportunities for advancing knowledge in many other areas of astronomical science, both through a robust  Guest  Observer  Program  for  new  observations and a strong Guest Investigator Program for utilization of the data sets from the two core programs. It became clear  to  the  SDT  very  early  in  the  study  of  WFIRSTAFTA that even in a time of constrained resources, the 2.4-m diameter telescope made possible the rich programs envisioned by the Decadal Survey. This is discussed in detail in our 2013 Final Report (Spergel et al. 2013).  \nIt  also  became  clear  to  the  SDT  that  the  superb imaging  capability  of  this  telescope  made  a  coronagraph  on  WFIRST-AFTA  an  exciting  extension  of  its capabilities that not only would characterize giant planets and debris disks about nearby stars, but would also be an important step towards detecting habitable Earthlike exoplanets. NASA has decided to incorporate a coronagraph and selected a design concept. Thus, in this report we are able to discuss the potential scientific advances in more detail.  \nWe  emphasize  the  power  and  flexibility  of  the WFIRST-AFTA mission for scientific  studies,  see  e.g., §2.2.1. This mission is exploring frontier areas and it is quite  possible  that  there  will  be  scientific  surprises  requiring  adjustments  to  the  core  programs.  Also,  there may be changes in the scientific landscape by the time the  mission  commences  requiring  changes  in  the  observing  program.  The  SDT  expects  that  the  WFIRSTAFTA science team will evaluate the data available early in the mission and, if necessary, modify the strategy to take advantage of their findings. Also because of the mission's power and flexibility, we expect, just as in the case of HST, the Guest Observer and Guest Investigator communities will find ways to exploit the mission capabilities in novel and unforeseen ways.  \nIn  §2.2,  we  discuss  in  detail  the  dark  energy  program with a three pronged campaign of baryon acoustic oscillations, weak lensing of galaxies, and Type Ia supernovae to measure the evolution of the universe and possible  departures  from  the  model  of  gravitation  as detailed in the general theory of relativity.  \nThis  program  will  produce  a  survey  map  of  2000 deg 2 with  superb  imaging  in  the  field  of  the  LSST.  In addition  to  outstanding  imaging,  the  WFIRST-AFTA survey  will  provide  both  infrared  colors  and  redshifts accurate to better than 1 part in 1000. Such a map will be invaluable for a wide range of astrophysical studies. Both these astrophysical studies and the LSST data will significantly improve the analysis of the WFIRST-AFTA data,  reducing  systematic  errors,  both  those  we  know about or suspect as well as the surprises.  \n§2.3  describes  the  potential  impact  on  a  wide range  of  astronomical  science  by  the  WFIRST-AFTA High-Latitude  Surveys,  both  the  wide  field  map  discussed above as well as deep drilling surveys based on the supernovae fields. These surveys will provide exciting new information on issues ranging from the first billion  years  of  cosmic  history  to  stellar  streams  in  the Milky Way.  \nIn §2.4 we show how WFIRST-AFTA will advance our  understanding  of  exoplanets  through  two  complementary studies: the statistical approach of determining the demographics of exoplanetary systems and the detailed  approach  of  characterizing  the  properties  of  a handful of nearby exoplanets. In §2.4.2 we set out the gains to be had with WFIRST-AFTA for the second core program,  the  microlensing  search  for  thousands  of planets down to below Mars mass, in orbit around F, G, K, and M stars and 'beyond the snow line.' This survey is  an  essential  complement  to  the  Kepler  mission. WFIRST-AFTA will provide significant advantages over previous WFIRST designs in determining the absolute, not just the relative, masses of these planets.  \n§2.4.3  presents  how  the  WFIRST-AFTA  mission will  push  ahead  one  of  the  Decadal  Survey's  highest priorities: not just finding, but measuring the properties of exoplanets, with an extremely high-contrast coronagraph.  The  large  aperture  WFIRST-AFTA  telescope can provide the first platform to test this new and rapidly improving  technology  in  a  way  that  no  other  available telescope  can  do  and  take  the  first  scientific  steps  in detailing the characteristics of non-transiting extrasolar planets,  something  that  the  last  two  Decadal  Surveys have  identified  as  one  of  the most  important  fields  in astrophysics  in  2020  and  beyond.  Directly  imaging planets around nearby stars is a step that is in keeping with  the  spirit  of  the  mission  as  described  in  NWNH . The Coronagraph Instrument (CGI) on WFIRST-AFTA will directly image exoplanets and disks around nearby stars.  For  disks,  the  CGI  will  produce  images  in  blue and  red  filters,  at  two  polarizations,  measuring  the amount of dust, and its interaction with planets. For ex-  \nplanets, the targets include about a dozen known radial-velocity  (RV)  planets.  A  significant  number of currently-unknown  planets  will  be  within  our  reach  as well. One of the most striking discoveries from the Kepler mission is the large number of planets with radii 2-4 times that of Earth - planets with no analog in our solar system but detectable by WFIRST-AFTA. The CGI will image these planets in multiple filters and two polarizations, and obtain spectra of many of these at red wavelengths with a resolving power of 70, using water, methane,  and  ammonia  features  to characterize  their  atmospheric composition and properties. Combined with systematic Doppler measurements, WFIRST will extend our understanding of planetary properties around solartype and earlier stars, complementing the late-type focus of TESS..  \n§2.5 points out that the wealth of data on the galactic bulge field obtained by the microlensing program will enable a wide range of studies of stars, time dependent objects and the structure of the Milky Way.  \nA robust Guest Observer Program is a requirement for the WFIRST program. We present some of the opportunities  for  guest  observations  to  accomplish  a broad range of astronomical objectives in §2.6. As emphasized earlier in this subsection, WFIRST-AFTA is a powerful and flexible observatory. We fully expect, as in the case of HST, the guest observer community will find ways to use the WFIRST-AFTA observatory for objectives that, at this time, no one has even considered.  \nThe 2020 and beyond time frame will provide remarkable  opportunities  to  synergize  and  relate  the WFIRST-AFTA data sets  with  those  from  other  major facilities such as JWST and LSST. We discuss some of the possibilities in §2.7, but it is likely that combinations of these data sets will provide new, unexpected insights not even contemplated here.  \nWe  have  not  presented  a  final  subsection  listing the WFIRST-AFTA Science Requirements similar to the one in the 2013 Final Report. During its 2014 activities, the SDT has worked with the WFIRST-AFTA Study Office scientists and engineers towards the preparation of detailed  documents  describing  the  Science  Requirements and the Mission Requirements derived from the Science Requirements. This work is ongoing. High-level requirements  have  not  changed  substantially  from those in the 2013 Final Report, and we take these as the basis for the Design Reference Mission presented in the following sections.", '2.2 Dark Energy & Fundamental Cosmology': "The accelerating expansion of the universe is the most  surprising  cosmological  discovery  in  many  decades, with profound consequences for our understanding  of  fundamental  physics  and  the  mechanisms  that govern the evolution of the cosmos. The two top-level questions of the field are:  \n- 1. Is  cosmic  acceleration  caused  by  a  new  energy component or by the breakdown of General Relativity (GR) on cosmological scales?\n- 2. If the cause is a new energy component, is its energy density constant in space and time, or has it evolved over the history of the universe?  \nA  constant  energy  component,  a.k.a.  a  'cosmological constant,'  could  arise  from  the  gravitational  effects  of the  quantum  vacuum.  An  evolving  energy  component would imply a new type of dynamical field. Gravitational explanations  could  come  from  changing  the  action  in Einstein's GR equation, or from still more radical modifications  such  as  extra  spatial  dimensions.  Observationally,  the  route  to  addressing  these  questions  is  to measure the histories of cosmic expansion and growth of structure with the greatest achievable precision over the widest accessible redshift range.  \nAs  defined  by  NWNH,  one  of  WFIRST's  primary mission goals is to 'settle fundamental questions about the nature of dark energy, the discovery of which was one of the greatest achievements of U.S. telescopes in recent years.' (Following common practice, we will use 'dark energy' as a generic term that is intended to encompass  modified  gravity  explanations  of  cosmic  acceleration as well as new energy components.) It will do so using three distinct surveys that enable complementary measurements of the expansion history and structure growth. The Supernova Survey will combine widefield imaging and Integral Field Unit (IFU) spectroscopy to  measure precise distances to thousands of Type Ia supernovae  (SNe).  The  High-Latitude  Imaging  Survey (HLS  Imaging)  will  enable  weak  lensing  shape  measurements of hundreds of millions of galaxies, which will in  turn  yield  precise  measurements  of  distances  and matter  clustering  through  measurements  of  cosmic shear,  galaxy-galaxy  lensing,  and  the  abundance  and mass  profiles  of  galaxy  clusters.  The  High-Latitude Spectroscopic Survey (HLS Spectroscopy) will measure redshifts  of  tens  of  millions  of  galaxies  via  slitless (grism) spectroscopy. Measurements of baryon acoustic oscillations (BAO) in these enormous 3-dimensional maps will pin down the cosmic distance scale and ex-  \npansion rate at  lookback  times  of  8  -  11  billion  years (redshift  z  =  1  -  3),  while  measurements  of  redshiftspace distortions (RSD) will determine the growth rate of matter clustering over the same period. Background on these measurement techniques and the forecasting methods used below to predict their  performance  can be found in the Green et al. (2012) report on WFIRSTDRM1, in papers by Wang et al. (2010, 2012, 2013) on cosmological  constraints  from  galaxy  redshift  surveys, and in the comprehensive review article of Weinberg et al. (2013).  \nRoughly speaking, current cosmological observations measure distances and expansion history with uncertainties of 1 - 3% and matter clustering with uncertainties of 5 - 10% (see, e.g., Aubourg et al. 2014 for  a  recent  analysis  that  combines many state-of-theart  measurements).  WFIRST-AFTA,  like  other  dark energy experiments of the 2020s, seeks to improve the precision  of  these  measurements  to  the  0.1  -  0.5% level  for both expansion  history  and  structure  growth observables,  while  simultaneously  extending  them  to previously  unexplored  redshift  regimes.  This  ten-tohundred-fold  improvement  in  multiple  measurement techniques  has  two  key  implications.  First,  the  newly opened  discovery  space  is  large:  many  theories  of cosmic  acceleration  that  are  consistent  with  current data will  be  easily  distinguished  and  stringently  tested by  WFIRST-AFTA.  Second,  the  great  improvement  in statistical  precision  demands  equal  improvements  in the  control  of  systematic  uncertainties  associated  with the measurements themselves and with their theoretical interpretation.  \nThe WFIRST-AFTA dark energy program has been designed  with  control  of  systematics  as  a  paramount consideration. For the supernova survey, IFU observations enable powerful approaches to photometric  calibration,  exact  matching  of  rest-frame wavelength intervals for comparisons across redshifts, and  spectroscopic  diagnostics  to  control  evolutionary effects  in  the  supernova  population.  For  weak  lensing observations, the use of 4 - 5 dither positions at each of two telescope roll angles enables excellent reconstruction of image shapes, and shape measurements in three bands enable cross-correlation analyses  that  can  test  for  and  diagnose  systematic effects  while  simultaneously  adding  statistical  power. For  galaxy  clustering  analyses,  the  high  sampling density  of  the  galaxy  redshift  survey  enables  studies that  divide  the  galaxies  into  populations  with  different clustering properties, allowing consistency  checks across  these  populations  and  multi-tracer  approaches  \nthat amplify statistical precision.  \nFigure  2-1  presents  an  overview  of  the  baseline dark  energy  program  described  in  §2.2.2-2.2.4.  The methodology of performance forecasts is  described  in §2.3 and Appendix C of the 2013 report (Spergel et al. 2013). We have updated these forecasts based on the expectations for the data sets described in §2.2.2-2.2.4 below.  The  supernova  survey  will  measure  'standard candle' distances with an aggregate precision of 0.20% at z < 1 (error-weighted z = 0.50) and 0.34% at z > 1 (z = 1.32). Galaxy clustering provides 'standard rulers' for distance measurement in the form of the baryon acoustic  oscillation  (BAO)  feature  and  the  turnover  scale  of the galaxy power spectrum. The galaxy redshift survey (GRS) enables measurements of the angular diameter distance  DA(z)  and  the  expansion  rate  H(z)  using  H α emission line galaxies at 1 < z < 2 and [OIII] emission line  galaxies  at  2  <  z  <  3.  The  aggregate  precision  of these measurements ranges from 0.49% to 2.05% (see Figure  2-1).  The  imaging  survey  will  enable  measurements of  dark  matter  clustering  via  cosmic  shear  and via the abundance of galaxy clusters with mean mass profiles calibrated by weak lensing; we expect 40,000 M ≥ 10 14 Msun clusters in the 2200 deg 2 area of the highlatitude  survey.  These  data  constrain  the  amplitude  of matter fluctuations at redshifts 0 < z < 2, and they provide  additional  leverage  on  the  distance-redshift  relation. Treating the fluctuation amplitude σ m(z) as a single-parameter change, we forecast aggregate precision of  0.24%  (z  <  1)  and  0.88%  (z>1)  from  clusters  and 0.21% (z<1) and 0.78% (z>1) from cosmic shear. In the GRS,  the  distortion  of  structure  in  redshift  space  induced by galaxy peculiar velocities provides an entirely independent  approach  to  measuring  the  growth  of structure, with forecast aggregate precision of 1.1% at z = 1 - 2 and 3.5% at z = 2-3.  \nThese  high-precision  measurements  over  a  wide range of redshifts in turn lead to powerful constraints on theories of cosmic acceleration. If the cause of acceleration is a new energy component, then the key physical characteristic is the history w(z) of the equation-of-state parameter w = P/ ε , the ratio of pressure to energy density.  A  cosmological  constant  has  w  =  -1  at  all  times, while dynamical dark energy models have w ≠ -1  and an evolutionary history that depends on the underlying physics of the dark energy field. If the cause of acceleration  is  a  breakdown  of  GR  on  cosmological  scales, then  it  may  be  detected  in  a  deviation  between  the measured growth history G(z) and the growth predicted by GR given the measured expansion history. Alternatively,  some  modified  gravity  theories  predict  a  mis-  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!", 'WFIRST-AFTA Dark Energy Roadmap': "!  \n!  \n!  \n!  \nFigure 2-1: A high-level view of the WFIRST-AFTA dark energy program. The supernova (SN) survey will measure the cosmic expansion history through precise spectrophotometric measurements of more than 2700 supernovae  out to redshift z = 1.7. The high-latitude survey (HLS) will measure redshifts of 18 million emission-line galaxies and shapes (in multiple filters) of 380 million galaxies. The former allow measurements of 'standard ruler' distances through characteristic scales imprinted in  the galaxy clustering  pattern, while the latter allow measurements of matter  clustering through the 'cosmic shear' produced by weak gravitational lensing and through the abundance of galaxy clusters with masses calibrated by weak lensing. As indicated by crossing arrows, weak lensing measurements also constrain distances, while the galaxy redshift survey provides an alternative measure of structure growth through the distortion of redshift-space clustering induced by galaxy motions. Boxes in the middle layer list the forecast aggregate precision of these measurements in different ranges of redshift. These high-precision measurements of multiple cosmological observables spanning most of the history of the universe lead to stringent tests of theories for the origin of cosmic acceleration, through constraints on the dark energy equation-of-state parameter w(z), on deviations Δ G(z) from the growth of structure predicted by General Relativity, or on deviations between the gravitational potentials that govern relativistic particles (and thus weak lensing) and non-relativistic tracers (and thus galaxy motions).  \n<!-- image -->  \n!  \nmatch between the gravitational potential inferred from weak lensing (in Figure 2-1, cosmic shear and clusters) and  the  gravitational  potential  that  affects  motions  of non-relativistic  tracers,  which  governs  redshift-space distortions (RSD) in the galaxy redshift survey.  \nThis flow diagram necessarily simplifies some key points,  most  notably  (a)  that  the  SN  distance  scale  is calibrated  in  the  local  Hubble  flow  while  the  BAO  distance  scale  is  calibrated  in  absolute  (H0-independent)  \nunits, so they provide complementary information even when measured at the same redshift, and (b) that cosmic shear, cluster abundances, and RSD probe the expansion history as well as the growth history. The combination  of  WFIRST-AFTA  dark  energy  probes  is  far more powerful  than  any  one  probe  would  be  in  isolation,  allowing  both  cross-checks for unrecognized systematics  and  rich  diagnostics  for  the  origin  of  cosmic acceleration. We discuss the anticipated constraints on  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \n!  \ntheoretical models below, in §2.2.5.  \nAs  described  in  §2.1  and  subsequent  sections  of this  report,  the  data  sets  obtained  for  the  dark  energy programs  will  be  an  extraordinary  resource  for  a  vast range of astrophysical studies through Guest Investigator programs, while the WFIRST-AFTA facility enables  revolutionary  approaches  to  a  still  broader range of astronomical problems through Guest Observer programs.", '2.2.1 The Power of WFIRST-AFTA for Dark Energy Investigations': "The strength  of  WFIRST-AFTA as a tool for dark energy investigations derives from its wide FoV coupled to an unprecedented near-IR pixel count (~300Mpix), its 2.4-m aperture that affords both high sensitivity and exquisite  angular  resolution,  and  a  design  of  both  hardware  and  operations  that  enables  excellent  control  of systematic  uncertainties,  including,  for  example,  IFU spectrophotometry  of  supernovae  and  fully  sampled weak lensing shape measurements in multiple bands. It is  these  elements  that  allow  WFIRST-AFTA to pursue extremely powerful programs with three complementary methods: Type Ia supernovae, weak lensing and clusters, and redshift-space galaxy clustering.  \nThe  baseline  design  of  the  supernova  and  highlatitude  surveys,  and  forecasts  of  their  expected  performance  for  dark  energy  studies,  are  described  in §2.2.2-2.2.4  below.  However,  an  essential  strength  of WFIRST-AFTA is the great flexibility it offers in designing a dark energy program that responds to the changing landscape of the field. Between now and the launch of WFIRST-AFTA we will learn more about the power of and  critical  challenges  for  individual  measurement methods;  we  will  develop  better  understanding  of theoretical  modeling  uncertainties  and  strategies  to mitigate  them;  we  will  develop  a  clear  picture  of  the capabilities of complementary ground-based and space-based  dark  energy  experiments;  and  ongoing observations may highlight particular redshift ranges or classes  of  measurements  as  the  most  important  for probing  tensions  in  the  data  and  decoding  their implications  for  cosmic  acceleration.  The  WFIRSTAFTA  dark  energy  program  can  respond  flexibly  to these  developments  by  varying  the  balance  among surveys  and  making  trades  among  area,  depth,  and wavelength  coverage  within  individual  surveys.  It  can also respond to lessons learned from early observations with WFIRST-AFTA itself.  \nFigure  2-2  and  Figure  2-3  illustrate  the  trades between  area  and  depth  for  the  imaging  and  \nspectroscopic  components  of  the  HLS.  The  imaging exposure  time  of  the  baseline  survey  is  174  sec  per filter,  for  each  of  the  4-5  dithers  at  each  of  two  roll angles,  which  with  overheads  yields  a  time  of  about 0.055  days  per  filter  to  cover  1  deg 2 ,  at  the  depths marked  by  the  gray  squares  in  Figure  2-2.  With  1.33 years  allocated  to  the  HLS  imaging  survey,  the  total area  covered  is  2227  deg 2 .  An  H-band  only  survey could  cover  about  four  times  the  area  in  the  same  \n2  \nFigure 2-2: The survey time per unit area per filter, including  overheads,  for  imaging  surveys.  The  gray  squares indicate  the  baseline  HLS  survey depth. The right  hand axis marked in deg 2 covered per filter per year of observing time. The upper axis shows the effective weak lensing source density in H-band as function of depth.  \n<!-- image -->  \nFigure  2-3:  The  survey  time  per  unit  area  for  the  grism spectroscopy required to observe a certain number density of H α emitters at 7 σ , at redshift z = 1.5. The corresponding  flux  limit  for  an  reff  =  0.3  arcsec  source  is marked on the upper axis. The gray square indicates the baseline strategy. The right axis is marked in number of deg 2 covered per year of observing time.  \n<!-- image -->  \namount of time and thus provide shape measurements for  many  more  galaxies,  at  the  price  of  losing  color information for photometric redshifts and crosscorrelations of shape measurements in different filters. Alternatively, a four-filter survey could cover about twice as much area if the limiting depth were reduced by 1.2 magnitudes, or it could go 0.7 magnitudes deeper and cover half the area. The asymmetry of this trade reflects the  transition  from  being  limited  by  read  noise  and overheads to being limited by sky noise. The baseline exposure time is at the 'knee' between these limits, a choice that yields (approximately) the largest number of source galaxies in a given observing time. There are of course  many  variations  within  this  trade  space, including  hybrid  strategies  that  obtain  deep  four-band imaging over a smaller area and shallower imaging in one or two bands over a larger area.  \nFor spectroscopy, the baseline strategy covers the same  2227  deg 2 area  as  the  imaging  survey  to  a limiting 7 σ line flux of 1.2 x 10 -16 erg/cm 2 /s (for an reff = 0.3 arcsec extended source at z = 1.5), in a total of 0.68 years.  Figure  2-3  shows  the  relation  between  survey speed and the density of galaxies in the redshift survey at z = 1.5. Raising the flux limit to 2.4 × 10 -16 erg/cm 2 /s would make it possible to cover twice as much area in the  same  amount  of  time.  Because  the  H α luminosity function is so steep, the total number of galaxies would be smaller by a factor of 2.1, although because of the larger volume surveyed the BAO constraints would only weaken by 13%. As with the imaging survey, the baseline exposure time is close to the value that yields the largest number of source galaxies in a given observing time.  \nTo  maximize  the  discovery  potential  of  the WFIRST-AFTA dark energy program, it will be essential to  review  the  survey  strategies  and  balance  among methods periodically, both before and after launch. Early observations will provide testing and validation of the assumptions about instrument performance that underlie these strategies, which can be adjusted accordingly.", '2.2.2 Supernovae': 'For the baseline WFIRST-AFTA supernova survey, we adopt a total observing time of just over six months, spread over a two-year interval. The survey described here is an existence proof of a possible WFIRST-AFTA observing sequence. Its purpose is to demonstrate that an observing plan meeting WFIRST-AFTA science objectives  is  possible  with  the  reference  hardware  and orbit. This survey design is based on a first optimization of  the  dark  energy  Figure  of  Merit  (FoM)  (defined  in  \n§2.2.4) from SNe for a fixed observing time, given starting assumptions about statistical and systematic errors described below.  \nFor this survey, supernova observations take place with  a  ~5-day  cadence  (with  possibly  a  somewhat shorter cadence for the lowest-redshift tier), with each set of observations taking a total of 30 hours of imaging and spectroscopy.  There are three nested tiers  to  the survey: a shallow survey over 27.44 deg 2 for SNe at z < 0.4, a medium survey over 8.96 deg 2 for SNe at z < 0.8, and a deep survey over 5.04 deg 2 for  SNe  out  to  z  = 1.7. These survey regions will be observed in advance with multi-filter  imaging both from the ground and with the  WFIRST Wide Field Imager (and, ideally, with the spectra from the Wide Field Grism, as well) before the cadenced supernova observations begin. These observations  will  provide  photometric  redshifts  (and,  where possible, spectroscopic redshifts) for most of the galaxies that will later host supernovae.', 'Supernova Discovery 2.2.2.1': 'The  survey  will  use  the  wide-field  imager  to  discover  supernovae  in  two  filter  bands:  Y  and  J  for  the shallow,  low  redshift  tier  and  J  and  H  for  the  medium and deep tiers. The exposure times are designed to be sensitive to supernovae 12 rest-frame-days before peak brightness in each redshift tier.  Supernova candidates are  selected  that  show  up  with  S/N  greater  than  4  in two  filters,  that  were  not  detected  on  previous  visits. Supernovae  will  thus  be  discovered  no  later  than  between 7 and 12 rest-frame-days (depending on redshift) before peak brightness, and this two-band ~5-day observing  cadence  will  continue  through  the  entire lightcurve,  at  least  40  rest-frame  days  past  maximum light for any supernova that will be followed (as shown schematically  in  the  upper  panel  of  Figure  2-4).  With two-band  detections  and  an  estimate  of  redshift  from the pre-cadence observations, early screening and triggering of supernova candidates will be possible before the first IFU spectroscopy begins.', 'Supernova ID and Typing 2.2.2.2': "To get the detailed light curves started as early as possible,  the  photometry-and-redshift-screened  candidates will be scheduled for an IFU spectrum in the next supernova visit (IFU Visit 1, as shown schematically in the bottom panel of Figure 2-4). This first IFU spectrum while the supernova is still just brightening will only be used later to build the lightcurve, if the candidate ends up being followed, and is not intended to have sufficient signal-to-noise  for  supernova  typing.  During  that  visit  \nFigure 2-4: An example WFIRST-AFTA observing sequence for discovering and studying SNe Ia across the range of redshifts between z = 0.2 and 1.7, demonstrating an observing plan that meets WFIRST-AFTA science objectives. The left panels show an example sequence for SNe discovered at z ~ 0.5, and the right panels are for SNe discovered at z ~ 1.5. The upper panel shows the cadence of the broad-band filter observations that will, over 2 years, find the supernovae and provide continuous broad-band photometry with two observer-frame filters. At the specific redshifts of the supernovae, these observer-frame filters will be sampling points on the SN lightcurve with a 'blue-shifted' restframe filter (indicated schematically by the color of the scheduled points). The supernova discoveries will be 'triggered' before peak brightness (as shown by the grey line and red-arrow connecting to the bottom panel) and then the IFU follow-up spectrophotometry Visits will begin on one of the next 5-day-observer-frame cadences. These Visits are shown schematically in the bottom panel, along with their visit number and S/N per 2-pixel resolution element. Photometry points calculated from the IFU spectrophotometry integrated over synthetic-filter bandpasses are shown in the middle panel, plotted as a function of the rest -frame days for this panel (to be compared with the observer -frame days of the top and bottom panels). The same restframe B, V, and R filters are used for both the z=0.5 and 1.5 example supernovae to show the similar observations available at the full range of redshifts.  \n<!-- image -->  \nObserver-Frame Phase  \nObserver-Frame Phase  \nthere will also be another observation of the candidate xwith the imager, as part of the ongoing regular search cadence.  Candidates  whose  brightnesses  have  then increased  since  their  discovery  5  days  before,  and whose color differences are consistent with a Type Ia supernova at the host-galaxy redshift, will be scheduled for an SN-typing spectrum during the next visit (IFU Visit 2), when the supernova is yet brighter. This spectrum and the two-band photometry will be used to screen out most of the remaining non-Type Ia supernovae and to sharpen  the  photo-z  (or  grism)  redshift  estimate;  the observing time budget allows for twice as many of these screening spectra as there are Type Ia supernovae  \nthat will then continue to be followed. The selected supernovae will almost all be Type Ia, and these will then be  scheduled  for  a  deep  IFU  spectrum  (IFU  Visit  3). Both the typing spectrum and the deep spectrum will be near peak SN brightness, and together they will (1) confirm the Type Ia classification and remove any possible small remaining contamination of non-Type Ia supernovae, (2) provide spectral diagnostics that can help distinguish intrinsic color variations from the effects of dust extinction (Chotard et al. 2011, Mandel et al. 2014), and (3) match high and low-redshift SNe with similar properties  to  suppress  evolutionary  effects  in  the  mix  of  supernovae.", 'Spectra for Obtaining Light Curves 2.2.2.3': "The  spectrophotometric  measurements  used  for the  light  curves  for  the  cosmological  analysis  will  also be derived from observations with the IFU spectrometer.  Thus,  for  each  supernova,  six  further  IFU  spectra (IFU  Visits  4  through  9)  will  continue  to  be  obtained along  the  light  curve  with  a  roughly  5-day rest -frame cadence (but, for efficiency, observed during the nearest 5-dayobserver -frame cadence visit), until ~30 restframe days past peak. IFU spectrophotometry reduces systematic uncertainties by (a) removing filterphotometry's  need  for  K-corrections  (Saunders  et  al. 2014),  as  the  same  rest-frame  wavelength  range  can be chosen for SNe at different redshifts and (b) allowing better separation of SN and background galaxy light as a function of wavelength than is possible with a grism. Moreover,  (c),  flux  calibration  is  a  limiting  systematic uncertainty  in  current  ground-based  SN  surveys  (e.g., Sullivan  et  al.  2011)  and  a  critical  consideration  for  a space-based  survey,  and  highly  accurate  flux  calibration  is  much  more  straightforward  for  an  IFU  system than  for  a  wide-field  filter  photometry  system.  For  the IFU,  the  effective  wavelength  of  a  spectral  resolution element is independent of the spectral distribution of a SN, but that is not the case for a broadband filter because  SN  features  vary  strongly  relative  to  the  filter resolution.  Moreover in  situ calibration  of  the  spectral response is trivial for an IFU, but is not generally feasible for a wide-field imager.  \nEven though IFU observations are one object at a time, they prove more efficient than slitless spectroscopy over the 0.28 deg 2 FoV because the exposure time can be chosen for each supernova individually instead of  being  driven  by  the  faintest  object  in  the  field,  and because IFU observations have dramatically lower sky noise  per  pixel,  allowing  much  better  isolation  of  the faint SN signal.", 'Signal-to-Noise for the IFU Observations 2.2.2.4': "The  IFU  measurements  used  for  most  of  the lightcurve  photometry  (IFU  Visits  1,  and  4  through  9) are intended only to provide S/N = 15 when integrated over broad synthetic filter bands, so these observations have relatively short exposure times calculated 3 to give  \n3 The exposure times to obtain a given S/N were here calculated for an IFU design with one spatial pixel per 0.15' image-slice, while the design outlined in §3.3.1.2 uses 2 spatial pixels per 0.15' slice. More detailed studies of the optimal slice scale, and the optimal sampling of these slices, will drive the later iterations of this de-  \nS/N ~ 3 per 2-pixel resolution element. (The S/N per 2pixel resolution element is defined here as the average signal-to-noise per 2-pixel resolution element in the observer-frame 1.02 to 1.28 micron band. Thus the S/N, as well as the actual resolution in the IFU design, will vary  with  wavelength.)  The  SN-typing  spectrum  (IFU Visit  2)  is  deeper  and  observed  near  peak  SN  brightness,  with  exposure  times  calculated  to  yield  S/N  =  6 per  2-pixel  resolution  element,  which  is  equivalent  to S/N=24 per synthetic filter band, when used as part of the  lightcurve  photometry  set.  The  deepest  spectrum (IFU Visit 3) is also observed near peak SN brightness, with exposure times calculated to yield S/N = 10 per 2pixel resolution element, which is equivalent to S/N=40 per synthetic filter band. (The S/N for each IFU Visit is listed in the lower panel of Figure 2-4, and shown in the corresponding error bars of the synthetic-filterphotometry points in the middle panel.)  \nFinally,  one  galaxy-only  reference  spectrum  (IFU Visit 10) will be taken about a year later after the supernova has faded, for galaxy subtraction, with S/N = 6 per 2-pixel  resolution  element.  Since  the  galaxy  reference spectra must be taken well after the SN has faded, they will not be observed during the first year of the survey. The time saved will be used in the third year to take the galaxy spectra for the supernova discovered in the second year. On average, in each 30 hour visit of observations  roughly  8  hours  will  be  spent  on  imaging  discovery, 5 hours for typing spectra, 9 hours on spectra for  light  curves,  5  hours  on  the  deep  spectra,  and  3 hours for the galaxy reference spectra.  \nFigure  2-5  shows  simulated  spectra  with  the  S/N levels of the SN-typing spectrum (IFU Visit 2) and the deepest spectrum (IFU Visit 3) at a range of redshifts. The  comparison  of  the  two  solid  lines  shows  that  the template of a Type Ia SN spectrum (dark line) can be distinguished  from  the  (light  gray  line)  example  of  a Type  Ib/c  SN  spectrum.  The  Type  Ibc  have  the  most similar spectra to the Type Ia, but are clearly spectroscopically distinguishable with S/N = 6 per 2-pixel resolution element, by, e.g., the region around the Type Ia 'sulfur W' feature, visible around 1.08 microns in the z  \nsign, and hence the actual exposure times for a given S/N. These calculations will also be affected by the final choice  of  detector  chip  characteristics  specified,  particularly the asymptotic read-out noise and dark current. Finally,  the  optimizations  will  also  have  to  account  for the actual distribution of host-galaxy-to-SN light ratio in a pixel.  \nFigure 2-5: Simulations of Type Ia SNe observations with the IFU, showing S/N = 6 and 10 (left and right columns) per 2pixel resolution element, for redshifts z = 0.5, 1.0, and 1.5 (top, middle, and bottom rows). (The S/N per 2-pixel resolution element is defined here as the average signal to noise per 2-pixel resolution element in the observer frame 1.02 to 1.28 micron band.) The dark solid line shows the template Type Ia SN spectrum, while the light gray line shows an example of a Type Ibc SN spectrum. The Type Ibc have the most similar spectra to the Type Ia, but are clearly spectroscopically distinguishable with S/N = 6 per (2-pixel) resolution element, by, e.g., the region around the Type Ia 'sulfur W' feature, visible around 1.08 microns in the z = 1 plots.  \n<!-- image -->  \n= 1 plots. It can also be seen how the photometric accuracy  of  IFU  spectroscopy  allows  broad-wavelength color  differences  between  the  SN  types  to  be  used  in the  type  identification.  (The  SN  typing  is  also  much more  accurate  because  of  the  host-galaxy  redshift knowledge available.) As a final cross-check, the twoband imaging lightcurves, which extend at least 40 restframe days past maximum light, can also provide SN Ia identification  information  up  to z ~  1.3,  since  they  will show  the  characteristic  second  lightcurve  peak  in  the redder restframe wavelengths.", 'The Data Sample 2.2.2.5': 'Figure 2-6 shows the number of SNe expected in each Δ z = 0.1 bin of redshift. The drops at the redshift boundaries  of  the  shallow  and  medium  tiers  are  evident.  In  the  deep  tier  we  choose  a  fixed  number  of N=136 in each redshift bin for IFU follow-up, from the larger  number  discovered  in  the  imaging  survey,  to keep the time for IFU spectra within the time allocated to the supernova survey. The total number of predicted SNe is 2725, with a median redshift z = 0.7.  \nTo guide the design and forecast the performance of the supernova survey, we have adopted the following error  model.  The  photometric  measurement  error  per supernova  is σ meas  =  0.08  magnitudes  based  on  the seven IFU spectra with S/N=15 per synthetic filter band,  \nthe  one  typing  spectrum,  the  one  deep  IFU  spectrum, and the one galaxy reference spectrum. We assume an intrinsic dispersion in Type Ia luminosities of σ int = 0.09 magnitudes  (after  correction/matching  for  light  curve shape and spectral properties). This is based on stud-  \nFigure  2-6:  Expected  number  of  Type  Ia  SNe  to  be  followed in each Δ z = 0.1 redshift bin. For z > 0.6 there are, by design, 136 SNe followed up with spectroscopic observations in each bin (from a larger number detected). The total number of SNe is 2725.  \n<!-- image -->  \nes of nearby supernovae that use full spectral time series (which the IFU spectroscopy will provide). The other  contribution  to  statistical  errors  is  gravitational lensing magnification, which we model as σ lens = 0.07 × z mags. The overall statistical error in a Δ z = 0.1 redshift bin is then  \nσ stat = [( σ meas) 2 + ( σ int) 2 + ( σ lens) 2 ] 1/2 / √ NSN ,  \nwhere NSN is the number of SNe in the bin. For the current estimates, we assume a systematic error per bin of  \nσ sys = 0.01 (1+z) / 1.8 mag,  \nwith no correlation of errors between redshift bins. (Development of a more realistic, fully-correlated systematics  error-matrix  study  has  also  been  initiated,  and  the preliminary  results  yield  somewhat  better  FoM  results than those used in this document; this work will continue.)  \nThe total error for a bin is just the quadrature sum of  the  statistical  and  systematic  errors.  Diamonds  in Figure 2-7 show the total distance error (which is half the flux error) based on the WFIRST-AFTA design and the  error  model  above;  these  are  the  same  errors shown for luminosity distance in Figure 2-1. By design, the  statistical  and  systematic  errors  are  comparable, except  in  the  lowest  redshift  bin  where  the  volume  is small.  In  general,  one  gains  by  improving  statistics  in low redshift bins (where the exposure times are shorter) until one hits the systematics limit, and then one gains by going to higher redshifts, which continue to provide new information. (A similar result is seen in the preliminary analysis from the fully-correlated systematics error matrix study.) The total error in distance is about 0.5% per bin near z = 0.5, then climbs to 1% at the highest redshifts  because  of  the  increased  contribution  of lensing to the statistical error and the assumed redshift behavior of the systematic error.  \nOur error model is based on current empirical understanding  of  the  supernova  population,  which  is  improving  rapidly  thanks  to  extensive  surveys  of  nearby and moderate redshift SNe. The design and analysis of the  WFIRST-AFTA  SN  survey,  including  the  optimal division of observing time among redshift tiers, will ultimately depend on lessons learned from ground-based surveys and HST/JWST observations between now and the launch of WFIRST-AFTA. It is clear, however, that the near-IR coverage, sharp imaging, and large collecting area of WFIRST-AFTA will allow a supernova cosmology  survey  of  extraordinary  quality,  far  surpassing  \nFigure 2-7: Fractional errors in distance per Δ z = 0.1 bin. Squares and crosses show the statistical and systematic contributions, respectively, and diamonds show the total error.  \n<!-- image -->  \nthat  of  any  other  planned  facility  on  the  ground  or  in space.', 'Complementary  Ground-Based  SN  Obser2.2.2.6 vations': 'A large sample of well studied low redshift (0.03 < z  <  0.1)  supernovae  is  crucial  for  the  WFIRST-AFTA supernova  survey:  to  anchor  the  Hubble  Diagram,  to identify  subclasses  of  the  Type  Ia  supernovae  which can be paired with similar subclasses at high redshift to reduce the intrinsic spread of the supernova peak luminosities, and generally to sharpen our understanding of these objects as cosmological distance indicators. Because of the volume effect, the low redshift supernovae are much rarer per area on the sky, so while the supernova  at z >  0.2  can  be  found  with  WFIRST-AFTA  by searching tens of square degrees, the low redshift supernova search has to extend over thousands of square degrees for many years. The low redshift (z < 0.1) supernovae are, however, much brighter, and their light is in the optical, so this part of the supernova work is best done in a ground-based survey.  \nIn the WFIRST-AFTA supernova survey discussed in this report, a sample of 800 low-redshift (z < 0.1) supernovae  was  assumed,  each  one  measured  with  a spectrophotometric time series comparable to that obtained  by  WFIRST-AFTA  for  the  high-redshift  SNe (though with better S/N and cadence). Simply from the improved anchoring of the Hubble diagram, the availability  of  such  a  sample reduces the errors on the cosmological  parameters  obtained  by  the  supernova  survey by a factor of two, as shown in Figure 2-8, and the resulting FoM of the survey is increased by a factor of close to three as shown in Figure 2-9. However, even  \nthese large improvement factors underestimate the importance of the low-redshift spectrophotometric sample for WFIRST-AFTA, because of their key role in identifying and matching the subclasses of Type Ia supernovae that  would  otherwise  introduce  significant  systematic errors after accounting for population drift over time and redshift.  \nCurrently,  the  Nearby  Supernova  Factory  is  completing the spectrophotometric time series, comparable to those planned for WFIRST-AFTA, for approximately 300 low-redshift Type Ia supernovae. To build the larger  sample of ~800 low-redshift supernovae with spectrophotometric  time  series,  there  are  many  projects (such  as  the  iPTF,  ZTF,  SkyMapper,  La  Silla/QUEST, and eventually LSST) that can find the low-redshift supernovae,  but  few  that  can  perform  the  spectrophotometric follow up. It will be important to develop the capability to follow these discoveries with precision spectrophotometry. Fortunately, this work requires relatively small telescope(s) and instruments.', 'High-Latitude  Imaging  Survey:  Baseline 2.2.3.1 Design': "The WFIRST-AFTA high-latitude survey (HLS) will image 2227 deg 2 in  4  NIR  bands  (Y,  J,  H,  and  F184) spanning the range from 0.92-2.00 ∝ m to magnitudes 25.8-26.7 AB (depending on band), and reaching the diffraction  limit  in  J  and  redder  bands.  Figure  2-10 shows this imaging depth in comparison to LSST (after 10 years of operation) and Euclid. In an AB-magnitude sense, WFIRST-AFTA imaging is well matched to the iband depth of LSST. The AB magnitude limits for LSST in g and r are fainter, but galaxies are red - for example,  the  median  WFIRST-AFTA  weak  lensing  source galaxy has i-H=0.8, r-H=1.2, and g-H=1.7, so even here the  WFIRST-AFTA  and  LSST  imaging  depth  remains well  matched. The Euclid NIR imaging covers a wider area than WFIRST but is 2.6 magnitudes shallower. It is under-sampled with 0.3' pixels, and not used for galaxy shape measurements. The Euclid visible imaging depth is  comparable to LSST, but in a single very wide filter rather  than  the  ~5  optical  bands  necessary  for  photometric  redshift  determination.  WFIRST-AFTA  provides multicolor  space-resolution  imaging  (PSF  half-light  radius  0.12-0.14').  The  combination  of  Euclid/VIS  and the  WFIRST-AFTA  imaging  will  provide  5-band  photometry over the area of overlap. They will provide approximately the same physical resolution and sensitivity and cover a similar rest-frame wavelength range at z=1  \n<!-- image -->  \n0#  \nFigure 2-8: Error ellipse in the wa vs. w0 plane without a low  redshift  sample,  the  large  ellipse,  and  with  800 ground based low redshift supernova, the small ellipse. This forecast assumes a flat universe and a dark energy equation of state w(a) = w0 + wa(1-a) with a = 1/(1+z). It incorporates  anticipated  constraints  from  Planck  CMB measurements  and  WFIRST-AFTA  supernova  measurements, and the low redshift SN data set, but no other data.Figure 2-9:  The DETF  Figure  of  Merit  (see  definition  in §2.2.5)  of  the  WFIRST-AFTA  supernova  survey  as  a function  of  the  number  of  ground  based  low  redshift supernovae,  taking into  account  just  the  improvement in  the  anchoring  of  the  Hubble  diagram  provided  by larger  numbers  of  low-redshift  SNe.  (Improvements from the better constraints on SN-Ia subclasspopulation drift are not shown here.)  \n<!-- image -->  \nSensitivities of LSST, WFIRST, and Euclid  \nFigure 2-10:  Depth in  AB magnitudes of the WFIRST-AFTA (red), Euclid (green), and LSST (blue) imaging surveys. Labels below each bar indicate the size of the PSF (specifically, the 50% encircled energy radius) in units of 0.01 arcsec. The  near-IR  depth  of  the  HLS  imaging  survey  is  well matched to the optical depth of LSST (10-year co-add).  \n<!-- image -->  \nas the Sloan Digital Sky Survey (SDSS) has done with its 5-band imaging at z=0.1. 4", 'Weak Lensing 2.2.3.2': 'The  HLS  imaging  survey  will  make  weak  lensing (WL) shape measurements of 380 million galaxies over an area of 2200 deg 2 . Weak lensing directly probes the clustering  of  matter  between  the  observer  and  the lensed  source  galaxies,  so  it  measures  the  growth  of structure  without  uncertainties  associated  with  galaxy bias. The weak lensing signal also depends on distances to the sources and the lensing matter distribution, so it  provides expansion history constraints that are competitive with those from other methods. However, away from  massive  clusters  the  typical  distortion  of  source galaxy shapes is only about 1%. Measuring the lensing signal with high precision, in the face of intrinsic ellipticity variations that are ~ 0.4 rms, requires enormous galaxy samples and exquisite control of systematic errors. Space-based measurements offer potentially enormous advantages for weak lensing because of high angular resolution and stability of the observing platform, allowing  accurate  characterization  of  the  instrumental  point spread function (PSF). The large aperture of WFIRST-', 'Weak lensing source distribution': 'Figure  2-11:  The  distribution  of  weak  lensing  source redshifts for WFIRST-AFTA, as forecast using data from the CANDELS GOODS-S field (Guo et al. 2013, Hsu et al. 2014).  The  total  effective  number  density  for  the  J+H band combined sample is 45 arcmin -2 .  The median redshift is 1.0 and the mean is 1.1.  \n<!-- image -->  \nAFTA yields a high effective surface density 5 of lensed source galaxies, neff = 45 arcmin -2 in  the  HLS  and  potentially  200-300  arcmin -2 in  longer,  targeted  observations,  much  higher  than  any  other  ground-based  or space-based facilities equipped for large area surveys.  \nThe  HLS  follows  a  dithering  strategy  (see  Figure 3-54 below) so that images in J, H, and F184 are fully sampled  for  shape  measurements,  even  when  some exposures  of  a  galaxy  are  lost  to  chip  gaps,  cosmic rays,  or  detector  array  defects.  We  have  chosen  the exposure  time  of  174  secs  for  the  HLS  so  that  read noise and sky noise make roughly equal contributions in  individual  exposures.  The  survey  area  then  follows from the total observing time devoted to the HLS imaging survey, which is here taken to be 1.33 years. Basic characteristics  of  the  wide-angle  HLS  imaging  survey are shown in Table 2-1, and the anticipated redshift distribution  of  weak  lensing  sources  is  shown  in  Figure 2-11. These yield forecasts are lower than those in the 2013 WFIRST-AFTA report primarily because we have updated  the  COSMOS  Mock  Catalog  used  for  these forecasts  to  incorporate  an  empirical  NIR  colormagnitude diagram for faint  galaxies  based  on  recent  \nFigure 2-12: The predicted cosmic shear angular power spectrum  and  associated  statistical  errors  for  the  WL survey,  for  17  tomographic  bins  of  source  photometric redshift  as  labeled.  L  is  the  angular  multipole,  and L(L+1)C L γγ is the contribution to the variance of cosmic shear per logarithmic interval Δ ln L.  \n<!-- image -->  \nTable 2-1: Properties of the HLS imaging survey in each filter. Weak lensing yields are averaged over the distribution of depths of the tiling, taking into account losses due to cosmic rays. Weak lensing cuts are based on detection S/N>18, ratio of half light radii of galaxy to PSF > 0.82, and ellipticity error σ e<0.2.  \nobservations from the CANDELS survey. The increase of  the  adopted  telescope  operating  temperature  to 282K has resulted in a separate reduction of neff by 1%, 6%, and 18% in the J, H, and F184 bands, respectively.  \nFigure 2-12 shows the predicted cosmic shear angular power spectrum for 17 tomographic bins of source galaxy photometric redshift together with the projected statistical errors for the WFIRST-AFTA WL survey. For multipole L less than a few hundred, the statistical errors  are  dominated  by  sample  variance  in  the  lensing mass  distribution  within  the  survey  volume,  while  for high L or the extreme redshift bins the errors are dominated by shape noise, i.e .,  the  random  orientations  of the  source  galaxies  that  are  available  to  measure  the shear.  For  a  given  photo-z  bin  the  statistical  errors  at different  L  are  uncorrelated.  Across  photo-z  bins,  the errors  at  lower  L  are  partly  correlated  because  the same foreground structure contributes to the lensing of all galaxies at higher redshift; the errors decorrelate at high L when they become dominated by shape noise, which  is  independent  for  each  set  of  sources.  While Figure 2-12 displays the auto-spectra for the 17 photo-z bins,  there  are  also  17 × 16/2  =  136  cross-spectra  that provide additional information.  \nIn  addition  to  statistical  measurements,  the  HLS imaging survey can produce maps of the projected or 3dimensional  dark  matter  distribution.  The  dark  matter maps from the 2 deg 2 COSMOS survey (Massey et al. 2007) have been among the most popular cosmological results  from  HST,  yielding  tests  of  theoretical  models, as well as an accessible illustration for public outreach (see Figure 2-13).  \n<!-- image -->  \nL  \nThe  HLS  weak  lensing  survey  provides  the  raw statistical precision to measure the amplitude of matter fluctuations σ 8  to  0.12%  with  other  parameters  fixed. Measuring the weak lensing signal (itself only a 1% distortion  of  source  galaxies  that  are  typically  <1  arcsec across) to an accuracy commensurate with this statistical precision makes enormous demands on the control of  systematic  errors,  including  the  optical  PSF,  understanding of the detector arrays, and calibration of photometric  redshifts  (discussed  below).  The  required knowledge  of  PSF  ellipticity  (4.7x10 -4 per  component) will  be  obtained  via  observations  of  stars  through  the same optical path and on the same detector arrays as used  for  the  galaxy  measurements.  Wavefront  drifts must be kept to <0.7 nm rms per exposure so that the PSF  can  be  measured  faster  than  it  changes,  and short-timescale  wavefront  disturbances  from  the  reaction  wheels  and  high-gain  antenna  must  be  kept  to  a similar  level.  Detailed  integrated  modeling  shows  that WFIRST-AFTA meets these requirements with margin. (see §3.8) Line of sight motion will be tracked using the FGS, and high-frequency  jitter  will  be  fit  to  the  stellar images  in  each  observation.  Finally,  and  most  importantly,  WFIRST-AFTA  will  carry  out  multiple  shape measurements of each galaxy, using 3 different filters, 2 roll orientations per filter, and 4-5 dither positions per orientation  (with  at  least  2  remaining  after  accounting for  chip  gaps  and  cosmic  ray  losses).  This  enables  a  \nFigure 2-13: Maps of the projected surface density of dark matter of a 5 deg 2 field of view (left panels) and an expanded region (25 arcmin 2 ) on a side (right panels). The underlying mass distributions are taken from a large cosmological Nbody simulation. The bottom left panel shows a map with the weak lensing shape noise expected from the WFIRSTAFTA HLS, at a source density n\\_eff = 45 arcmin -2 . The lowest levels shown (blue) are 1 σ above the background. This map accurately recovers the large scale features of the true mass distribution (top left panel). The zoomed panels (with contours spaced at 0.5 σ starting at 1.5 σ ) compare the fidelity of maps at the HLS depth to maps with the 15-30 arcmin -2 source  density  characteristic  of  ground-based  or  Euclid  observations,  which  miss  much  of  the  fine  detail  at  small scale. Over selected areas of tens of deg 2 , WFIRST-AFTA could carry out deeper imaging to achieve source densities of 200-300 arcmin -2 (bottom right panel), yielding projected mass maps that are virtually indistinguishable from noiseless maps (not shown). Figure credit Julian Merten/Alina Kiessling (Caltech/JPL).  \n<!-- image -->  \nrobust program of internal cross-checks and null tests in  the  weak  lensing  program.  Cross-correlations  between  observations  taken  many  months  apart  can  be compared with auto-correlations. Features in the effective PSF fixed to the focal plane, their dependence on wavelength,  and  dependences  on  source  and  sky background  brightness  will  be  measured.  Finally,  the multiple passes per filter support internal self-calibration as has been performed in SDSS (e.g. Padmanabhan et al.  2008).  Exquisite  relative  photometric calibration, as required for e.g. photometric redshifts, will be enabled by combining these techniques with the inherent stability of a temperature-controlled telescope in space.  \nWFIRST-AFTA is the only platform that will provide both the  high  resolution  and  stability  offered  by  space and  the  internal  redundancy  required  of  a  precision measurement.  However,  the  WFIRST-AFTA  weak lensing  measurements  are  strongly  synergistic  with those of other large surveys. The cosmological interpre-  \ntation  of  the  signal  requires  optical  data  such  as  that provided  by  LSST  (see  below),  and  the  combination with LSST and Euclid weak lensing maps provides additional opportunities for consistency checks. The synergy with Euclid and LSST is discussed extensively in Appendix H.', 'Clusters of Galaxies 2.2.3.3': "The abundance of rich galaxy clusters as a function of mass and redshift offers an alternative route to measuring the growth of structure. The key uncertainty in  this  approach  is  accurate  calibration  of  the  cluster mass  scale  ---  the  average  virial  mass  of  clusters  at redshift z as a function of a mass-correlated observable such  as  galaxy  richness  or  X-ray  luminosity  ---  which must be known to sub-percent accuracy to exploit the statistical potential of cluster surveys. The HLS imaging survey  is  an  ideal  tool  for  carrying  out  this  calibration through  measurements  of  the  average  weak  lensing  \nprofiles  of  large  cluster  samples.  The  clusters  themselves can be identified in WFIRST-AFTA imaging, together  with  optical  imaging  from  LSST,  or  from  X-ray surveys  (the  eROSITA  mission  in  particular)  or  radio surveys that utilize the Sunyaev-Zel'dovich (SZ) effect.  \nThe strategy of stacked weak lensing mass calibration  of  clusters  for  cosmological  constraints  has  been successfully implemented by Rozo et al. (2010) for optically  selected  clusters  and  Mantz et al.  (2014)  for  Xray selected clusters, yielding some of the tightest current  constraints  on  the  amplitude  of  matter  clustering. Forecasts for surveys like WFIRST and LSST by Oguri &  Takada  (2011)  and  Weinberg  et  al.  (2013)  indicate that  constraints  from  cluster  weak  lensing  should  be competitive  with  and  largely  independent  of  those  derived  from  cosmic  shear  analyses  of  the  same  weak lensing  surveys.  These  forecasts  may  underestimate the  power  of  this  approach  because  they  do  not  consider  the  additional  constraints  from  cluster  weak lensing at large separations, well beyond the virial radius. Furthermore, comparison of weak lensing mass profiles with galaxy velocity distributions for matched cluster  samples  can  directly  test  modified  gravity  models that  predict  differences  in  the  gravitational  potentials that affect relativistic and non-relativistic particles.  \nCluster weak lensing is analogous in many ways to galaxy-galaxy lensing (GGL): both of them involve correlating the galaxy shear map with a foreground tracer population. These forms of lensing analysis bring in the additional information provided by the cluster or galaxy maps,  which  mark  the  expected  locations  (including photometric and in some cases spectroscopic redshifts) of  dark  matter  overdensities.  The  measurement  systematics  of  cluster-galaxy  and  galaxy-galaxy  lensing are also likely to be smaller than those affecting cosmic shear.  GGL provides insight  into  the  dark  matter  halo masses and extended environments of different classes of galaxies (e.g., Mandelbaum et al. 2006). In combination with galaxy clustering measurements, it can also be used to derive constraints on dark matter clustering. We have not included cosmological forecasts for GGL because  they  depend  on  uncertain  assumptions  about how well one will be able to model the non-linear bias of galaxies with respect to dark matter. However, plausible forecasts  suggest  that  constraints  on  structure  growth from this approach will be competitive with and perhaps even  more  powerful  than  those  from  cosmic  shear alone (Yoo & Seljak 2012). We have also not included constraints from higher order lensing statistics (e.g., the shear bispectrum), which could have substantial power at the high neff of the WFIRST-AFTA WL maps.", 'Photometric Redshifts 2.2.3.4': "Accurate photometric redshifts are required for the WFIRST-AFTA  weak  lensing  program.  The  predicted cosmic  shear  signal  for  a  sample  of  source  galaxies depends  on  the  redshift  distribution  of  the  sources;  a 1% change in the mean redshift for typical source galaxies produces a 1-2% change in the predicted shear power spectrum, an observable that WFIRST-AFTA will measure with an aggregate precision better than 0.2%. Dividing the sources into tomographic bins of different redshift is necessary to break degeneracies in cosmological parameter constraints. Photometric redshifts are also essential for modeling and removing the effects of intrinsic galaxy alignments, which can be distinguished from  true  weak  lensing  signals  by  cross-correlating shear maps derived from source samples with distinct redshift  separations.  These considerations lead to two different  challenges  for  WFIRST-AFTA  photometric redshifts  (as  for  any  other  weak  lensing  survey).  The first is to obtain precise photometric redshifts with small catastrophic  outlier  fractions  for  all  sources,  to  enable tomography  and  intrinsic  alignment  analysis.  The  second is to calibrate  the  error  distribution  of  the  photometric  redshifts  -  mean  offset,  rms  width,  skewness, outlier distribution - to high accuracy, so that uncertainties  in  this  distribution  do  not  limit  the  cosmological constraints.  \nThe photometric redshifts will rely on a combination of  WFIRST-AFTA  data  and  optical  data  from  the ground. The  baseline HLS  survey  embeds  the WFIRST-AFTA footprint in the sky area to be observed by  LSST,  although  Northern  Hemisphere  fields  could also be considered if appropriate optical data were obtained. We have simulated the photometric redshift performance of the combination of WFIRST-AFTA (NIR) + LSST  (optical)  photometry.  These  simulations  started with the WFIRST-AFTA lensing cuts and a mock catalog  based  on  the  COSMOS  intermediate  band,  UltraVista  (H=24.5),  Spitzer  SPLASH  (reaching  a  3.6 ∝ m depth of 25.5 AB), and HST/ACS data. The mock catalog  is  generated  using  the  spectral  energy  distribution fits to the data catalog following the method outlined in Ilbert et al. (2013) to obtain photometric redshifts. This simulation produces a catalog of galaxies matching the redshift and color distribution of actual galaxies on the sky.  The  WFIRST-AFTA depths are as reported here; the LSST depths assumed are those at the end of the planned 10-year LSST survey.  \nThe simulated performance is displayed in  Figure 2-14,  where  it  is  seen  that  the  combination  of WFIRST+LSST provides excellent performance out to  \nz>3.  The  simulated  sample  has σ z/(1+z)=0.043,  and the fraction of objects with fractional redshift uncertainty <0.04 is 95%.  \nHowever,  this  simulation  is  still  somewhat  idealized. The actual redshifts of some galaxies (~3-5%, typically  AGN  and  z>3  galaxies)  are  mis-assigned  in  the simulation,  meaning  the  simulated  outlier  fraction  is likely a lower bound. Furthermore, the simulation does not account for blending with nearby objects, calibration error and other issues with photometry. Based on experience  with  COSMOS  and  GOODS,  adding  these  effects  to  simulations  will  increase  the  width  and  outlier fraction of the photo-z error distribution. When we correct based on scaling from such experiments, our estimated  rms  uncertainty  increases  to σ z/(1+z)=0.061, and our estimated fraction of objects with fractional redshift  error  <  0.04  decreases  to  78%.  While  there  is more work to be done, both developing more complete simulations  and  optimizing  photo-z  algorithms,  these results  are  an  encouraging  indication  that  photometric redshifts  based  on  WFIRST-AFTA  +  LSST  can  meet the needs of the WFIRST-AFTA weak lensing program. Of  course,  photometric  redshifts  for  a  sample  of  hundreds  of  millions  of  galaxies  out  to  z=3  will  also  be  a huge asset to studies of the evolution and clustering of galaxies and AGN.  \nCalibrating photometric redshift performance to extremely high accuracy is a separate challenge that will likely  require  a  multi-faceted  approach.  The  most straightforward approach to direct calibration requires a sample  of  ~30,000  -  100,000  spectroscopic  redshifts that  spans  the  full  flux  and  color  range  of  the  weak lensing source galaxies (Abdalla et al. 2008, Newman et  al.  2015).  These  samples  must  have  reliable  spectroscopic redshifts for a very high fraction of the galaxies. However, existing large spectroscopic surveys from 8-m telescopes have flux limits 1-2 magnitudes brighter than the HLS photometric limit and achieve high reliability redshifts for only 60-75% of sample galaxies.  \nThere  are  several  strategies  for  overcoming  this problem,  discussed  at  length  in  the  community  white paper by Newman et al. (2015). The first is to improve the direct spectroscopic calibration samples using new wide-field spectroscopic instruments and large observing programs designed with photo-z calibration in mind. The advent of 30-meter class telescopes in the 2020s will  make  it  feasible  to  obtain  spectroscopic  redshifts down  to  the  WFIRST-AFTA  photometric  limit,  though doing so for samples of tens of thousands of galaxies may be prohibitively expensive. Spectroscopic redshifts obtained with the WFIRST-AFTA IFU will play a crucial  \nFigure  2-14:  The  simulated  photometric  redshift  perfordashed line indicates 'perfect' performance, zout=zin.  \n<!-- image -->  \nrole in creating large samples to the HLS flux limit. Our preliminary  estimates  indicate  that  the  IFU  will  yield ~30,000  spectroscopic  redshifts  for  galaxies  that  serendipitously fall within the IFU FoV during HLS observations, to the flux limit of the WL measurements. mance for combined  LSST (10-year) and WFIRST-AFTA data,  for  the  WFIRST-AFTA  lensing  sample.  The  red  \nA  second  strategy  is  to  focus  on  calibrating  the conditional  color-redshift  distribution  (Bordoloi  et  al. 2012) rather than directly calibrating photo-z error distributions. With optimal choices, this approach probably allows  significantly  smaller  spectroscopic  samples, making  it  more  feasible  to  pursue  high  completeness with large telescopes. One can also decide to focus the cosmological weak lensing analysis on source galaxies in bins of color-flux space where the spectroscopic calibration is most reliable, though this comes at a statistical price as the source galaxy population is reduced in size.  \nA third strategy (Newman 2008) is to calibrate the redshift distribution of faint sources through their angular  cross-correlation  with  spectroscopic  samples  of bright  sources,  from  the  WFIRST-AFTA  GRS  and ground-based surveys like the SDSS, DESI, and Subaru PFS. The amplitude of the cross-correlation is proportional to the fraction of the photo-z sample that is at the  same  redshift  as  the  spectroscopic  galaxies.  This method is a subject of active investigation with simulations  and  observational  data,  examining  performance, optimal methods of incorporating non-linear information and  modeling  the  evolution  of  galaxy  bias,  and  requirements for the spectroscopic clustering samples.  \nThe final analysis of WFIRST-AFTA weak lensing data will likely involve describing photo-z error distributions  with  'nuisance'  parameters  that  are  constrained through combinations of direct spectroscopic calibration  \nfrom  IFU  observations  and  ground-based  data,  crosscorrelation  with  large  spectroscopic  samples,  and  the redshift  dependence  of  the  cosmic  shear,  cluster lensing, and  galaxy-galaxy  lensing  measurements themselves. Fully defining and testing this strategy is an important objective for continuing work.", 'High-Latitude Spectroscopic Survey: Base2.2.4.1 line Design': 'Over the same 2200 deg 2 area as the HLS imaging survey,  the  baseline  WFIRST-AFTA  program  incorporates a grism slitless spectroscopic survey to map the distribution of emission line galaxies. The primary target is H α (0.6563 µ m) at 1.05<z<1.88, but it is also possible to extend out to z=2.77 using galaxies with strong [O  III]  emission  (0.5007 µ m).  The  large  aperture  of WFIRST-AFTA  allows  a  survey  significantly  deeper than  the  Euclid  galaxy  redshift  survey,  thus  providing much more complete sampling of structure in the highredshift universe. Figure 2-15 shows the limiting flux of the HLS spectroscopic survey for a point source and for an extended source with reff = 0.3 arcsec and an exponential  profile.  Table  2-2  and  Table  2-3  present  forecasts  of  the  total  number  and  redshift  distribution  of galaxies detected in the HLS spectroscopic survey.  \nOur forecasts for H α emitters are based on a compilation of luminosity function estimates in the literature (Pozzetti et al. in prep, average of Models 1-3). There are  fewer  studies  on  the  [O  III]  luminosity  function  in blind surveys; we have based our forecasts on WFC3 grism  data  (Colbert  et  al.  2013).  For  WFIRST-AFTA sensitivity and 70% completeness, we expect to measure 16.4 million H α emitting galaxies and 1.4 million [O III]  emitters  at  1.88<z<2.77.  Forecasts  are  based  on ≥ 7 σ detections to provide margin.  \nThe predicted number of H α emitting galaxies was estimated  at  20  million  in  the  2013  SDT  report.  The changes are due to improvements in the grism efficiency  and  wavefront  budget  and  operational  efficiency (+18%), which are, unfortunately, offset by a downward revision of the luminosity function (-21%). The change of the assumed telescope operating temperature to 282 K  makes  a  further  reduction  (-12%),  for  an  overall change of -18%.  \nA simulation effort is underway to refine the completeness  estimates  for  WFIRST-AFTA  and  optimize grism  parameters  and  observing  strategies.  An  exam-  \nFigure  2-15:  The  emission  line  sensitivity  for  the WFIRST-AFTA  HLS  spectroscopy  survey.  The  blue curve shows 7 σ point source sensitivities (for six exposures),  and  the  red  curve  shows  extended  source (reff  = 0.3 arcsec, exponential profile) sensitivities. The depth  is  observed-frame  (not  corrected  for  Galactic extinction).  This  depth  is  computed  for  the  mean  sky brightness in the GRS.  \n<!-- image -->  \nple image from the first phase of this effort is shown in Figure 2-16.', 'Baryon Acoustic Oscillations and Redshift2.2.4.2 Space Distortions': "The  galaxy  redshift  survey  (GRS)  allows  measurement  of  the  cosmic  expansion  history  through  the use  of  baryon  acoustic  oscillations  (BAO).  Sound waves that travel in the photon-baryon fluid of the prerecombination universe imprint a characteristic scale on the clustering of matter, which is subsequently imprinted on the clustering of  galaxies  and  intergalactic  gas. The BAO method uses this scale as a standard ruler to measure the angular diameter distance  DA(z)  and  the  \nTable 2-2: Properties of the galaxy redshift survey, including forecast BAO errors in the tangential and radial directions  and  the  overall  error  on  the  scale  of  the  universe. Systematic  errors  are  projected  to  be  sub-dominant,  at 0.1% or lower (Weinberg et al. 2013).  \nTable 2-3: The comoving number density and surface density of emission line galaxies that WFIRST-AFTA will  detect.  We  include  H α when  it  is  in  the  grism wavelength range, and [O III] at higher redshift.  \nHubble  parameter  H(z),  from  clustering  in  the  transverse  and  line-of-sight  directions,  respectively.  The BAO  method  complements  the  Type  Ia  supernova method  in  several  respects:  it  measures  distances against an absolute scale calibrated via CMB observations  (instead  of  relative  to  the  low-redshift  Hubble flow), its precision increases towards high redshifts because of the larger comoving volume available for clustering measurements, and it can directly measure H(z), which  is  tied  to  the  dark  energy  density  through  the Friedmann equation. Our current understanding of the BAO  method  suggests  that  it  will  be  statistics-limited even for the largest foreseeable surveys; small corrections  are  required  for  the  effects  of  non-linear  gravitational  evolution  and  non-linear  galaxy  bias,  but  these can be computed at the required level of accuracy using analytic and numerical techniques. Forecasts for the  \nprecision  of  BAO  distance  and  expansion  rate  measurements are included in Table 2-2.  \nThe broad-band shape of the galaxy power spectrum  P(k)  provides  a  second  'standard  ruler'  for  geometrical measurements via the turnover scale imprinted by the transition from radiation to matter domination in the early universe, as well as a diagnostic for neutrino masses, extra radiation components, and the physics of inflation.  \nThe galaxy redshift survey conducted for BAO also offers  a  probe  of  the  growth  of  structure  via  redshiftspace  distortions  (RSD),  the  apparent  anisotropy  of structure  induced  by  galaxy  peculiar  velocities.  RSD measurements (in the large scale regime described by linear perturbation theory) constrain the product of the matter  clustering  amplitude  and  the  clustering  growth rate (specifically, the logarithmic derivative of clustering amplitude with expansion factor), complementing weak lensing observations that measure the matter clustering amplitude in isolation. Comparison of weak lensing and RSD  growth  measurements  can  also  test  modified gravity  theories  in  which  the  potential  that  governs space curvature can depart from the potential that governs 'Newtonian' acceleration of non-relativistic tracers.  \nFor  measurements  of  BAO  distances  and  expansion rates, the most important metric of a redshift survey is its total comoving volume and the product nPBAO of the mean galaxy space density n and the amplitude of  the  galaxy  power  spectrum  P(k)  at  the  BAO  scale, approximately given by P(k = 0.2h Mpc -1 ). For nPBAO > 2, the BAO measurement error is dominated by sample variance of the structure within the finite survey volume and would not drop much with a higher tracer density. For nPBAO < 1, the measurement error is dominated by shot  noise  in  the  galaxy  distribution.  For  any  given nPBAO, the error on DA(z) and H(z) scales with comoving volume as V -1/2 . To predict nPBAO for the space densities in  Table  2-3,  we  adopt  the  prescription  of  Orsi  et  al. (2010)  for  the  bias  factor  between  galaxy  and  matter clustering, b=1.5+0.4(z-1.5), which is based on a combination of semi-analytic model predictions and observational  constraints.  The  clustering  measurements  of Geach et al. (2012) suggest a somewhat higher bias for H α emitters, which would lead to more optimistic forecasts.  \nFigure 2-17 plots nPBAO vs. z. The BAO scale is fully sampled (nPBAO > 1) over the whole range 1.05 < z < 1.88 probed by H α emitters, with nPBAO > 2 at z < 1.8. The  strong  decline  at  z  >  1.5  arises  because  we  assume that the H α luminosity  function  does not evolve beyond the maximum redshift probed by the Colbert et  \n360 x 360 WFIRST pixels (0.00012 deg?)  \n<!-- image -->  \nTotal Spectroscopic Area (in red: 2227 deg2)  \nFigure 2-16: A simulated 1 st order grism image at WFIRST-AFTA resolution and sensitivity, and at 347 s exposure time as planned for the HLS. Each field in the HLS will be covered with a median of 7 grism exposures at 4 roll angles. This image covers 40x40 arcsec; the instantaneous field of view of WFIRST-AFTA is 2300 times larger.  \nal.  (2013) data; this assumption could prove pessimistic, though extrapolation of a fixed luminosity function to z = 2.2 gives reasonable agreement with the measurements  of  Sobral  et  al.  (2013)  at  this  redshift.  While nPBAO ≈ 3  is  'overkill'  for  BAO  measurement  at  this scale,  a  high  density  survey  allows  better  measurements  of  structure  at  smaller  scales,  better  measurements of higher order clustering statistics, better characterization  of  galaxy  environments,  and  more  complete sampling of the population of star-forming galaxies,  all  beneficial  for  studies  of  galaxy  formation  and galaxy evolution. [OIII] emitters provide a sparse sampling of structure at z > 2; because of the large comoving  volume,  this  sample  of  ~  2  million  galaxies  yields useful  cosmological  constraints  despite  its  relatively high shot noise.  \nGround-based  surveys  like  BOSS  and  the  proposed MS-DESI experiment are likely to achieve nPBAO >  1  out  to  z  ~  1.1,  but  reaching  full  sampling  with ground-based  observations  becomes  very  difficult  at higher  z.  Estimated  space  densities  from  the  Euclid Red Book (Laureijs et al., 2011), corrected for a known factor  of  ln10  error  that  arose  in  luminosity  function conversion, imply space densities roughly 3.0, 8.6, and 19 times lower than those of WFIRST-AFTA at z = 1.1, 1.5, and 1.85, respectively, so Euclid BAO errors will be dominated by galaxy shot noise. Figure 2-18 presents a visual  comparison  of  structure  sampled  at  WFIRSTAFTA density and Euclid density, based on slices from  \nthe  Millennium  simulation  (Springel  et  al.  2005)  populated  with  semi-analytic  galaxy  formation  modeling  \nFigure  2-17:  Product  nPBAO  of  the  mean  galaxy  space density and the amplitude of the galaxy power spectrum at  the  BAO  scale  as  a  function  of  redshift  for  the WFIRST-AFTA GRS, based on the luminosity function of H α emitters  (squares)  and  [OIII]  emitters  (filled  triangles).  Open  triangles  show  our  estimate  of  the  Euclid sampling density based on values from the Euclid Red Book. For nPBAO > 2, the statistical errors of BAO measurements  are  dominated  by  the  sample  variance  of structure within the survey volume, while for nPBAO < 1 they are dominated by shot noise in the galaxy distribution.  \n<!-- image -->  \n] 9  \n<!-- image -->  \nFigure 2-18: Tracing large scale structure at the sampling density of WFIRST-AFTA (left) and Euclid (right). Each panel shows a slice 500 h -1 Mpc on a side and 30 h -1 Mpc thick from the Millennium simulation at z = 1.5. Points in the left panel show semi-analytic galaxies (Bower et al. 2006) selected at a luminosity threshold that yields our predicted space density for WFIRST-AFTA. Thin and thick red circles mark clusters with virial mass exceeding 5 × 10 13 MSun and 10 14 MSun,,  respectively.  The  right  panel  shows  the  galaxy  distribution  with  a  higher  luminosity  threshold  that  yields  the space density predicted for the Euclid GRS at this redshift, which is lower by a factor of 8.6. Conversely, the Euclid area is about seven times larger, so the two surveys have complementary properties. At z = 1.5 this slice would subtend a solid angle (9.2 × 9.2) deg 2 with redshift depth Δ z = 0.022, so it represents a minuscule fraction (~ 10 -3 ) of the GRS survey volume. Figure courtesy of Ying Zu.  \n<!-- image -->  \n(Bower  et  al.  2006).  A  survey  at  the  WFIRST-AFTA depth recovers much of the fine detail present in the full dark  matter  distribution,  which  is  lost  at  the  much sparser  sampling  of  the  Euclid  survey.  Conversely, Euclid covers a volume several times larger.  We note that  WFIRST-AFTA  could  carry  out  a  shallow-wide GRS  of  10,000  deg 2 in  about  one  year  of  observing time,  but  this  would  be  largely  redundant  with  Euclid, while  the  deeper  survey  adopted  in  the  baseline  HLS design is complementary. 6", '2.2.5 Tests of Cosmic Acceleration Models': "The WFIRST-AFTA supernova, imaging, and spectroscopic  surveys  will  enable  multiple  independent measurements of cosmic expansion history and structure growth over the redshift range z = 0-3, each with aggregate precision at the ~0.1 - 0.5% level. This extremely high statistical precision demands that system-  \natic  biases  be  very  tightly  controlled  to  avoid  compromising the measurements. The WFIRST-AFTA mission is  designed  with  control  of  systematics  foremost  in mind,  so  that  it  can  in  fact  realize  the  promise  of  its powerful statistics. For SNe, the use of a space-based observatory and near-IR observations already mitigates key  systematics  affecting  ground-based  surveys,  and the use of an IFU on WFIRST-AFTA reduces systematics  associated  with  photometric  calibration  and  kcorrections  and  provides  spectroscopic  indicators  that can  be  used  to  mitigate  evolutionary  effects.  For  WL, unique aspects of WFIRST-AFTA are the high surface density of sources and the control of systematics enabled  by  eliminating  the  atmosphere  and  having  highly redundant  multicolor  data,  with  an  observing  strategy that provides good sampling even when some of a galaxy's exposures are lost to cosmic ray hits or detector array defects. For the GRS, the high space density of galaxies in the WFIRST-AFTA survey will make it possible  to  measure  higher  order  clustering  statistics  and split  the  data  into  subsamples  to  constrain  models  of galaxy bias, which are the primary source of uncertainty in  deriving  cosmological  constraints  from  RSD  and  intermediate-scale P(k) measurements. Cross-correlation  \nwith the WL shear maps (which have significant statistical power even out to z=2) will provide further tests of galaxy  bias  models  and  improved  cosmological  constraints.  In  all  of  these  aspects  of  systematics  control, the  large  aperture  and  sharp  PSF  of  WFIRST-AFTA play a crucial role.  \nTo characterize the ability of these measurements to test theories for the origin of cosmic acceleration --i.e., to address the two questions posed at the start of §2.2, we adopt the framework put forward by the Dark Energy Task Force (DETF) (Albrecht et al. 2006). We assume a parameterized model in which the dark energy equation-of-state parameter evolves with redshift as w(a) = w0 + wa(1-a) = wp + wa(ap-a), where a = (1+z) -1 is the expansion factor and zp = ap -1 -1 ≈ 0.5 is the 'pivot' redshift at which the errors on wp and wa are uncorrelated  and  the  value  of  w(a)  is  best  determined.  Additional  parameters  that  must  be  constrained  by  the measurements  are  the  baryon  and  matter  densities Ω bh 2 and Ω mh 2 , the Hubble parameter h, the curvature Ω k,  and  the  amplitude  and  spectral  index  of  the  inflationary  fluctuation  spectrum.  For  some  forecasts  we also  allow  deviations  from  GR-predicted  structure growth parameterized by a free value of the index γ in the growth rate evolution equation dlnG/dlna ≈ [ Ω m(a)] γ , where γ ≈ 0.55 for GR-based dark energy models. Our analysis  takes  into  account  the  degeneracies  among these  parameters  and  the  ability  of  complementary cosmological observables to break these degeneracies.  \nWith  the  assumptions  described  in  the  preceding sections,  we  have  computed  Fisher  matrices  for  the WFIRST-AFTA SN, GRS, and WL surveys, which we combine with the Fisher matrix for Planck CMB measurements. In addition to WFIRST-AFTA and Planck, our forecasts  assume  a  local  SN  calibration  sample  with 800 SNe, and they include the anticipated BAO measurements  at  z  <  0.7  from  the  SDSS-III  BOSS  survey (Anderson et al. 2014). Our WL Fisher matrix is based on cosmic shear only and does not include more uncertain contributions from higher order statistics or galaxygalaxy lensing, which might significantly strengthen the anticipated  constraints.  We  do  include  the  expected constraints  from  clusters  calibrated  by  weak  lensing, using a Fisher matrix computed for us by Michael Mortonson  and  Eduardo  Rozo  following  the  methodology described by Weinberg et al. (2013). Our overall forecasting methodology is similar to that described in the 2013 report (Spergel et al. 2013). For BAO/RSD we use the approach described in detail by Wang et al. (2013), assuming no non-linear correction (pNL=1.0) and maximum fitting wavenumber kmax = 0.25 h/Mpc (comoving).  \nFor clusters, we have made the approximation of scaling  error  variances  and  covariances  computed  for  the 2013 report by 480/380 to account for the changed estimate of the number of WL sources in the HLS.  \nFor the fiducial combination of measurements, we forecast  1 σ errors  of  0.0089  on  wp  and  0.114  on  wa, after marginalizing over all other cosmological parameters in the model. The solid black ellipse in Figure 2-19 illustrates these constraints in the form of a Δχ 2 =1 error ellipse.  This  represents  a  dramatic  improvement  over the current state of the art, represented in Figure 2-19 by the green ellipse, with errors Δ wp = 0.12 and Δ wa = 0.6  taken  from  Aubourg  et  al.'s  (2014)  combination  of the main current BAO, SN, and CMB data constraints. While  current  cosmological  data  are  consistent  with  a cosmological constant, we obviously do not know what WFIRST-AFTA will find. For the purpose of Figure 2-19, we have imagined that the true model (marked by the x) has wp = -1.022 and wa = -0.18. A value of w < -1 is exotic but possible in some theories, and it leads eventually to an accelerating rate of acceleration that causes the universe to end in a 'Big Rip' at a finite time in the future. The baseline WFIRST-AFTA would discriminate this model from a cosmological constant at > 2 σ significance ( Δχ 2 = 8.6). The red ellipse, smaller in area by a factor of 1.7, represents the more stringent constraints that could be obtained with a factor of 1.5 improvement over our forecast errors. Such improvement could plausibly be achieved by a combination of improved control of supernova measurement systematics, improved theoretical  modeling  that  extracts  non-linear  information from  galaxy-galaxy  lensing  and  redshift-space  clustering in the HLS, and some level of additional observing in  an  extended  mission.  These  measurements  would distinguish  the  adopted  model  from  a  cosmological constant with Δχ 2 = 14.2.  \nAs a FoM for dark energy experiments, the DETF proposed the inverse of the constrained area in the wpwa plane. We find FoM = [ σ (wp) σ (wa)] -1 = 987 assuming GR (and  922  when  we  allow  a  free  growth  index γ ). This  value  is  represented  by  the  shaded  'Baseline' block in the upper panel of Figure 2-20. As a representation  of  likely  pre-WFIRST-AFTA  constraints,  the dashed blue block in this panel marks the forecast FoM = 131 for a combination of Planck and 'Stage III' dark energy experiments such as BOSS and the Dark Energy Survey, taken from Table 8 of Weinberg et al. 7 The  \n<!-- image -->  \nlower  panel  represents  the  growth  index γ ---  as  with the FoM, we plot 1/ σγ so that higher values correspond to better constraints. Our forecast error for the baseline Figure  2-19: Δχ 2 =  1  error  ellipses  on  the  value  of  the dark energy equation-of-state parameter w at redshift z = 0.47  (the  redshift  at  which  it  is  best  determined  by WFIRST-AFTA) and its derivative with respect to expansion factor dw/da. The green ellipse, centered here on the cosmological constant model (w = -1, dw/da = 0), represents current state-of-the-art parameter uncertainty from a combination of CMB, SN, and BAO data (Aubourg et al. 2014).  For  this  figure,  we  have  imagined  that  the  true cosmology is w(z=0.47) = -1.022 and dw/da = -0.18, well within  current  observational  constraints.  The  black  ellipse shows the error forecast for the baseline WFIRSTAFTA SN, GRS, and WL surveys, combined with CMB data from Planck, a local supernova calibrator sample, and BOSS BAO and RSD measurements at z < 0.7. The red ellipse  shows  the  'enhanced'  case  in  which  the  precision  of  the  WFIRST-AFTA  measurements  (but  not  the Planck,  local  SN,  or  BOSS  measurements)  is  increased by a factor of 1.5, as a result of better control of systematic uncertainties, improved modeling of non-linear clustering,  and  possible  additional  observations  in  an  extended  mission.  Legends  indicate  physically  distinct  regions  of  the  parameter  space:  a  cosmological  constant ( Λ ), scalar  field  models  that  are  'freezing'  towards  or 'thawing' from w = -1, and models with w < -1 (often referred  to  as  'phantom  energy')  in  which  increasing  acceleration leads to a 'big rip' at a finite time in the future.  \n<!-- image -->  \nall offset in the amplitude of matter fluctuations in addition  to  free γ .  This  makes  little  difference  to  the FoM, but it makes the error on γ larger.  \nFigure 2-20: Top: Figure of Merit FoM = [ σ (wp) σ (wa)] -1 for various assumptions. The shaded block shows the baseline case of FoM = 987 corresponding to the solid black contour of Figure 2-19. The blue dashed block shows the forecast  FoM  =  131  from  Stage  III  experiments  from Weinberg et al. (2013).  Red, green, and cyan bars show the effect of increasing the measurement precision from the GRS, WL, or SN survey by a factor of 1.5,  while the purple bar shows the effect of increasing the precision of all three sets of measurements by a factor of 1.5, as described  in  the  text.  Errors  for  Planck,  local  SNe,  and BOSS are held fixed  throughout.  Bottom:  Same  as  top, but for the (inverse) 1 σ error on the growth index γ .  \n<!-- image -->  \nprogram is σϒ = 0.015, compared to the Stage III forecast of 0.15.  \nThe  measurement  forecasts  that  are  the  basis  of our FoM calculations are necessarily uncertain, and we think they are more likely to prove conservative than to prove  overoptimistic.  In  the  case  of  weak  lensing,  for example, we are not including the potential gains from galaxy-galaxy  lensing.  For  the  GRS,  we  have  not included gains in full P(k) and redshift-space distortion analysis that could be enabled by theoretical modeling  \nimprovements over the next decade. More generally, as emphasized in §2.2.1, there is considerable flexibility to optimize  the  WFIRST-AFTA  dark  energy  program based  on  new  knowledge  about  techniques  and  their sources  of  uncertainty.  This  optimization  will  likely improve performance relative to our baseline strategy. The  colored  bars  in  Figure  2-20  show  the  impact  of reducing  the  error  bars  of  the  GRS,  WL,  or  SN measurements by a constant factor of 1.5 (multiplying the  Fisher  matrix  by  2.25),  improvements  that  could plausibly be achieved without increasing the observing time allocated to the dark energy program. These bars illustrate the complementarity of the three prongs of the program: a 1.5 × improvement of the SN measurements has the largest single impact on the DETF FoM, a 1.5 × improvement of the WL measurements has the largest single  impact  on σϒ , and  a  1.5 × improvement  in  the GRS measurements has a noticeable  impact  on  both constraints.  If  all  three  sets  of  measurements  are improved by 1.5 × , yielding the purple bar at right, then the  DETF  FoM  increases  from  987  to  1645  and  1/ σγ increases from 68 to 88.  \nFor Figure 2-19 and Figure 2-20, we have included only minimal external data that are strictly independent of  WFIRST-AFTA:  Planck  CMB,  local  SN  calibrators, the BOSS BAO and RSD measurements at z < 0.7, and (implicitly)  ground-based  data  for  the  photometric  redshifts  of  the  WFIRST-AFTA  lensing  source  galaxies. These are important complementary data sets that are impossible  (or  do  not  make  sense)  to  acquire  from WFIRST-AFTA  itself.  The  inclusion  of  other  preWFIRST-AFTA data sets would, of course, increase the cumulative FoM. By the time of WFIRST-AFTA, there is a good chance that ground-based redshift surveys such as eBOSS, the DESI experiment, and the SuMIRe project with the Subaru PFS, will have measured BAO and RSD out to z = 1 over 10 4 deg 2 or more. At z > 1 they may  no  longer  be  strictly  independent  of  WFIRSTAFTA, but because they will cover large sky areas at low sampling density (nPBAO < 1) instead of 2200 deg 2 at high sampling density, the measurements can probably be combined as though they are effectively independent. The ability to add pre-WFIRST-AFTA SN and WL measurements to the cosmological constraints depends on whether they are limited by statistics or systematics  and  whether  the  systematics  are  correlated with any systematics in the WFIRST-AFTA analyses.  \nIf  WFIRST-AFTA  development  follows  the  schedule proposed in this report, then the LSST, Euclid, and WFIRST-AFTA dark energy experiments will be essentially contemporaneous, with all three of them reporting  \nmajor results in the mid-to-late 2020s. As with groundbased surveys, it should be straightforward to combine WFIRST-AFTA  GRS  results  with  Euclid  GRS  results because of the complementarity between their narrowdeep and wide-shallow data sets. For SNe, we expect that the quality of IFU observations from WFIRST-AFTA will  make  its  (spectro)photometry  far  better  than  anything achievable from the ground, but there may be advantageous  ways  to  coordinate  WFIRST-AFTA  and LSST campaigns to get smaller statistical or systematic errors  through  additional  light  curve  monitoring,  better data on host galaxies, or the use of galaxy counts and shear  maps  to  reduce  the  impact  of  lensing  noise  at high  redshift  (where  it  dominates  the  statistical  error budget). The inclusion of SNe is a critical difference between WFIRST-AFTA and Euclid, so it is worth noting that  our  flat-universe  forecast  for just WFIRST-AFTA SNe + local SN calibrators + Planck CMB (and including  Stage III  priors,  unlike  the  forecasts  in  Figure  2-9) yields an FoM of 582, more than a threefold improvement over the Stage III forecast.  \nFor WL, the critical first task will be to cross-check LSST,  Euclid,  and  WFIRST-AFTA  measurements  to test  for  systematics.  Direct  cross-correlation  of  shear maps from different observatories is a powerful test for shape  measurement  systematics,  as  these  should  be quite  different  among  the  three  facilities.  Photometric redshift  uncertainties  can  be  well  constrained  by  combining WFIRST-AFTA and LSST data, to get deep 10band  photometry  and  good  morphological  information for all galaxies in the joint sample, to calibrate photo-z distributions via clustering cross-correlation with the imaging catalog (Newman 2008), and perhaps to obtain a direct  spectroscopic  calibration  sample  at  faint  magnitudes  with  the  WFIRST-AFTA  IFU.  If  these  crosschecks and joint calibrations demonstrate that all three experiments are statistics-limited rather than systematics-limited,  then  their  measurements can be combined to yield results much stronger than those from any one in isolation.", '2.3 High-Latitude Surveys: General Astrophysics': 'WFIRST-AFTA  will  produce  large  data  sets  with homogenous observing conditions for each set. These data sets will  be  a  treasure  trove  for  Guest  Investigators. The HLS will map ~2,200 deg 2 of sky in four broad NIR passbands down to a 5-sigma limiting AB magnitude of J=26.7 and will include a slitless spectroscopic survey component that will obtain R=~600 spectra with a 7-sigma line flux sensitivity of 10 -16 erg cm -2 sec -1 over the  same  region  of  sky  (see  Figure  2-15).  While  the survey is designed to obtain constraints on the dark energy  equation  of  state  from  weak  lensing  and  BAO measurements, a remarkable range of new astrophysical investigations will be enabled by the HLS data. We focus below on a few of the science cases that are especially well enabled by the access to a 2.4-meter widefield survey telescope in space and that require no additional  time  other  than  that  already  allocated  to  the HLS.', '2.3.1 The First Billion Years of Cosmic History': "Mapping  the  formation  of  cosmic  structure  in  the first  1  billion  years  after  the  Big  Bang  is  essential  for achieving  a  comprehensive  understanding  of  star  and  \ngalaxy  formation.  Little  is  known  about  this  critical epoch when the first galaxies formed. Determining the initial condition and abundances of the primordial interstellar  gas  as  well  as  the  dynamical  properties  of  the first  galaxies  is  critical  in  order  to  understand  (1)  how the  first  galaxies  were  formed  through  a  hierarchical merging process; (2) how the chemical elements were generated  and  redistributed  through  the  galaxies;  (3) how the central black holes exerted influence over the galaxy formation and the overall star formation process; and (4) how these objects contributed to the end of the 'dark ages.'  \nFinding candidate z > 7 galaxies has been pursued in two ways - from moderate area but very deep imaging surveys (e.g., UDF, Subaru Deep Field, CANDELS) and from images of strongly lensing clusters of galaxies (e.g., Bradley et al. 2008, Postman et al. 2012). Recent observations  have  identified  at  least  3  candidate  objects at z > 9 (Bouwens et al. 2011, Zheng et al. 2012, Coe et al. 2013). Two of these candidates were found in  a  survey  of  massive  galaxy  clusters.  One  of  the lensed  candidates  is  shown  in  Figure  2-21.  While  unlensed  sources  at  these  redshifts  are  expected  to  be extremely faint, with total  AB magnitudes greater than  \nFigure  2-21:  A  candidate  for  a  galaxy  at  z=9.6,  magnified  by  a  factor  of  ~15  by  the  foreground  cluster  MACS J1149+2223 (z = 0.54). The object was found in an HST survey using the WFC3IR camera (Zheng et al. 2012). This young object is seen when the universe is only about 500 million years old.  \n<!-- image -->  \n28, lensed sources can be 10 - 30 times brighter. This enhancement  is  particularly  important  because  it  puts some of these sources within the reach of the spectrographs on the James Webb Space Telescope and from very  large  ground-based  telescopes.  Luminous  z  >  7 galaxies are extremely valuable as their spectra can be used  to  determine  the  amount  of  Ly α photons  produced by stars and galaxies escaping from neutral IGM. These objects will also enable the determination of the time when the epoch of reionization occurred up to its completion. Since only a tiny fraction of neutral hydrogen is needed to produce the high opacity of Ly α observed at z ∼ 6, the damped Ly α absorption profile that results  from  even  a  partially  neutral  IGM  (MiraldaEscude 1998) can be measured at low-spectral resolution. Furthermore, the early star formation rate (via Ly α and H α emission  measurements; Iye et al. 2006) can be estimated from the spectra of bright high-z galaxies.  \nThe  HLS  performed  by  the  WFIRST-AFTA  telescope as part of its  weak  lensing  program  will  be  superb  for  finding  and  studying  objects  in  the  early  universe.  A  key  advantage  that  the  2.4-meter  aperture provides  is  that,  in  the  same  amount  of  time,  the WFIRST-AFTA HLS will reach ~0.9 magnitudes fainter than the corresponding DRM1 HLS. The final 5-sigma limiting depth of the WFIRST-AFTA HLS is estimated to be  J=26.7  AB  mag.  Figure  2-22  shows  the  predicted cumulative number of objects that would be found at or higher  than  a  given  redshift  for  both  gravitationallylensed and unlensed regions in a 2,000 square degree survey. The predicted counts (Bradley et al. 2012)  for z~8 are extrapolated to higher redshifts  using  the  few known z>9 candidates and bounded by assuming both a pessimistic (dM*/dz = 1.06) and optimistic (dM*/dz = 0.36) evolution of the characteristic magnitude of galaxies.  The  lensed  source  count  predictions  assume  ~1 strongly  lensing  cluster  per  square  degree.  The  mass models  were  adopted  from  the  CLASH  Multi-cycle treasury program (Postman et al. 2012). The larger collecting  area  of  WFIRST-AFTA  relative  to  DRM1  will yield, in some redshift ranges, as much as 20 times as many z > 8 galaxies (Figure 2-23).  \nHaving 10,000 or more luminous z > 8 galaxies will allow very stringent constraints to be placed on the early star formation rate density, on the amount of ionizing radiation  per  unit  volume,  and  on  the  physical  proper ties  of  early  galactic  structures.  With  its  ~0.1  -  0.2 arcsecond  resolution,  combined  with  lens  magnifications in the 10 - 30 range, the HLS images will allow us to  measure  structures  on  scales  of  20  to  50  parsecs,  \nFigure  2-22:  Cumulative number of high-z galaxies expected  in  the  HLS.  JWST  will  be  able  to  follow-up  on these high z galaxies and make detailed observations of their properties. For understanding the earliest galaxies, the synergy of a wide-field telescope that can discover luminous or highly magnified systems and a large aperture  telescope  that  can  characterize  them  is  essential; WFIRST-AFTA and JWST are much more powerful than either one alone.  \n<!-- image -->  \nFigure 2-23: The ratio of the cumulative number of high redshift  galaxies  detected  with  WFIRST-AFTA  to  the number  detected  with  a  smaller  DRM1  version  of WFIRST. The 2.4 m aperture yields up to 20 times more high-z galaxies.  \n<!-- image -->  \nthanks to the boost in spatial resolution provided by the  cluster  lenses.  The  HLS  will  certainly  herald  a remarkable era in probing the first 1 billion years of cosmic history.", '2.3.2 Mapping  Dark  Matter  on  Intermediate  and Large Scales': "Clusters of galaxies are important tracers of cosmic structure  formation.  All  of  their  mass  components  including dark matter, ionized gas and stars are directly  \nor indirectly observable. By its design, the HLS will be superbly  suited  to  mapping  weak  lensing  signatures. The signal-to-noise ratio of the shear signal is proportional  to  the  square  root  of  the  surface  density  on  the sky  of  galaxies  that  can  be  used  to  map  the  lensing. The WFIRST-AFTA HLS will produce catalogs with surface densities of 60 - 70 galaxies per square arcminute in  a  single  passband  and  potentially  as  high  as  80  100  galaxies  per  square  arcminute  in  co-added  multiband images. Achieving such densities for weak lensing measurements has already been demonstrated with the WFC3/IR camera on the Hubble Space Telescope. The WFIRST-AFTA HLS will thus enable WL maps that are a  factor  3  -  5  higher  number  density  of  galaxies  than any maps produced from the ground (even with 8 to 10 meter  telescopes)  as  illustrated  in  Figure  2-24.  The larger telescope and multiple bands will produce much more  robust  and  higher  quality  WL  maps  than  Euclid (see Figure 2-13). On cluster scales (200 kpc - 2 Mpc), this  higher  galaxy density will allow the dark matter to be  mapped  to  a  spatial  resolution  of  ~40  -  50  kpc. When combined with strong  lensing  interior  to  clustocentric radii of ~200 kpc, the central dark matter distribution can be mapped down to a resolution of 10 - 25 kpc. Comparing such maps around the hundreds of intermediate  redshift  clusters  expected  in  the  HLS  to  \nthose from numerically simulated clusters would give us unprecedented  insight  into  the  main  mechanisms  of structure formation.  \nAn especially interesting class of clusters are those in  the  process of merging / colliding (see Figure 2-25) where all mass components are interacting directly during the creation of cosmic structure. Multiple such mergers have been observed, with the Bullet Cluster being the most prominent example (Clowe et al. 2006). Paired with  follow-up  numerical  simulations,  such  systems gave important insight into the behavior of the baryonic component (Springel & Farrar 2007) and set upper limits  on  the  dark  matter  self-interacting  cross  section (Randall et al. 2008), which is of great importance in the search  for  the  nature  of  dark  matter.  Recently,  more complicated merging systems have been identified (e.g. Merten  et  al.  2011,  Clowe  et  al.  2012,  Dawson  et  al. 2012) offering a great opportunity to better characterize the nature of cosmic dark matter. The HLS will be well suited  to  producing  highly  accurate  strong  and  weak lensing mass maps in the environs of these informationrich merging systems.  \nOn the largest scales (>10 Mpc), the distribution of matter  can  best  be  measured  via  weak  gravitational lensing, owing to the fact that the mass is predominantly  dark  matter  and  thus  can  only  be  detected  gravita-  \nFigure 2-24: Mass density contours around the cluster MACS J1206.2-0848 derived from a ground-based weak lensing survey with Subaru (red) vs. a weak lensing study with HST/ACS+WFC3 (white). The 10x higher surface density of lensed galaxies achieved from space yields ~3x higher spatial resolution maps. The HST data shown here is representative of the WFIRST-AFTA HLS. WFIRST-AFTA will make a map of this quality over 2,000 square degrees as part of its high latitude survey, a thousand-fold increase over the HST COSMOS mass map.  \n<!-- image -->  \nFigure 2-25: Dark matter and cluster gas distribution around the merging cluster Abell 2744. Such maps require wide-field  imaging. To  map  the  entire  area  above  with  HST  WFC3  or  ACS  would require 100 -  200  separate pointings, due to their small field of view. The same field is mapped with a single WFIRST-AFTA pointing (red outline.  \n<!-- image -->  \ntionally. The WFIRST-AFTA HLS's unique combination of spatial resolution, infrared observations and wide area  will  provide  mass  maps  that  have  extremely  high scientific impact. Mapping the large-scale distribution of dark matter can help identify and eliminate systematic effects: unexpected spatial variations in the mass distribution can hint at exciting new physics but could also indicate observational systematics not discoverable via a power spectrum measurement like the one that will be used to constrain dark energy via the HLS.", '2.3.3 Kinematics  of  Stellar  Streams  in  our  Local Group of Galaxies': "The  HLS  will  sample  each  patch  of  sky  twice  for each filter, with the visits distributed over the duration of the full survey. This will enable absolute proper motions to  be  derived  for  a  very  large  number  of  field  stars. From the ground, only bright galaxies and quasars can be  used  as  high-precision  absolute  astrometric  reference  points.  Unfortunately,  their  low  density  requires either very wide-field transformations or a bootstrapping approach that measures a target star relative to its local  \nfield  population  and  larger  field  population  relative  to fixed  reference  points.  WFIRST-AFTA  will  provide  access to an enormous number of slightly resolved medium-brightness  galaxies,  and  absolute  motions  can  be measured directly within  the  field  of  each  detector  array.  \nThis local approach to measuring absolute motions has  recently  been  used  in  the  optical  with  HST  to measure the absolute motions of the globular clusters, LMC, SMC, dwarf spheroidals and even M31, in addition  to  individual  hyper-velocity  and  field  stars.  The strategy involves constructing a template for each galaxy so that a consistent position can be measured for it in  exposures  taken  at  different  epochs.  This  template can be convolved with the PSF to account for any variations  in  focus  or  changes  of  the  PSF  with  location  on the  detector  array.  The  same  approach  that  worked with HST in the optical should work with WFIRST-AFTA in the IR. The WFIRST-AFTA detector array pixel scale and sensitivity  should  be  very  similar  to  that  of  HST's WFC3/IR detector array pixel scale. HST images of the Ultra Deep Field through the F160W (1.6 micron) pass-  \nFigure 2-26: A stellar PSF (left most image) compared to 5 galaxy images from the Ultra Deep Field as seen with HST's WFC3/IR detector - an imager with similar resolution to the WFIRST-AFTA imager. Each of these objects enables a position uncertainty good to 0.02 pixel (2 mas) in a single exposure.  \n<!-- image -->  \nband show that there should be about 30 galaxies per square  arcminute  for  which  WFIRST-AFTA  could measure a position to better than 5 mas in a 360 second exposure (see Figure 2-26). This gives us about 500 reference objects in each WFIRST-AFTA detector array, enabling us to tie down the absolute frame to better  than  0.5  mas  in  each  exposure.  The  HLS  2-year baseline  would  allow  absolute  motions  to  be  derived with  systematic  accuracies  of  about  125 ∝ as/year. Folllow-on GO programs could extend this baseline to 5-years,  enabling  accuracies  of  about  50 ∝ as/year. There are about 10 stars in the ~5 square arc-minute FoV of the UDF that can be measured with this accuracy,  implying  about  18  million  halo  stars  in  the  highlatitude imaging survey.  \nGaia  will  overcome  the  sparse-galaxy  issue  by measuring  positions  across  the  entire  sky  in  a  single global solution, but it will not be nearly as sensitive as WFIRST-AFTA. Gaia will achieve the above precision for  G  stars  down  to  about  V  =  17,  which  allows  the plentiful  turnoff-star  population  to  be  probed  out  to about  2.5  kpc.  WFIRST-AFTA  will  achieve  the  above precision for G stars down to V=20 and will allow turnoff stars  to  be  probed  out  to  about  10  kpc  (see  Figure 2-27). There are about five times more stars within one magnitude  of  the  turnoff  than  there  are  on  the  entire giant branch, and ten times more within two magnitudes of the turnoff, so WFIRST-AFTA's depth will allow us to probe well beyond the thin disk with very good statistics.  \nThe typical dispersion of stars in the halo is ~150 km/s, but since stream stars were gently stripped from objects with low dispersion, they typically have motions that  are  coherent  to  better  than  10  km/s.  Such  225:1 concentrations in phase space are easy to detect. Current  ground-based  stream  studies  are  focused  on HB/RGB/SGB stars, but access to the much more plentiful  stars  below  the  turnoff  will  increase  by  more  than an order of magnitude the number of stars we have access  to  and  the  distance  out  to  which  we  can  study  \nFigure  2-27:  Velocity  uncertainty  of  different  components of the Galaxy's stellar population as a function of distance from the Sun. These errors are typical of what WFIRST-AFTA  can  achieve  over  a  5-year  period.  As part  of  its  high  latitude  survey,  WFIRST-AFTA  will  be able to measure parallax distances to over 200 million stars  and  will  be  able  to  track  the  motions  of  stars much fainter than those observed by the Gaia satellite.  \n<!-- image -->  \nstreams.  By  comparing  the  physical  locations  of streams and the motions within them, we can tease out the structure of the Galactic potential.  \nThese  stellar  streams  are  powerful  probes  of  the distribution of dark matter in our Galaxy and can determine whether our Galaxy has the large number of million solar mass subhalos predicted in the cold dark matter  model.  If  the  dark  matter  is  not  cold,  but  warm  as suggested  in  some  theories,  these  massive  subhalos will not exist, and the stellar streams will be smooth and unperturbed (Johnston et al. 2002).", '2.3.4 Discovering  the  Most  Extreme  Star  Forming Galaxies and Quasars': "The supermassive black holes that sit in the centers  of  galaxies  power  active  galactic  nuclei  (AGNs). There  has  been  growing  evidence  that  these  supermassive  black  holes  not  only  power  these  AGNs  and quasars, but also play an essential role in the evolution of  galaxies:  (1)  the  stunning  correlation  between  the masses of supermassive black holes, the AGN, with the masses of their host galaxies over a wide range of galaxy  masses  and  galaxy  types  (Gebhardt  et  al.  2000, Ferrarese & Merritt 2000) and (2) numerical simulations show that star formation in the most massive galaxies must be suppressed by processes more powerful than supernovae and stellar winds in order to simulate galaxies resembling those we actually observe (e.g. Borgani et al. 2004). The most massive galaxies in the universe are the most affected by AGN feedback - they host the most massive black holes, and their star formation was truncated  drastically  about  10  billion  years  ago.  The more  massive  the  galaxy,  the  earlier  this  truncation happened, a trend called 'downsizing' (Heavens et al. 2004,  Thomas et al.  2005,  Neistein  et  al.  2006).  With the HLS spectroscopic survey, we will be able to probe the epoch of downsizing of the most massive galaxies in  the  universe: z~2, which is the peak of the star formation density and near the peak of the quasar activity.  \nThe HLS spectroscopic survey will enable the largest census yet performed of powerful emission-line galaxies  and  quasars  up  to  (and  possibly  beyond)  lookback times of ~90% of the current age of the universe. It  will  enable  us  to  better  understand  the  relationship between the accretion of matter by active galactic nuclei  and the star formation occurring in the most massive galaxies in the universe. Several key star formation indicators in the spectral range of the grism will be usable to track star formation rates (SFR) in galaxies over the range 1 < z < 4.2. The H-alpha line will probe SFR that are at least 10 - 20 solar masses per year over the range 1 < z < 2, a cosmic epoch that is particularly challenging  to  study  from  the  ground.  The  estimated  surface  density  of  such  galaxies  is  about  10 4 per  square degree, implying the total survey will produce H-alpha measurements for over nearly 20 million galaxies. The OII[3727] line can be detected from star-forming galaxies lying between z = 2.6 and z = 4.2, but only for those systems with SFR in excess of ~200 solar masses per year.  While  such  systems  are  less  common,  the WFIRST-AFTA HLS spectroscopic survey will allow us to accurately determine their space density over the key redshift range where the cosmic star formation rate has  \nreached its highest value. At cosmic times from 200 600  million  years  since  the  Big  Bang  (8  <  z  <  15), Lyman-alpha  emitting  galaxies  may  be  detectable  if they have 'attenuated' SFRs of at least 100 - 200 solar masses per year.  \nThe  HLS  grism  survey  will  discover  ~2600  z  >  7 quasars  with  H  magnitude  <  26.5,  with  an  estimated 20% of those quasars being at z > 8. These are the luminous quasars whose existence tracks the assembly of  billion  solar  mass  black  holes  a  mere  few  hundred million  years  after  the  Big  Bang,  and  whose  light  can potentially illuminate the transition of intergalactic gas in the  universe  from  neutral  to  an  ionized  phase  (GunnPeterson  effect  Gunn  &  Peterson  1965,  Becker  et  al. 2001,  Djorgovski  et  al.  2001,  Fan  et  al.  2003).  Such quasars must be found before their visible red light can be  studied  at  high  spectral  resolution  with  JWST  and ground-based  10-30-m  class  telescopes.  The  fainter quasars are particularly important to find because their region  of  local  influence  is  smaller  (e.g.  Goto  et  al. 2011). These are the same quasars that would be used to  identify  CIV  in  the  IGM  allowing  the  study  of  the chemical enrichment as a function of cosmic time. The HLS grism survey will also be a rich source of backlight targets  for  higher  resolution  spectroscopy  with  other facilities.", '2.3.5 HLS-Embedded Deep Fields Option': 'The notional design for the HLS calls for a uniform depth  survey  of  about  2200  deg 2 in  four  passbands. The survey depth and area are dictated by the requirement  to  ensure  an  ample  yield  of  usable  galaxies  for the weak lensing component of the dark energy survey. However, there are advantages to consider a version of the  HLS  that,  in  addition  to  a  wide  area  survey  of  at least 2000 deg 2 , includes one or more regions of significantly greater depth (1.5 to 2.5 magnitudes fainter) but covering  more  modest  areas  (e.g.,  20  to  50  deg 2 ).  At depths of +1.5 mag fainter than the nominal HLS wide field survey, a WFIRST deep field, performed as part of a larger HLS, would provide NIR depths that are comparable to the ugriz limits of ~28 AB mag expected for the LSST survey. This deeper imaging would provide a superb  training  set  for  assessing  the  reliability  of  the photometry  and  shapes  of  galaxies  near  the  limits  of the  wide-field  shallower  HLS  and  would  also  improve the robustness of such measurements for the full LSST survey. These HLS-embedded deep fields could cover 4 to 10 times more sky area than the WFIRST SN deep fields  and  in  more  passbands.  An  extra  1.5  mag  of depth would require exposure times that are ~10x long-  \ner than the nominal HLS exposures. A deep tier to the HLS of 20 to 50 deg 2 could thus be completed in about 10% - 20% of the time required for the full HLS. The exciting science enabled by including selectively targeted  deep  fields  within  the  HLS  includes  (1)  Measurements of the large-scale distribution and clustering of z > 7 galaxies and of high-redshift AGN, (2) Characterizing the properties of z > 2 galaxy clusters, (3) Ultra-faint surveys of the Milky Way Halo, and (4) Tracking AGN and QSO variability.', '2.4.1 Extrasolar Planet Science Landscape': "The  first  discovery  of  planetary  companions  to Sun-like stars was, along with the discovery of dark energy, one of the greatest breakthroughs in modern astronomy  (Latham  et  al.  1989,  Mayor  &  Queloz  1995, Marcy & Butler 1996). These discoveries have excited the astronomical community and the broader public as well.  Since  then,  the  pace  of  exoplanet  discovery  has increased each year. There are now nearly 1500 confirmed  exoplanets  and  Kepler  has  identified  another 3300  candidates  that  await  confirmation  (Burke  et  al. 2014).  \nNature  has  surprised  astronomers  with  the  enormous  and  unexpected  diversity  of  exoplanetary  systems,  containing  planets  with  physical  properties  and orbital architectures that are radically different from our own Solar System. Since the very first discoveries, we have struggled to understand this diversity of exoplanets, and in particular how our solar system fits into this menagerie.  \nWFIRST-AFTA will advance our  understanding  of exoplanets along two complementary fronts: the statistical  approach of determining the demographics of exoplanetary  systems  over  broad  regions  of  parameter space and the in-depth approach of characterizing the properties of a handful of nearby exoplanets.  \nFirst,  through  its  comprehensive statistical census of the outer regions of planetary systems using microlensing,  including  planets  with  separations  spanning from  the  outer  habitable  zone  to  free  floating  planets, and  analogs  of  all  of  the  planets  in  our  Solar  System with  the  mass  of  Mars  or  greater,  WFIRST-AFTA  will complete  the  statistical  census  of  planetary  systems begun by Kepler. This science is described in §2.4.2.  \nSecond, using a coronagraphic instrument, WFIRST-AFTA will be capable, for the first time in human history, of directly imaging planets similar to those in our Solar System. It will make detailed studies of the properties  of  giant  planets  and  debris  disks  around nearby  stars.  It  will  also  measure  photometric  properties of the 'mini-Neptune' or 'super-Earth' planets  - objects  that  Kepler  has  shown  to  be  the  most  common planets in our galaxy, but with no analog in our own solar system. It will also be the testbed for future coronagraphs capable of detecting signs of life in the atmospheres  of  Earth-like  exoplanets.  This  science  is  explored in §2.4.3 .  \nWith these two complementary surveys, WFIRSTAFTA will provide the most comprehensive view of the  \nformation,  evolution,  and  physical  properties  of  planetary  systems.  In  addition,  information  and  experience gained from both surveys will lay the foundation for, and take the first steps toward, the discovery and characterization  of  a  'pale  blue  dot'  -  a  habitable  Earth-like planet orbiting a nearby star.", '2.4.2 Completing the Census of Planetary Systems': "After  nearly  two  decades  of  exoplanet  discovery, our statistical census of exoplanets, as well as our understanding  of  planet  formation  and  evolution,  remain incomplete.  Ground-based surveys for exoplanets, initially  using the radial velocity method, and now including  the  transit,  direct  imaging,  and  microlensing  methods, are generally only sensitive to exoplanets occupying  relatively  narrow  ranges  of  parameter  space.  Furthermore, this parameter space is largely disjoint from both the planets in our solar system, and from the three largest reservoirs of planets that are predicted by many planet formation theories (e.g. Ida & Lin 2004, Mordasini et al. 2009).  \nJust  over  five  years  ago, Kepler ushered  in  the next phase in the study of exoplanets by beginning the process  of  creating  a  broad  and  complete  statistical census  of  exoplanetary  systems. Kepler has  been enormously successful, discovering thousands of candidate  exoplanets  in  a  bewildering  array  of  architectures.  However,  Kepler  can  only  tell  part  of  the  story: the  transit  method  used  by  Kepler  is  not  sensitive  to planets  in  orbits  significantly  larger  than  that  of  the Earth, including analogs to all of the outer giant planets in  the  Solar  System.  Thus  Kepler  is  only  sensitive  to one  of  the  primary  reservoirs  of  planets  predicted  by planet  formation  theories:  'hot'  to  'warm'  planets (Howard et  al.  2012,  Ida  &  Lin  2004,  Mordasini  et  al. 2009).  \nThe crucial next step is to assay the population of planets in the cold, outer regions of planetary systems, and to determine the frequency of free-floating planets. These latter two populations of planets are invisible to Kepler, yet constitute the two other main reservoirs of planets  predicted  by  many  formation  theories.  Fortunately,  the  gravitational  microlensing  method  provides the  perfect  complement  to  the  transit  method,  and  so can  be  used  to  complete  the  census  of  exoplanetary systems  begun  by  Kepler,  and  provide  a  nearly  complete picture of exoplanet demographics.  \nWhile  providing  a  complete  census  of  exoplanets is,  by  itself,  sufficient  justification  for  a  space-based gravitational microlensing survey, there are also specific  and  compelling  science  questions  that  can  be  ad-  \ndressed  with  such  a  survey.  Below  we  outline  two  of these, namely understanding the origin and evolution of planetary systems, and informing the frequency of potentially habitable worlds.", 'Understanding the Origins and Evolution of 2.4.2.1 Planetary Systems': "Canonical theories  of  planet  formation  and  evolution  originally  developed  to  explain  our  Solar  System (e.g.,  Lissauer  1987)  did  not  anticipate  the  incredible diversity of planetary systems that have been observed. They have since been expanded and altered to better describe the wide range of planetary systems that we see.  For  example,  the  discovery  of  gas  giant  planets orbiting  at  periods  of  only  a  few  days,  as  well  as  evidence for the migration of the giant planets in our own Solar System, have highlighted the fact that these theories must also account for the possibility of large-scale rearrangement of planet positions during and after the epoch of planet formation (Lin et al. 1996, Rasio & Ford 1996). Many of these theories also predict a substantial population  of  'free-floating'  planets  that  have  been ejected  from  their  planetary  systems  through  interactions with other planets (Juric & Tremaine 2008, Chatterjee et al. 2008).  \nIn  the  most  general  terms,  these  formation  theories  should  describe  all  of  the  relevant  physical  processes by which micron-sized grains grow through 1314  orders  of  magnitude  in  size  and  38-41  orders  of magnitude in mass to become the terrestrial and gasgiant planets we see today. These physical processes are  ultimately  imprinted  on  the  architectures  of  exoplanetary systems, specifically, the frequency distributions of planet masses and orbits (e.g. Ida & Lin 2004, Mordasini  et  al.  2009).  Measuring  these  distributions, i.e., determining the demographics of large samples of exoplanets , is  our  best  opportunity  to  gain  insight  into the physical processes that drive planet formation.  \nWFIRST-AFTA will  be  uniquely  sensitive  to  three general  classes  of  planets,  which  will  provide  crucial constraints  on  planet  formation  theories:  cold  planets, free-floating planets, and sub-Mars-mass planets.  \nCold planets : Kepler's intrinsic ability to detect planets declines rapidly for small planets with large separations. As a result, Kepler has been unable to find small planets with periods longer than about one year. Simply put: Kepler is sensitive to 'hot' and 'warm' planets, but not to  the  'cold'  planets  in  the  outer  regions  of  planetary systems, including analogs of all of the planets in our Solar  System  from  Mars  outward.  In  contrast,  the  ex-  \noplanet survey on WFIRST-AFTA is sensitive to planets from roughly the outer habitable zone outwards, including rocky planets with the mass of Earth up to the largest gas giant planets, and analogs of the ice giant planets in our Solar System.  \nSub-Mars-mass embryos: WFIRST-AFTA is uniquely capable of detecting planets with mass as small as the mass of Ganymede (twice the mass of the moon) in significant numbers. Since Mars-mass bodies (about 0.1 MEarth) are thought to be the upper limit to the rapid growth of planetary 'embryos', determining the planetary mass function down to a few hundredths the mass of the Earth uniquely addresses a pressing problem in understanding the formation of terrestrial-type planets.  \nFree-Floating Planets: WFIRST-AFTA's microlensing survey can detect old, 'free-floating' planets in numbers sufficient to test planet-formation theories. It will extend the search for free-floating planets down to the mass of Earth and below, a task not possible with other techniques and not possible from the ground. This will allow it to address the question of whether ejection of planets from young systems is a phenomenon associated only with giant planet formation or also involves terrestrial planets and planetary embryos.", 'Informing the Frequency and Habitability of 2.4.2.2 Potentially Habitable Worlds': "Obtaining a census of planetary systems is also an important first step in the paramount goal of determining how common life is in the universe. Particularly essential is a measurement of the frequency of potentially habitable  worlds,  commonly  denoted η ⊕ .  An  accurate measurement  of η ⊕ provides  a  crucial  piece  of  information  that  informs  the  design  of  direct  imaging  missions intended to search for biomarkers around nearby potentially  habitable  planets.  Indeed,  the  primary  goal of  Kepler  is  to  provide  a  robust  measurement  of η ⊕ . However, this number is so important that a confirmation of the value determined by Kepler is highly desirable, which can be provided by WFIRST-AFTA.  \nWFIRST-AFTA will improve the robustness of our estimate of η ⊕ by measuring the frequency of terrestrial planets just outside the habitable zone, as well as the frequency of Super-Earths in the habitable zone. With this information, WFIRST-AFTA will be able to estimate η ⊕ with  only  modest extrapolation. The combination of WFIRST-AFTA and Kepler data will make it possible to robustly interpolate into the habitable zone from regions just  outside  of  it,  even  if  the  frequency  of  habitable  \nplanets  turns  out  to  be  small.  In  addition,  Kepler's measurement of radius combined with WFIRST-AFTA's measurement  of  mass  will  allow  for  statistical  constraints  on  the  densities  and  heavy  atmospheres  of small planets in the habitable zone.  \nFurthermore,  a  measurement  of η ⊕ will  only  provide  our  first  estimate  of  the  frequency  of potentially habitable  planets.  The  factors  that  determine  what makes a potentially habitable planet actually habitable are not entirely understood, but it seems likely that the amount of water is a contributing factor. However, the origin of the water in habitable planets is uncertain. One possible source is delivery from beyond the snow line, the  part  of  the  protoplanetary  disk  beyond  which  it  is cold enough for water ice to exist in a vacuum. As a result, the number, masses, and orbits of planets beyond the snow line likely have a dramatic effect on the water content of planets in the habitable zone (e.g., Raymond et al. 2004, Lissauer 2007). Therefore, an understanding  of  the  frequency  of  habitable  planets  requires  the survey  of  planets  beyond  the  snow  line  enabled  by WFIRST-AFTA.", 'Expecting the Unexpected 2.4.2.3': 'As compelling as these questions are, it is perhaps the  unexpected  and  unpredictable  returns  of  an  exoplanet  microlensing  survey  with  WFIRST-AFTA  that will  prove  to  be  the  most  enlightening  for  our  understanding of the formation, evolution, and habitability of exoplanets. One of the most important lessons from the past  two  decades  of  exoplanet  research  is  that  there exists an enormous diversity of exoplanetary systems, generally  far  exceeding  theoretical  expectations.  Indeed, one hallmark of the field is the fact that, whenever  new  regions  of  parameter  space  are  explored,  the subsequent  discoveries  necessitate  revisions  of  our planet formation theories. Kepler is currently revolutionizing  our  understanding  of  the  demographics  of  small, short-period planets. Because it will open up a similarly broad  expanse  of  parameter  space  with  a  similarly large yield of planets (thus implying good sensitivity to rare systems), WFIRST-AFTA is essentially guaranteed to do the same. Furthermore, it will do so in a region of parameter space that is almost certainly critical for our understanding of both planet formation and habitability.', 'Summary of Science Motivation 2.4.2.4': 'In summary, a microlensing survey from space with WFIRST-AFTA, when combined with Kepler, will yield a composite census of planets with the mass of Earth and greater on both sides of the habitable zone, overlapping', 'WFIRST-AFTA Exoplanet Discoveries': "WFIRST-AFTA will be sensitive to exoplanets with mass  greater  than  Ganymede,  or  roughly  twice the  mass  of  the  moon.  It  will  detect 2600 total bound exoplanets in the range of 0.03-1,000 Earth masses,  including 1030 'Super-Earths'  (roughly 10  times  the  mass  of  Earth), 370 Earth-mass planets,  and 50 Mars-mass  planets.  This  would enable the measurement of the mass function of cold exoplanets to better than ~7% per decade in mass for masses >0.3 MEarth,  and  an  estimate  of the frequency of Mars-mass embryos accurate to ~15%.  \nWFIRST-AFTA will measure the frequency of freefloating planetary-mass objects in the Galaxy over nearly  six  orders  of  magnitude  in  mass,  and  will detect 30 free-floating Earth-mass planets, if there is one per star in the Galaxy.  \nThese  estimates  are  likely  conservative.  With more  observing  time,  better  optimization  of  the target fields, and more accurate event rates in the target fields,  the  exoplanet  yield  of  WFIRST may be up to a factor of two higher.", 'Characterization  of  Systems  Discovered  by WFIRST-AFTA': 'Data  from  WFIRST-AFTA  will  likely  allow  estimates of the mass and distance to the host stars and planets to better than ~10% for the majority of the  detected  systems.  In  addition,  spectroscopic follow-up  with  JWST  will  allow  for  the  measurement of host star temperature and metallicities for a  subset  of  the  most  massive  hosts  in  the  disk and bulge.', 'Detection of transiting giant planets': "WFIRST-AFTA will be sensitive to the transits of giant  planets  around  200  times  more  stars  than Kepler,  and  40  times  more  stars  than  TESS. WFIRST-AFTA will discover about 20,000 transiting planets with orbits less than a few tenths of an AU,  with  sensitivity  down  to  Neptune-radius  objects.  By  combining  the  transit  and  microlensing discoveries, WFIRST-AFTA will determine the frequency of giant planets over all orbital separations (from 0 to infinity) from a single survey.  \nat almost precisely that zone, thus allowing it to achieve its  primary  goal  to  ' Complete  the  statistical  census  of planetary systems in the Galaxy, from the outer habitable zone to free floating planets, including analogs of all of  the  planets  in  our  Solar  System  with  the  mass  of Mars or greater.' With such a census, WFIRST-AFTA will be able to address the three fundamental and interrelated questions: ' How do planetary systems form and evolve?', 'What determines the habitability of Earth-like planets?', and ' What kinds of unexpected systems inhabit  the  cold,  outer  regions  of  planetary  systems?' Without  WFIRST-AFTA's  survey,  we  will  have  essentially  no  knowledge  of  the  frequency  of  solar  systems like our own, no knowledge of the demographics of exoplanets  in  vast  regions  of  parameter  space  that  include  analogs  of  Mars,  Saturn,  Neptune,  and  Uranus. Without  WFIRST-AFTA,  basic  questions  of  the  formation, evolution, and habitability of exoplanets will remain unanswerable.", 'The WFIRST-AFTA Microlensing Survey 2.4.2.5': "The  microlensing  technique  for  discovering  exoplanets,  illustrated  in  Figure  2-28,  is  well  developed and  mature  (Gaudi  2012).  Its  capabilities  have  been amply  demonstrated  from  the  ground  through  several  \ndiscoveries  that  have  provided  important  new  insights into the nature and diversity of planetary systems. These include the discovery of a substantial population of cold 'Super-Earths' (Beaulieu et al. 2006, Bennett et al. 2008, Muraki et al. 2011), the first discovery of a planetary system with an analog to our own Jupiter and Saturn (Gaudi et al. 2008, Bennett et al. 2010), and the detection  of  a  new  population  of  Jupiter-mass  planets loosely bound or unbound to any host star (Sumi et al. 2011). Importantly, ground-based microlensing surveys have determined that cold and free-floating giant planets are ubiquitous: on average, every star in the Galaxy hosts  a  cold  planet  (Cassan  et  al.  2012)  and  'freefloating'  giant  planets  may  outnumber  the stars in our galaxy by two to one.  \nWhile exoplanet microlensing from the ground has had well-documented successes, realizing the true potential  of  the  microlensing  method,  and  achieving  the primary science goals outlined above, is only possible from  space  with  an  instrument  like  WFIRST-AFTA (Bennett & Rhie 2002). Microlensing requires monitoring a very large number of stars in very crowded, heavily  reddened  fields  toward  the  Galactic  bulge  continuously  for  months  at  a  time.  Therefore,  reaching  the needed sensitivity and number of planet detections requires  steady  viewing  in  the  near-infrared  without  in-  \nPlanets are revealed as short-duration deviations from the smooth; symmetric magnification of the source due to the primary star:  \n<!-- image -->  \nDetailed fitting to the photometry yields the parameters of the detected planets:  \nFigure 2-28: Schematic illustration of how WFIRST-AFTA discovers signals caused by planetary companions in primary microlensing events, and how planet parameters can be extracted from these signals. The left panel shows a simulated primary microlensing event, containing a planetary deviation from an Earth-mass companion to the primary lens. The offset of the deviation from the peak of the primary event, when combined with the primary event parameters, is related to  the  projected  separation  of  the  planet.  The  right  panel  shows  an  enlargement  of  the  planetary  perturbation.  The width and precise shape of the planetary deviation yield the mass of the companion relative to that of the primary host lens.  \nterruptions for weeks at a time, as well as high angular resolution, stable images over very wide-area fields. In other words, it requires a wide-field infrared survey telescope in space. Figure 2-34 shows a comparison of a field  toward  the  Galactic  center  observed  from  the ground with a simulated field  with  similar  crowding  as would be observed with WFIRST. Without such a mission,  we  will  not  be  sensitive  to  Mars-mass  embryos, we will not determine the frequency of low-mass freefloating planets, and we will not complete the census of planets begun by Kepler.", 'Methodology  for  the  Estimate  of  WFIRST2.4.2.6 AFTA Yields': 'We  estimate  the  exoplanet  yields  for  WFIRSTAFTA using the simulation methodology described in a series of papers by Penny et al. (2013, 2015a, b, c) and Penny  (2014).  This  simulation  methodology  was  also used to estimate the yields of the WFIRST-DRM1 and WFIRST-DRM2 designs, as well as Euclid. We expect the  relative  yields  between  different  survey  designs (given our assumptions) to be more robust than the absolute  rates,  for  reasons  described  in  Appendix  K.  To convert sensitivities to expected yields, we have adopted our best estimate of the planet distribution function from Cassan et al. (2012), which has the form', 'dN/dlogMpdloga = f (Mp/95M ⊕ ) α': 'where f = 0.24/dex 2 and α = -0.73. We assume that this power-law distribution saturates at a constant value of 2/dex 2 for  Mp<5.2  M ⊕ .  This  is  likely  conservative,  as Kepler  has  found  several  multi-planet  systems  that have more than 2 planets per decade in semi-major axis (e.g., Lissauer et al . 2011, Gautier et al. 201 2 ). Note that  the  exponent  of  this  power-law  distribution  with planet  mass is slightly  steeper  but  of  opposite  sign  to the  exponent  of  the  approximately  power-law  dependence  of  the  detection  efficiency  on  planet  mass,  and thus  the  number  of  expected  planets  is  a  relatively slowly rising function of decreasing mass in this model in the regime where we assume the exponent α holds. Note  also  that  the  cold  planet  frequency  below ~10MEarth is very poorly constrained. This ignorance is, of  course,  one  of  the  primary  justifications  for  an  exoplanet survey with WFIRST-AFTA.  \nFigure 2-29: The upper figure shows an image of the Galactic  plane  from  2MASS,  whereas  the  bottom  panel zooms in on the ~36 square degrees around the Galactic center. In the bottom panel, the solid black lines show the footprints of the 10 baseline WFIRST-AFTA fields in Galactic  coordinates,  with  a  total  active  area  of  2.81  deg 2 . These are compared to rates of bound Earth-mass planet detections as a function of location shown as the solid circles, and a map of the extinction in H-band from Gonzalez et al. (2012). The WFIRST-AFTA fields are centered on  locations  of  relatively  low  extinction  and  relatively high planet detection rates.  \n<!-- image -->  \nWe chose 10 target fields toward the Galactic center 8 ,  with  locations  indicated  in  Figure  2-29.  The  total survey area is 2.81 square degrees. Note that we did not fully optimize the survey relative to the number, location,  and  cadence  of  the  target  fields.  We  therefore expect our results to be conservative. We also note that our choice for the number of fields in the baseline survey design (10) is better optimized for high-mass planets  than  low-mass  planets.  Therefore,  choosing  a  \n8 Although the primary microlensing survey will focus on fields  located  toward  the  Galactic  center,  a  unique capability of microlensing is its sensitivity to very distant planetary systems, including planetary systems in other galaxies. Relatively modest surveys of serveral weeks towards M87 or the bulge of M31 would have significant sensitivity  to  Jupiter-mass  planets  (Baltz  &  Gondolo 2001) and be able to probe the frequency of planets in environments with stellar populations and star formation histories that differ substantially from those of the Milky Way disk and bulge.  \nsmaller  number  of  fields  could  further  increase  the yields  of  low-mass  planets,  although  of  course  this would come at the expense of the number of high-mass planet  detections.  It  may  also  be  possible  to  increase the sensitivity to other classes of planets that are at the edges  of  the  sensitivity  of  WFIRST-AFTA,  e.g.,  very small  separation  planets  and  massive  habitable  planets.  As  outlined  in Appendix  K ,  optimizing  the  survey strategy  with  respect  to  the  survey  parameters  and target planet population is an important future activity.  \nAs outlined in the operations concept (§ 3.1 0),  we assume a total  of  6  microlensing  seasons  of  72  days each. Because of the proximity of the Galactic center to the  ecliptic,  the  moon  moves  through  our  target  fields two to three times per season, resulting in losses of 4 to 5 days per lunation due to the moon avoidance angle. Thus  for  our  nominal  6  seasons  observing  campaign, there are a total of 357 days of observations. We also consider the yields for an extended campaign of 7 seasons, which yields a total of 417 days of observations.  \nEach field will be observed every 15 minutes in the wide W149 filter, and once every 12 hours in the Z087 filter. The exposure times in these filters will be 52 secs (W149) and 290 secs (Z087). Due to the layout of the detectors  in  the  focal  plane,  ~85%  of  the  survey  footprint  is  observed  for  the  full  time  while  the  remaining 15% is observed only in either the Spring or Fall seasons.  \nFigure 2-30 illustrates an example simulated microlensing  event,  which  includes  the  signal  of  a  Ganymede-mass planet, with roughly twice the mass of the moon.  The  clear,  unmistakable,  and  unambiguous planet signature highlights two of the intrinsic strengths of the microlensing method, namely that the majority of  \nplanetary  signals  are  detected  at  high confidence (in this case with a total signalto-noise ratio of roughly 27), and the signals  are  not  prone  to  astrophysical  false positives.', '2.4.2.7.1 Bound Planets': "The basic results are summarized in Box 2, Table 2-4, and illustrated in Figure 2-31.  In  order  to  highlight  the  intrinsic sensitivity  of  the  survey,  Figure  2-31 shows  the  region  of  parameter  space where WFIRST-AFTA is expected to detect at least 3 planets, assuming that every  star  has  one planet at the given mass  \nFigure 2-30: Example of a microlensing event light curve from  simulations  of  a  WFIRST-AFTA  exoplanet  survey, illustrating the signal of a planet with a mass of roughly twice  the  mass of the  Moon (roughly the mass of Jupiter's  giant  moon Ganymede)  orbiting a  0.29  solar  mass star  with  a  semi-major  axis  of  5.2  AU.  The  detection  is highly significant, with a Δχ 2 =710, roughly corresponding to a 27 σ detection.  \n<!-- image -->  \nand  semimajor  axis.  For  example,  if  every  star  has  a planet with a mass of 0.1 M ⊕ and a semimajor axis of 1 AU, WFIRST-AFTA will detect roughly three such planets.  Table  2-4  then  reports  the  predicted  yields  for planets of a range of masses assuming the Cassan et al.  mass function, where we have averaged the yields for a given mass over a range of semi-major axes between 0.03-30 AU.  \nWe find that for the nominal six-season observing campaign, WFIRST-AFTA  will  detect  roughly  2600 bound planets in the range of 0.1-1,000 M ⊕ and semimajor axes in the range of 0.03-30 AU. This is compa-  \nTable  2-4:  Predicted  yields  for  bound  planets  for  various  mission  designs.  The  yields  adopted  the  planet  distribution  function  for  cold  exoplanets as measured from ground-based microlensing surveys by Cassan  et  al.,  and  normalized  to  the  most  recent  microlensing  event  rates (Sumi et al. 2013) measured in fields that overlap a subset of the WFIRSTAFTA target fields.  \nNumber of planet detections (assuming per star)  \nFigure  2-31:  The  colored  shaded  regions  show  approximate  regions  of sensitivity  for  Kepler  (red)  and  WFIRST-AFTA  (blue).  The  solar  system planets are also shown, as well as the Moon, Ganymede, and Titan. Kepler is sensitive to the abundant, hot and warm terrestrial planets with separations less than about 1.5 AU. On the other hand, WFIRST-AFTA is sensitive to Earth-mass planets with separations greater than 1 AU, as well as planets  down  to  roughly  twice  the  mass  of  the  moon  at  slightly  larger separations.  WFIRST-AFTA  is  also  sensitive  to  unbound  planets  with masses as low as Mars. The small black points show planets detected by radial  velocity,  ground-based  transits,  direct  imaging,  and  microlensing surveys  (i.e.,  all  known  exoplanets  not  found  by  Kepler).  The  small  red points show candidate planets from Kepler, whereas the small blue points show simulated detections by WFIRST-AFTA; the number of such discoveries will be large, with roughly 2600 bound and hundreds of free-floating planet  discoveries. Thus,  WFIRST-AFTA  and  Kepler  complement  each other, and together they cover the entire planet discovery space in mass and  orbital  separation,  providing  the  comprehensive  understanding  of exoplanet demographics necessary to fully understand the formation and evolution  of  planetary  systems.  Furthermore,  the  large  area  of  WFIRSTAFTA discovery space combined with the large number of detections essentially guarantees a number of unexpected and surprising discoveries.  \n<!-- image -->  \nrable  to  (about  60%  of)  the  yield  of  planet  candidates from  Kepler's  prime  mission,  although  of  course WFIRST-AFTA's  planets  will  be  located  beyond  the 'snow line', a region that is largely disjoint from that accessible to Kepler. With an additional seventh season, WFIRST-AFTA  will  detect  another  440  planets,  for  a total  of  roughly  3040  bound  planets.  As  illustrated  in Figure  2-31,  while  massive  planets  can  be  detected over  nearly  the  entire  range  of  separations  between 0.03-30 AU, lower-mass planets can only be detected over a narrower range of separations of 0.1-10 AU. At least 15% of the detected bound planets will have mass less  than  three  times  the  mass  of  the  Earth  and WFIRST-AFTA will have significant sensitivity down to  \nplanets of roughly twice the mass of the Moon.  WFIRST-AFTA  will  measure  the mass  function  of  cold  planets  to  ~3%15% in bins of one decade in planet mass down to the mass of Mars.", '2.4.2.7.2 Estimating  the  Frequency  of Habitable Planets': "Microlensing's  sensitivity  to  planets falls rapidly  for  projected  separations smaller  than  the  Einstein  radius.  At  projected  separations  of  the  order  of  1/3  of the Einstein ring radius or smaller we expect  the  size  of  planetary  deviations  of the  order  of  1%  or  smaller.  For  typical combinations of the lens and source distances, a solar-mass star has an Einstein radius of ~4 AU, compared to a habitable zone that stretches from ~1-1.7 AU (Kopparapu  et  al.  2013).  Therefore,  the  signals  of  rocky  habitable  zone  planets  will be short and of small amplitude (~1% or less),  so  careful  control  of  photometry systematics to a millimagnitude or less on bright  stars  will  be  essential  for  reliable detections.  Figure  2-32  shows  an  example  WFIRST-AFTA  simulated  light  curve of the perturbation due to an Earth-mass habitable-zone planet, demonstrating the low  amplitudes  and  short  durations  expected for such detections. Furthermore, the  detection  probabilities  for  low-mass planets  at  projected  separations  much less than the Einstein ring are also small, implying  that  the  signals  of  Earth-mass habitable-zone planets will be rare, even if the intrinsic frequency of such planets is high.  Finally,  because  the  ratio  of  the  \nhabitable  zone  distance  to  the  Einstein  ring  radius scales as the host mass M 1.5 ,  WFIRST-AFTA will only be able to detect habitable zone planets around stars close to or above the mass of the sun. This is in contrast  to  Kepler,  which  is  most  sensitive  to  (and  has found) planets in the habitable zones of M- and K-dwarf stars, but is less sensitive to such planets orbiting solarmass stars. Note however, that the old age of the bulge means that stars more massive than the Sun have already evolved off the main sequence.  \nTable  2-5  lists  the  expected  number  of  habitable zone  planets  that  WFIRST-AFTA  will  find.  Assuming that  there  is  one  Earth-mass  planet  in  the  habitable  \nM 0. = 1.46 AU 0. Axz 939 95Mo  \nFigure 2-32:  Example of a WFIRST-AFTA detection of a habitable-zone planet. Such a detection of an Earth-mass habitable-zone planet is unlikely, but  WFIRST-AFTA will be able to detect only slightly more massive planets in the  habitable zone  and Earth-mass  planets just  outside the habitable zone. The HZ planets that WFIRST-AFTA is sensitive to will orbit F-, G- or upper K-dwarf stars, complementing  the  planets  Kepler  and  TESS  can  detect  in the  habitable zones of lower  G-, K- and M- dwarf stars. The signals of rocky habitable zone planets will be short and of small amplitude (~1% or less), so careful control of photometry systematics to a millimagnitude or less on bright  stars  will  be  essential  for  habitable  zone  planet detection.  \n<!-- image -->  \nzone  of  each  main-sequence  star,  WFIRST-AFTA would  detect  one  planet.  However,  for  slightly  largermass planets or at  slightly  larger  distances,  WFIRSTAFTA  can  expect  to  detect  many  more  planets.  So, while it is unlikely that WFIRST-AFTA will measure the abundance of Earth-mass habitable-zone planets, it can measure the abundance of planets just outside the habitable zone and the abundance of more-massive habitable-zone planets. This situation is very similar to that of Kepler, which, for solar-type stars, can measure the abundance  of  planets  with  radii  similar  to  that  of  the Earth just inside the habitable zone, or the abundance of larger planets in the habitable zones. Combined, the results of both Kepler and WFIRST-AFTA can be used to effectively and robustly interpolate into the habitable zone of Sun-like stars.", '2.4.2.7.3 Free-floating Planets': "Free-floating  giant  planets  cause  a  simple,  onetime,  symmetric,  and  achromatic  point-mass  microlensing event with a duration that is proportional to the square  root  of  the  planet  mass  (but  degenerate  with distance and velocity). For the overwhelming majority of  \nTable 2-5: The number of WFIRST-AFTA planet detections expected in and near the habitable zone, assuming a planet abundance of one planet of a given mass per  habitable  zone  (or  4.35  per  decade  of  semimajor axis) per star.  \nTable  2-6:  Predicted  yields  for  free-floating  planets, assuming one free-floating planet per star in the Galaxy,  and  assuming  the  Cassan  et  al.  (2012)  mass function.  \nsources,  i.e.,  main  sequence  stars  in  the  Galactic bulge,  the  angular  source  radius θ *  is  larger  than  the angular Einstein ring radius θ E  for  free-floating  planets with  mass  less  than  about  0.1  Earth  masses.  In  this case, the source is effectively 'resolved' by the planetary lens, and so microlensing events due to such lowmass free-floating planets have a morphology similar to a one-time inverse transit, with a duration that is proportional to twice the source crossing time, and an amplitude of θ E/(2 θ *). Therefore, in this regime, the durations of the events are independent of the free-floating planet mass,  but  the  amplitude  decreases  with  decreasing mass.  Figure  2-33  shows  an  example  WFIRST-AFTA simulated light curve due to a free-floating Mars-mass planet, which illustrates these features.  \nWe show the expected yields for free-floating planets  in  Table  2-6  under  two  assumptions:  one  freefloating planet with a given mass per star in the Galaxy, and assuming the same Cassan mass function as we assumed  for  the  bound  planets.  In  both  cases,  the yields  are  given  for  a  357-day  survey.  For  the  augmented  campaign  of  417  days,  the  yields  are  ~17%  \nFigure 2-33: WFIRST-AFTA will be uniquely sensitive to free-floating planets down to the mass of Pluto. On the left is shown the 95% confidence upper limit on the abundance of free-floating objects that WFIRST-AFTA would infer if it did not detect any free-floating planets. The abundance is plotted as the total mass of ejected objects per star, rather than the number of ejected objects. For comparison, we show (a) the Jupiter-mass free-floating planet abundance that was measured by Sumi et al. (2011), (b) the mass distribution of solar system objects, (c) the Cassan et al. (2012) mass function that was used for the free-floating planet realization in Figure 2-31 and yields in Table 2-4, (d) predictions of the number of planetesimals and planets ejected in dynamical simulations of newly-formed systems with gas giant planets, assuming that only 20% of stars form giant planets (Raymond et al. 2010, 2011) and (e) the upper limit on the abundance of compact objects as measured by the MACHO and EROS surveys (Alcock et al. 1998) and from 2 years of Kepler data (Griest et al. 2014). Also shown in the lower panel are the masses of Solar System objects (planets, dwarf planets and moons), with the planets and dwarf planets color-coded by their semimajor axis objects like those with blue hues would stand a reasonable (Neptune, Uranus) or high chance of being identified as free-floating planets by WFIRST-AFTA due to their large distance from the sun. On the right is an example of the detection by WFIRST-AFTA of a free-floating Mars-mass planet. From Penny et al. 2015b.  \n<!-- image -->  \nhigher.  The  lowest  mass  free-floating  planet  that WFIRST-AFTA  is  sensitive  to  is  set  by  the  sourcediameter  crossing  time  that  is  critically  sampled  by WFIRST-AFTA's 15-minute cadence, while at the same time  providing  enough  photons for  a  significant  detection  of  magnification  at  each  epoch.  These  criteria  result in an optimum free-floating planet mass of the order of 0.1 MEarth (roughly the mass of Mars), and a relatively sharp  cutoff  below  about  10 -3 MEarth  (roughly  half  the mass of Pluto).  \nOne  complication  with  identifying  free-floating planets is that they can be mistaken for planets on very wide  orbits.  Indeed,  a  planet  at  a  large  separation (greater than a few tens of AU, Han et al. 2005) from its host  can  produce  an  identical  light-curve  to  that  produced  by  a  free-floating  planet,  with  no  detectable magnification  due  to  the  host  star,  unless  the  source trajectory has a special geometry aligned with the hostplanet separation axis. It is therefore impossible to determine  whether  such  short  timescale  light  curves  are due to bona fide free-floating planets, or instead due to a bound planet in a wide orbit around a faint star. How-  \never,  by  analyzing  blended  light  (or  the  lack  thereof), together  with  analysis  to  rule  out  subtle  binary-lens magnification features in the light curve, it will be possible to put strong limits on the brightness of any distant host. Follow-up AO imaging with JWST or ELTs may be able to further constrain such scenarios (see §2.7).  \nRather  than  thinking  in  terms  of  a  bound/freefloating dichotomy, it may be more productive to think in terms of the total mass budget of loosely bound objects with binding energies lower than a certain threshold. As shown  in  Figure  2-33,  WFIRST-AFTA  will  be  able  to measure the mass budget of loosely- or un-bound objects  down  to  a  total  mass  of  one  Earth  masses  per star,  over  nearly  6  orders  of  magnitude  in  mass,  from objects  the  mass  of  Pluto  (10 -3 MEarth)  to  the  mass  of Jupiter  (300  MEarth).  At  its  most  sensitive  point,  it  will measure the mass down to less than 0.1 Earth masses per  star  for  objects  the  mass  of  Mars  (i.e.,  down  to  a limit  of  one  such  object  per  star).  The  loosely-  or  unbound mass function that WFIRST-AFTA measures will be a boon to planet formation studies, potentially enabling an era of 'precision planet formation'. This is be-  \ncause in comparison to the multidimensional problem of bound planets (mass, semimajor axis, eccentricity, multiplicity, etc.) in one dimension (mass) it will be relatively simple  to  both  empirically  measure  WFIRST-AFTA's sensitivity  to  free-floating  or  loosely  bound  objects  (allowing  conversion  of  the  number  of  detections  to  a mass  function)  and  produce  predictions  of  the  mass function  from  dynamical  planet  formation  simulations. This  is  illustrated  in  Figure  2-33,  which  compares  the predictions of the total mass of ejected planets and embryos from an illustrative planet formation simulation to the expected limits that can be achieved with WFIRSTAFTA.", 'Physical  Parameters  of  the  Detected  Sys2.4.2.8 tems': 'In addition to a large yield of planets over a broad region  of  parameter  space,  the  other  dramatic  improvement of a space-based microlensing mission over ground-based surveys is the ability to automatically and systematically  estimate  the  masses  of  the  majority  of the  planetary  host  stars  and  thus  planetary  companions. This qualitatively new capability is enabled by the small  and  stable  point-spread  functions  (PSFs)  in space,  which  allow  for  many  different  types  of  measurements  that  are  difficult  or  impossible  from  the ground.  \n- ∞ Measurement  of  the Host Starlight: The WFIRST-AFTA PSF with angular size of ~0.14" in the W149 filter essentially resolves out the majority of the background stars even in the crowded fields monitored by the microlensing survey. In particular, we find that the probability of any given source being  blended  with  an  interloper  star  with  HAB<26  is <15%.  Given  that  the  overwhelming  majority (>90%)  of  the  main-sequence  lenses  are  brighter than  this,  interloper  stars  are  likely  to  contribute negligibly to the total flux of the target. Therefore, during or soon after most microlensing events, any photometered target will contain only flux from the lensed  source  and  the  lens  star  itself.  Therefore, the flux of the lens can be measured by subtracting the  time-variable  flux  of  the  microlensed  source from the target. One complication is that the target may also contain light from unresolved stellar companions to the lens or source, resulting in an overestimate of the lens flux (and thus lens mass) if this light is falsely attributed to the lens. In fact, based on simulations of binary companions to the lenses and sources (Henderson 2015), we find that such  \ncompanions will result in catastrophic misestimates (>50%)  of  the  lens  mass  for  less  than  10%  of events.  Nevertheless,  even  these  rare  situations may  be  resolved  via  direct  measurements  of  the lens-source proper motion, as described below. A measurement  of  the  lens  flux  can  be  combined with a measurement of the lens-source proper motion,  inferred  from  the  light  curves  or  directly  from images taken well after the microlensing event, to infer the lens (and thus planet) mass.  \n- ∞ Direct Measurement of the Lens-Source Proper Motion: For  luminous  lenses,  the  relative  lenssource  proper  motion  can  be  measured  directly from images taken over a very wide time baseline before or after the microlensing event  (Bennett et al.  2007).  While  the  time  baseline  of  the  nominal WFIRST-AFTA six-year mission is sufficiently short that  essentially  none  of  the  lens-source  pairs  will be completely resolved, it will be possible to measure  the  lens-source  proper  motion  for  marginally resolved  pairs  by  measuring either  the  elongation of  the  PSF,  or  the  differential  centroid  shift  of  the PSF  in  two  different  pass  bands  if  the  lens  and source  have  substantially  different  colors.  Importantly, these measurements also yield not only the  magnitude,  but  also  the  direction  of  the  lenssource  proper  motion.  This  vector  proper  motion can  then  be  combined  with  one-dimensional  \'microlens parallax\', which will be routinely measured for roughly half of WFIRST-AFTA microlensing light curves  with  detectable  Earth-mass  planets,  to  directly  measure  the  lens  mass  (Gould  2014a).  In many  cases,  it  will  be  possible  to  measure  the lens-source proper motion from the light curve as well as the images. This redundancy will allow one to check for contamination from light from companions to the lens or source.\n- ∞ Measurement of Higher Order Effects in the Microlens Lightcurves :  The small and stable PSFs delivered  by  WFIRST-AFTA  will  result  in  precise and  accurate  photometry  during  the  microlensing events,  with  substantially  higher  precision  and smaller  systematics  than  is  possible  from  the ground. This will enable the measurement of subtle but information-rich \'parallax\' distortions in the microlens  light  curves  due  to  the  orbit  of  WFIRSTAFTA about the Sun (Gould 1992) and in the case of  a  geosynchronous  orbit,  the  orbit  of  WFIRSTAFTA about the Earth (Gould 2013). In the case of  \nan  L2  orbit,  simultaneous  observations  from  the ground will enable parallax measurements for highmagnification  events  (Yee  2013).  Similarly,  for  a geosynchronous  orbit,  simultaneous  observations from  a  satellite  at  L2  (e.g.,  JWST)  would  enable parallax measurements for high-magnification events.  One-dimensional  parallax  measurements will  be routinely measured for WFIRST-AFTA survey data alone (Gould et al. 2003), which can then be  combined  with  the  vector  lens-source  proper motions, inferred directly from images or from astrometric  microlensing  effects,  to  infer  the  lens mass  and  distance  (Gould  2013,  Gould  &  Yee 2014). For a subset of detections, it will be possible to measure the full two-dimensional microlens parallax; when combined with the relative lens-source proper motion that is routinely measured in planetary microlens lightcurves (Gould 1994), this will also allow one to measure the mass and distance to the  host.  Subtle  distortions  in  the  microlens  light curves due to the orbital motion of the planet about the host will also enable constraints on the period, inclination, and eccentricity of the orbit in a subset of cases.  \n- ∞ Astrometric Shifts due to Microlens Image Motions: During a microlensing event, multiple images of the source are created whose positions and brightnesses vary as a function of time. While these images are typically separated by of order the Einstein ring radius θ E~1 mas and thus cannot be resolved, the changing fluxes and positions lead to a  time-varying  centroid  shift  of  the  unresolved source image, whose magnitude is proportional to θ E  (Walker 1995, Dominik & Sahu 2000). Ensemble  (mission-integrated)  astrometric  precisions  of order  100  µas  (roughly  10 -3 of  a  pixel)  or  better should be easily achievable with WFIRST-AFTA for a  large  fraction  of  microlensing  events,  enabling the  robust  measurement  of θ E  using  astrometric centroid  shifts  for  more  massive  and/or  nearby lenses.  When combined with the measurement of the host light for luminous lenses, this will allow for a  measurement  of  the  distance  and  mass  of  the host. When combined with full two-dimensional microlensing  parallax  measurements,  this  effect  will allow for the detection and mass measurement of a significant  sample  of  isolated  neutron  stars  and black holes, thereby allowing for a determination of the mass function of isolated high-mass remnants, providing crucial constraints on supernovae explo-  \nechanisms (Fryer et al. 2012). These measurements cannot be obtained in any other way. If systematics can be controlled at the level of 10µas (roughly 10 -4 of  a  pixel),  then  astrometric  centroid shift measurements will be possible for substantially  lower-mass  lenses,  including  the  majority  of main-sequence hosts  (Gould  &  Yee  2014).  When combined with the routinely-measured onedimensional  microlens  parallax,  it  will  be  possible to measure the masses and distances to the host stars  (and  thus  planets)  of  a  large  fraction  of  the planetary  systems  detected  by  WFIRST-AFTA, thus enabling a relatively uniform and unbiased determination  of  the  cold  planet  mass  function  and Galactic distribution of planets.  \n- A  quantitative  assessment  of  the  potential  of WFIRST-AFTA to measure the above effects and thus infer host star masses and distances generally requires detailed  simulations,  as  well  as  an  understanding  of systematics  at  a  level  that  is  one  to  three  orders  of magnitude smaller than has been explored to date with existing  analogous  observations.  While  there  have been  some  preliminary  explorations  of  these  effects (Gould 2013, Yee 2013, Gould & Yee 2014), substantially more work needs to be done. Nevertheless, using conservative assumptions, Bennett et al. (2007) demonstrated  that  a  significantly  less  capable  spacebased  microlensing  mission  would  enable  measurement of the host star and planet masses to an accuracy of  ~10% for the majority of the detected systems. We expect WFIRST-AFTA to measure the masses to a similar accuracy for an even larger fraction of systems.', 'Detection of Giant Exoplanets via Transits 2.4.2.9': "WFIRST-AFTA will measure time-series photometry  at  precisions  1%  or  better  for  around  20  million dwarf stars, sufficient to detect transits of giant planets. It will thus survey 200 times more stars for giant planets than monitored by Kepler, and a factor of 40 more than will be monitored by TESS. Detailed simulations of the transiting planet yield of WFIRST-AFTA have not been performed, but McDonald et al. (2014) estimated that a Euclid  optical  microlensing  survey  would  find  about 5000  transiting  planets,  most  of  them  giants  but  with some  limited  sensitivity  down  to  Neptune-radius  objects.  Because  WFIRST-AFTA's  infrared  microlensing survey will collect nearly six times as many epochs as McDonald  et  al.  assumed  for  Euclid,  and  will  monitor nearly twice the area of sky, we conservatively estimate twenty thousand transiting planet detections by  \nWFIRST-AFTA.  These  planets  will  have  separations out to a few tenths of an AU. Since this region of sensitivity  to  transits  overlaps  significantly  with  that  of  the microlensing survey, comparison of the results from the two techniques allows for a further statistical check on the planet candidates, and ultimately the determination of the frequency of giant planets over all orbital separations (from 0 to infinity) from a single survey.  \nContamination  by  false  positives  is  a  significant concern, but the rate of this contamination can be quantified  statistically  using  population  synthesis  analyses, and verified through follow-up observations in favorable cases  (Sahu  et  al.  2006).  That  said,  confirmation  of WFIRST-AFTA's transiting planet candidates will not be trivial,  and  there will be far too many for individual follow-up  efforts.  However,  a  combination  of  proper  motions and in/out-of-transit centroid shifts can be used to rule  out  background  eclipsing  binaries  and  the  ~800 color  epochs  can  be  used  to  reject  a  range  of  hierarchical triples. Many of the planets will have more than just  planet-star  radius  ratio  measurements,  with  a measurement  of  the  1-2  micron  secondary  eclipse depth possible for hundreds of the planets. It should be possible  to  obtain  metallicity  and  kinematic  data  for thousands of hosts using upcoming multi-object infrared spectrographs on 8-m telescopes, and many more using  instruments  on  JWST  and  ELTs.  These  measurements  would  be  particularly  interesting  for  measuring the  Galactic  distribution  of  hot  Jupiters,  as  the  planet hosts will belong to both the disk and bulge populations.", 'Improvements Over Previous Designs 2.4.2.10': 'WFIRST-AFTA is intrinsically more capable than all previous WFIRST designs. For comparison, Table 2-4 shows  the  yields  of  the  previous  WFIRST  designs (WFIRST-IDRM, WFIRST-DRM1, and WFIRST-DRM2), along with the yields of WFIRST-AFTA for the two observing scenarios discussed above. All of these yields assume  the  same  Cassan  et  al.  mass  function.  Note that the yields assume campaigns of duration 432 days (IDRM and DRM1) and 266 days (DRM2), as compared to 357 days for our nominal WFIRST-AFTA campaign, or  417  days  for  the  extended  campaign.  Under  these assumptions, WFIRST-AFTA will be substantially more capable than any of these missions, resulting in overall yields  (averaged  over  planet  mass)  that  are  larger  by factors of ~1.3 to 1.8. The improvements in the yields of WFIRST-AFTA  range  between  factors  of  ~1.2  to  1.6 times larger for giant planets, to factors of 1.7 to 2.8 for Mars-mass planets. The larger relative increase in the yields  of  the  lowest-mass  planets  simply  reflects  the  \nfact that these planets are near the edge of the mission sensitivity for IDRM.  \nIn addition to the improvement in the planet yields, we expect the WFIRST-AFTA to have substantially improved  ability  to  infer  the  physical  parameters  of  the detected  planetary  systems.  This  enhanced  capability follows  directly  from  the  smaller  PSF  of  the  WFIRSTAFTA design (see Figure 2-34) due to the larger aperture.  The  better  image  quality  results  in  more  precise photometry  and  astrometry,  reduced  blending  due  to chance alignment of unrelated stars, and reduced time baselines required to partially or completely resolve the lenses and sources after the microlensing events. The magnitude of this improvement has not been quantified, but is expected to be substantial.  \nFigure 2-34: Left column: Section of a VVV H band image (Saito et al. 2012) from near (l, b) = (1.1°, -1.2°), which lies close to the center of the assumed WFIRST-AFTA fields (see Figure 2-29). Right four columns: Simulated images in the primary wide band of each WFIRST-AFTA design of the same mock field drawn from the Besancon model sightline at (l, b) = (1.1°, -1.2°). The top panels show a 1 x 1 arcminute region and the bottom panels show a 4.6 x 4.6 arcseconds (~13x) zoom-in. The pixel sizes are 0.339, 0.18, 0.18, 0.18 and 0.11 arcseconds from left to right respectively. The Vista Variables in the Via Lactea (VVV) image is based on data products from observations made with ESO Telescopes at the La Silla or Paranal Observatories under ESO programme ID 179.B-2002. From Penny et al. 2015a.  \n<!-- image -->', '2.4.3 Discovering and Characterizing Nearby Exoplanets with a Coronagraph': "Our understanding of the internal structure, atmospheres,  and  evolution  of  planets  was  originally  developed through models that were tuned to explain the detailed observations of the planets in our own solar system. Our surveys of exoplanetary systems have led to the realization that there exists a diversity of worlds with very different properties and environments than those in our solar system, including gas giants under strong stellar irradiation, gas giants with massive heavy cores, water  worlds,  and  'super-Earths'  with  masses  intermediate to the rocky planets and ice giants in our solar system.  Subsequently,  these  models  have  had  to  be  expanded  and  generalized  to  explain  the  properties  of these new worlds but our understanding is still rudimentary.  \nThe best hope of understanding the physical properties of this diversity of worlds is through comparative planetology:  detailed  measurements  of,  and  comparisons  among,  the  properties  of  individual  planets  and their  atmospheres.  These  measurements  provide  the primary empirical constraints on our models.  \nUnderstanding  the  structure,  atmospheres,  and evolution of a diverse set of exoplanets is also an important step in the larger goal of assessing the habitability of Earth-like planets to be discovered in the habitable zones of nearby stars. It is unlikely that any such planets  will  have  exactly  the  same  size,  mass,  or  atmosphere as our own Earth. A large sample of characterized systems with a range of properties will be necessary to understand which properties permit habitability  and  to  properly  interpret  these  discoveries.  A  key uncertainty is the nature of the so-called 'Super-Earths' -  are  they  large  rocky  worlds,  potentially  habitable,  or 'mini-Neptunes'  with  icy  cores  and  hydrogen  atmospheres?  \nCurrently, detailed characterization is only possible for  relatively  rare  transiting  systems.  Unfortunately, transiting  planets  are  a  relatively  small  subset  of  systems.  Those  that  are  bright  enough  for  significant  follow-up tend to be discovered from the ground. Groundbased  transit  discoveries  are  strongly  biased  to  large planets  with  short  orbital  periods  that  are  subject  to strong stellar irradiation. Of course, Kepler has detected many smaller and longer period transiting planets, but nearly all of these systems are far too faint for atmospheric characterization of the planets. Furthermore, atmospheric studies of transiting planets are only sensitive  to  very  specific  planet  geometries  and/or  atmospheric pressures, therefore providing an incomplete  \n<!-- image -->  \n30 zodi disk  \nview  of  the  physical  processes  at  work  in  the  atmospheres of these systems. TESS and JWST will extend this sample, providing near-IR characterization of planets orbiting bright nearby stars, though still emphasizing short periods and lower-mass stars (see Figure 2-36). Figure  2-35:  Simulated  WFIRST-AFTA  coronagraph  image of the star 47 Ursa Majoris, showing two directly detected  planets.  Simulation  parameters:  10  hr  exposure time,  525-580  nm,  Hybrid  Lyot  Coronagraph.  Field  of view of 0.518 arcsec radius. A PSF reference has been subtracted, improving the raw contrast by a factor of 10.  \nDirect  imaging  surveys  of  planets  orbiting  nearby stellar  systems  offer  a  complementary  and  critical  approach  to  studying  the  detailed  properties  of  exoplanets. First, planets detected by direct imaging tend to be at  longer  orbital  periods  and  are  less  irradiated  than those found by transits. Second, spectra of directly imaged  planets  provide  powerful  diagnostic  information about  the  structure  and  composition  of  the  atmospheres. Finally, these planets can be found around the closest stars, which tend to be the best characterized. While ground-based direct imaging surveys have made enormous strides in recent years, with new, much more capable surveys coming on line soon, such surveys are ultimately limited by the contrast achieved in the kinds of planets they can study, being sensitive only to warm and massive young planets. WFIRST-AFTA will detect many analogs to our cold Jupiter for stars in the solar neighborhood,  and  reach  into  the  regime  of  the  miniNeptunes or Super-Earths.  \nPhotometry or spectra will be obtained from more than a dozen of the currently known radial velocity (RV) planets  and  from  new,  lower-mass planets discovered through future RV surveys or by WFIRST-AFTA itself. Combined  with  demographics  from  Kepler  and  micro-  \nFigure  2-36:  Known  exoplanets  as  of  1/2015.  Although more than a thousand extrasolar planets are now known, only a much smaller subset have had their atmospheric composition characterized through transit spectroscopy, secondary  eclipse  studies,  or  direct  imaging;  these  are highlighted. Also shown are the currently-known planets (detected  through  RV  techniques)  that  are  within  the WFIRST-AFTA  coronagraph's  reach,  and  planets  drawn from a Monte Carlo simulation of a WFIRST-AFTA search for new planets.  \n<!-- image -->  \nlensing, astrometric information from RV and Gaia, and TESS/JWST transits, the atmospheric characterization achieved  by  WFIRST-AFTA  with  a  coronagraph  will provide  comprehensive  comparative  planetology  for planets outside the solar system. This new information will  not  only  revolutionize exoplanet science, but it will also serve as an essential first practical demonstration of  high-contrast  imaging  technology.  This  lays  the groundwork  for  a  future  mission  that  will  achieve  the ultimate  goal  of  directly  detecting  a  'pale  blue  dot' around  a  nearby  star  and  searching  for  signatures  of life on that planet.  \nThe  WFIRST-AFTA  Coronagraphic  Instrument (CGI) is designed to provide this characterization. It has a  flexible  coronagraph  architecture  (§3.4),  using  two deformable mirrors and selectable masks to block diffracted light and control residual speckles. In the baseline design, the CGI has two primary modes - a Hybrid Lyot  Coronagraph  (HLC)  using  a  focal-plane  phaseplus-amplitude  mask,  allowing  a  small  inner  working angle that will be used primarily for exoplanet discovery and  photometry,  and  a  Shaped  Pupil  Coronagraph (SPC), relying primarily on binary apodization of the input  pupil,  giving  broader-band  performance  that  is  ro-  \nust  against  telescope  aberrations  or  jitter;  it  is  used primarily  for  spectroscopy.  These  coronagraphs  feed either  a  high-spatial-resolution  imager  or  an  integral field spectrograph (§3.4).  \nIn  the  remainder  of  this  section  we  describe  the exoplanet  science  that  can  be  expected  from  a WFIRST-AFTA coronagraph with our current best estimate of performance. The key direct imaging targets fall into  two  categories:  planets  (giant  planets  and  subNeptunes), and disks (zodiacal disk and Kuiper belt analogs). We will show that with reasonable assumptions on  coronagraph  parameters,  the  advances  in  our knowledge of exoplanet atmospheres and disk structure as  well  as  the  increase  in  our  understanding  of  highcontrast imaging technology will be great. Furthermore, the  importance  and  value  of  such  an  instrument  as  a technology  advancement  cannot  be  overstated.  The number one priority at  medium scale for NASA in the 2010 Decadal Survey was technology advancement of high-contrast  imaging  in  space.  A  coronagraph  on WFIRST-AFTA directly responds to this recommendation,  providing  an  unparalleled  opportunity  for  spaceflight experience with a very high-contrast coronagraph and wavefront control system. WFIRST-AFTA is by no means a coronagraph-optimized telescope-but it is likely that future coronagraphs will also not have the luxury of a perfect unobscured telescope, since flagship missions will have to satisfy a range of science goals just as  WFIRST does. The gap between the current coronagraph  state  of  the  art  and  what  will  someday  be needed to characterize a truly Earth-like planet is large (Figure 2-44). Ultimately, the best way to address that gap is to fly an intermediate-performance coronagraph instrument such as the one on WFIRST-AFTA.", 'Giant Planet Atmospheres 2.4.3.1': "The  Coronagraph  Instrument  (CGI)  on  WFIRSTAFTA will be the first instrument to characterize the atmospheres of gaseous planets around nearby Sun-like stars using reflected visible-light images (430-970 nm) and low resolution (R ~ 70) spectra in three bands from 600  to  970  nm.  This  characterization  technique  has been refined and calibrated over the past 100 years on our Solar System planets Jupiter, Saturn, Uranus, and Neptune. These data will give us unique information on planetary compositions, temperatures, and cloud layers that  are  not  available  via  transmission  and  emission spectroscopy  of  transiting  planets  that  have  been  observed by HST and Spitzer.  \nReflected light spectra probe deep into the atmospheres  of  giant  planets,  up  to  ~10  bar  depths  (e.g.,  \nMarley et al. 2014). Near-IR spectra of transiting planets taken with HST WFC3 (and soon JWST) probe only much  higher  altitude  regions,  only  to  ~1  mbar  (e.g., Kreidberg  et  al.  2014).  Therefore  WFIRST-AFTA  data will  probe  much  greater  volumes  of  exoplanet  atmospheres  than  do  transit  spectra,  and  this  is  the  only technique that can be used to do so for cool planets.  \nWe  already  have  a  sample  of  dozens  of  RVdiscovered planets that  the  CGI  will  be  able  to  detect via  imaging.  Knowing their masses (with m*sin(i) from RV and inclination (i) from the CGI) will constrain their gravities.  There  will  also  be  adequate  mission  time  to characterize  a  subset  further  via  spectroscopy,  and knowing their gravities will aid the interpretation of their spectra.  \nMost  planets  observable  by  the  WFIRST-AFTA CGI have equilibrium effective temperatures of ~150 350 K, and they are expected to show numerous bands of CH4 (methane) and a moderately strong band of H2O (water) in their spectra over the λ =  600 -  970 nm region, the sensitivity range of the CGI IFS (see 3.4.1.2). The strengths of these bands and the shape of the continuum at shorter wavelengths ( λ =430 - 600 nm) are diagnostic  of  the  atmospheric  temperature,  the  mixing ratios  of  C  and  O,  and  the  amount  and  location  of clouds  in  the  planet's  atmosphere.  Figure  2-37  shows that  signal-to-noise  (SNR)  =  5  -  20  WFIRST-AFTA spectra  of  Jupiter-like  planets  would  show  multiple spectral features of CH4 (to the right of the green line). The blue contimuum in Figure 2-37 is a combination of Rayleigh  scattering  from  H2  molecules  (not  modeled here) plus cloud reflectivity and will be measurable with the 465 nm and 565 nm filters.  \nThe  detection  and  measurement  of  the  600-970 nm  absorption  features  constrain  the  methane  mixing ratio  and  cloud-top  pressures  of  giant  planet  atmospheres  (Hu  2014,  Marley  et  al.  2014,  Burrows  2014). Warmer planets will also show H2O absorption, allowing constraints  on  water  abundance.  Combining  methane and  water  abundances  will  constrain  the  C/O  ratio,  a value  that  is  diagnostic  of  determining  the  location  of planet  formation  in  circumstellar  disks  (Bond  et  al. 2010, Helling et al. 2014). The Hu (2014) and Marley et al. (2014) studies show that WFIRST-AFTA CGI spectra  will  provide  good  constraints  (to  factors  of  ~  3)  on these  abundance  values  and  planet  temperaturepressure  profiles.  These  studies  and  Burrows  (2014) show that that the expected WFIRST-AFTA CGI planets (from known RV) are expected to have diverse photometric  and  spectroscopic  signatures,  so  WFIRST-  \nFigure  2-37:  Simulated  WFIRST-AFTA  CGI  spectra  of  a Jupiter-like  planet at  SNR = 5 -  20. The  green  line  indicates the short wavelength limit of the CGI IFS. Multiple methane  absorption  features  are  detectable  over  600  970  nm,  and  the  blue  continuum  slope  is  measurable (Marley et al. 2014). 0.5 0.6 0.7 0.8 0.9 1 0  \n<!-- image -->  \nAFTA  CGI  observations  will  reveal  their  physical  and chemical differences and diversities. Fig. 19.GLYPH<209> A comparison of the planet/star reGLYPH<223>ection spectrum for a model 1-M J /5 Gyr giant exoplanet at 3 AU from  \nMeasuring atomic abundance ratios (e.g., C/H and O/H)  is  also  important  for  understanding  how  planet compositions are related to those of their host stars and how  and  where  planets  formed  in  circumstellar  disks (Figure 2-38). The Marley et al. (2014) retrieval molecular  technique  also  holds  promise  for  determining  or constraining  atomic  abundances  from  WFIRST-AFTA CGI spectra, and it is important to pursue future investigations  to  evaluate  how  well  the  WFIRST-AFTA  CGI will  be  able  to  constrain  planet  atmosphere  atomic compositions. a G2 V star, as a function of spectral resolution ( R = λ glyph[triangleleft] ∆ λ ) from 100 to 20. various R s for a representative 1.0 M J planet at 3.0 AU from a G2V star. A baseline model at R ∼ 700 is shown for reference. One can see that the methane and water features for the R = 100 and R = 70 models are easily decernible, but that below these R s features are washing out. At R = 20, aside for the general slope of the curve (which can be used to derive gross properties about the underlying cloud and possible chromophore), critical compositional information is quite lost.  \nFig. 20.GLYPH<209> A study of planet geometric albedo spectra for homogeneous model giant exoplanet atmospheres at T = 200 K as a function of atmospheric metallicity (1, 10, and 30 × solar). These models are cloud-free and use opacities at a presFigure  2-38:  Giant  planet  albedo  spectra  for  homogenous model atmospheres at T=200K as a function of atmospheric  metallicity.  These  models  are  cloud-free. From Burrows (2014).  \n<!-- image -->  \nsure of 0.5 atmospheres. Gas-phase opacities are not strong  \nfunctions of pressure, but are strong functions of temperature  \nand metallicity.  \nEach methane feature of Figure 4 is formed at a dif-  \nferent altitude and pressure.  \nTherefore, changing the  \nmethane abundance changes the strength of each feature  \n1  \n0.8  \n0.6  \n0.4  \n0.2  \n0  \n0.4  \nFig. 21  \nstrating  \nupon te  \n10  \n×  \nsola  \nparamet  \nto the  \nY  \n= 0 a  \nroughly  \nmonia c  \nY  \npara  \neral alb  \nthat the  \nvery clo  \nK and  \nalbedo s  \nthe tem  \nof  \n∼  \n0.65  \nθ  \nm,  \ncan be  \n∼  \nfrom o  \ndepe  \na homo  \ncloud-fr  \nresult i  \nθ  \nm. T  \nparticul  \n∼  \n0.94  \nhigher  \nlate the  \nlengths  \nof Jupi  \nFigur  \ngeomet  \nand clo  \nlicity of  \nassume  \nare not  \nclearly  \nplanet  \nperatur  \n21 also  \nof clou  \nthat m  \napproxi  \nPhotometric linear polarization measurements may also be helpful in characterizing exoplanets. Madhusudhan  &  Burrows  (2012)  show  that  Rayleigh scattering  in  giant  planet  atmospheres  causes  a  very large variation (0 to ~50% or more) of linear polarization with planet phase. This effect may be very useful in using RV measurements to determine unambiguous orbit parameters  and  planetary  masses  (see  also  Fluri  & Berdyugina  2010).  Successful  application  will  require planets with strong Rayleigh scattering with high signalto-noise  polarized  light  detections  at  blue  (Rayleigh) wavelengths. Polarization could also be useful at longer visible  wavelengths  for  discriminating  between  giant planet  atmospheres  that  are  clear,  have  tropospheric clouds, or stratospheric hazes (Stam et al. 2004).  \nIn short, high contrast sensitivity and these photometric and spectroscopic capabilities make  the WFIRST-AFTA CGI uniquely suited for probing the atmospheres of cool giant planets around nearby Sun-like stars. Existing techniques of transiting planet transmission and emission spectroscopy have given us the first glimpses  into  the  atmospheres  of  hot  giant  planets strongly irradiated by their host stars, but these methods  are  not  applicable  to  cool,  non-transiting  planets and are often less able to probe the bulk atmospheres  \nof planets. The WFIRST-AFTA CGI will give us a clearer and deeper look.", 'Super-Earths and mini-Neptunes 2.4.3.2': "With the performance of the baseline coronagraph, WFIRST-AFTA can only see the smallest planets (<1.5 RE) when they are physically close to their parent stars, and hence only around the very nearest stars. It is unlikely  (but  not  impossible)  that  WFIRST-AFTA  will  be able to see a truly Earth-like planet (<1.5 RE, located in the  classical  habitable  zone.)  Still,  WFIRST-AFTA has the potential for major discoveries in the study of subgiant planets.  \nOne of the most striking discoveries about extrasolar planets made in the past decade is the large population of objects with radius between 1 and 4 times that of the Earth. Based on Kepler observations (Fressin et al. 2013, Marcy et al. 2014) these planets - which have no analog in our solar system - may be the most common kind  of  planet  in  the  universe  (see  Figure  2-39).  The exact  nature  of  these  planets  is  poorly  known.  They could  be  so-called  'super-Earths'  with  rocky  compositions, or 'mini-Neptunes' with massive hydrogen envelopes, or even stranger objects, partially or mostly water and  ice.  Only  a  small  number,  mostly  in  tight  orbits,  \nFigure 2-39: Mass vs. radius of known exoplanets, with the regions of rocky composition and low-density (hydrogen/helium/water) indicated. From Marcy et al. 2014  \n<!-- image -->  \nhave measured densities or even density upper limits. The smallest planets seem to generally (but not always) have  high  densities  consistent  with  rocky  composition (Marcy et al. 2014) while planets >1.6 RE seem to have lower  densities  consistent  with  large  hydrogen  envelopes  and/or  water  compositions  (Rogers  2014).  The atmospheres of these planets could span a huge range from gas-giant hydrogen to water vapor to CO2 to oxygen or  hydrocarbons  (Hu  et  al.  2012),  with  or  without clouds. Even fewer planets in this size range have had their  atmospheric  properties  measured  through  transit and  secondary-eclipse  observations  (Morley  et  al. 2013, Caceres et al. 2014) and those spectra are relatively  featureless,  indicating  that  high-altitude  clouds are veiling the lower atmosphere.  \nThe K2 and TESS missions, combined with JWST, will  help  illuminate  this  population  through  transit  and secondary  eclipse  observations  of  planets  orbiting brighter nearby stars for planets with short <60 day orbits.  Direct  imaging  with  the  WFIRST-AFTA  coronagraph  is  a  powerful  complement.  Even  though  these planets are challenging targets for direct imaging (contrast  ~10 -9 ),  because  they  are  so  common,  there  will likely  be  multiple sub-Neptune planets within the coronagraph's reach. Compared to transits, WFIRST-AFTA will primarily be sensitive to planets in wider orbits, 0.5 5 AU (Figure 2-50). Transit observations are most sensitive to the higher layers of a planet's atmosphere (P < 1  mbar),  particularly  for  cloudy  or  hazy  atmospheres. Imaging  measures  the  planet's  reflectance,  which probes  deep  into  the  atmosphere  (potentially  all  the way  to  the  surface,  if  the  atmosphere  is  sufficiently thin).  Imaging  photometry,  or  spectroscopy  of  the brightest targets, can constrain atmospheric parameters including  clouds  even  at  relatively  low  SNR  (Figure 2-40).", 'Circumstellar Disk Science 2.4.3.3': "The WFIRST-AFTA CGI will deliver uniquely sensitive images of the planetary disks around nearby stars, resolving much smaller amounts of dust at much closer distances  than  possible  with  HST  or  other  observatories. The small inner working angle (IWA) and high contrast of the WFIRST-AFTA CGI will allow unique study of several types of circumstellar disks:  \n- 1. Low  density,  zodiacal-like  disks  down  to  the HZs of nearby Sun-like stars\n- 2. Inner  regions  (HZ  to  ~10  AU)  of  known massive, extended debris disks\n- 3. Inner  regions  (HZ  to  ~10  AU)  of  warm  disks discovered but not resolved at IR wavelengths  \nFigure  2-40:  Comparison  of  transit  (top)  and  directimaging (bottom) spectra of a GJ1214b analog (a hot super-Earth) for three different cloud compositions. Figure from Caroline Morley. SNR of 5-10 broadband photometry would distinguish between these three cases.  \n<!-- image -->  \nObserving  a  significant  sample  of  systems  spanning these areas will significantly address a number of currently  outstanding  questions  about  circumstellar disks  and  their  role  in  planet  formation  and  planetary systems evolution (c.f. Schneider 2014):  \n- 1. What  are  the  levels  of  circumstellar  dust  in, and  exterior  to, the habitable zones  of exoplanetary systems?\n- 2. Will  dust  in  habitable  zones  interfere  with future planet-finding space observatories?\n- 3. How do dust sub-structures seen in disks trace the presence of seen or unseen planets?\n- 4. What veneer is delivered to planetary atmospheres  and  surfaces  by  asteroids, comets, and other material?\n- 5. How  do  disks  of  protoplanetary  materials evolve to make Solar System-like architectures?  \nStudying zodiacal-like disks may be the most exciting  circumstellar  disk  frontier  that  WFIRST-AFTA  CGI will open. Disks with dust masses on the order of ~10 times  that  of  the  solar  system's  zodiacal  disk  can  be detected in multiple resolution elements in under 1 day of integration time for many Sun-like stars within ~15 20 pc. Figure 2-41 shows a simulated CGI image of a  \n30 zodi disk around the nearby star 47 UMa (G2V, 14 pc  distance),  easily  detected  at  SNR  ~  10  in  multiple resolution elements (Schneider 2014). The disk position angle and radial profile parameters are recovered from the simulated data with only small biases and small uncertainties.  \nThe  stars  selected  for  both  blind  and  known  RV planet  searches  will  make  an  ideal  target  sample  for zodiacal disk searches. In fact, the planet search data alone can be used for these disk searches given that both  investigations  require  similar  imaging  integration times  (~10  hours).  The  presence  or  absence  of  disks and planets together will address some specific aspects of these nearest solar systems:  \n- ∞ Planets  without  disks  indicate  little  recent collisional activity, like our solar system\n- ∞ Disks without planets indicate significant interaction of small bodies only\n- ∞ Disks  and  planets  together  will  reveal  the dynamics  of  their  interactions  via  disk  nonuniformities\n- ∞ Neither disks nor planets will indicate efficient clearing of the pre-planetary disk  \nThese  will  likely  be  the  highest  priority  WFIRSTAFTA CGI disk observations since they probe planetary systems uniquely down to the habitable zones of nearby stars with good sensitivities. The ground-based LBTI  instrument  will  also  search  for  HZ  zodiacal  dust  in  a number of the same stars, but in the thermal IR range with less spatial resolution. WFIRST-AFTA probes the same  wavelength  that  future  space  coronagraphs  will use. Combined visible WFIRST and mid-IR LBT-I data  \nwill provide the albedos of the grains, constraining their compositions.  \nWFIRST-AFTA  CGI  images  will  also  extend  our knowledge  of  known,  more  massive  debris  disk  systems. Their similar resolution, high contrast, and small IWA will perfectly complement the much larger area of HST visible and near-IR scattered-light images of massive  extended  debris  disks  around  relatively  young stars  (~  50  Myr)  in  nearby  (~20  -  50+  pc)  moving groups. Approximately two dozen such disks have been studied  by  HST  (e.g.,  Schneider  et  al.  2014),  but  we know very little about their inner regions due to the poor contrast  and  IWA  of  existing  observations.  WFIRSTAFTA CGI images will reveal whether the inner regions (~few - 20+ AU) are clear or dusty and will show the dynamical impact of any discovered planets.  \nDebris disks detected but poorly resolved by warm thermal  IR  emission  will  also  be  good  targets  for WFIRST-AFTA CGI. Spitzer detected λ =  24 ∝ m (T ~ 150  K)  disks  around  several  nearby  main  sequence stars  (e.g.,  Beichman et al. 2006),  indicative  of  recent collisions that likely occur in the asteroid belt regions of these systems. More recently, WISE and Herschel have detected  dozens  of  such  disks  (e.g.,  Padgett  et  al. 2012), and WFIRST-AFTA CGI images should be sensitive  enough to detect and resolve these in scattered light. This combination of IR and visible-light images will reveal the albedo and hence constrain the compositions of the grains in these disks.  \nDetermining the compositions and sizes of the dust in  debris  disks  is  important  for  understanding  the  formation  and  collisions  of  planetesimals  in  other  solar systems. Debris disks have been found to be highly linearly polarized, varying from ~0 to ~50% as a function  \nFigure  2-41:  Simulated  WFIRST-AFTA CGI images of a 30 zodi disk around 47 UMa. The noiseless zodipic model is shown at left, a 10 hour simulated shaped pupil coronagraph image is in the middle, and the significance of the detection is shown on the right. The right panel shows signal-to-noise per 1.2 λ /D resolution element (about 10 pixels), scaled from SNR = 1 - 15 (from Schneider 2014). The system's 2 known RV planets are detectable with WFIRST-AFTA but are not included in the simulations.  \n<!-- image -->  \nof angle from the central star. Studying this variation of linear  polarization  with  scattering  angle  constrains  the size  distributions  and  compositions  of  disk  materials (e.g., Perrin et al. 2009). Measuring the degree of polarization  in  two  well-separated filters  (e.g.  ~465  nm  and ~885  nm  wavelength)  in  multiple  resolution  elements significantly  improves  the  separate  determination  of dust compositions and sizes, allowing unique determinations in some cases (see §8.1 of Schneider 2014).  \nThe imaging capabilities of the WFIRST-AFTA CGI instrument  are  sufficient  for  making  progress  in  all  of these  circumstellar  disk  science  areas.  Its  images  will measure the amount, location, size, and composition of dust in nearby solar systems, indicate the presence of both  seen  and  unseen  planets,  and  trace  the  history, frequency,  and  severity  of  planetary  collisions.  These observations  are  essential  for  understanding  the  formation and evolution of the nearest planetary systems.", 'Principals and Concepts of Coronagraphy 2.4.3.4': "This  section  provides  a  narrative  overview  of  the principles  of  coronagraphs  in  the  context  of  WFIRSTAFTA. For a quantitative overview, see the chapter 'Direct  Imaging  of  Exoplanets'  by  Traub  and  Oppenheimer,  in  the  book  'Exoplanets',  edited  by  S.  Seager (2010).  \nDirect  imaging  is  challenging  because  exoplanets are orders of magnitude fainter than their parent stars. To image these planets thus requires a system to create high contrast at small angular separations, by which we  mean  the  suppression  of  the  diffraction  pattern  of the  host  star,  allowing  the  faint  planet  to  be  detected. Such  a  system  of  internal  optics  is  called  a coronagraph ,  named  for  the  first  such  device  invented  by Bernard Lyot in the early '20s and used to image the Sun's  corona.  Nevertheless,  astronomers  could  make little use of it for imaging other stars to find planets due to the distorting effects of the atmosphere. The advent of  space-based  observatories,  however,  removed  this impediment and motivated the first discussions on how to isolate the light of a planet outside the Solar System from its host star (Spitzer 1962, Kenknight 1977, Davies 1980). In fact, several coronagraphs were included onboard HST. However, various aberration and alignment problems limited their efficacy (Krist et al. 2003).  \nAdaptive  optics  (AO)  technology  eventually  advanced to the point of making exoplanet imaging feasible  from  the  ground  (Angel  1994).  In  the  mid  1990s, coupled  with  the  atmospheric  correction  provided  by new AO systems, the Lyot coronagraph was revised to cancel  starlight  instead  of  sunlight,  thereby  enabling  \nsearches  for  faint  companions  around  nearby  stars (Lyot  1939,  Golimowski  et  al.  1992,  Nakajima  1994). The illustration in Figure 2-42 shows how on-axis starlight is rejected by a classical Lyot coronagraph, when there are no aberrations present. In the first focal plane, an opaque occulting spot blocks the core of the star's point  spread  function  (PSF).  Light  from  the  fainter  diffraction rings surrounding the PSF continues to propagate,  and  is  collimated  to  a  reimaged  pupil  plane. Fraunhofer diffraction theory dictates that the field distribution in this reimaged pupil is equal to the difference between  the  entrance  pupil  (a  bright  annulus  in  this case), and the convolution of a circular tophat function of  the  same  width  as  the  occulting  spot  with  the  entrance pupil. The latter subtrahend term is equivalent to a low-pass filtered copy of the entrance pupil. The resulting  energy  distribution  is  concentrated  near  the edges  of  the  open  annulus.  Therefore,  by  adding  a mask of similar  shape  as  the  original  telescope  pupil, but with the width of the open annulus slightly reduced, much of the remaining starlight is blocked. Because of this Lyot stop , the diffraction rings around the occulting spot  in  the  final  focal  plane  are  strongly  suppressed with respect to the original telescope PSF. For a succinct  mathematical description of this concept, see Sivaramakrishnan et al. (2001).  \nPupil  apodization  is  another  tool  for  suppressing starlight.  As  a  natural  consequence  of  Fraunhofer  diffraction theory, altering the shape or transmission profile  of  the  entrance pupil redistributes the on-axis starlight  in  the  image  plane.  As  shown in Figure 2-43 this relationship can be used to form a PSF with a zone of very high-contrast near the star, without any additional coronagraphic masks.  A particular  subset  of  apodized pupils  is  the  shaped  pupil,  where  the  transmission  is forced  to  be  binary,  that  is,  fully  transmissive  or  fully opaque  at  any  given  point  across  the  pupil.  Various classes  of  shaped  pupils  have  been  developed  using optimization  tools  (Spergel  2001,  Kasdin  et  al.  2003, Vanderbei et al. 2003). Another class of apodized pupil coronagraphs is the Phase Induced Amplitude Apodization where the pupil apodization is achieved by aspheric mirrors remapping the distribution of light. These have the  advantage of much higher throughput and smaller inner  working  angle  at  the  cost  of  complexity.  The Apodized  Pupil  Lyot  Coronagraph  (APLC)  combines both  an  apodized  entrance  pupil  with  a  focal  plane mask and Lyot stop to improve on the starlight rejection of  the  classical  design and better allow for central obstructions (Aime et al. 2001, Soummer et al. 2003).  \nFigure 2-42: Diagram of the propagation of on-axis starlight through a classical Lyot coronagraph, for the case of a perfect, monochromatic wavefront. In each of the two critical intermediate planes, the intensity  is  displayed  immediately  before  and after  passing  through  the  mask.  This  diagram, based  on simulations by A. Sivaramakrishnan, appears in a review article by R. Oppenheimer & S. Hinkley (2009).  \n<!-- image -->", 'Ground-Based Coronagraphs 2.4.3.5': 'Ground-based  coronagraphs  typically  operate  in the near-IR, where AO correction is better and surveys targeting  young  stars  can  take  advantage  of  the  selfluminous characteristic of gas giants and brown dwarfs, which radiate in the infrared for tens of millions of years after  their  formation  (Burrows  et  al.  1995).  They  have produced  a  dozen  notable  successes  (Kalas  et  al. 2008,  Marois  et  al.  2008,  Lagrange  et  al.  2010,  Rameau et al.  2013,  Kuzuhara  et  al.  2013,  Currie  et  al. 2014,  Kraus  et  al.  2014) but  the  systems  discovered, with supermassive (3-10 MJ) young (<100 Myr) planets in  wide  (20-200  AU)  orbits  are  very  different  than  our own.  Taking  the  Gemini/NICI  campaign  as  a  representative example of a large completed survey, statisti-  \ncal  analysis  shows  that  for  a  typical  target  star,  the planet mass corresponding to 95% detection likelihood at  0.5  arcsec  separation  (~30  AU)  was  about  10  MJ (Biller et al. 2013).  \nEven  with  high-order  AO  correction,  coronagraph detection  limits  are  severely  limited  by  uncorrected quasi-static aberrations within the instrument, and their resultant  speckle  noise  in  the  image  (Racine  et  al. 1999, Marois et al. 2005, Hinkley et al. 2007). Speckles can be partially subtracted if certain diversity properties of the data are exploited - in practice either FoV rotation  (angular  differential  imaging)  or  spectral  differencing (Marois et al. 2006, Sparks & Ford 2002). The latter approach, relying on the chromatic scaling of the speckle halo, motivated the next generation of ground-based instruments to rely on integral field spectrographs (IFS)  \nFigure 2-43: Diagram showing how shaped pupil coronagraphs use apodization to  create  regions of  high  contrast in the  image plane.  For reference, the  upper pair of graphics show the Airy function PSF created by a clear, unapodized circular aperture. When a smooth apodization is applied-in this case a circular prolate spheroidal profile-the concentration of energy within some radius is maximized,  and  the  outer  diffraction  rings  are  suppressed  by  many  orders  of  magnitude. Purely  binary apodizations, as shown  in the bottom pair, can achieve the same effect, although generally at some cost in the size of the search area.  \n<!-- image -->  \nto improve the dynamic range. As an added benefit, the spectroscopic data provided by the IFS reveal precious insights  about  the  atmosphere  of  the  detected  planet. Exoplanet  imaging  surveys  combining  AO,  coronagraphy, and integral field spectroscopy are underway at Palomar  Observatory,  Gemini  Observatory,  and  the ESO Very Large Telescope; soon another will begin at Subaru Telescope (Hinkley et al. 2011, Macintosh et al. 2014, Langlois et al. 2014, Groff et al. 2014). As illustrated  in  the  angular  separation-contrast  parameter space  of  Figure  2-44,  only  these  newest  instruments (GPI and VLT-SPHERE) can reach true, young Jovian analogs (planets with mass 1 MJ and semi-major axis 5 AU),  and  only  around  a  small  number  of  stars.  No ground-based  coronagraph  can  detect  the  reflected light from mature planets.  \nFuture 20-40 m ground-based telescopes may also incorporate  advanced  adaptive  optics  coronagraphs (though likely not until ~2030.) Such large aperture telescopes will dramatically reduce the accessible angular separation,  simply  due  to  the  scaled-down  diffraction width. However, even under the most optimistic wavefront calibration (speckle control) assumptions, the contrast floor will be set by the AO performance.  \nELTs  observations  will  complement WFIRST-AFTA exoplanet imaging  in  wavelength  coverage, as  ground-based  adaptive  optics is most effective in near-IR. While WFIRST-AFTA  will  provide  reflected  light  images  of  mature planets in visible light, ELTs will be probing  planet  formation  processes  and  image  a  large  number  of self-luminous giant planets around young  stars.  The  physical  and chemical evolution of giant planets will  be  probed  from  formation  / young  age  phases  dominated  by internal  heat  (observed  by  ELTs and JWST) to mature phases during which stellar radiation is a significant/dominant source of energy (observed  by  WFIRST).  At  intermediate  ages  and/or  for  massive (~1  MJ  and  more)  planets,  both thermal  emission  in  the  near-IR with  ELTs  and  reflected  light  in visible  light  with  WFIRST  can  be measured,  allowing  the  energy input (stellar radiation, internal  \nheat) and output (emission in near-IR) to be measured. Together  with  mass  measurement  from  RV,  the  main physical characteristics of the planet (radius, mass, effective temperature, internal heat output, surface gravity)  can  be  derived,  allowing  detailed  and  robust  interpretation  of  WFIRST-AFTA  exoplanet  spectra.  While the overlap between ELT-observable and the WFIRSTimaged exoplanets may be limited to a few giant planets, it will provide representative templates for interpretation of additional WFIRST exoplanet spectra.  \nELTs will also observe reflected light exoplanets in near-IR. While ELTs will not be able to reach the deep and  stable  contrast  levels  accessible  from  space  with WFIRST,  they  offer  IWA  about  5x  smaller  in  near-IR than accessible with WFIRST in visible light. The same type of planet (radius, albedo), if moved 5x closer to its host star, becomes 25x brighter in reflected light: ELTs will  compensate  for  lack  of  deep  contrast  by  smaller IWA. ELTs will therefore observe planets that are statistically  closer  in  to  their  host  stars,  and  more  strongly illuminated,  than  WFIRST-AFTA.  Direct  comparison between  ELTs  and  WFIRST  spectra  will  help  understand how exoplanets physical and chemical character-  \nFigure 2-44: Exoplanet detection limit of the HLC coronagraph on WFIRST-AFTA, compared to other high-contrast systems. The contrast values of RV planets detectable by HLC on WFIRST-AFTA are shown as open blue circles, along with the detection floor set by residual speckle noise (solid blue line, from Figure 2-48); note that this does not include photon noise. Other high contrast systems (Hubble Space Telescope, James Webb Space Telescope, Gemini Planet Imager, and the European Extremely Large Telescope) are shown for 1-hour exposures on fiducial targets, including photon  noise.  There  are  two  important  complementary  areas  here:  (1)  WFIRST-AFTA  vs.  GPI  and  JWST,  and  (2) WFIRST-AFTA vs. E-ELT and TMT. Regarding (1) for GPI and JWST, the limiting sensitivities are much poorer in absolute terms (see the labeled curves), but the wavelength range of operation is the near-infrared, where hot, young planets are bright, so the type of planet probed is completely different than for WFIRST-AFTA, which will observe the much more numerous mature, cool planets. Regarding (2) for the E-ELT and TMT, which have roughly similar sensitivities, the complementarity is that the ELTs will be able to observe planets closer to their stars than WFIRST-AFTA (owing to their 12 to 17 times larger diameters), and collect more photons per planet (allowing a poorer raw contrast but enabling a greater post-processing factor), so the ELTs will be best at observing habitable zones of nearby late-type stars, whereas  WFIRST-AFTA  will  be  best  at  nearby  solar-type  stars.  The  shaded  blue  cloud  indicates  the  range  of  expected WFIRST-AFTA discoveries of new nearby Neptunes and Super-Earths.  \n<!-- image -->  \nistics transition from cold Jupiter-like planets to hot Jupiters observable by transit spectroscopy.  \nWFIRST will provide deep, well-calibrated contrast levels not accessible from the ground, and will thus allow  direct  imaging  of  sub-Jupiter  mass  exoplanets in/near habitable zones of Sun-like stars. Such planets  \nwill be very challenging for ELTs to observe due to the extreme contrast and ELTs detection limits are currently poorly understood in this regime. Ultimately, WFIRSTAFTA will  push  the  low-mass  detection  limit  for  direct imaging further than possible with any other observatory (Figure 2-44).', 'WFIRST  Coronagraph  Design  and  Perfor2.4.3.6 mance': 'As described above, a coronagraph is a set of optical elements that modifies the PSF of the telescope to create  a  region  around  the  stellar  image  where  a  dim companion  can  be  extracted.  Due  to  optical  errors  in any  system,  all  coronagraphs  must  be  designed  together with wavefront control via one or more deformable mirrors (DMs) to correct wavefront errors. The combined  coronagraph  and  wavefront  control  system  is characterized by the contrast, inner working angle, and stability  achieved.  Contrast  is  the  degree  to  which  the instrument can suppress scattered and diffracted starlight in order to reveal a faint companion. Inner Working Angle (IWA) is the smallest angle on the sky at which it can reach its designed contrast. This angle is typically only  a  few  times  larger  than  the  theoretical  diffraction limit of the telescope. The resulting residual stellar halo must also be stable over the time scale of an observation, so that the halo can be subtracted to reveal an exoplanet  or  disk.  In  principle,  with  a  well  characterized and stable PSF, various subtraction methods that have been developed and used on both ground and space images  can  be  employed  to  average  the  background photon  noise  and  extract  faint  planets  that  are  below the raw contrast level. The limit of an observable planet is  then  determined  only  by  the  photon  noise  and  the available  integration  time.  In  practice,  there  is  a  systematic limit to the contrast of a recoverable planet given  by  the  stability  of  the  telescope  (how  rapidly  the background speckle pattern changes) and the structure of the exozodiacal light (a confusion limit set by clumping in a disk).  \nThe performance of a  coronagraph instrument on WFIRST will also be partially determined by the orbital environment  and  resulting  stability  of  the  telescope. Additionally, the recent history of planet imaging shows that  recovering  planets  with  up  to  factors  of  10  fainter contrast than the background is regularly accomplished, both on large ground telescopes and from the Hubble Space Telescope. In some cases, factors of 100 have been achieved. We thus characterize the coronagraph instrument  by  its  detection  limit,  that  is,  the  limiting magnitude  of  a  recoverable  planet  relative  to  the  star from the combination of the coronagraph and wavefront control and data processing.  \nOver the last decade and a half there has been an astounding growth in research on coronagraphy with an outpouring  of  new  coronagraph  concepts,  differing  in architecture (pupil plane masks vs. image plane masks, phase  vs.  amplitude),  performance  (contrast,  inner  \nworking angle, and throughput), and robustness (sensitivity  to  wavefront  aberrations,  thermal  distortions,  and jitter).  Until  recently,  almost  all  approaches  assumed off-axis  telescopes,  eliminating  the  need  to  cope  with diffraction  induced  by  central  obstructions  and  spiders (a severe challenge for most coronagraph approaches). It  has  only  been  in  the  last  several  years  that  breakthroughs  in  the  design  of  certain  coronagraphs  have allowed  high  contrast  with  obstructed  telescopes  or segmented  mirrors  (albeit  with  reduced  performance). In the Fall of 2013 a study was performed (Traub et al. 2014)  to  examine  the  expected  performance  and  robustness of 5 such coronagraphs if combined with the extremely  complex  pupil  of  the  WFIRST-AFTA  telescope:  shaped  pupil  (SPC),  hybrid  Lyot  (HLC),  vector vortex  (VVC),  phase  induced  amplitude  apodization/complex mask (PIAA/CMC) and visible nulling coronagraph (VNC). At the end of the study it was clear that the VVC could not be designed for the AFTA pupil, while VNC designs and components were not sufficiently mature to be developed in the time frame consistent with  the  anticipated  WFIRST-AFTA  mission  schedule. While  the  PIAA  /  CMC  had  the  potential  for  the  best performance  in  inner  working  angle  and  throughput, designs  with  sufficiently  high  contrast  were  hard  to achieve and it was by far the most sensitive to jitter and aberrations.  The  result  was  the  selection  of  the  SPC and  HLC  as  the  two  baseline  coronagraphs  with  the PIAA/CMC  as  backup  pending  further  theoretical  and laboratory work. The SPC had the advantage of being the  simplest  to  implement  with  the  least  sensitivity  to spacecraft  jitter,  and  potentially  broader  bandwidth (well-matched  to  spectroscopy).  HLC  had  potentially much higher contrast at a smaller inner working but with somewhat  more  manufacturing  and  performance  risk and a higher sensitivity to jitter.  \nThe HLC and SPC architectures are described in §3.4 . The HLC (Figure 3-27) uses a combination of a focal plane mask and a Lyot stop to cancel on-axis starlight.  However,  unlike  the  classical  Lyot  coronagraph shown earlier, the focal plane mask has a continuous, non-monotonic,  radial  transmission  profile.  This  transmission profile  is  band-limited  in  spatial  frequency,  so that  field  cancellation  in  selective  regions  of  the  Lyot plane is much deeper than the classical case, as well as achieving a smaller inner working angle (Kuchner & Traub 2002). The HLC focal plane mask is composed of layers of metal and dielectric deposits on glass. The pattern  of  layers  makes  use  of  the  wavelengthdependent, phase-shifting film transmission function to  \nachieve the desired reimaged pupil over a broad bandpass (Trauger et al. 2011).  \nThe  SPC  (Figure  3-28)  uses  a  binary-valued apodization of the telescope pupil to create a region of suppressed starlight in the image plane (Spergel 2001, Kasdin et al. 2003). The pattern of dark islands that define the shaped pupil are the outcome of a linear optimization program (Vanderbei et al. 2003). The program determines what parts of the pupil must be blocked, at minimum, and in addition to any existing obscurations, in  order  to  create  destructive  interference  over  some range  in  separation  and  position  angle  (Carlotti  et  al. 2012, 2013). The SPC focal plane mask is a diaphragm matched to this dark region. This mask tends to diffract a large fraction of residual on-axis energy to the edge of the  reimaged  pupil  and  beyond  it.  Therefore,  a  Lyot stop serves to further reject starlight before it is brought to a final focus (Riggs et al. 2014).  \nThe WFIRST pupil geometry - with its large central obstruction and six support struts - is challenging for  any  coronagraph  design.  The  HLC  and  SPC  work around these obscurations in different ways. Upstream of  the  HLC,  the  two  DMs  apply  large  static  figures  to remap  the  obscurations,  and  make  use  of  the  bandlimited occulting mask (Trauger et al. 2013). The peakto-valley  DM  stroke  used  in  the  latest  HLC  design  is less  than  300  nm.  The  SPC, on the other hand, uses the  apodization  pattern  of  the  shaped  pupil  to  confine diffraction from the obstructions to the masked-off area of the focal plane. As a consequence, more throughput is sacrificed than in a coronagraph with a purely phasebased approach. However, by not relying on the DMs to remap the discontinuities, the SPC operates in a regime of lower technological risk than the HLC.  \nTeams at JPL and Princeton are leading the HLC and  SPC  designs,  respectively.  Both  teams  have worked  through  several  design  iterations  to  maximize performance within  the  constraints  of  WFIRST.  These efforts  take  into  account  the  pupil  geometry,  the  expected level  of  spacecraft  jitter,  low-order  aberrations, and the expected distribution of planet signals in separation-contrast space. These designs are then used in a complete simulation of the entire optical system based on the PROPER propagation code developed by John Krist at JPL. PROPER accounts for all optical surfaces in the instrument and performs a diffraction simulation, including  closed  loop  wavefront  control,  polarization, and jitter to reach a prediction for the final stellar image. More details on the modeling approach and simulation can be found in Appendix F. The resulting contrast prediction  is  then  used  in  the  science  yield  model  (de-  \nscribed in Appendix F) to estimate the number and type of  detectable  planets.  For example, Figure 2-46 is the result of a polychromatic simulation of the shaped pupil shown in  Figure  2-45.  Figure  2-47  is  the  result  of  the Milestone  1  tests  at  the  JPL  High  Contrast  Imaging Testbed  (HCIT)  showing  a  contrast  better  than  the 1x10 -8 that  the  shaped  pupil  was  designed  for,  both monochromatically  and  in  a  10%  band.  Detailed descriptions of the CGI instrument, the imaging camera, and the integral field spectrograph can be found in §3.4.', 'Exoplanet Science Yields 2.4.3.7': "The  SDT  and  collaborators  have  carried  out  detailed modeling of WFIRST-AFTA's ability to detect and characterize planets. See Appendix F for detailed discussion.  We  take  the  known  RV  planets  in  the  solar neighborhood  and  compute  their  detectability  (Table 2-7) based on their radius and separation from the parent  star.  Coronagraph  models  predict  the  residual speckle halo. Final sensitivity is set by an absolute floor from residual speckles after PSF subtraction, as well as the  random  noise  contributions  from  foreground  and background zodiacal light. The residual speckle floor is usually  expressed  as  a  fraction  of  the  input  speckle noise. Preliminary simulations show that even relatively simple algorithms can achieve a factor of ten attenuation of PSF halo noise, with a factor of thirty possible, and we evaluate science yield for both. We also evaluate science yield as a function of residual image motion (after  correction  by  the  coronagraph  fast  steering  mirror) from 1.8 mas to 0.4 mas. For each target planet we estimate  the  exposure  time  required  to  obtain  SNR=5 photometric  measurements  in  a  standard  WFIRSTAFTA band (Figure 2-48, Table 2-7).  \nAlthough  Doppler  surveys  of  particular  low-mass stars  can  be  sensitive  to  near-Earth-mass  planets  in short-period orbits, Doppler surveys of the best coronagraph  targets  -  higher-mass  stars  in  the  solar  neighborhood - are marginally complete only to Saturn or Jupiter-mass planets in the range of orbits WFIRST-AFTA can access. (Figure 2-49, Howard & Fulton 2014), and of  course  are  also  incomplete  for  early-type  stars  and young stars.  WFIRST-AFTA can potentially  characterize  much  lower-mass  planets  (§2.4.3.2  and  Appendix F),  particularly  if  they  are  observed  at  optimal  phase angle, but the individual planets that will be seen have not  yet  been  discovered.  Evaluating  the  ability  of WFIRST-AFTA itself to discover these planets requires a  complete  DRM-like  simulation.  We  can,  however, evaluate the completeness of WFIRST-AFTA observations of any given star as a function of mass and semi-  \nFigure 2-45: Shaped pupil coronagraph characterization mask , shown to the right of the WFIRST-AFTA telescope pupil. This mask has 30% transmission with respect to the available open area, and is designed for a bowtie-shaped focal plane mask open between 2.5 lambda/D and 9 lambda/D, with a 65 degree opening.  \n<!-- image -->  \nFigure 2-46: Polychromatic simulation of the PSF corresponding to the mask shown in Figure 2-45, shown here at three wavelengths: 728 nm, 800 nm, and 872 nm (spanning an 18% bandwidth). This simulation includes a 2-DM wavefront control, but with no aberrations.  \n<!-- image -->  \nFigure 2-47: Testbed measurements of the first-generation WFIRST-AFTA SPC design, demonstrating the achievement of two milestones: raw contrast below 10^-8 in a narrow band, and raw contrast below 10^-8 in a 10% band.  \n<!-- image -->  \nTable 2-7: WFIRST-AFTA detectable RV planets. Separation and contrast are given for a 60 degree phase angle. Integration times shown are to obtain SNR=5 photometry at 565 nm with 10% bandpass using Hybrid Lyot coronagraph, assuming albedos of 0.4 and 0.4 mas of post-control image jitter. See Appendix F for details.  \nFigure  2-48:  Contrast  vs.  radius  plot showing  known  RV  planets  detectable with the WFIRST-AFTA Hybrid Lyot Coronagraph  (HLC).  Upper  contrast  curve  is for worst-case performance modeling (1.8 mas  residual  image  motion,  x10  speckle attenuation  from  PSF  subtraction)  and lower curve is for the best-case (0.4 mas motion,  x30  attenuation).  Solid  triangles represent  detections  of  planets  in  less than  one-day  for  the  worst-case  performance,  open  triangles  are  additional  detections in the optimistic  case.  The dashed-green  line  is  the  estimated  contrast  of  a  target  zodiacal  dust  cloud  ten times that of the solar system, for a target at 10 pc.  \n<!-- image -->  \n1  \nmajor  axis  (see  e.g.,  Brown  2005,  Savransky  et  al. 2010).  Averaging  these  completeness  values  over  a likely sample of targets gives a good idea of the range of planets WFIRST-AFTA is sensitive to (Figure 2-50). Also,  in  Appendix  F,  we  use  a  random  distribution  of planets  consistent  with  the  measured  Kepler  populations  to  evaluate  potential  detectability  of  low-mass planets.  We evaluate the number of such planets that could be discovered in a 50-day and 180-day survey for various  target  priorities.  Table  2-8  summarizes  the complete exoplanet yield of various categories.  \nWFIRST-AFTA  could  potentially  discover  these targets through blind observations of nearby stars, but such  a  survey  will  require  significant  amounts  of  telescope time. A sustained high-precision Doppler survey of  nearby  stars  would  both  speed  identification  of  potential targets, and provide mass constraints that will be crucial to interpreting WFIRST-AFTA spectra.", 'Conclusions 2.4.3.8': "Although WFIRST-AFTA is by no means a coronagraphically  optimized  telescope,  exoplanet  imaging technology  -  coronagraphy,  wavefront  control,  and post-processing  -  has  advanced  to  the  point  where very  high  levels  of  performance  appear  practical  with general-purpose  telescopes.  The  baseline  coronagraphic  instrument  will  achieve  detectable  planet/star contrast ratios of at least 10 -9 (after post-processing) at separations >0.2 arcseconds. This opens up enormous science  possibilities,  including  photometric  and  spectroscopic  characterization  of  a  large  sample  of  giant planets,  mapping  of  structure  in  extrasolar  zodiacal  \nCompleteness vs. Semi-major axis  \nFigure 2-49: Completeness of Doppler surveys of 76 potential WFIRST-AFTA target stars, from Howard & Fulton (2014). The lines show the 50% completeness contour for each individual star, with the median completeness indicated by the thick line.  \n<!-- image -->  \ndisks,  and  potentially  characterization  of  'super-Earth' planets around the nearest stars.  \nTable 2-8: Summary of expected coronagraph science yields - number of RV planets that are potentially detectable and photometrically or spectrally characterizable and mean number of planets discovered in simulated searches for new planets. Not listed are the additional planets from future expanded RV searches. The numbers are uncertain, but may be comparable to the current known RV yield (see Figure F-6).  The yield is evaluated for 0.4 mas residual image motion and x30 speckle post-processing attenuation. See Appendix F for details.  \nFigure 2-50: Single-visit completeness (probability of a planet being detected, if one is present, as a function of radius and semi-major-axis) for the WFIRST-AFTA HLC assuming 0.4 arcseconds of post-correction jitter and x30 speckle removal. Left: completeness for a single visit to a median star. Right: average completeness of a 6month 46-star survey.  \n<!-- image -->", '2.5 Galactic Bulge Field: General Astrophysics': 'The  WFIRST-AFTA  microlensing  survey  toward the  Galactic  bulge  will  potentially  enable  a  very  broad range of astrophysics, well beyond the primary goal of completing  the  census  of  cold  exoplanetary  systems. This enormous additional potential of the survey follows from  the  large  number  of  stars  being  surveyed,  the large  number  of  measurements  that  will  be  made  for each of these stars, and the quality of the photometric and astrometric precision that will be achieved for these stars, which will range from good to exquisite, depending on the brightness of the star and the level to which systematics can be controlled.  \nIn this section, we provide a sampling of the range of the science that may be possible, including auxiliary science from the microlensing events themselves, stellar  astrophysics,  Galactic  structure,  and  solar  system science.  In  §2.4.2.9  we  discussed  the  additional  exoplanet  science  that  can  be  obtained  from  the  survey from the detection of tens of thousands of transiting giant planets.  \nThere are a few things to note. First, this overview contains an admixture of potential applications, some of which have been worked out in some detail, and some of which have merely been suggested, with no real effort  made  to  demonstrate  their  viability.  These  latter topics  provide  an  important  line  of  future  work  to  vet their applicability. Second, we are primarily concentrating on auxiliary science that can potentially be extracted without  changing  the  microlensing  survey  specifications. However, some of these applications will require new data reduction algorithms or precursor or follow-up observations in order to extract their full science potential.  Finally,  we  note  that  several  of  these  applications require  excellent-to-exquisite  control  of  systematics  in the  photometric  and  astrometric  measurements.  The extent to which these systematics can be controlled at the levels required is unclear. However, we note that it is  likely  that  the  microlensing  survey  itself  will  provide the best opportunity to characterize and remove these systematics  by  its  very  nature  of  requiring  many  repeated observations of a large number of point sources. We discuss this in a bit more detail below.', '2.5.1 Properties of the Survey': 'We begin by summarizing the properties of the microlensing survey.  As currently envisioned, the survey will  consist  of  ten  contiguous  fields  (see  Figure  2-29) between  Galactic  longitudes  of  roughly  -0.5  and  1.8, and Galactic latitudes of -1 and -2.2, for a total area of roughly 2.81 square degrees. The fields will be imaged  \nin  six  72-day  campaigns  spread  over  the  nominal  sixyear mission lifetime, but due to losses from the moon moving through our field,  the  total  survey  time  will  be 357 days. During each campaign, each field will be observed  every  15  minutes  in  a  wide  (W149)  filter  that spans 0.9-2 microns, and once every 12 hours in a bluer filter (Z087) that spans 0.77-0.97 microns. The exposure time per epoch in these filters with be 52 secs for W149 and 290 secs for Z087. Because of the layout of the  detectors  in  the  focal  plane,  ~85%  of  the  survey footprint is observed for the full time while the remaining 15% is observed only in either the Spring or Fall seasons. For stars in the primary area, there will be a total of ~33,000 epochs in W149 and ~700 in Z087. The single-measurement photon-noise photometric and astrometric precisions will be ~0.06% and 0.05 mas for the one million stars with HAB<14.0, ~0.4% and 0.7 mas for the 12 million stars with HAB<19.6, and ~1.2% and 1.7 mas for the 56 million stars with HAB < 21.6. WFIRSTAFTA  will  collect  ~2.5  billion  photons  for  a  star  with HAB=19.6 in the wide filter over the course of the mission.', '2.5.2 Microlensing Auxiliary Science': 'The microlensing survey will be sensitive to microlensing due to isolated compact objects with masses from that of Mars to roughly 30 times the mass of the Sun.  We  expect  37,000  microlensing  events  due  to known  populations  alone  (stars  and  stellar  remnants) (Penny et al. 2015a). Thus it will be able to measure or constrain  the  mass  function  of  compact  objects  over roughly  8  orders  of  magnitude  in  mass.  This  includes free-floating  planets,  brown  dwarfs,  stars,  and  stellar remnants.  For  the  upper  end  of  this  range,  it  will  be possible to measure the masses of the objects directly from higher-order microlensing effects from the survey data itself (Gould & Yee 2014), whereas for lower-mass objects,  either  additional  measurements  may  be  required, or the mass function will only be determined statistically. It will also be possible to probe the binarity of these  compact  objects,  including  the  companion  frequency and mass ratio and separation distribution, for binaries with separations within roughly a decade of the Einstein ring radius of the primary. It will also be possible to detect tertiaries in some cases.  \nWith  the  large  number  of  microlensing  events,  it will  be  possible  to  measure  the  microlensing  optical depth and event rate over the ~3 square degrees of the target fields. The optical depth, in particular, is proportional  to  the  integral  of  the  total  mass  density  of  compact  objects  along  the  line  of  sight,  and  as  such  is  a  \nvery sensitive probe of the mass distribution of the Galactic  disk  and  the  Galactic  bulge  (Griest  et  al.  1991, Kiraga  &  Paczynski  1994).  In  particular,  the  optical depth can be used to probe the total mass, shape, and orientation  of  the  Galactic  bar  (Paczynski et  al.  1994, Zhao et al. 1995). The event rate is additionally sensitive to the velocity distribution and mass function of the compact objects in the stellar populations.  \nRoughly 5% of all microlensing events exhibit clear signatures  of  caustic  crossings  due  to  the  lens  being composed of a nearly equal mass binary with a projected  separation  near  the  Einstein  ring  radius  (Alcock  et al.  2000).  With  the  near-continuous  sampling  and  15 minute  cadence,  nearly  all  of  the  caustic  crossings  of giant  sources  (which  last  ~10  hours)  will  be  wellresolved,  thus  allowing  one  to  measure  the  limbdarkening for these stars in the wide filter (Albrow et al. 1999).', '2.5.3 Stellar Astrophysics': 'With a typical total exposure time of ~20 days per field in the wide (W149) filter and ~2.3 days per field in the  blue  (Z087),  it  will  be  possible  to  construct  a  very deep color-magnitude diagram over the ~3 square degrees targeted by the microlensing survey. The limiting magnitude in both filters is uncertain, but will likely be set  by  confusion,  rather  than  photon  noise.  Nevertheless,  it  should  be  possible  to  measure  the  luminosity function of stars in the bulge down to nearly the bottom of the main sequence, as well as identify unusual stellar populations  down  to  quite  faint  magnitudes,  including potentially young stars, blue stragglers, stellar clusters, cataclysmic  variables,  and  white  dwarfs.  Such  studies will  be  enhanced by the fact that it will be possible to measure the proper motion and potentially parallax for a  significant  subset  of  the  sources  in  the  bulge  field, thus allowing for discrimination between bulge and disk populations.  Such  science  would  be  significantly  enhanced by observations in one or more bluer filters at similar  angular  resolution,  either  with  WFIRST-AFTA itself,  or  with  Hubble  Space  Telescope  precursor  observations.  \nOf course, it will be possible to identify many variable sources in the fields, over a broad range of amplitudes and time scales. Variables can be identified with amplitudes  greater  than  a  few  millimagnitudes,  with time scales from tens of minutes up to the ~6-year duration of the mission. This will allow for the identification of  a  large  number  of  stellar  flares,  eruptive  variables, and pulsating variables, thereby enabling a wide variety of stellar astrophysics.  \nPerhaps most exciting, however, is the potential for WFIRST-AFTA  to  do  asteroseismology  on,  and  thus determine the mass and radii of, a significant number of stars  in  the  survey  area.  Gould  et  al.  (2015)  estimate that  WFIRST-AFTA  will  obtain  asteroseismic  information on the roughly one million giant stars with HAB < 14 in the target fields (see Figure 2-51). They also estimate  that  WFIRST-AFTA  will  obtain  precise  (~0.3%) distances  to  these  stars  via  parallax.  This  is  the  only way to measure masses and radii of a large number of bulge giants, which are postulated to have abundances that are substantially different than local populations.', '2.5.4 Galactic Structure': 'WFIRST-AFTA  will  obtain  photon-noise  limited parallaxes  of  <10%  and  proper  motion  measurements of  <0.3%  (0.01  mas/yr)  for  the  ~56  million  bulge  and disk stars with HAB<21.6 in its field of view. When com-  \nFigure 2-51: Asteroseimologic spectrum for KIC2836038 as observed by Kepler (top panel) and as simulated for WFIRST-AFTA (bottom panel). Red lines are the power spectra smoothed with a boxcar width of 1µHz. The insets show the autocorrelation function  of the smoothed power spectrum between 20 -60µHz after  correcting the granulation  background.  The  dotted line marks the published value for the large frequency separation Δυ .    WFIRST-AFTA will be able to measure Δυ for the roughly one million giant stars with HAB<14 in  the  microlensing  survey  fields.  From  Gould  et  al. (2015).  \n<!-- image -->  \nbined  with  multicolor  photometry  in  at  least  one  bluer filter  (to  complement  the  measurements  in  W149  and Z087), it will be possible to estimate the effective temperature,  metallicity  age,  luminosity,  and  foreground extinction for all of these stars. This is a larger number of stars with such measurements than will be achievable with Gaia, although of course the population of stars will  be  very  different  and  complementary  to  that  obtained by Gaia. From this dataset, it will be possible to extract  an  enormous amount of Galactic structure science, including a determination of the bulge mass and velocity distribution (including bar structure), the stellar density and velocity distribution of the Galactic disk, the metallicity  and  age  distribution  of  the  disk  and  bulge, and the three-dimensional distribution of dust along the line of sight toward the bulge fields.', '2.5.5 Solar System Science': 'Gould  (2014b)  estimates  that  WFIRST-AFTA  will detect ~5000 Trans-Neptunian objects (TNOs) down to absolute magnitudes of HAB~29.6 (corresponding to diameters  of  D~10  km)  over  ~17  square  degrees,  enabling a precise determination of the size distribution of TNOs down to, and substantially below, the collisional break at ~100 km (see Figure 2-52). Furthermore, the orbital  elements  of  these  objects  will  be  measured  to fractional  precisions  of  a  few  percent,  allowing  for  dynamical classification into the canonical classical, resonant, and scattered populations, as well as identification of  objects with new or unusual orbits. Binary companions to these objects will be discovered down to fainter magnitudes of HAB~30.4, corresponding to diameters of 7 km, thus allowing for the determination of the binary size and separation distribution as a function of dynamical  class.  Finally,  there  will  be  ~1000  occultations  of stars  due  to  these  TNOs  during  the  bulge  survey (Figure  2-52),  allowing  for  a  statistical  estimate  of  the size and albedo distributions of TNOs as a function of magnitude  and  dynamical  class.  The  several  dozen TNOs discovered  with  HAB<25  (D>100  km)  will  occult multiple stars during the survey, allowing for crude constraints on the shapes of these large TNOs.', '2.5.6 Related Projects and Precursor Observations': 'The  Galactic  bulge  survey  of  WFIRST-AFTA  is unique in  terms  of  its  resolution,  area,  exposure  time, total  number  of  observations,  and  total  number  of sources. Therefore, it is essentially guaranteed to produce  revolutionary  science  in  all  of  the  areas  listed above.  Nevertheless,  there  are  a  number  of  existing, planned,  or  proposed  surveys  with  similar  science  \nFigure  2-52:  The  expected  number  of  Trans-Neptunian Object (or KBO) detections (light solid line) and TNO occultations  (heavy  solid  line)  per  magnitude  that  can  be detected  from  the  WFIRST-AFTA  microlensing  survey. Magnitudes here are in the Vega system, which is related to the AB system used in the text by HVega = HAB - 1.39. WFIRST-AFTA will detect TNOs significantly fainter  the current survey limits of HVega = 26. KBOs with HVega < 23.5 will occult more than one star during the survey, potentially  allowing  for  crude  constraints  on  their  shape. From Gould (2014b).  \n<!-- image -->  \ngoals, which will motivate, enhance, and/or complement the  science  potential  of  the  WFIRST-AFTA  bulge  survey.  These  include  the  ground-based  near-infrared: Vista Variables in the Via Lactea (VVV) Survey (Minniti et al. 2010), and optical: Blanco DECam Bulge Survey (BDBS),  the  Hubble  Space  Telescope  Galactic  Bulge Treasury Program (Brown et al. 2009) and Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS) (Sahu et al. 2006), and the proposed Japan Astrometry Satellite  Mission  for  Infrared  Exploration  (JASMINE) (Gouda et al. 2005). The science goals of the JASMINE mission concepts, in particular, have significant overlap with the auxiliary science topics listed above 9 .  \nAs discussed in Appendix G and advocated in the recent  NASA  ExoPlanet  Analysis  Group  (ExoPAG) Study Analysis Group 11 report, precursor observations with  HST  of  some  or  all  of  the  area  targeted  by  the WFIRST-AFTA  bulge  survey  would  significantly  enhance  many  of  the  auxiliary  science  goals  discussed above.  HST  imaging  is  well  matched  to  that  of WFIRST-AFTA  in  terms  of  resolution  and  sampling,  \nwhile  providing  both  bluer  filters  and  the  possibility  of obtaining a longer time baseline of observations than is possible with WFIRST-AFTA alone. Precursor observations  with  HST  could  then  be  combined  with  the WFIRST-AFTA  data  to  provide  color-magnitude  diagrams of the survey area in several colors, confirmation of low signal-to-noise ratio astrometric and proper motion measurements made internal to the WFIRST-AFTA bulge survey, and to provide locations and colors of all the point sources with higher resolution and fidelity than is possible with WFIRST-AFTA alone.', '2.5.7 Detector Characterization': "With  its  ~33,000  dithered  images  of  ~10 8 point sources with known colors and nearly constant fluxes, the bulge survey will likely provide one of the best datasets  with  which  to  characterize  WFIRST-AFTA's wide-field  imager.  In  particular,  we  imagine  that  the bulge survey pipeline will measure the fluxes and positions of all of the stars in the field of view, while simultaneously measuring the response function of each of the  WFI pixels,  and  how this  response function varies with time. This time-variable response function will then be used to calibrate and remove detector artifacts such as  persistence,  inter-pixel  capacitance,  reciprocity  failure, non-linearity, and intrapixel response variations.", '2.6 Opportunities  for  the  Guest  Observer  Program': 'The  guest  observer  (GO)  science  program  of WFIRST-AFTA  will  have  high  impact  over  a  broad range  of  modern  astrophysics.  Taking  Hubble  as  a guide,  the  GO  program  of  WFIRST-AFTA  will  be  at least  as  important  to  the  astronomical  community  and the  interested  public  as  the  dark  energy,  microlensing planet,  and  high  contrast  imaging  components.  The very wide field, large aperture, deep near-IR reach, and excellent  spatial  resolution  of  the  observatory  will  ensure  that  a  multitude  of  GOs  pursue  numerous  programs  requiring  degree-sized  fields  in  the  statistical realm  for  the  first  time.  Examples  include  studies  of stellar populations in the Milky Way and its neighboring galaxies  and  mapping  large-scale  structure  through cosmic time. Many of these will be logical outgrowths of single  object  and  small  sample  studies  with  HST, JWST,  and  other  observatories,  but  they  are  likely  to have outsized impacts just as SDSS, Kepler, and other wide field surveys already have. GO science programs can  also  make  full  use  of  grism  spectroscopy,  IFU spectroscopy, and coronagraphic imaging on WFIRSTAFTA. For examples, the COPAG recently compiled a set of exciting cosmic origin science programs with the WFIRST-AFTA coronagraph.  \n(see http://cor.gsfc.nasa.gov/copag)  \nSome capabilities of WFIRST-AFTA are unrivaled. For the foreseeable future, atmospheric seeing ensures that  no  ground-based  facility  will  produce  comparably sharp ultra-wide field images that compare to WFIRSTAFTA. Likewise, the earth\'s atmosphere is opaque between the near-IR atmospheric J, H, and F184 bands, and even where it is not opaque, OH airglow ensures that  the  background  will  be  large  and  highly  timevariable compared to space. Compared to other spacebased facilities, WFIRST-AFTA has 288x as many pixels as Hubble/WFC-3, and 210x JWST/NIRCam\'s FoV. Compared to Euclid, WFIRST-AFTA has approximately 4x the collecting area and about 2.5x the near-IR angular  resolution  (>6  improvement  in  PSF  area).  Euclid\'s dark energy surveys will certainly be useful for numerous other astrophysics  investigations,  but  at  this  point Euclid is not planning to have a dedicated program for conducting GO pointed observations (Laurei j s et al. 2011).  \nWFIRST-AFTA  will  be  complementary  to  these other  observatories,  and  their  combined  data  will  be invaluable for attacking numerous problems in modern astrophysics. In particular, the wide field and moderately deep reach of WFIRST-AFTA will be highly comple-  \nmentary  to  the  narrow  field,  higher  resolution,  and deeper  reach  of  JWST  in  their  overlapping  near-IR wavelength regions (see §2.7.1 and Appendix B). Likewise, WFIRST-AFTA will provide complementary wavelength coverage with much better spatial resolution and depth to LSST while still being able to sample wide areas of sky (see Appendix H). For many scientific investigations, WFIRST-AFTA\'s impressive imaging capabilities also provide natural synergies with powerful spectrographs from the next generation 30-meter telescopes (examples of TMT and GMT synergies are included in Appendix J)  \nCompared  to  previous,  smaller-aperture  concepts of  WFIRST, the significantly  increased  sensitivity,  and higher spatial resolution over a similar field of WFIRSTAFTA will substantially increase the potential and value of its GO program. This is true for both dedicated GO observations and for guest investigator (GI) use of data sets produced in the high-latitude, supernovae, and microlensing surveys. As for nearly all other missions, the astronomical community will be quite creative and will use WFIRST-AFTA for GO programs that the mission SDTs and SWGs will not conceive. If history is a guide, then these may prove to be among the highest impact programs executed with the telescope, rivaling or surpassing the results of the mission\'s primary dark energy and microlensing surveys. To illustrate this, the greater community has contributed  ~40  GO  ideas  on  a  multitude  of  science  themes.  These  1  page  descriptions span  a  very  broad  range  of  topics  including  the  solar system, exoplanets, stellar astrophysics, nearby galaxies, extragalactic astrophysics, and the complementarity / synergy of WFIRST-AFTA and other missions and surveys.  These  papers  clearly  illustrate  that  WFIRSTAFTA will truly be a \'Great Observatory\' for the Twentyfirst  Century. These papers are included as an appendix to this report.  \nWe  now  highlight  some  illustrative  GO  observations  that  would  take  advantage  of  WFIRST-AFTA\'s strengths. These have been culled from the much more detailed GO examples presented in the earlier WFIRST SDT  report (Spergel  et  al.  2013)  and  the  Princeton Workshop white paper (Dressler et al. 2012), and many of these themes and programs are related to the community  1  page  GO  submissions.  Because  of  the  enhanced  capability  for  a  broad  class  of  GO  programs due to the larger aperture and the loss of capability for long wavelength (> 2.0 micron) studies, we have reallocate the galactic plane survey time to the GO program for the WFIRST-AFTA DRM.  \nStatistical  studies  of  the  stellar  populations  of  the Milky Way and nearby galaxies may be one of the most obvious  areas  of  WFIRST-AFTA  GO  science  that  will have outsized impacts. However, the higher resolution and  speed  of  WFIRST-AFTA  suggests  a  huge  opportunity  in  deep  studies  of  specific  regions  of  the  Milky Way disk. A prime example is the nature and origin of the initial mass function (IMF), particularly its extension to  very  high  and very low masses. Surveys of the numerous low- to intermediate mass star forming regions within 1 kpc are still woefully incomplete. Ground-based near-IR surveys are either spatially complete with completely  inadequate  sensitivity  (2MASS),  or  else  they provide somewhat better but still inadequate sensitivity and resolution (e.g., UKIDSS now and VISTA in the future) over inadequate fields. WFIRST-AFTA surveys of the ~10 best studied young embedded clusters within 1 kpc to ~25 mag AB would reveal young brown dwarfs as well as some of the youngest Class 0 protostars in these nurseries. Combining WFIRST-AFTA and Spitzer mid-IR  survey  data  will  leverage  these  identifications and reveal much about the accretion properties of these stars early in their lives. Surveying more distant (D ~ 25 kpc) massive star forming regions will constrain highmass star formation (numbers, luminosities) with only a single or a few deep WFIRST-AFTA fields in each nearIR broadband filter.  \nClosest to home, the wide field and excellent nearIR  sensitivity  will  allow  for  sensitive  surveys  of  both nearby field and open cluster brown dwarfs. A puzzling discovery from WISE surveys is a severe deficiency of brown  dwarfs  within  the  local  volume,  D  <  8  pc:  33 brown dwarfs versus 211 normal stars is far less than typically predicted ratio of ~ 1:1 (Kirkpatrick et al. 2012). Cataloging the substellar populations of nearby young clusters with WFIRST-AFTA will reveal the brown dwarf fraction with age and location, giving insight to their dispersal into the field. Broadband 1 - 2 micron photometry with WFIRST-AFTA will locate brown dwarfs in color -  color  and  color-magnitude  diagrams  (CMDs);  these diagrams will also shed light on the mystery of why the near-IR  colors  and  spectra  of  field  brown  dwarfs  and extrasolar planets differ. Field brown dwarfs have colors and spectra consistent with a clearing of clouds as effective temperatures decrease to ~900 K (the L-T spectral type transition), but cool giant exoplanets, like those around  HR  8799,  seem  to  keep  their  clouds  at  these low  temperatures,  perhaps  due  to  their  lower  surface gravities (e.g., Marley et al. 2012). Surveying the brown dwarfs in a number of different young open clusters will revel  the  precise  age-dependence  of  this  effect.  Pro-  \nFigure  2-53:  2MASS  near-IR  image  of  the  Andromeda Galaxy  M31.  The  dust  lanes  disappear  at  these  wavelengths, revealing embedded and obscured stellar populations.  The  full  field  of  the  image  is  1.4  x  1.4  degrees. The  WFIRST-AFTA  FoV  is  indicated  by  the  red  outline, and the field of the HST WF3 IR instrument is shown by the  filled  red  rectangle.  Both  instruments  have  similar spatial  resolutions  and  sensitivities,  but  WFIRST  provides ~200 times the field of view of HST WFC3/IR.  \n<!-- image -->  \ngress  in  understanding  the  relations  between  brown dwarfs  and  giant  planets  will  be  crucial  to  interpreting WFIRST-AFTA\'s  own  coronagraphic  exoplanet  observations.  \nContinuing out from the Galactic disk to its stellar halo, deep maps of the Milky Way halo will reveal the distribution  and ages of the oldest stars in the Galaxy as well as its dwarf satellites (see Kalirai 2012, Kalirai et al. 2012). WFIRST-AFTA will also be able to resolve individual stars in nearby galaxies and better separate stars  from  distant  nearly  point-like  galaxies,  providing accurate  studies  of  their  stellar  populations  and  star formation  histories  for  the  first  time.  Near-IR  performance  is  an  important  feature  for  these  studies;  the ability  of  near-IR  light  to  penetrate  dust  lanes  (Figure 2-53 of M31) and unique age-sensitive features in nearIR CMDs are key for these investigations. More details appear in §5.4.1 of the Dressler et al. (2012) Princeton whitepaper, Kalirai et al. (2012a, 2012b), and the Belsa & van der Marel, Geha, and van der Marel & Kalirai 1 page GO papers.  \nMany  of  the  ~450  galaxies  within  12  Mpc (Karachentsev  et  al.  2004)  have  been  studied  with Spitzer, GALEX, and other missions / surveys, but few have  been  observed  at  high  spatial  resolution.  \nWFIRST-AFTA images of these galaxies would provide CMDs that allow discerning their stellar populations and determining their ages. This would greatly leverage the existing  data  as  well,  providing  a  good  look  at  the makeup of our local volume. Similarly, WFIRST-AFTA imaging data would probe the population and dynamical history of the core of the Virgo. These and related ideas appear  in  §5.4.2  of  Dressler  et  al.  (2012)  Princeton whitepaper as well as in the Dalcanton & Laine 1 page GO contribution.  \nThe  HLS  will  discover  numerous  galaxy  clusters that  can  be  followed  up  by  WFIRST-AFTA  itself  with deeper fields. Likewise, medium - deep WFIRST-AFTA observations  of  LSST  deep  drilling  fields  will  probe structure  formation  and  lensing  discoveries  will  test Λ CDM models. For example, WFIRST-AFTA could carry out a deep galaxy census covering 100 times the area of the famous Hubble Ultra Deep fields. Numerous AGN will be detected in these and other surveys, and these data will allow for some study of their co-evolution with their host galaxies. Coronagraphic WFIRST-AFTA observations will allow more detailed study of individual AGN host galaxy morphologies and halos. These studies are presented in more detail in §2.6.3 and 2.6.5 of the Green et al. (201 2 ) SDT report, §5.5 of the Dressler et  al.  (2012)  Princeton whitepaper, and the Conselice, Merton & Rhodes, and Donahue 1 page GO papers.  \nWFIRST-AFTA  data  could  also  address  the  Cosmic  Dawn  theme  of  the  NWNH  Decadal  Survey  by characterizing the epoch, speed, and shape of cosmological reionization and perhaps characterizing reionization  sources.  This  would  be  done  with  the  luminosity function of high redshift quasars (mostly from the HLS), the  high  redshift  galaxy  luminosity  function  (Lymanbreak galaxies), and Ly α emitters. The details of this exploration are presented in §5.6 of the Dressler et al. (2012) Princeton whitepaper, and related ideas appear in the Fan and Teplitz 1 page GO contributions.  \nWFIRST-AFTA will complement JWST in its quest for "first light" objects by searching for primordial stars too  faint  to  be  recognized  as  individuals  by  any  telescope. The majority of the first light quasars and stars will  not  be  seen individually, but their combined radiation may be detectable in the form of the cosmic infrared  background  (CIB).  The  source-subtracted  CIB Spitzer/IRAC maps show no correlations with the visible HST/ACS sources down to AB mag >~28 and the signal has now been measured to ~ 1 degree scale (Kashlinsky et al. 2012). The amplitude and shape of this rise is  a  direct measurement of the clustering properties of the sources responsible for the fluctuations, thus a pri-  \nmary key to understanding the nature of these sources. WFIRST-AFTA  HLS  data  will  reveal  the  power  spectrum  of  the  CIB  at  sub-degree  scales  and  help  determine whether it is dominated by radiation from the first stars  (Kashlinsky  et  al . 2007),  lower  redshift  stripped halo stars (Cooray et al. 2012), or other sources.  \nWe list a number of these and other potential GO programs in Table 2-9. We intend this list to be a representative but by no means complete list of GO program areas that will likely take good advantage of the observatory\'s  capabilities  and  have  incredible  scientific  impact  in  the  2020  decade.  WFIRST-AFTA  will  also  be capable  of  conducting  a  reasonable  number  of  these programs given that it will have ~1.5 years dedicated to its GO program.  \nTable 2-9: Examples of GO programs.', '2.7 Relation to Other Observatories': 'WFIRST-AFTA  observations  will  be  synergistic with other major astronomical facilities planned for the next decade. The WFIRST-AFTA science program has many unique aspects that will enhance the science return  from  upcoming  space  missions  including  JWST and  Euclid,  wide  imaging  and  spectroscopic  surveys being undertaken by Subaru, and ambitious upcoming ground based facilities including LSST and multiple 30meter class telescopes.  \nIn this section, we first briefly describe some of the general synergies between WFIRST-AFTA and JWST (§2.7.1).  This  includes  science  investigations that  both  take  advantage  of  the  WFIRST-AFTA  HLS data  and  ones  that  would  involve  possible  GO  programs  with  various  JWST  and  WFIRST-AFTA  instruments. We also refer the reader to Appendix B of the WFIRST-2.4  2013  report  for  a  broader  discussion  of WFIRST-JWST synergies. In the following subsections, § 2.7.2 to 2.7.5, we briefly describe how LSST ( § 2.7.2), Euclid ( § 2.7.3),  the  giant  segmented mirror telescopes ( § 2.7.4), and wide-field imaging and spectroscopy with Subaru ( § 2.7.5) all help aid in the primary dark energy science goals of WFIRST. These missions also provide tremendous synergies with WFIRST-AFTA in other areas of broad astrophysics, a few of which are captured in other areas of this report (e.g., Appendix H for LSST and Euclid;  §2.3.5  for  LSST  and  Deep  Drilling  Fields; Appendix J for TMT, GMT, and Subaru).', '2.7.1 JWST': "WFIRST-AFTA has  its  foremost  synergy  with  the James Webb Space Telescope, the descendent of the Hubble  Space  Telescope  and  the  premier  space  science facility for the 2020's. This synergy is a traditional one, pioneered by the construction seventy years ago at  Palomar  Observatory  of  the  48-inch  wide-field Schmidt  Telescope, designed  to  assist,  complement and  augment  the  science  potential  of  the  giant Hale 200-inch Telescope . A more recent example is the 2.5m  Sloan  Digital  Sky  Survey  (SDSS),  which  has  surveyed  vast  areas  of  the  sky,  finding  special  and  rare targets for today's largest and most powerful observatories including the Keck 10-m, Magellan, and VLT telescopes.  These  facilities  provide  the  high  spectral  and spatial resolution, coupled with extreme sensitivity, that is essential for detailed study of faint and often complex sources. However, telescopes with these critical capabilities  are  necessarily limited to  relatively  small fieldsof-view.  For  this  reason,  powerful  large-aperture  telescopes have been paired with smaller, wide-field tele-  \nscopes that can survey very large areas of the sky to find the high value and/or rare targets for the larger telescope.  \nJust  as  importantly,  wide-field  surveys  open  new science  frontiers.  For  example,  the  serious  study  of clusters of galaxies, which led to the foundational field of galaxy evolution, began with the Palomar Sky Survey by  the  Schmidt  Telescope:  such  programs  nourished the  Hale  telescope  for  a  half-century.  SDSS's  measurements  of  large-scale  structure  in  maps  of  galaxies and quasars have played a central enabling role in establishing today's consensus cosmological model. This dual capability --- providing the most important targets in a well-established class, and surveying for new phenomena --- enhances the value of the larger telescope and helps both kinds of facilities realize their full scientific potential.  \nWe see both synergies in the pairing of WFIRSTAFTA with JWST. Appendix B, which was largely compiled from community input by interested astronomers, describes several exemplary studies that depend upon the  science  capabilities  of  WFIRST-AFTA  and  JWST. Perhaps  the  foremost  example  in  JWST's  prime  mission is to study 'first light,' the appearance of the first stars,  galaxies,  and  quasars  in  a  previously  dark  universe. While the sky may be crowded with such inhabitants  of  the  first-billion-years  of  cosmic  history,  comparatively rare are those bright enough to study, and to use as probes of the intergalactic medium - the womb of  this  cosmic  birth.  First-generation  galaxies  are  the likely  drivers of the reionization of the universe at redshifts 6 < z < 12. Detailed study of the interactions between primordial gas and galaxies will be a major goal for JWST. Assembling sufficiently large samples of these  early  galaxies  using  JWST's  own  comparatively small-field  cameras  would  be  next-to-impossible.  On the  other  hand,  WFIRST-AFTA  --  with  a  field-of-view 100  times  greater  --  will  provide  plentiful  samples  of embryonic galaxies and supermassive black holes that JWST  can  dissect  through  deeper  imaging  and  panchromatic  spectroscopy  at  near-to-mid-infrared  wavelengths.  A  particularly  powerful  approach  to  studying the more numerous but fainter objects would be to use clusters  of  galaxies  discovered  in  the  HLS  as  gravitational telescopes that amplify the light (and magnify the size) of very distant galaxies.  \nJWST has powerful capabilities for studying highredshift supernovae, possibly even those of Population III stars  (the  true  'first  stars,'  lacking  heavy  elements). Again, the field-of-view of JWST is far too small to survey  for  such  rare  objects  efficiently,  so  they  must  be  \ndiscovered  with  other  facilities.  WFIRST-AFTA  is  unquestionably the best telescope to find such high redshift  (z  >  2)  supernovae,  because of its  ability  to  conduct deep searches in the near-IR over very wide fields. JWST's  superior  IR  spectrographs  can  make  detailed characterizations  of  these  supernovae,  both  for  studying  the  first  generations  of  stars  in  the  early  universe, and  for  cosmological  studies  to  improve  our  understanding  of  supernovae  as  'standard  candles'  at  redshifts z <  1.5  and  to  perhaps  extend  such  measurements to higher redshift.  \nStar  formation  in  the  Milky  Way  and  its  nearest neighbors,  including  the  Magellanic  Clouds,  our  Galaxy's dwarf companions, M33, and M31 (Andromeda), will be prime targets for joint study with WFIRST-AFTA and JWST. WFIRST-AFTA will be the first facility capable of deep near-IR observations, with high spatial resolution, over fields of many square degrees. Star birth in places  like  the  Taurus  Star  Forming  Cloud  ranges across a wide area, covering a vast collection of young stellar objects in different phases of formation. The energy release from these young stars is powerful enough to  drive  winds  through  the  birth  cloud,  stripping  some young stars to their demise, and at the same time probably  inducing  the  birth  of  other  new  stars.  WFIRSTAFTA  will  provide  a  roadmap  of  the  most  interesting destinations  in  many  star-forming  clouds  and  young star clusters, in the Milky Way and its neighbors. However,  understanding  the  dynamic  processes  underway will require detailed spectroscopy from the near-to-mid infrared, a prime capability of JWST.  \nWFIRST-AFTA  panoramas  of  the  youngest  star forming  regions  will  pinpoint  the  locations  of  young stars with accretion or debris disks. These will provide JWST with  an  abundance  of  targets  for  mid-IR  spectroscopy  that  will  inform  our  knowledge  of  how  exoplanets  are  born.  Many  of  these  systems  will  be  at least partly obscured by dense clouds of gas and dust. But,  the  unprecedented  sensitivity  and  resolution  of JWST's near-IR and mid-IR instrument will easily slice through the gas and dust with angular resolution comparable to WFIRST-AFTA's. WFIRST-AFTA and JWST will  provide  far  more  comprehensive  insight  into  star and planet formation processes than either observatory alone,  by  collecting  panchromatic  images  and  spectra across a range of masses, ages, and environments.  \nWorking  together,  WFIRST-AFTA  and  JWST  will provide  a  tremendous  opportunity  for  exploring  how galaxies  formed  in  the  early  universe  by  studying  the stellar  populations  of  nearby, present-day galaxies. Deep, wide-field imaging will uncover the archaeologi-  \ncal history of how these galaxies were built in previous generations of star formation. For example, streams of stars  have  been  found  in  the  stellar  halo  of  our  Milky Way and its neighbor Andromeda that record the accretion and tidal disruption of satellite galaxies in the distant  past,  a  primary  process  in  the  building  of  galaxy (See  Appendix  B  'Galactic  streams  in  nearby  galaxies').  This  is  an  excellent  example  of  synergy  among facilities:  wide-field  maps  from  SDSS  have  been  used to  find  such  structures,  color-magnitude diagrams with HST have been used to obtain the histories of star formation,  and  large  aperture  telescopes  such  as  Keck, Magellan,  and  VLT  have  made  spectroscopic  measurements  for  the  kinematics  and  abundances  of  the stellar populations.  \nThere  are  dozens  of  other  more-distant  neighbor galaxies,  each  with  a  unique  history,  which  could  be studied in this way. However, only WFIRST-AFTA has the sensitivity and wide field-of-view to make such studies practical. Following up with JWST for deeper imaging  and  spectroscopy  of  selected  regions  in  the  disks and halos of these galaxies will paint a more complete picture of their construction history, including the history of the buildup of heavy chemical elements over cosmic time. Likewise, globular clusters - richly populated star clusters that record a unique episode of star formation with a certain abundance - are valuable tools for deciphering  the  path  of  galaxy  evolution  (see  Appendix  B 'Globular  clusters  in  nearby  galaxies').  WFIRSTAFTA's  wide  field  will  provide  huge  samples  of  these objects  in  many  nearby  galaxies,  providing  targets  for deeper  imaging  with  JWST  to  determine  the  age  and heavy  element  abundance  of  each  star  cluster.  Deep imaging of the dwarf galaxy companions of large neighbor galaxies will also help us understand how galaxies of  very  different  masses  and  environments  evolved over cosmic time.  \nPerhaps the richest form of synergy is when many facilities,  each  using  its  unique  capability,  combine  to open and explore a new field of astrophysics. There is no better example than the search for and study of exoplanets. Planetary transit detections from Kepler, and in  the  future  made  by  TESS,  will  provide  a  wealth  of targets for JWST spectroscopy. This is an example of a synergy  between  Kepler,  JWST,  and  TESS.  With  regard to WFIRST-AFTA, ground-based Doppler searches  have  provided  a  sample  of  nearby  stars  for direct imaging  and  spectroscopy  with  WFIRST-AFTA's coronagraph.  Taken  collectively,  studies  like  these  will greatly  increase  our  knowledge  of  the  orbits,  mass,  \ndensity,  and  atmospheres  of  both  terrestrial  and  giant planets.  \nIn addition, the demographic study of planets within ~1  AU  of  their  host  stars  by  Kepler,  when  combined with  the  WFIRST-AFTA  microlensing  survey  that  is sensitive to planets more than 1 AU from their stars, will lead to great progress in the theory of planet formation. Size  and  mass  distributions  for  planets,  when  considered  together  with  locations  and  orbits  in  stellar  systems,  will  for  the  first  time  allow  tests  of  theories  of planet  formation  and  migration  as  planetary  systems evolve.  WFIRST-AFTA's  coronagraph,  JWST's  spectrographs, and the imaging cameras of both, building on the data from Kepler and the future TESS mission, will provide  a  multi-facility  synergy  that  will  establish  exoplanet research as a leading field of 21 st century  astronomy.", '2.7.2 Euclid': 'While WFIRST-AFTA produces deep images of the sky  at  infrared  wavelengths,  Euclid  will  produce  deep images  of  the  sky  at  optical  wavelengths  (see  Figure 2-10).  Euclid  performs  optical  imaging  to  a  magnitude of  ~24.5  over  15,000  square  degrees  in  a  single  very wide optical filter. This is complemented by NIR imaging in 3 filters to the same depth. Thus, Euclid will perform a survey that is on par with LSST in area but at significantly higher angular resolution and with the stable PSF afforded by space. WFIRST-AFTA\'s larger mirror  just  about  balances  the  longer  wavelength  (IR  vs. optical) to give the two observatories comparable angular resolution so their combined galaxy images will provide  a  more  complete  picture  of  galaxy  properties. There are two primary areas of overlapping science between  Euclid  and  WFIRST,  but  different  strategies  to accomplish those goals. Both Euclid and WFIRST aim to provide new insights into the nature of the dark energy via imaging and spectroscopy. Euclid uses a combination of NIR spectroscopic galaxy clustering (BAO and RSD)  measurements  and  gravitational  lensing  shape measurements  in  a  single  optical  band  to  study  dark energy.  WFIRST  also  uses  these  techniques.  Euclid performs  its  wide  survey  in  a  \'single  string\'  fashion, covering  as  much  survey  area  as  possible  in  a  given amount of time. Euclid\'s survey is shallower and wider than  that  of  WFIRST;  hence  the  missions  are  highly complementary.  While WFIRST covers less area than Euclid, its spectroscopic redshift survey has an order of magnitude higher density of galaxies. Its weak lensing survey  measures  a  2.5x  higher  density  of  galaxies  at higher  redshifts,  and  will  observe  in  multiple  filters  in  \nmultiples passes over the sky to maximize the robustness  of  its  results.  WFIRST\'s  philosophy  differs  from Euclid  in  that  WFIRST  seeks  to  make  multiple  redundant measurements  to  allow  a  variety  of  selfconsistency checks and cross checks in both the galaxy clustering  and  weak  lensing  measurements.  WFIRST will  also  use  supernovae  as  distance  indicators.  This technique  complements  BAO in  multiple  ways,  including unequaled precision in the late-time universe when dark energy becomes dominant. If launched early in the next decade, the 6-year prime mission of WFIRST will be  contemporaneous  with  the  6.25-year  Euclid  prime mission,  so  the  two  projects  will  carry  out  their  major dark  energy  analyses  largely  independently  (at  first) and  be  able  to  cross-check  findings  in  detail.  Later, more  robust  dark  energy  measurements  can  be  attained by simultaneous processing of WFIRST, Euclid, and  LSST  data  (see  Appendix  H).  Per  unit  time, WFIRST  is  a  very  powerful  "dark  energy  machine". Thus,  if  important  discoveries  about  dark  energy  or modified gravity emerge from Euclid or other WFIRST precursors, they can be well characterized in WFIRST extended-mission  observations  beyond  the  6-year  primary mission.', '2.7.3 LSST': 'The Large Synoptic Survey Telescope (LSST) will perform a 10-year survey over a significant fraction of the sky at optical wavelengths at depths comparable to WFIRST (see Figure 2-10). The combination of the two telescopes will measure the photometry of stars, galaxies, and quasars in nine colors spanning nearly a decade in wavelength. The WFIRST images will be much sharper,  with  a  PSF  that  is  12  times  smaller  in  area. However,  LSST  optical  data  will  provide  an  important complement that  will  enable  astronomers  to  identify  a host  of  interesting  astronomical  objects  in  this  9-color space.  LSST  optical  photometry  (at  or  near  the  full depth of the LSST 10-year survey) is required to calculate photometric redshifts for the WFIRST weak lensing experiment (see the LSST Cadence paper in Appendix J). LSST will survey a larger area (and observe it many times  over),  but  the  ~2200  deg 2 overlap  with  the WFIRST  HLS  will  allow  better  exploitation  of  the  full LSST  area.  Benefits  to  LSST  include  characterizing correlations  of  optical  colors  with  the  near-IR  spectral energy distributions (SED), high resolution morphology, and providing robust photometric redshifts in the overlap area to calibrate the wide LSST weak lensing survey. LSST will also require spectroscopic calibration of photometric redshifts (as does WFIRST) and will benefit  \nfrom  the  WFIRST  IFU  spectra  (see § 2.2.5).  The  tightest  constraints  on  dark  energy  will  come  from  a  combined  analysis  and  processing  of  LSST  and  WFIRST (and Euclid) data. The benefits of jointly processing the LSST and WFIRST data include a more thorough understanding of SEDs and the effects of color gradients for  weak  lensing  as  well  as  better  star/galaxy  and blended object separation afforded in LSST data by using WFIRST-generated isophotes.', '2.7.4 Giant Segmented Mirror Telescopes': "Several thirty-meter class telescopes are being developed  for  first  light  in  the  2020s  (ELT,  GMT,  TMT). These  telescopes,  with  their  huge  mirrors  but  limited (compared  to  WFIRST)  fields  of  view,  will  be  well placed to follow up on unusual and rare objects found in the groundbreaking deep 2,200 square degree WFIRST HLS. These telescopes will be geographically dispersed to provide coverage of nearly the whole sky, forming a powerful  complement  to  WFIRST.  Furthermore,  the depth of the WFIRST HLS creates a challenge in calibrating  photometric  redshifts).  Thirty-meter  class  telescopes play an important role in acquiring the complete sample of spectra to the full depth of the HLS imaging survey.  Some  of  the  spectra  necessary  for  calibration will only be accessible from these telescopes and they thus will help in enabling WFIRST's weak lensing objectives. These facilities have not only larger aperture mirrors,  but  also  near-infrared  optimized  instruments  in combination with a new generation of adaptive optics. These instruments will allow single-object spectroscopy of z>7 candidates galaxies (TMT/IRIS) as well as multiobject capabilities which give such telescopes the possibility to cover a few arc minutes squared field at any given time (e.g. 2 arcmin squared for TMT/IRMS). The spectral  resolution,  provided  by  such  instruments (R=2000-10000) enables the identification  of  emission lines (H α ,  Oxygen nebular lines) needed to characterize  physical  properties  of  primordial  galaxies  (starformation,  metallicity,  and  dust  content).  Also,  giant segmented mirror telescopes will help calibrate WFIRST redshifts  via  the  determination  of  absorption line  features  red  ward  of  the  Ly α line  usually  due  to metals (Iron, Magnesium, and Calcium) which are likely produced by supernovae explosions and AGB stars.", '2.7.5 Subaru': 'The  8-m  Subaru  telescope  in  Hawaii  will  be  the best  survey  telescope  in  the  Northern  Hemisphere when WFIRST flies. With powerful imaging (Hyper Suprime-Cam/HSC)  and  spectroscopic  (Prime  Focus  \nSpectrograph/PFS) capabilities, it will be able to follow up on WFIRST surveys that are inaccessible to LSST. While  the  HLS  will  be,  at  least,  mostly  covered  by LSST,  there  are  benefits  to  spreading  WFIRST  deep and medium depth survey fields across the sky. These fields will be visited multiple times in SN searches, and obtaining  optical  photometry  will  be  key  to  those  science goals. These dispersed deep fields will also provide  targets  for  the  full  range  of  the  30-meter  telescopes described above.', '3.1 Overview': "The  WFIRST-AFTA  Design  Reference  Mission (DRM)  defines  the  payload,  spacecraft,  and  ground system architectures and hardware required to meet the WFIRST-AFTA science requirements. A wide field instrument provides the wide-field imaging and slitless spectroscopy capability  required  to  perform  the  dark energy, exoplanet microlensing, and NIR surveys and a coronagraph instrument provides high contrast imaging and spectroscopy to perform the exoplanet coronagraphy  science  (see  Figure  3-1  for  a  fields  of view layout).  \nThe  payload  features  a  2.4-meter  partially  obscured aperture telescope, which feeds two different instrument  volumes  containing  the  wide  field  instrument  and  the  coronagraph  instrument  (see  Figure 3-2). The telescope hardware was built by Exelis under contract to another agency and was provided to NASA.  This  existing  hardware  significantly  reduces the  development  risk  of  the  WFIRST-AFTA  payload (see §3.2.1).  \nThe wide-field instrument provides two channels, a  wide-field  channel  and  an  integral  field  unit  (IFU) spectrograph  channel.  The  wide-field  channel  includes three mirrors (two folds and a tertiary) and an element  (filter/grism)  wheel  to  provide  an  imaging mode  covering  0.76  -  2.0 ∝ m  and  a  spectroscopy mode covering 1.35 - 1.89 ∝ m. The wide-field focal plane  uses  2.5 ∝ m  long-wavelength  cutoff  4k  x  4k HgCdTe detector arrays. The HgCdTe detector arrays are arranged in a 6x3 array, providing an active area of 0.281 deg 2 . The IFU channel uses an image slicer and  spectrograph  to  provide  individual  spectra  of each slice covering the 0.6 - 2.0 ∝ m spectral range over  two  subfields:  a  3.00  x  3.15  arcsec  field  with 0.15' slices and a 6.00 x 6.30 arcsec field with 0.30' slices. Both subfields are imaged onto a singe 2k x 2k HgCdTe  detector  array.  The  instrument  provides  a sharp PSF, precision photometry, and stable observations for implementing the WFIRST-AFTA science.  \nThe  coronagraph  instrument  provides  highcontrast  imaging  and  spectroscopy.  A  flexible  frontend  provides  low-order  wavefront  sensing  and  control,  a  fast  steering  mirror,  and  two  coronagraphic modes selectable via interchangeable masks to produce  a  contrast  on  the  order  of  10 -9 (after  postprocessing). Direct imaging is provided over a bandpass  of  430  -  970  nm,  and  spatially-resolved  spectroscopy  is  provided  by  means  of  an  integral  field  \nFigure 3-1: The WFIRST-AFTA fields of view layout as projected on the sky showing the wide-field instrument fields  (wide-field  and  IFU  channels)  and  the  coronagraph field (shared between the imager and the IFS).  \n<!-- image -->  \nspectrograph  over  the  spectral  range  of  0.6  -  0.97 ∝ m with a spectral resolution of ~70.  \nSeveral  different  orbit  choices  were  considered for  WFIRST-AFTA  including  geosynchronous  Earth orbit,  Sun-Earth L2, and highly elliptical Earth orbits, with the best two options being Sun-Earth L2 and geosynchronous orbit. For this study, we have chosen to baseline a 28.5° inclined geosynchronous orbit with a mean longitude of 105 ϒ W and an initial right ascension of the ascending node (RAAN) of 228 ϒ . The primary factor that drove the selection of this orbit is the ability  to  continuously  downlink  data  to  a  dedicated ground station enabling a much higher science data downlink  rate.  These  benefits  were  weighed  against the higher radiation environment and slightly less stable thermal environment versus the Sun-Earth L2 orbit chosen by the previous WFIRST SDT. Preliminary radiation analysis was performed during this study to assess the impact of the electron flux environment on the HgCdTe detector arrays and to size the radiation shield  around  the  focal  plane.  A  future  analysis  will optimize the shielding design by accounting for partial shielding  provided  by  the  remaining  elements  of  the Observatory.  As is  typical  for  all  spacecraft  in  GEO, additional shielding is required on both the spacecraft and payload electronics for the higher total dose radiation environment. Structural/Thermal/Optical (STOP) analysis  was  performed  to  assess  the  impact  of  the thermal environment in the geosynchronous orbit on the instruments performance. As detailed in §3.8, this slowly varying thermal environment is easily managed by the instruments with sufficient margin over the entire  orbit.  A  more  detailed  assessment  of  the  orbit trade  study  can  be  found  in  Appendix  C.  The  Study", 'Wide Field Instrument': 'Figure 3-2: WFIRST-AFTA payload optical block diagram.  \n<!-- image -->  \nOffice  and  SDT  will  continue  to  evaluate  the  orbit trade study to better quantify the assessment in Appendix C.  \nA Delta IV Heavy launch vehicle is baselined to directly inject the observatory into the baseline 28.5 ϒ inclined,  geosynchronous  orbit,  eliminating  the  need for the large bi-propellant system carried in the 2013 SDT Report. The mission life is 6 years with consumables  sized  to  allow  an  extension  for  a  total  of  10 years.  The  spacecraft  uses  mature  technology  and redundant hardware to protect against any one failure prematurely  ending  the  mission.  It  provides  a  fixed solar  array/sunshield  that  allows  continuous  operations over the full field of regard (see § 3.6 ).  \nThe  SDT  charter  specified  that  the  WFIRSTAFTA  observatory  be  serviceable.  For  this  study,  it was decided to  provide  servicing  at  a  module  level, i.e. an entire instrument or a spacecraft module containing multiple electronics boxes. The modularity will also be a benefit during integration and test of the observatory (see Figure 3-3).  \nThe  WFIRST-AFTA  design  reference  mission has been specifically tailored to meet the unique requirements of each of the WFIRST science programs.  \nThe coronagraph, as a technology demonstration instrument, is not allowed to drive mission requirements beyond  what  is  required  to  meet  the  science  programs specified for WFIRST by NWNH (e.g. pointing requirements).  For  example,  high-accuracy  pointing, knowledge,  and  stability  are  all  required  to  resolve galaxy  shapes  and  precisely  revisit  both  the  microlensing and SN fields and these requirements support coronagraphy  as  well.  Additionally,  the  design  reference mission has been tailored to accommodate the coronagraph and analysis demonstrates that the observatory design provides an excellent platform enabling the coronagraph science program.  \nThe  GRS  measurement  requires  NIR  spectroscopy to centroid H α emission lines and NIR imaging to  locate  the  position  of  the  galaxy  image  relative  to the dispersion window. Dispersion at R=461 λ (2  pixels)  enables  centroiding  the  H α or  other  emission lines to a precision consistent with the redshift accuracy requirement. To address completeness and confusion issues, grism observations over at least 3 roll angles, two of which are approximately opposed, are obtained  over  ~90%  of  the  mapped  sky.  The  band-  \nFigure  3-3:  WFIRST-AFTA  Observatory  configuration  featuring the 2.4-m telescope, two modular instruments and a modular spacecraft.  \n<!-- image -->  \ns range of 1.35 - 1.89 ∝ m provides the required redshift range for H α emitters.  \nThe SN survey measurement requires large light gathering power (collecting effective area times FoV) to  perform  the  visible  and  NIR  deep  imaging  and spectroscopy  needed  to  discover,  classify,  and  determine the luminosity and redshift of large numbers of  Type  Ia  SNe.  Precise  sampling  of  the  light  curve every  five  days  meets  the  photometric  accuracy  requirement, and the use of three NIR imaging bands in conjunction with IFU spectroscopy spanning 0.6 - 2.0 ∝ m allows measurements of SNe in the range of 0.2 < z < 1.7, providing better control of systematic errors at  low  z  than  can  be  achieved  from  the  ground  and extending  the  measurements  beyond  the  z  ~  0.8 ground limit.  \nThe  WL measurement requires  an  imaging  and photometric  redshift  (photo-z)  survey  of  galaxies  to mag M ~24.6. A pixel scale of 0.11 arcseconds balances  the  need  for  a  large  FoV  with  the  sampling needed  to  resolve  galaxy  shapes.  Observations  in three NIR filters, with ≥ 5 random dithers in each filter, are  made  to  perform  the  required  shape  measurements  to  determine  the  shear  due  to  lensing,  while observations in an additional NIR filter are combined with color data from the shape bands and the ground  \nto  provide  the  required  photo-z  determinations.  The GRS  grism  and  the  IFU,  along  with  overlapping ground observations, are used to perform the photo-z calibration  survey  (PZCS)  needed  to  meet  the  WL redshift accuracy requirement.  \nThe  microlensing  survey  measurement  requires precise  photometric  observations  of  the  Galactic Bulge and a fine PSF to detect star + planet microlensing events. Multiple fields are observed repeatedly to monitor lightcurves of the relatively frequent stellar  microlensing  events  and  the  much  rarer  events that involve lensing by both a star and a planet. In the latter  case  the  planetary  signal  is  briefly  superposed on the stellar signal. Microlensing monitoring observations  are  performed  in  a  wide  filter  spanning  0.93  2.0 ∝ m,  interspersed  ~twice/day  with  brief  observations in a narrower filter for stellar type identification. Pointing to between 54˚ and 126˚ off the Sun enables the  observation  of  microlensing  fields  for  up  to  72 continuous days during each of the twice yearly Galactic Bulge viewing seasons.  \nThe  coronagraphy  measurements  require  highcontrast  imaging  and  spectroscopy  to  detect  and characterize exoplanets. Coronagraphy requires high thermal  stability  and  low  jitter  of  both  the  telescope and  the  coronagraph  during  observations.  Although the coronagraph is not allowed to drive these observatory requirements, high-accuracy pointing, knowledge,  and  stability  are  all  required  to  resolve galaxy  shapes  and  precisely  revisit  both  the  microlensing and SN fields and these requirements support coronagraphy as well. Two deformable mirrors (DM) form  a  sequential  wavefront  control  system  (WFCS) that  compensates  for  both  phase  and  amplitude  errors in the telescope and coronagraph optics. A Low Order Wavefront Sensor (LOWFS) provides the aberration measurements for the wavefront control system while a Fast Steering Mirror (FSM) is used in an internal  pointing  control  loop  to  meet  the  coronagraph pointing  requirements.  The  relatively  short  initial  observations focus on discovery of planets near the target  star,  while  longer  observations  are  required  for planet spectroscopic characterization.', '3.2.1 Hardware Description': "The  WFIRST-AFTA  telescope  is  existing  hardware provided to NASA. It was built by Exelis and has been  structurally  qualified  and  partially  assembled. The application for WFIRST-AFTA changes the ther-  \nmal interfaces and orbit from that which the hardware was  originally  designed.  These  differences  in  environment and operation have different impacts on the telescope,  from  slight  changes  in  the  optical  design, to a more robust thermal control system. However, all are  within  the  design  and  qualification  of  the  hardware. In particular, the nominal operating temperature of 282K leaves the telescope within its qualified range of performance.  \nThe  telescope  is  separated  into  two  main  assemblies, the forward optics assembly (FOA) and the Outer Barrel Assembly (OBA). The FOA includes the primary and secondary mirrors and their baffles, the secondary  mirror  support  tubes  and  strut  actuators (integral  to  the  forward  metering  structure),  the  secondary mirror focus actuators located at the secondary mirror, and the aft metering structure (AMS). The aft  metering  structure  is  the  primary  interface  to  the rest  of  the  observatory.  The  OBA  acts  as  a  thermal shroud for the FOA and AMS and includes recloseable  doors.  An  outer  barrel  extension  (OBE)  will  be added to lengthen the outer barrel for additional stray light  control.  The  new  suite  of  instruments  (coronagraph and wide-field) will interface with the observatory through the instrument carrier rather than the AMS. This  is  done  to  provide  load  margins  well  within  the original design and qualification of the AMS.  \nIn order to restore the telescope to its operational state,  some components will need to be rebuilt from existing  designs  as  they  were  not  provided  with  the telescope.  These  include  the  actuators  for  the  secondary mirror  struts,  and  the  telescope  control  electronics. The actuators will be rebuilt to the design of the original hardware. The telescope control electronics design leverages existing electronics boards from Exelis' inventory of recent commercial flight hardware. Many of these boards are build-to-print, while a few of the boards will have minor modifications, e.g. adding a heritage circuit to a design or updating an FPGA.  \nThe design and test documents for the heritage hardware  and  the  flight  hardware  itself  have  been handled and maintained to retain full flight traceability. All  of  the  heritage  program  documentation  can  be shared with no barriers to restrict use of information. Support hardware is also required to bring the reconfigured  telescope  to  operational  readiness,  including test chambers, disassembly hardware, coating chambers and reassembly and integration hardware. Much of  this  hardware  already  exists  at  Exelis.  Support hardware subsumed by other projects can be rebuilt to print.  \nThe  key  components  of  the  telescope  are  illustrated in Figure 3-4. The existing hardware is shown in magenta and includes the substantive elements of the  assembly.  The  elements  shown  in  green  represent  new  designs,  and  include  ancillary  hardware such  as  baffles  and  struts.  The  elements  shown  in blue will be remade from existing designs (e.g., only four of the required six alignment drive actuators are available  and  two  must  be  rebuilt).  The  elements  in red represent existing hardware requiring slight modifications.    This  includes  the  Primary  and  Secondary Mirrors, which will be slightly refigured. The elements in  yellow  represent  existing  flight  qualified  designs requiring  slight  modifications,  such  as  electronics boards.  \nAlthough  the  2.4-meter  telescope  has  been largely qualified and is flight ready, adaptation to the WFIRST-AFTA mission ten years after  development brings its own unique set of potential risks. These include,  but  are  not  limited  to,  operation  in  a  different environment for which it was designed, different loads from an all new suite of instruments, hardware degradation  due  to  age,  and  the  consistency  of  hardware heritage and pedigree with NASA standards.  \nThe  baseline  WFIRST-AFTA  design  reference mission contributes to significantly reducing a number of  these  concerns.  First,  operation  of  the  Telescope within its original operating temperature range (282K for the FOA, 232K for the OBA) mitigates any concern the  telescope  structure  will  not  perform  as  designed due to thermo elastic deformations. Operating the telescope within its qualified temperature range also reduces the need to re-qualify the hardware, which minimizes the cost and schedule of telescope integration and test activities. Second, mounting the FOA as well as  the  instruments  to  a  central  Instrument  Carrier structure,  as  opposed  to  mounting  the  instruments directly to the existing FOA instrument interface, mitigates the risk of the instrument mass growing beyond the  designed  load  limits  of  the  original  telescope structure and actually reduces the load supported by the telescope.  \nSince the telescope was built and qualified over 10  years  ago,  aging  of  the  structure  and  materials must be evaluated and this activity is already well underway. Specifically, the mechanical properties of the composite  materials  that  comprise  the  bulk  of  the precision telescope structure must be verified. To address this  concern,  the  coefficient  of  thermal  expansion  (CTE)  of  existing,  aged  coupons  was  remeasured and compared to original measurements. In the", 'Outer Barrel Assembly (OBA)': "Figure 3-4: The telescope key components identifying which components will be reused, remade, or will be built to a new design.  \n<!-- image -->  \ncase  of  composite  materials,  CTE  is  a  proxy  for strength, stress, strain, and other properties. As stated in the Exelis report documenting the results of this testing 'All samples were tested at room temperature to  form  a  baseline  to  compare  against  historical measurements. The measured CTE for all laminates was the same as the measured CTE when originally fabricated within the test uncertainty.'  \nA comprehensive list of all materials in the telescope sub-structures has been assembled with each material  evaluated  for  aging  and  life  expectancy.  A test  program  is  planned  for  all  materials  with  unresolved  life  expectancy.  Materials  identified  to  be  at risk of degeneration will be replaced.  \nExelis,  JPL,  and  GSFC  mission  assurance  experts  are  developing  a  plan  to  evaluate  the  original build  books,  hardware  pedigree  and  heritage  documentation and reconcile those with NASA guidelines based on a Class B mission.", '3.2.2 Integration & Test': 'A  collaborative  effort  between  Exelis,  JPL  and GSFC has defined an integration and test approach that produces a fully aligned and tested FOA and Tel-  \nescope. The two highest-level planning flows of activity for the FOA and Telescope are shown in Figure 3-5 and  Figure  3-6.  It  should  be  noted  that  the  optical testing  planned  at  the  FOA  and  telescope  levels  intentionally  provide  traceability  to  mitigate  risk  and  to streamline  payload  and  observatory  level  optical tests.  \nThe  secondary  mirror  (SM)  and  primary  mirror (PM) will be refigured and recoated at Exelis to meet mission requirements. These processes are routinely performed by Exelis so there is very low risk to this rework activity. In order to rework these mirrors, they must be removed from the FOA. Following the mirror rework, the FOA will be reassembled per flight certified  processes  with  full  flight  documentation  that meets  mission  assurance  requirements.  Component level tests will be conducted as required prior to FOA installation.  \nThe first major optical test will occur at the complete  FOA  level,  where  the  use  of  ground  support equipment to off load the gravity effect on the PM can be  incorporated.  This  approach  has  a  long  heritage on Exelis flight hardware and will use the gravity off loader support equipment from the original program.  \nFigure 3-5: An FOA high level assembly, integration and test (AIT) flow has been established and is analogous to the original program flow.  \n<!-- image -->  \nFigure 3-6: Telescope high level AIT flow has been established using mission requirements and past experience.  \n<!-- image -->  \nTo provide a higher fidelity optical test with the PM off loaded,  a  simulator  or  Mechanical  Ground  Support Equipment  (MGSE)  for  the  flight  Instrument  Carrier (IC) will be used. This IC simulator will represent the critical mechanical and optical interfaces to the FOA. In addition, the use of the IC simulator allows a Wide Field optical verification unit (OVU) and the front-end optics of the flight Coronagraph to be installed as part of the FOA optical test. The FOA optical test will align the SM-PM system, as measured at the instruments optical interfaces. After the initial alignment, the tests will  be  repeated  with  and  without  the  PM  gravity  off loader support equipment in place. This test will provide a baseline for subsequent telescope and payload tests where the configuration prevents use of the PM gravity off loader. Additionally, the integrated modeling team will develop a gravity-correlated model of the FOA after this testing.  \nThe  FOA  will  undergo  baseline  electrical  functional tests prior to modal survey and vibration tests, which will be followed by a repeat of the optical test. The IC simulator and the Wide Field OVU will remain in place.  \nThe telescope build will continue with installation of  the  FOA  on  the  IC  simulator  on  a  piece  of  GSE representing  the  spacecraft  interface.  The  OBA  will then be integrated to this spacecraft GSE. The telescope electronics box and remaining cables will then be installed, which will be followed by a baseline electrical functional test of the telescope. A telescope level optical test will be conducted, which will essentially be a repeat of the FOA test without the PM gravity off loader.  The  telescope  will  undergo  an  acoustic  test and a thermal vacuum (TVAC) test, which will consist of thermal cycles plus a thermal balance phase. A final post-environmental optical test will be conducted prior  to  final  cleaning  to  verify  that  optical  performance  continues  to  meet  all  requirements  after  the environmental testing is completed.', '3.2.3 Development Schedule': "The  overall  schedule  for  the  telescope  delivery meets the WFIRST-AFTA program needs. Beginning with  the  start  of  long  lead  procurements,  the  telescope delivery can easily be completed in 40 months. This  duration  includes  margin  at  key  phases  of  the hardware  build,  per  Exelis'  standard  practice  (and consistent with industry standard practices) based on flight hardware heritage.  \nThe schedule for telescope delivery includes design & fabrication of new baffles for the SM and PM.  \nAlso, changes to the OBA door and the OBE will be designed, fabricated and tested in parallel with other telescope activities.  \nFor  the  rebuild  and  retest  of  the  FOA  and  telescope, Exelis  defined  a  detailed  integration  and  test sequence  that  reflects  their  long  heritage  of  testing optical  systems.  In  addition,  Exelis  evaluated  similar integration and test tasks across a number of recent telescope  and  payload  programs  to  validate  the WFIRST-AFTA  development  schedule. Example tasks  included  installation  of  thermal  control  hardware, SM assembly test program, PM alignment and system level acoustic and TVAC tests.  \nFor  the  telescope  electronics,  Exelis  is  building upon  current  flight  hardware  supply  lines,  so  they have  an  established  timeline  for  parts  procurement and  box  integration  and  test.  Thus,  Exelis  has  high confidence in the integrity of the telescope schedule.", '3.3.1 Hardware Description': 'The  Wide-Field  Instrument  (WFI)  is  divided  into two modules, a cold instrument module (referred to as the  instrument  module  below),  containing  the  optics and the focal plane assembly, and the warm electronics  module  housed  on  the  spacecraft.  Optically,  the instrument  is  divided  into  a  wide-field  channel,  with both imaging and spectroscopy modes, and an integral  field  unit  (IFU)  channel.  The  key  instrument  parameters are shown in Table 3-1.  \nThe instrument module is kinematically mounted to and thermally isolated from the instrument carrier, which provides the optical metered load path between the  telescope  and  the  instrument  module  structure. The  instrument  module  design  is  similar  to  the HST/WFC3 design  (see  Figure  3-7)  and  reuses  the design of the WFC3 latches, which can be robotically engaged and disengaged, to kinematically mount the wide-field  instrument  to  the  instrument  carrier.  The instrument module includes a grapple fixture to enable  its  removal  by  a  robotic  servicing  vehicle.  Guide rails  on  the  instrument  carrier  and  the  instrument module align the instrument module latches with the instrument  carrier  latches.  Connectors  on  the  instrument module mate to a bulkhead connector panel on the  spacecraft  top  deck.  This  panel  provides  access to  enable  robotic  connector mate/demate to the harness  that  runs  to  the  warm  instrument  electronics module on the spacecraft.  \nThe instrument module consists of an outer enclosure structure, which is flexured off of the latches and supports the instrument radiators and MLI blankets, and an inner structure, the optical bench, which supports  the  instrument  cold  electro-optical  components (see Figure 3-8). The mechanical latches interface directly to the optical bench, via thermally isolat-  \n<!-- image -->  \nFigure 3-7: Instrument comparison  to  HST/WFC3. WFIRST-AFTA wide-field is designed to be similar to the WFC3. Both use composite optical benches, radial latches, passive radiators, and heat pipes for thermal control.  \n<!-- image -->  \ning  struts,  providing  a  direct  load  path  between  the instrument  carrier  and  the  alignment-critical  optical bench.', 'Wide-Field Channel 3.3.1.1': "The wide-field channel optical train consists of a pair  of  fold  flats,  a  tertiary  mirror  (M3),  an  element wheel (EW), and the HgCdTe Focal Plane Assembly (FPA), see Figure 3-2. The FPA uses 18 4k x 4k 10 ∝ m  pixel  (H4RG)  HgCdTe  Sensor  Chip  Assemblies (SCAs), with a detector array wavelength cutoff of 2.5 ∝ m (optical cutoff is  limited  to  2.0 ∝ m via bandpass filters)  and proximate Sensor Cold Electronics (SCE) units. The SCAs are arranged in a 6x3 layout with a pixel scale of 0.11 arcseconds/pixel (Figure 3-1). An 8-position  EW  provides  6  filters,  a  dark  position  (for calibration), a grism assembly for the GRS, and pupil masks  to  block  in-band  telescope  radiation  for  the grism  and  the  filters  with  bandpasses  extending  beyond  1.5 ∝ m.  The  imaging  mode  is  designed  to  be diffraction limited at 1.2 ∝ m.  \nThe  filters  are  fused  silica  substrates  with  ion-  \nElement'Wheel'  \nFigure 3-8: Cut-away view of the Wide-Field Instrument showing the major elements. The instrument electronics are located in a serviceable spacecraft module. The optical bench and outer  enclosure  are  Al  honeycomb  panels  with  composite facesheets. Harnessing is not shown.  \n<!-- image -->  \nassisted,  highly  stable  bandpass  filter  coatings  with heritage to recent HST instruments. The Study Office is  procuring coupons of the most difficult to fabricate coatings  from  coatings  vendors  to  validate  that  they can  be  manufactured  to  WFIRST-AFTA  specifications.  These  will  be  fully  characterized  for  spectral transmission, uniformity, and effects on wavefront error for orders zero and one.  \nThe 3-element GRS grism consists of 3 fused silica  elements  with  diffractive  surfaces  on  two  of  the elements.  The  grism  has  a  spectral  range  of  1.351.89 ∝ m, with a spectral resolving power (per 2 pixels) of R=461 λ . The equivalent dispersion, D Θ = λ /( δλ / δΘ ) ,  is  obtained  by  multiplying  by  the  an-  \ne of a 2-pixel resolution element. Thus, for a value  of λ =1.5, the corresponding  value  D Θ is 461*1.5*2*0.11=  152  arcsec.  The  grism  wavefront error  is  diffraction  limited  across  the  bandpass.  The grism design residuals are smaller than the diffraction limit  and  the  design's  chromatic  error  is  improved over the design described in the 2013 SDT report.  \nThe main challenge with the grism is the optical design due to its wide FoV, large dispersion, and relatively  small  F/#.  The  second  challenge  is  to  make high  efficiency  diffractive  surfaces.  The  main  challenge is solved using an innovative optical design with two  diffractive  surfaces.  The  second  challenge  is solved  by  early  interaction  with  vendors.  The  Study Office  is  currently  building  an  Engineering  Development  Unit  to  demonstrate  that  the  grism  assembly can be designed and fabricated with acceptable margins.  This  engineering  activity  will  help  establish  the wide field spectrometer requirements. Multiple potential vendors have been engaged to study, design, and fabricate  optical  elements  to  WFIRST-AFTA  specifications  and  the  wide-field  optical  team  will  test  the performance of the fully assembled grism at the nominal operating temperature.  \nA description of the EW complement is shown in Table 3-2. The H158, F184 and W149 filters and the grism are mounted with proximate cold pupil masks.  \nAn  Optical  Test  Demonstrator  of  the  WFI  is planned  to  mitigate  schedule  risks  associated  with alignment  in  a  confined  instrument  structure,  alignment  requirements  for  large  mirrors  and  FoV,  and alignment procedure and analysis development. This room temperature test system will enable validation of the  alignment  portion  of  the  wavefront  error  budget assumptions and support the development of metrology and wavefront sensing alignment procedures and aids. First use is targeted for October 2015.  \nTable 3-2:  Filter and disperser  descriptions in the wide-field  channel spectral  selection  element wheel. GRS  grism dispersion is wavelength dependent and the resolving power is over 2 pixels.", '3.3.1.1.1 Mechanical': 'The  instrument  structure,  both  the  outer  enclosure and the optical bench, will be made from aluminum honeycomb panels with composite facesheets of cyanate siloxane resin in a carbon fiber matrix. This mature, strong, light, low-moisture absorption composite  material  is  a  good  low-thermal  expansion match to the ULE ® mirrors used in the instrument. The mirrors are stiff lightweight ULE ® sandwich designs with heritage  from  Kepler,  GeoEye  and  other  programs. The optical bench structure has top and bottom panels  with  structural  bulkheads  between  them,  and  is kinematically  supported  by  and  precisely  aligned  to the  instrument  carrier  at  three  latch  locations  via thermally isolating struts. Mirror and filter mounts are made from Ti and other materials, as needed, to appropriately athermalize the design. Thermally isolating flexures on the outer enclosure tie it to the instrument side of the latches in three locations without distorting or impacting the alignment of the optical bench. The outer  enclosure  supports  inner  and  outer  MLI  blankets that thermally isolate it from the optical bench, a two-zone  radiator  that  cools  the  optical  bench  and provides  the  heat  sink  for  a  reverse  Brayton  Cycle cryocooler, and the instrument servicing grapple.  \nA  radiation  shield,  consisting  of  a  three-layer sandwich of graphite epoxy and lead, surrounds the focal  plane,  except  for  the  light  path  leading  to  the focal  plane,  reducing  the  event  rate  in  the  detector arrays, caused by trapped electrons, to a level below that  of  Galactic  cosmic  rays.  A  thick  outer  layer  of graphite  epoxy  stops  the  electrons,  the  lead  layer stops bremsstrahlung photons produced by the electrons  as  they  are  stopped,  and  the  inner  graphite epoxy  layer  stops  tertiary  electrons  produced  by the photons.  When  sizing  the  individual  layers,  the radiation analysis accounted for the shielding provided by the rest of the wide-field instrument structure.', '3.3.1.1.2 Mechanisms': "The element wheel is the only mechanism routinely  used  in  science  operations.  The  EW's  canted design allows for precise placement of any one of the elements in the  space-constrained volume of the instrument.  The  EW  assembly  includes  cold  pupil masks for three filters and the grism, which blocks the image of the highly emissive struts and obscurations in  the  telescope pupil so as to limit parasitic thermal input into the focal plane. A DC brushless motor with redundant windings drives the EW mechanism. Motor control  is  closed  loop  using  a  rotary  transducer  for  \nposition feedback. A detent system acts on the wheel via  roller  bearings  to  provide  repeatable  positioning for each element. The detent system also serves as a restraint during launch. No power is required to hold the  wheel's  position  during  science  operations.  All drive electronics for the wheel are fully redundant with completely independent wiring.  \nA second mechanism is attached to the F2 fold flat  and  allows  for  tip/tilt  and  piston  degrees  of  freedom. This mechanism provides compensation for optical alignment changes that occur both shortly following launch (e.g. gravity release and cool down corrections  during  initial  commissioning)  as  well  as  longer term. Operation of this mechanism after commissioning is expected to be on an as needed basis to correct for misalignments due to long term changes such as moisture outgassing from the composite structural components  in  the  telescope  or  instrument.  The mechanism uses stepper motor and lead screw actuators that do not require power to hold position. The resolution of the actuator is on the order of 2 ∝ m with a total travel of +/- 3 millimeters. All drive electronics for  the  actuators  are  fully  redundant  with  completely independent wiring.  \nEarly  funding  has  allowed  the  Study  Office  to begin  prototyping  the  Element  Wheel  and  F2  Mirror Assemblies to mitigate the risk that design or materials  deficiencies  will  be  discovered  late  in  the  devel-  \nFigure  3-9:  An  early  prototype  of  the  element  wheel. Pupil  masks  are  shown  on  representative  filters  and the grism is represented by a mass model.  \n<!-- image -->  \nopment flow. Engineering Development Units of both of these mechanisms are currently being built to verify their  cold  operational  performance  before  and  after vibration testing. Figure 3-9 shows the element wheel prototype.", '3.3.1.1.3 Thermal': 'The  wide-field  channel  meets  thermal  requirements in the GEO orbit by combining a passive, coldbiased thermal design with precise thermal control of the critical focal plane hardware by a reverse Brayton Cycle cryocooler. Active cryocooler control is used to meet  SCA  and  SCE  thermal  stability  requirements (±0.3K over a day, and ±10mK over any HLS imaging observation, currently 173.5 secs) in the presence of environmental changes. Thermal gradients across the large  focal  plane  array  are  on  the  order  of  1  K  (see Figure 3-10 and Figure 3-11).  \nThe cryocooler circulates gaseous neon as a refrigerant to heat exchangers thermally coupled to the wide-field  channel  and  IFU  SCA  base  plates.  The warm  cryocooler  compressor,  along  with  the  cryocooler electronics  box,  are  mounted and heat sunk to  a  warm  passive  radiator.  Constant  conductance heat pipes are used to transport optical bench dissipated  and  parasitic  heat  loads  to  a  separate,  cold, passive  radiator.  This  radiator  includes  integrated  \nFigure 3-10: Thermal map of the wide-field channel focal plane assembly, showing small (<~1.5K) gradients. This thermal stability is independent of observing season or Observatory pointing due to active thermal control.  \n<!-- image -->  \nspreader heat pipes to cool the optical bench to ≤ 170 K.  The  cryocooler  cools  the  SCA  mosaic  plate  to ≤ 100 K. Both the top and bottom panel of the optical bench  have  embedded  ethane  heat  pipes  that transport parasitic loads from the latches, optical ap-', 'WFIRST%Cycle5%WFI%Detector%Stability%(WIM)%': 'Figure 3-11: Thermal stability of each of the SCAs over several days in an inertially fixed attitude. Short and long term stability requirements are met using a cryocooler. The power allocated to the cryocooler can be traded against the detector temperature.  \n<!-- image -->  \nerture,  and  outer  enclosure  to  the  bench  radiator. Optical  bench  thermal  stability  is  maintained  using PID  controllers  that  drive  heaters  attached  to  the optical bench heat pipes.', '3.3.1.1.4 Focal Plane Assembly': "The FPA uses 18 H4RG SCAs mounted in a 6x3 pattern to a SiC mosaic plate. Each SCA has 4088 x 4088 active pixels, 10 ∝ m in size, plus 4 extra rows or columns of reference pixels on each edge. The f/7.9 optical system maps each pixel to 0.11 arcsec square on  the  sky,  providing  an  FPA  active  FoV  of  0.281 deg 2 .  Readout  wiring  and  stray  light  considerations limit the extent to which the SCAs can be packed on the mosaic baseplate, with the active pixel gap in the x (6 SCA) direction being 2.5 mm and the 2 gaps in the y (3 SCA) direction being 8.564 and 2.5 mm (see Figure 3-1 and Figure 3-12). The FPA includes a light shield to control stray light, limiting direct illumination to active pixels. Each SCA is constructed by hybridizing  an  HgCdTe  sensor  to  a  Si  Read  Out  Integrated Circuit (ROIC) and then mounting that unit to its own SiC base. Flex cabling connects each SCA to its own SCA Control Electronics (SCE), with all 18 SCEs being  mounted to an aluminum mounting plate located <30  cm  from  the  SCA  mosaic  plate.  Each  SCA  is (simultaneously, in sync with all others) read out nondestructively by its SCE in ~5.5 s via 32 parallel outputs operating at 100 KHz. One 16 x 16 pixel guide window is also read out in sync at 5.8 Hz from each SCA  (position  in  each  SCA  variable).  All  SCAharness-SCE  units  are  identical,  simplifying  production  and  sparing.  Each  SCE  mounting  plate  is  supported  off  the  FPA's  low  thermal  conductance  com-  \nsite truss structure using thermally isolating Ti flexures.  The  entire  assembly  is  surrounded,  except  for the  incoming  optical  beam,  by  a  combined  radiation and  stray  light  shield  enclosure.  The  shield  extends around the second fold flat (F2) and is primarily designed  to  minimize  the  exposure  of  the  SCAs  and SCEs to the trapped electron environment in the geosynchronous orbit.  \nThe H4RG 4k x 4k HgCdTe sensor itself is the only  technology  driver  for  the  instrument.  A  discussion of the technology development requirements and plan is given below in §3.3.2.", '3.3.1.1.5 Wide-Field  Electronics  and  Wide-Field Channel Signal Flow': 'The  wide-field  instrument  electronics  (handling both  the  wide-field  and  IFU  channels)  are  summarized (including redundancy) in the Figure 3-13 electronics block diagram. Three warm electronics boxes (Instrument  Command  and  Data  Handling,  or  ICDH, Mechanisms Control Electronics, or MCE, and Focal Plane  Electronics,  or  FPE)  are  mounted  to  the  serviceable instrument warm electronics module provided  by  the  spacecraft.  Fixed  harness  for  the  cold  instrument  module  on  the  instrument  carrier  and  the warm electronics module on the spacecraft connect at serviceable  connector  bulkheads  on  the  spacecraft top deck. The FPE formats the raw image data from the SCEs, performs multi-accum processing and lossless  compression  before  sending  the  data  to  the ICDH. A factor of 2 has been used in the data volume estimates  while  the  Wide-Field  team  studies  compression  methods  to  select  the  best  method  for  the data  content  and  sampling  strategy.  ICDH  functions  \nFigure 3-12: Focal plane assembly (center) with SCE sub-assembly (left) and Baseplate Assembly containing the 18 SCAs (right). The remaining radiation shielding is not shown for clarity.  \n<!-- image -->  \nFigure 3-13: Electronics block diagram for the wide-field instrument.  \n<!-- image -->  \nare noted in detail in the block diagram, with key areas  being  multiplexing  the  19  compressed  data streams for delivery to the spacecraft and processing the 18 SCA guide windows to deliver guide star centroid motion updates to the spacecraft Attitude Control System.  The  MCE  controls  the  EW  to  select  filter/grism positions on a routine basis, and the F2 fold flat  optical  alignment  mechanism  to  optimize  the wide-field channel WFE performance during commissioning.  The  signal  flow  off  the  focal  plane  is  controlled by the cold SCEs mounted in the FPA and the warm SCE Control Unit (SCU) boards mounted in the FPE box on the spacecraft (one dedicated SCE/SCU chain for every SCA, all processing data in parallel). During an integration, image frames interleaved with guide window data are delivered to an SCU for processing  every  ~5.5  secs.  The  guide  window  data  is stripped  out  and  sent  to  the  ICDH  for  centroid  processing.  \nThe  WFI  outputs  ~0.9  Gbps  of  science  and guide-window data from 19 detector arrays to one Kaband  downlink  so  effective  data  handling  and  interface  management  between  the  data  handling  elec-  \ntronics is essential. Therefore, the Study Office is focusing  on  early  instrument  science  data  stream  requirements and architecture definition to identify drivers to instrument design and evaluate competing architectures. An early multi-detector test bed of the WF Channel  focal  plane  and  FPE  concept  (including guide mode readouts) is being developed to demonstrate  and evaluate design details. This test bed will be  used  to  demonstrate  science  data  flow  from  the SCAs to the output of the transmitter. It is targeted for completion at the end of calendar year 2015.', 'Integral Field Unit Channel 3.3.1.2': 'The integral field unit is a separate channel contained  within  the  wide-field  instrument.  It  uses  two small FoV apertures (3.00 x 3.15 arcsec and 6.00 x 6.30 arcsec) to limit the sky background entering the instrument  channel  (see  Figure  3-1).  The  two  fields serve  different  science  needs.  The  smaller  field  is used for typing and spectroscopic follow-up of Type Ia SNe.  When  operated  in  parallel  with  the  HLS,  the larger field enables a spectroscopic redshift survey of a subset of galaxies observed in the HLS. This data  \nSlicer&Assembly&  \nFigure 3-14:  Optical layout  of the IFU. The  relay  is  not shown.  \n<!-- image -->  \nFigure 3-15: The image slicer has 2 sets of 21 mirrors, 0.5 mm and 1.0 mm wide, yielding field slices 0.15 and 0.30 arcsec wide.  \n<!-- image -->  \nwill be used to calibrate the photometric redshifts determined  in  the  HLS.  In  addition,  in  a  GO  program, the IFU channel could be used to observe objects of interest, as the data product is a data cube (imagex, imagey, spectral position) with good stability and high S/N.  \nAn optical relay reimages the two small fields onto an image slicer and spectrograph covering the 0.62.0 ∝ m spectral range (see Figure 3-14), resulting in  \na  detector  array  format  wherein  2  sets  of  21  slices, 3.0  x  0.15  arcsec  and  6.0  x  0.30  arcsec  each  (see Figure 3-15), are imaged onto separate pixel sections of a single H2RG detector. The pixel scale at the focal plane  is  0.075  arcsec  for  the  smaller  field  and  0.15 arcsec for the larger field. The resolving power is flattened  by  the  use  of  a  compound  prism  of  materials SF6G05 and ZnSe to a typical value of 100 (2 pixels), see Figure 3-16a.  \nThe  IFU  channel  elements  are  packaged  in  a separate optical bench that is installed into the widefield instrument housing. A tip/tilt/focus mechanism is included on the second relay mirror to allow removal of any residual pupil alignment or focus shifts due to gravity  release,  cool  down,  or  composite  desorption. The  opto-mechanical  assembly  is  designed  to  operate at the same temperature (170 K) as the wide-field instrument optical bench.  \nThe slicer  is  based  on  a  commercially  available reflective  image  slicer,  a  version  of  which  has  been through space environmental testing. While there are a  substantial  number  of  elements,  they  are  small  (a maximum 5 cm) and work in a slow optical beam with relaxed stability tolerances.  \nFigure  3-16:  The  variation  in  resolving  power  of  the  IFU over  the  bandpass  is  shown  in  a.  The  diffraction  limited imaging performance for the 3 arcsec aperture, across the instrument field of view is shown in b.  \n<!-- image -->  \nb"  \nFigure  3-17:  Expanded  view  of  the  IFU  channel  focal plane assembly. This assembly shares design heritage with JWST.  \n<!-- image -->  \nThe IFU Focal Plane Assembly consists of a single  SCA,  an  interconnect  cable,  cold  electronics (SCE) and optical mask integrated into a small housing to form a single assembly. The 18 ∝ m pixel H2RG SCA (2048 x 2048 pixels) is similar to those used on JWST and Euclid, but with a hybridized detector layer and  ROIC  mounted  onto  a  silicon  carbide  base  instead of a molybdenum base. The SCE is the same ASIC as used for the wide-field channel focal plane, mounted  to  the  opposite  side  of  the  housing baseplate (see Figure 3-17).  \nThe entire FPA structurally interfaces to the IFU metering  structure  through  thermally  isolating  flexures,  which  include  provisions  for  precise  optical alignment. The focal plane thermally interfaces to the cryocooler  through  a  simple  heat  exchanging  mount on the housing. The cryocooler removes the SCE and SCA dissipated  heat  loads  as  well  as  parasitic  heat loads  to  maintain  the  assembly  (and  specifically  the SCA  and  to  a  lesser  extent  SCE)  temperature  of 100K for low dark noise and read noise. The housing components are silicon carbide to  be  low  mass  and match the detector base material. The entire assembly shares design heritage with JWST.', '3.3.2 Enabling Technology': "H4RG-10  near-IR  array  detectors  are  critical  to enabling  WFIRST-AFTA.  The  H4RG-10  is  a  4096  x 4096  pixel  HgCdTe  detector  array  that  has  10 ∝ m pixels. While building on NASA's heritage developing 1k  x  1k  pixel  H1R,  18 ∝ m  pixel  detectors  for  Hubble/WFC3, and 2k x 2k pixel H2RG 18 ∝ m pixel detectors for JWST, the H4RG-10 advances the state of the  art  by  approximately  quadrupling  the  number  of pixels per unit focal plane area (see Figure 3-18). The higher pixel density simplifies mechanical and thermal system design, as well as integration and test. More-  \nbecause the cost of making an astronomy-grade HgCdTe SCA scales roughly with the photo-sensitive area,  the  H4RG-10  has  the  potential  to  significantly reduce the cost per pixel.  \nPreliminary  detector  requirements  have  been developed  as  part  of  the  detector  development technology  plan.  These  are  mostly  used  to  ensure that detector testing is sufficient to test (with margin) devices at this performance level. These requirements  are  listed in Table  3-3. Science simulations  are  in  process  to  validate  the  detailed flowdown of these requirements.  \nThe H4RG-10 ROIC was originally developed for use with visible wavelength Si PIN detectors. In this context,  NASA  worked  closely  with  the  U.S.  Naval Observatory to mature the H4RG-10 ROIC to TRL-6 for the Navy's Joint Milli-Arcsecond Pathfinder Survey (JMAPS) satellite. The only new element for WFIRST was  hybridizing  HgCdTe  detectors  to  the  H4RG-10 ROIC instead of Si PINs.  \nAs  a  proof  of  concept,  in  FY12  the  WFIRST Study Office built and tested a small test lot of H4RG10s.  This  was  a  success,  both  proving  the  concept and elevating the H4RG-10 to TRL-4. Out of a total of six devices constructed, five were functional, and four performed well enough to merit detailed characterization. Device testing is performed at GSFC in the Detector  Characterization  Laboratory,  a  state  of  the  art facility that has been used to develop and test candidate  detectors  for  many  previous  missions  including HST and JWST. The performance was very promising,  with  the  exception  of  about  20%  higher  readout noise than is desired. In FY13, a Process Optimization Lot was started to optimize the potential flight recipes. The growth and processing of the detector ma-  \nFigure 3-18: Comparison of the size of an H4RG (4k x 4k pixels, 10 ∝ m pixel size) on left to an H2RG (2k x 2k pixels, 18 ∝ m pixel size) on the right.  \n<!-- image -->  \nTable 3-3: Detector technology development requirements. The right two columns summarize the results from the two lots of detectors based on the results below.  \nterial  was  varied  among  different  devices.  'Banded' arrays with spatially dependent recipes for efficiently spanning  parameters  were  built.  In  addition  to  pixel design  parameters  such  as  contact  size,  the  passivation,  doping,  base  material,  and  backfill  epoxy were varied in a design of experiments across a total of 14 tested devices from three detector lots.  \nThe devices have all been tested and resulted in the downselect of a recipe to proceed to a full array fabrication. Some examples of the data are given below.  Here  we  emphasize  parameters  tested  for  the first  two  technology  milestones:  interpixel  capacitance, dark current, correlated double sample (CDS) noise, and quantum efficiency. Figure 3-19 shows the cross talk averaged per band for four devices. Figure 3-20 shows maps and band-averaged dark current of four devices from the initial lot. A faint glow is evident  \non  some  devices;  while  this  glow  is  well  below  the technology  development  requirement,  it  will  be  addressed as part of an opportunity to improve performance of  the  initial  H4RG  readout  integrated  circuit (ROIC).  Figure  3-21  shows  the  CDS  (or  short  term) noise maps and band averages for the same example devices,  showing  margin  against  the  technology  development requirement.  \nQuantum efficiency was also measured over the 0.8-2.0 ∝ m band for each device. Ongoing work includes improved reference photodiode calibration under  the  cold  conditions  and  low  ambient  light  levels necessary for these tests. The quantum efficiency is above the technology goal of 60% (averaged across this  spectral  bandpass),  and  detailed  spectral  efficiency will be available when the calibration activities  \nFigure 3-19: Example cross talk for each of two repeats of 8 band designs over four example H4RG test devices. The xaxis in the bottom row is band #, with two sets of curves for the 1st and 2nd occurrence of each band design. The yaxes indicate the average crosstalk that is found by averaging the crosstalk in the 4 adjacent pixels. The total (sum of) crosstalk in the 8 adjacent pixels is approximately 4 times the average crosstalk per pixel (the bulk of the total crosstalk is within the 4 adjacent pixels). The selected band (Band 1) is the bottom left, with a repeat being the bottom left of the upper right quadrant, in each array. The upper row shows band-averaged cross talk with black to white range of 1-4%.  \n<!-- image -->  \nFigure 3-20: Dark Current maps of the same example devices shown in Figure 3-19. Uncertainty: 0.003 e-/s/pixel; i.e., any values below 0.001 e-/s or negative are set to be 0.001 in the plots. All plotted dark current numbers are median values. Images are in log scale [black = 0.005 e-/s, white = 0.1 e-/s]. While a low level glow along readout register (bottom of SCA) is evident, this is within the technology development requirement. However, this will be addressed in a redesign/remake of the H4RG readout integrated circuit (ROIC).  \n<!-- image -->  \nare completed. the passivation type for the flight design. This will be Figure 3-21: Correlated double sample or short term noise for the same devices in Figure 3-19 and Figure 3-20.  All plotted CDS noise numbers are median values. Images are in linear scale: Black=0, White=30e-. Horizontal and vertical axes on the plots are band # and CDS rms noise averaged per band, respectively.  \n<!-- image -->  \nThe two rightmost columns in Table 3-3 above list the  performance  parameters  in  the  selected  band (Band 1) of the two lots of detectors, showing margin against the technology development requirements.  \nFull  array  lots  of  two  passivations  (PV2a,  PV3) are now being fabricated based on the most promising pixel design (Band 1) based on performance and yield  considerations.  Testing  of  these  arrays  will  be completed in 2015, and will result in a downselect of  \nfollowed by the final pre-flight lot, a yield performance lot, by the end of FY16.  \nThe  NIR  detector is the only technology development  required  for  the  WFI.  A  detector technology  plan  was  approved  in  March  2013 formalizing  the  plan  described  above.  Table  3-4 shows the technology milestones for the NIR detector technology development. Passing each milestone requires a formal review and concurrence by the inde-  \nTable 3-4: The Technology milestones for the near infrared detector technology development follow a progression from pixel design through full array and yield demonstration. The first two milestones have been passed.  \npendent  Detector  Technology  Assessment  Committee  (DTAC).  The  first  two  milestones  have  been passed, with the 3 rd milestone planned for the end of FY15.", '3.3.3 Integration & Test': 'The  wide-field  instrument  integration  and  test process provides early optical testing of small assemblies  prior  to  full  up  instrument  verification  testing  to minimize  instrument  I&T  risk.  All  optical  assemblies (optics plus mount) will be fully characterized prior to integration  into  the  instrument.  The  two  fold  mirrors, the  powered  M3  mirror,  and  the  Element  Wheel  will be  installed  and  initial  alignments  performed  using laser  metrology.  An  engineering  development  FPA, with  visible  wavelength  detector  arrays,  will  be  installed  to  enable  optical  alignment  using  wavefront sensing.  The  flight  FPA  will  then  be  installed  in  the instrument and final optical alignment will be verified by wavefront sensing measurements at the operating temperature  during  instrument  thermal-vacuum  testing. Separately, the IFU will be integrated by building up  the  relay  module,  the  slicer  assembly,  and  the spectrograph.  Again,  these  assemblies  are  verified  \nseparately  prior  to  testing  the  full  IFU  channel  and prior  to  its  installation  in  the  wide-field  optical  bench (see Figure 3-22).  \nThe  wide-field  instrument  verification  effort  is strengthened by the availability of the telescope and instrument carrier along with a full aperture autocollimation flat mirror. This allows the actual telescope to be used for performance of the instrument in a Test As  You  Fly  configuration.  During  payload  I&T,  the wide-field  instrument  is  tested  with  the  telescope  to provide the most realistic optical test.', '3.3.4 Development Schedule': 'The  WFIRST  schedule  includes  12  months  to complete  the  conceptual  design  and  12  months  to complete  the  preliminary  design  during  formulation. 42.5 months are budgeted for the final design, fabrication,  integration,  and  test  of  the  wide-field  instrument. These durations are standard for an instrument of this size and complexity. The only unusually longlead  subsystem  is  the  detector  subsystem  with  a budgeted  development  and  test  duration  of  43 months from start of fabrication of the flight SCA lots, through  characterization,  build-up  into  the  FPA,  and  \nFigure 3-22: I&T flow for the wide-field instrument. The instrument is built up and tested in small assemblies to minimize the risk of finding instrument optical anomalies late in the instrument development.  \n<!-- image -->  \nthrough testing with the FPE. Fabrication of the flight SCA lots will start early in Phase B to meet the need date for instrument integration. The detector subsystem  technology  development  plan  is  designed  and funded to support this schedule (see §3.3.2).', '3.4.1.1.1 Coronagraph  Optical  Design  and  Performance': "The coronagraph instrument will take advantage of the 2.4-meter telescope's large aperture to provide novel exoplanet imaging science at approximately the same cost as an Explorer mission, including the additional operations time. The coronagraph is also directly responsive to the goals of the Astro2010 by maturing direct imaging technologies to TRL 9 for an ExoEarth  Imager  in  the  next  decade.  The  coronagraph design  is  based  on  the  highly  successful  High  Contrast  Imaging  Testbed  (HCIT),  with  modifications  to accommodate  the  telescope  design,  serviceability,  \nvolume  constraints,  and  the  addition  of  an  Integral Field  Spectrograph  (IFS).  The  coronagraph  is  required  to  provide  very  high  contrast  between  inner and  outer  working  angles  to  maximize  the  science yield.  Previous demonstrations in the HCIT have exceeded 10 -9 contrast for on-axis unobscured pupil coronagraphs.  More  recent  work  in  the  HCIT  with  obscured  pupils  has  made  considerable  progress.  The Shaped Pupil Coronagraph, for example, has demonstrated better than 10 -8 contrast at 10% bandwidth. A detailed summary of the recent success in the technology development is found in §3.4.2.  \nFigure  3-23  shows  the  coronagraph  instrument layout,  which  comprises  a  single  optical  beam  train that, using mask-changing mechanisms, can operate in  either  a  Shaped  Pupil  Coronagraph  (SPC)  or  Hybrid  Lyot  Coronagraph (HLC) mode. A single optical beam train can thus operate alternatively as two different coronagraphs.  \nFigure 3-23: Collimator assembly and coronagraph core optics bench. The IFS is on a separate optical bench, which is not shown for clarity.  \n<!-- image -->  \nA pair of flat mirrors located at the output of the telescope serves to relay the off-axis output beam to the  coronagraph  input  where  a  tertiary  mirror  (M3) and collimator mirror  (M4)-both of which have loworder aspheric surfaces-significantly reduce the offaxis  low-order  wavefront  error  introduced  by  the  aspheric primary mirror (PM) and secondary mirror (SM) (see Table 3-5). The output of this collimator assembly (M3+M4) feeds the coronagraph core with a collimated  beam  with  extremely  low  residual  wavefront error over the FoV of the instrument. Thus the residual  wavefront  error  will  be  very  insensitive  to  off-axis pointing  changes  resulting  from  the  line-of-sight (LOS) jitter correction servo. The wavefront-corrected collimated beam forms a pupil image (primary mirror conjugate) on the two-axis Fast Steering Mirror (FSM) that corrects for LOS jitter. An off-axis parabola (OAP) relay following the FSM re-images the pupil conjugate onto  the  first  of  a  pair  of  deformable  mirrors  (DM). Each  DM  is  a  monolithic  module  consisting  of  a 48 × 48 array of Lead Magnesium Niobate (PMN) electrostrictive force actuators. The DM face sheet, bonded to the actuators, has a static optical surface figure of 10 nm rms in the unpowered state and the surface figure can be actively controlled to better than 0.025 nm rms.  \nJust downstream from the DM pair, another OAP relay  re-images  the  pupil  onto  a  shaped  pupil  mask which controls diffraction before light reaches the image  plane.  At  the  image,  an  occulting  mask  rejects most of the starlight and passes the light originating from  around  the  target  star.  The  rejected  starlight from  the  occulting  mask  is  fed  to  the  Low-Order Wavefront  Sensor  (LOWFS)  that  is  used  to  provide real  time  control  feedback  to  the  FSM  (for  pointing correction) and to a passive mirror (for focus correction).  This  critical  element  offloads  the  thermal  drifts of the telescope.  \nFollowing the image plane masks, an OAP collimates the beam and reimages the pupil onto a Lyot stop, a mask that strips away most of the remaining starlight  while  passing  the  planet  light.  The  coronagraph  core  optical  beamtrain  between  the  FSM  and the  Lyot  stop  must  be  maintained  at  a  cleanliness level  of  CL100  to  ensure  that  instrument  scatter  is well below the exozodiacal background light level. After  the  Lyot  plane,  a  filter  wheel  mechanism  selects either  a  10% or 18% wide band for wavefront sensing,  planet  detection  and  characterization  or  debris disk imaging. Following the color filter the light passes through  a  mechanical  rotation  mechanism,  by  which  \nTable 3-5: Correction of wave front error by M3 + M4. The table shows the correction of the low-order aberrations introduced by the telescope primary and secondary mirrors. Static  WFE is shown before and after correction by M3 + M4. The dynamic WFE residual after correction by M3 + M4 is shown for all low-order aberrations summed and for coma only.  \nthe  output  of  the  coronagraph core is directed to either  an  imaging  camera  or  a  lenslet-based  Integral Field Spectrograph (IFS). The light transmitted to the imaging camera is split by  a polarizing beamsplitter, allowing simultaneous detection of the two orthogonal polarization  states.  Since  the  SPC  is  highly  insensitive to the polarization induced by the telescope, the IFS beamtrain does not require a polarizer. Both the imaging camera and the IFS utilize the same 1K × 1K format electron multiplication CCD (EMCCD) with 13 micron pixel pitch. The same rotation mechanism can put  in  place  a  pupil  imaging  lens  for  focus  diversity estimation.  \nThe  IFS  has  a  76 × 76  format  lenslet  array  that samples the image plane with a 0.82x0.82 arcsec radius FoV for the entire array. A pinhole mask on the output of the lenslet array truncates the wings of the lenslet  PSF's,  thereby  reducing  spectral  crosstalk  of the IFS focal plane array (FPA). It has constant dispersion across the full 0.60 - 0.97 µm spectral range, with a free spectral range of 18%.  \nSome  key  coronagraphic  optical  design  specifications such as static and dynamic wavefront error at the  fast  steering  mirror,  optical  throughput  and  FoV are tabulated in Table 3-5.  \nThe  contrast  for  both  SPC  and  HLC  coronagraphs was simulated using an IDL based diffractive  \nFigure  3-24:  Model-predicted  contrast  for  the  HLC  in the  presence of LOS jitter.  Jitter values represent the variation  after  control  by  the  LOWFS,  which  is  expected  to  reduce  rms  jitter  to  a  fraction  of  a  milliarcsecond.  \n<!-- image -->  \n0.4 mas RMS  \nFigure 3-25: Model-predicted contrast for the SPC in the presence  of  LOS  jitter.  The  LOWFS  is  expected  to  reduce jitter  seen  by  the  coronagraph  to  a  fraction  of  a milli-arcsecond.  \n<!-- image -->  \nFigure 3-26: Log scale contrast maps for the HLC and SPC, in the presence of different levels of post-LOWFS jitter. Both designs show good tolerance to jitter.  \n<!-- image -->  \npropagation code. The results of the simulations (see Figure 3-24, Figure 3-25, and Figure 3-26) show that the  HLC  produces  better  than  10 -9 contrast  in  the presence of low LOS jitter, but is sensitive to increasing jitter, whereas the SPC produces better than 10 -8 contrast  and  shows  a  lower  sensitivity  to  increasing jitter.", '3.4.1.1.2 Coronagraph Implementation': 'High-contrast  coronagraphy  requires  extreme stability  of  the  optical  system  over  the  observation time  period.  Coronagraph  optics  require  ~0.25  µm relative  stability  during  an  observation.  The  coronagraph optical bench (shown in Figure 3-23) must be positioned with respect to the telescope with an accuracy  of  1  mm.  The  thermal  stability  of  this  position  \nmust fall within 0.5 µm during an observation period. To achieve this positional accuracy and stability, all of the coronagraph core optics are mounted on a stiff, athermalized, optical bench. The optical bench - made of  carbon  fiber  composite  material  -  is  actively  controlled to <10 mK to achieve 0.25 µm internal stability. The  coronagraph  optical  bench  assembly  will  be maintained at 290 K to ensure that the DMs are flat when unpowered. The LOWFS detector will be operated at 250 K and both the coronagraph imaging and IFS  detectors  will  be  operated  at  165  K  to  minimize dark  current.  All  three  detectors  will  be  passively cooled with radiators. Blanketing will isolate the coronagraph radiatively from the ~220 K instrument carrier.  The  coronagraph  temperature  will  be  maintained  \nTable 3-6: Coronagraphic mask/filter sets for each configuration.  The  table  shows  the  number  of  masks  or filters  required  in  each  configuration  at  each  location in the optical beamtrain.  \nwith its electronics power dissipation in addition to software-controlled heaters.  \nIn  order  to  optimally  satisfy  the  three  science objectives  of  planet  imaging,  planet  spectral  characterization  and  dust  debris  imaging,  the  coronagraph  is  designed  to  operate  in  two  different modes. Using active mechanisms that change pupil masks, focal plane masks, Lyot masks, and bandpass filters, a single optical beamtrain can be operated  as  either  a  Hybrid  Lyot  Coronagraph  or  a Shaped Pupil Coronagraph. The Hybrid Lyot Coronagraph mode will be used for planet imaging, whereas the Shaped Pupil Coronagraph mode will be used for planet spectral characterization and dust debris imaging.  This  unique  dual  mode  architecture  not  only  allows  the  optimum  coronagraph  configuration  to  be used for the different types of science investigation, it also serves as redundancy to mitigate risk of an operational problem with one of the two modes. The two coronagraph modes are shown schematically in Figure  3-27  and  Figure  3-28.  There  are  eight  electromechanical  mechanisms  in  the  coronagraph.  Six  of the  eight  use  an  identical  design.  The  other  two  are the  FSM  and  the  focus  adjust  mechanism.  The  six identical  wheel  mechanisms  are  in  sequence  from entrance to exit: the pupil mask wheel, the focal plane mask  wheel,  the  Lyot  mask  wheel,  the  field  stop wheel, the waveband filter wheel, and the camera selector wheel. The coronagraphic mask sets and color filters are shown in Table 3-6 and Table 3-7, respectively.', '3.4.1.1.2.1 Structural    Design': 'The output of the telescope is relayed to the coronagraph via  a  pair  of  fold  mirrors  mounted  on  the instrument carrier. The coronagraph instrument (CGI) consists  of  a  collimator  assembly,  the  coronagraph core optics, an integral field spectrograph (IFS), opti-  \nTable 3-7: Bandpass filters for planet imaging, spectroscopy, and dust debris disk imaging.  \ncal benches, support structure, a thermal cover, cameras,  and  electronics.  The  optical  beam  train  is  laid out in two geometric planes, with the exception of the two fold mirrors at the telescope output. The collimator  assembly  and  IFS  optics  exist  in  one  plane  and the  coronagraph  core  optics  including  imaging  camera and LOWFS fall in a single parallel plane. This is shown clearly in the right side image in Figure 3-29. The coronagraph instrument will be housed in a carbon  fiber  composite  frame  with  a  triangular  support structure. The support structure will be attached to the instrument  carrier  (IC)  via  three  latches  of  a  design class  that  has  been  proven  on  HST  (the  3-2-1  latch system).  The  coronagraph  support  structure  is  designed  to  enable  robotic  servicing  of  the  entire  instrument.  The  optical  beamtrain  consists  of  three separate opto-mechanical sub-systems: the collimator assembly, the coronagraph core optics and the IFS. Each sub-assembly consists of optics mounted to an optical bench. The optical benches, as well as the instrument  supporting  structure,  are  fabricated  of  carbon  fiber  composite  material  for  its  stiffness  and athermal  behavior.  The  structure  and  three  optical benches are shown in Figure 3-29.  \nAn integrated finite element model (FEM) of the coronagraph,  instrument  carrier  and  telescope  was developed  to  evaluate  the  structural  design.  The mass  for  the  coronagraph  instrument  including  all structure is 120 kg. A modal analysis of the integrated  \nFigure 3-27: The Hybrid Lyot Coronagraph mode is shown. The output is detected by the imaging camera (reimaging optics shown as lenses for simplicity).  \n<!-- image -->  \nFigure  3-28:  The  Shaped  Pupil  Coronagraph  mode  is  used  with  the  IFS  for  spectral  characterization (reimaging optics shown as lenses for simplicity).  \n<!-- image -->  \nFigure 3-29: Coronagraph supporting structure and three opto-mechanical benches.  \n<!-- image -->  \nFEM  was  carried  out  to  ensure  that  the  structure meets the resonance frequency requirements.', '3.4.1.1.2.2 Thermal    Design    and    Modeling': 'The  thermal  design  of  the  Coronagraph  utilizes  \nboth  passive  and  active  controls  to achieve the desired operating temperature and thermal stability while minimizing the heater power required and the  mass.  The  Coronagraph  consists of  the  fold  mirror  assembly,  optics, optical  benches,  support  structure, thermal cover, cameras, and electronics.  The  support  structure,  thermal cover,  cameras,  and  electronics  are all individually  wrapped  with  multilayer  insulation  (MLI).  The  Coronagraph support structure is attached via kinematic  mounts  to  the  instrument carrier,  on  which  the  fold  mirror  assembly is mounted. The optical benches and thermal cover are isolated  from  the  coronagraph  support structure.  There  are  three  cameras that  are  supported  off  the  electronics via bipods. The electronics are mounted to both the support structure and  optical  benches.  The  thermal  \nhardware  includes  multilayer insulation (MLI), heaters,  radiators,  thermal straps,  temperature  sensors, and heat pipes.  \nA thermal math model (TMM) of the Coronagraph was developed to support  structural  thermal optical (STOP) analysis and  trade studies. The TMM simulates all the major  components  and  structures  of  the  Coronagraph. Figure 3-30 shows  the TMM-generated  temperature  maps  of  the  coronagraph optical benches. The TMM was used to evaluate the  final  design  prior  to proceeding  to  the  STOP analysis of coronagraph performance.', '3.4.1.1.2.3 Electrical    Design    and    Data    Rates': "The  coronagraph  instrument  electronics  (shown in  Figure  3-31)  has  dual  string  redundancy  in  key electrical  subsystems  where  significant  risk  can  be  \nFigure 3-30: Coronagraph thermal math model simulation of the temperature profile on the three coronagraph optical sub-benches following a slew from a bright star to a science target star. This is representative of the temperature profiles  that  are  used  in  the  coronagraph  STOP  analysis.  The  gradients shown in the figure (~2.5 K) are from the preliminary thermal control design with further optimization possible.  \n<!-- image -->  \nFigure 3-31: Coronagraph electronics system block diagram.  \n<!-- image -->  \nretired. The spacecraft will supply redundant power at ≈ 29 V to redundant DC-DC converters in the instrument.  A  redundant  1553  interface  will  handle  commands  and  housekeeping,  while  redundant  SpaceWire  interfaces  will  be  used  for  science  data.  The spacecraft will read a limited number of internal coronagraph temperature sensors for  thermal  monitoring while  the  coronagraph  is  off.  Command  and  data handling will  be  performed by a RAD750 flight computer  and  a  field-programmable  gate  array  (FPGA). The  instrument  computer  is  single  string  due  to  its proven reliability. The two DMs will be driven by separate  power  supplies  and  electronics.  If  one  DM  or driver  completely fails,  the  second DM will still allow much of the planned science. The failure of discrete DM actuators or individual DM elements (or the drive electronics for individual DM elements) will result in a graceful  degradation  of  DM  performance.  All  actuators  will  have  redundant  windings,  with  redundant drive  electronics  (only  one  powered).  Detector  drive electronics will also be redundant.  \nThere are three cameras in the coronagraph, the imaging  camera,  the  IFS  camera  and  the  LOWFS camera.  The  average  raw,  uncompressed  data  rate for  the  coronagraph  instrument  is  estimated  to  be  a very  modest  235  kbps.  The  assumptions  underlying this estimate are as follows.  \nSince the CGI will observe over a small field, the two coronagraph science cameras have only 1 million pixels each. Only one of the two CGI science cameras  will  be  used  during  an  observation  or  diagnostic run and frame times will be in the 100's of seconds for target stars and many 10's for bright stars. Moreover, only a fraction of the pixels from each imaging camera frame will be used. The nearly raw IFS frames will be sent to the ground where spectral data cubes will be produced as part of the data post-processing activity.  Although  the  LOWFS  camera  will  be  operated nearly 100% of the observing time, only a very small subset  of  camera  pixels  will  be  used  to  capture  the wavefront.  \nThe coronagraph image plane and IFS detectors must  have  extremely  low  noise.  Dark  current  noise  \nTable  3-8:  Coronagraph  detector  requirements  and  e2v  CCD201  expected  performance. Expected quantum efficiency values correspond to the 'Basic Multi2' AR coating for standard thickness silicon reported by e2v. Expected CIC value as reported by NüVü in the EMN2 camera with CCCP controller. IMO = inverted mode operation.  \nmust be no more than 1 e- over a thousand to several thousand seconds, while read noise must be no more than 1 e- for the sum of 100-1000 reads. Silicon detectors  can  provide  the  requisite  low  dark-current when cooled to ≈ 165 K. Very low read noise is more difficult to obtain. A trade study, carried out to identify the best possible detector, resulted in the selection of the  e2v  model  CCD201  electron-multiplying  chargecoupled  device  (EMCCD)  as  the  baseline  coronagraph  detector  for  imaging  and  spectroscopy  (see Figure 3-32 and Table 3-8). As part of the trade study, other  devices  considered  were  standard  CCDs  (like the  type  flown  on  Kepler),  deep  depletion  CCDs (Gaia)  and  sCMOS  sensors.  Only  EMCCDs  have demonstrated the required low read noise, attained by means of  the  analog  gain.  The  e2v  model  CCD201 has a format of 1K × 1K pixels with 13 micron pitch and can be operated in three modes: i) standard CCD (no gain), ii) analog gain and iii) gain with photon counting.  For  most  of  the  coronagraph  operations  the EMCCD  detector  will  be  operated  in  the  latter  two modes  but  the  capability  to  operate  as  a  standard CCD provides good risk mitigation. The CCD201 is a high TRL device that is offered by e2v as a standard product,  used  not  only  by  astronomers  but  also  by medical  device  suppliers.  e2v  is  developing  4K × 4K version of the CCD201 which offers performance advantages  for  the  IFS.  The  WFIRST-AFTA  Coronagraph team will monitor the progress of this larger ar-  \ndevice  and  in  the  event  that  its  TRL  advances soon  enough  for  the  coronagraph,  the  baseline  design could change to utilize this newer device.  \nIn-orbit radiation damage to the detector can increase the read noise considerably. Work is currently underway  to  characterize  the  performance  degradation of the CCD201 in the relevant environment over the mission lifetime. In addition, operating techniques such as pocket pumping will be tested to determine to what extent the radiation induced degradation can be mitigated in flight.  \nFigure 3-32: e2v model CCD201 EMCCD is a frame transfer device. The dark region on the left is the light sensitive area whereas the frame transfer region on the right is coated with a blocking layer.  \n<!-- image -->", 'IFS Specifications': 'Table 3-9: Design specifications for the IFS', 'Integral Field Spectrograph 3.4.1.2': "The  WFIRST-AFTA Coronagraph's  integral  field spectrograph  (IFS)  was  designed  to  meet  the  baseline science requirements (see Table 3-9). The IFS is required to cover a spectral range from 600-970, corresponding to a full spectral bandpass of 47%. Due to chromatic effects, the wavefront control system is only able to correct at high contrast up to an 18% instantaneous  bandwidth  (see  §3.4.1.3).  To  date,  testbed demonstrations on unobscured pupils have achieved high contrast on up to 20% bandwidths. Simulations suggest similar bandwidths will be achievable with the selected coronagraphs, using the WFIRST-AFTA obscured pupil. Demonstration of high contrast with obscured pupils using the IFS will take place in the HCIT as  part  of  the  technology  program.  The  47%  IFS bandwidth is separated into three different 18% spec-  \nral bands each covering diagnostic spectral  features.  These  spectral  bands  have central  wavelengths  at  660nm,  770nm, and  890nm,  where  each  band  is  independent  and  does  not  overlap  with  the next.  \nThe  IFS  spectral  resolution  requirement  of  R~70  across  the  entire  spectral bandpass  requires  a  low-resolution  dispersion  element.  R~70  means  that  each spectral  channel  must  be  1.4%  in  width (B=1/R).  At  the  shortest  wavelength  of 600nm, the spectral resolution element is then required to be no more than 8.6 nm in  width.  The  line  spread  function,  i.e., resolution  element,  must  be  critically sampled  on  the  detector,  leading  to  4.4 nm/pixel.  At  the  longest  wavelength  of 970nm,  the  resolution  element  is  re-  \nquested to be less than 14.2 nm with a pixel scale of 7.14  nm.  The  intermediate  wavelengths  follow  the same scalings.  \nThe IFS must achieve high astrometric and spectrophotometric precision. The  spectrophotometric precision of the instrument should be 0.06 mag (5%) with  respect  to  the  host  star.  This  level  of  precision enables a S/N~20 spectrum to not be limited by the IFS.  \nThe  spatial  sampling  is  accomplished  using  a lenslet array placed at a focal plane within the instrument,  where  each  lenslet  focuses  the  incident  light into a well-separated grid of compressed images. The process of spatial sampling (lenslet array), spatial filtering  (pinhole  mask)  and  spectral  dispersion  (prism assembly)  is  schematically  represented  in  Figure 3-33.  At  the  lenslet  image  focus,  a  small  aperture  \nFigure 3-33: The coronagraph IFS uses a lenslet array for separating field points. The lenslets are clocked relative to the dispersion axis in the spectrograph so the spectra do not overlap on the focal plane.  \n<!-- image -->  \nmask blocks the light diffracted out of the core. The compressed  lenslet  images  are  collimated  (not shown),  dispersed  (not  shown),  and  focused  (not shown)  onto  an  EMCCD  detector  to  produce  more than  five  thousand  individual  small  spectra.  These can then be extracted and assembled to form a data cube.", 'Low-Order Wavefront Sensor 3.4.1.3': "To maintain the coronagraph contrast during the scientific  observation,  the  coronagraph's  wavefront needs to be stable at level of tens of picometers. Although the WFIRST-AFTA telescope is well-designed, it  has  LOS  jitter  originating  from  vibration  sources such  as  the  observatory  attitude  control  reaction wheel  and  High  Gain  Antenna  (HGA),  as  well  as some low-order wavefront  aberrations  resulting  from thermally induced optics surface distortions and optical  misalignment.  WFIRST-AFTA  dynamic  and  thermal analysis shows that during a typical observation period  the  telescope  suffers  LOS  jitter  (fast)  at  the milli-arcsecond level, pointing drift (slow) of a few milli-arcseconds, and RMS wavefront variation dominated  by  focus  and  coma  aberrations  of  approximately 100 picometers.  \nTo  achieve  the  required  coronagraph  performance  in  a  realistic  space  environment  WFIRSTAFTA  incorporates  a  Low-Order  Wavefront  Sensing and Control (LOWFS/C) subsystem. LOWFS/C uses the rejected star light from the coronagraph to sense and  suppress  the  telescope  line-of-sight  jitter,  the pointing drift, and the low order wavefront errors. The measured wavefront information will also be recorded and  used  in  ground  operations  for  the  coronagraph image post-processing needed to further remove the speckle field and enhance contrast.  \nThe WFIRST-AFTA LOWFS (low-order wavefront sensor)  uses  a  Zernike  phase  contrast  wavefront sensor. The concept of phase contrast was first introduced in 1935 by Frits Zernike to  enhance a microscope image by transforming an apparently transparent biological specimen fluid into a high-contrast object image outlining the specimen. The principle of the Zernike  wavefront  sensor  works  as  follows:  a  small phase disk is placed at the center of the focused star image or point-spread-function (PSF). The phase disk introduces an optical path difference (OPD) of a quarter  of  a  wavelength.  The  phase disk has a radius of about  1/2  that  of  the  first  Airy  ring  of  the  PSF.  The PSF light  outside  the  phase  disk  transmits  the  focal plane  without  any  phase  modulation.  When  light  is  \nFigure 3-34: A Hybrid Lyot Coronagraph (HLC) occulting (focal plane) mask dielectric profile map measured by  an  atomic  force  microscope.  The  area  shown  is about  100x100  microns.  The  recessed  center  area  is the Zernike phase disk used by the LOWFS.  \n<!-- image -->  \nobserved  at  the  reimaged  pupil  plane  the  star  light forms  an  intensity  variation  across  the  pupil  that  results  from interference between the light that experienced the phase delay induced by the phase disk and the light transmitted without modulation. The intensity pattern  from  the  interference  mimics  the  OPD  map from the wavefront aberration, which is the phase variation across the pupil. In essence, the Zernike wavefront  sensor's  phase  mask  at  the  focal  plane  transforms the wavefront phase map into an intensity map at the pupil plane which can then be directly observed by  a  low-noise,  fast-readout  (~1000  frame-persecond) CCD camera. The LOWFS uses differential image based software to calculate the wavefront error from  the  intensity  pattern.  The  measured  LOS  jitter and  LOS  drift,  manifested  as  the  wavefront  slope across  the  pupil,  is  sent  to  the  Fast  Steering  Mirror (FSM)  to  correct  and  stabilize  the  line-of-sight.  The measured focus error, which is usually the dominant low-order  wavefront  error,  is  sent  to  a  fast  focusing mechanism for correction.  The  other  measured  loworder wavefront errors, such as comas and astigmatisms,  are  sent  to  the  DM  that  is  conjugated  to  the system pupil for correction. The measured wavefront error is recorded along with the coronagraph science observation  and  used  in  post  processing  to  further reduce speckle and increase the image contrast.  \nTo implement the Zernike wavefront sensor, the coronagraph's  starlight rejecting mask  and  the LOWFS phase disk are consolidated into a single focal plane mask as shown in Figure 3-34. The combination  of  the  coronagraph  occulting  mask  and LOWFS phase mask into a single mask simplifies the design  of  the  LOWFS  optics  and,  more  importantly,  \nreduces the optical  non-common-path error which is the difference between the LOWFS measured wavefront and wavefront error experienced by the coronagraph. The latter is what LOWFS/C is trying to sense and correct. Because the occulting mask reflects only starlight while transmitting the nearby planet light, the occulting  mask  acts  as  a  low-pass  spatial  filter  for LOWFS. The light fed into the LOWFS contains only low spatial frequency wavefront information and thus the LOWFS can only sense low-order wavefront error. Fortunately,  the  coronagraph  wavefront  error,  resulting  from  vibrations  and  thermal  drift,  is  primarily  low order in nature. This ensures the LOWFS is suitable for the WFIRST-AFTA coronagraph.  \nFollowing the occulting mask, the rejected light is collected by the LOWFS imaging optics and forms a pupil  image  on  the  LOWFS  sensor,  a  fast  readout CCD  camera.  Since  LOWFS  senses  only  low-order wavefront  error  this  pupil  image  is  sampled  by  8 × 8 pixels. Concentrating the LOWFS light in a relatively small number of pixels has the advantage of low photon  statistical  noise,  which  limits  LOWFS  performance, as well as rapid CCD frame read-out enabling fast jitter correction. A LOWFS test-bed is part of the Coronagraph  technology  development  program.  The goal is  to  advance  the  LOWFS technology to NASA TRL-5 in accordance with the Coronagraph Technology Development Plan (see §3.4.2.1).  \nAs part of the technology development effort the  \nHLC occulting mask with LOWFS phase disk was recently tested. Preliminary testing and calibration have shown that the Zernike sensor is quite sensitive to the low-order  wavefront  error  and  is  capable  of  sensing an equivalent of sub-milli-arcsecond LOS tilt needed for  the  WFIRST-AFTA  coronagraph.  The  sensor clearly  measures  the  wavefront  error  caused  by  the atmospheric  turbulence.  When  a  wavefront  tilt  is  introduced  by  a  PZT-actuated  tilt  mirror,  the  Zernike sensor responds with corresponding sign and amplitude.  An  example  of  the  Zernike  sensor  readout  is shown in Figure 3-35. The test data agrees well with the model predictions.", 'Calibration Hardware 3.4.1.4': "To  simulate  the  WFIRST-AFTA  telescope  jitter and drift  a  representative  Optical  Telescope  Assembly (OTA) Simulator is being designed and built. It will be used as the surrogate for the WFIRST-AFTA telescope. The OTA Simulator also serves as the calibration  gauge  for  the  LOWFS  performance  evaluation and testbed model validation.  \nThe OTA Simulator, shown in Figure 3-36, consists of a pinhole star source, a small scale replica of the  WFIRST-AFTA  telescope  with  a  primary  mirror diameter of 2 inches, a pupil mask which contains the central  obscuration  and  secondary  mirror  supporting struts,  a  jitter  mirror,  an  actuated  off-axis  paraboloid (OAP), and pupil relay optics. The OTA telescope mirrors and an OAP are moved with PZT actuators and  \nFigure 3-35:  LOWFS in-air experimental results. The jitter mirror has three PZT actuators, each was driven by +0.5V which introduces an equivalent on-sky line-of-sight tilt of ~3 milli-arcseconds. The driven actuator (channel) is indicated by the red dot in the upper row plots. The corresponding LOWFS signal, which is from the image differences between the tilted and reference images are shown in the plots in the lower row. The signature of wavefront tilt is shown as the positive and negative blobs of image intensity variation in the LOWFS signal. The signals morphology matches the modeled signal well.  \n<!-- image -->  \nFigure 3-36: OTA Simulator design. The OTA Simulator uses precise motion of the optics generated by the PZT actuators to simulate the WFIRST-AFTA telescope jitter of order of milli-arcsecond and wavefront drift of 10s of picometers. The optics of the OTA Simulator sit on the 1.5' x 2.5' optical bench. The optical components are labeled in this CAD plot.  \n<!-- image -->  \ncan  be  controlled  precisely  with  displacements  as small as a fraction of a nanometer. This displacement creates a precisely controlled low-order wavefront error on the order of picometers. The jitter mirror, actuated  by  PZT  tilt  stages,  can  introduce  the  hightemporal frequency LOS  jitter, simulating the WFIRST-AFTA  wavefront  jitter  from  the  vibration sources.  The  color-filtered  light  source  is  fed  to  the OTA  Simulator  via  a  single  mode  optical  fiber.  The spectral  bandwidth  and  intensity  is  controlled  in  the source  module  located  outside  the  OTA  Simulator. The  OTA  Simulator  optics  sit  on  a  small  1.5'  x  2.5' optical  bench.  The  light  from  the  OTA  Simulator  is collimated  and  pupil  imaged  at  the  FSM  and  then transmitted into either the LOWFS/C optics for standalone  testing  or  the  dynamic  High  Contrast  Imaging Testbed (HCIT). The entire LOWFS/C testbed will be operated in a vacuum chamber to avoid atmospheric turbulence. The OTA Simulator sub-bench is thermally insulated by MLI to enhance its stability.  \nSince  the  OTA  Simulator  can  produce  small wavefront  errors,  it  can  be  used  to  calibrate  the LOWFS, as well  as  during  the  coronagraph  testbed model verification. Later, it may also be used as the surrogate WFIRST-AFTA telescope during the Coronagraph Instrument integration and test.", 'Coronagraph  Technology  Development 3.4.2.1 Plan and Milestones': "Soon  after  the  WFIRST-AFTA  CGI  architecture downselect  results  were  announced  in  December 2013, the coronagraph technology development plan (TDP) was drafted and approved in March 2014. The main objective of the TDP is to mature the WFIRSTAFTA  coronagraph  to  Technology  Readiness  Level (TRL) 5 by the planned Project Phase A start at the beginning  of  FY  2017.  To  track  the  technology  progress  along  the  way,  the  TDP  calls  out  9  key  milestones  in  FY  2014-2016,  which  are  listed  in  Table 3-10.  Passing  each  milestone  requires  a  formal  review and concurrence by the independent Technology  Assessment  Committee  (TAC).  The  first  3  milestones  scheduled  for  completion  during  calendar 2014  were  successfully  reviewed  and  approved  by the TAC.  \nThe coronagraph technology development is split into  2  phases:  static  and  dynamic.  During  the  static phase  in  FY  2014-2015,  the  experimental  validation of  both  primary  coronagraph  models  and  the  development  of  the  low-order  wavefront  sensor  are  pursued  in  parallel  on  separate  testbeds.  This  includes fabrication  of  pupil-plane  and  focal-plane  masks  de-  \nTable 3-10: Key coronagraph technology development milestones.  \nsigned  for  the  WFIRST  CGI,  and  demonstration  of wavefront  control  using  these  masks  to  achieve  the required  starlight  suppression  with  a  static  input wavefront.  During  the  same  time,  the  LOWFS/C demonstration task involves designing and fabricating the  optical  telescope  assembly  (OTA)  simulator  and using it to produce wavefront changes, which are then sensed and corrected by the LOWFS/C subsystem.  \nIn the dynamic testing phase during FY 2016, the components and subsystems developed and validated  during  the  static  phase  will  come  together  to demonstrate  TRL  5  coronagraph  performance.  With the  OTA  simulator  injecting  wavefront  disturbances expected  on  orbit  -  both  the  line-of-sight  jitter  and slow  thermally  driven  wavefront  changes  -  the  Occulting Mask Coronagraph (OMC) testbed, convertible between  HLC  and  SPC  modes  and  integrated  with LOWFS/C subsystem, will demonstrate starlight sup-  \npression in a representative environment, as required for  meeting  NASA's  TRL  5.  The  PIAACMC  backup coronagraph  will  demonstrate  the  required  starlight suppression  with  a  static  input  wavefront  and  go through an 'open loop' testing of contrast sensitivities to wavefront tip, tilt, and defocus. The rest of this section  will  describe  in  more  detail  each  coronagraph technology development area and the most significant results achieved during 2014.", 'Shaped Pupil Coronagraph Status 3.4.2.2': "The shaped pupil coronagraph is one of the OMC instrument's two operating modes. With a design pioneered  by  the  High  Contrast  Imaging  Laboratory (HCIL)  at  Princeton  University,  the  SPC  has  a  relatively simple architecture and uses an optimized binary pupil apodizer to diffract on-axis starlight in a way that creates a dark hole in the PSF, as described in  \n§2.4.3.6.  A  field  stop  in  the  image  plane  blocks  the bulk  of  the  starlight  outside  the  dark  hole,  while  the slightly off-axis planet light is passed through the field stop and reimaged onto a detector. Thus, the starlight suppression  is  largely  achieved  by  the  pupil  mask, with DM wavefront control improving the coronagraph performance,  and  the  field  stop  reducing  the  signal dynamic range on the detector. The shaped pupil is relatively insensitive to observatory jitter, and the pupil mask design is achromatic.  \nShaped pupil apodizing  masks designed for the WFIRST-AFTA  telescope  pupil  have  small  'island' features and are not suitable for the traditionally used transmissive  mask  fabrication  approach  (Balasubramanian et al. 2013). A new reflective mask fabrication approach, with high-reflectivity aluminum regions and absorptive  black-silicon  regions  (Figure  3-37),  was developed  and  validated  at  JPL  and  produced  on  a silicon wafer. A number of masks using this approach have  been  fabricated  at  JPL  and  Caltech  in  2014,  \nwith significant quality improvements along the way. A mask designed to produce two 60 ϒ 'bow-tie' shaped dark holes was delivered to the SPC static testbed in April  of  2014.  Prior  to  delivery,  this  mask  underwent extensive  characterization  for  a  variety  of  imperfections and analysis/modeling of their expected impact on coronagraph contrast, with the results summarized in  Table  3-11.  These  results  showed that the reflective  mask  quality  is  consistent  with  achieving  good SPC  testbed  (and  on-orbit)  performance,  and  were approved by the TAC as meeting Milestone 1 success criteria.  \nDuring the summer of 2014, high contrast (starlight suppression) was obtained with this mask in the static shaped pupil coronagraphic testbed, using both narrowband light (a 2% spectral band around 550 nm) and broadband light (a 10% spectral band around 550 nm), as shown in Figure 3-38. Since two deformable mirrors  were  not  available  at  that  time  for  the  SPC testbed,  these  experiments  were  performed  with  1  \nFigure 3-37: Reflective shaped pupil: (a) a processed wafer with 2 discovery and 2 characterization masks, (b) a fabricated characterization mask, (c) design details showing absorbing black silicon and highly reflective aluminum. Colored tints on (a) and (c) are caused by microscope illumination.  \n<!-- image -->  \nTable 3-11: Reflective Shaped Pupil Mask characterization results.  \n<!-- image -->  \nFigure 3-38: Shaped pupil testbed results: (a) narrowband and broadband contrast as a function of working angle. (b) 2D image of the dark hole with 2% light. Light outside the dark hole is blocked by a field stop. A single-sided dark hole was created with 1 DM.  \n<!-- image -->  \nDM, producing a one-sided dark hole.  Testbed  conversion to the 2 DM configuration was recently completed,  which  will  enable  demonstration  of  2-sided dark  holes  in  2015.  The  results  in  Figure  3-38  were used to pass Milestone 2: narrowband shaped pupil contrast  demonstration.  In  fact  they  are  also  consistent with the SPC portion of Milestone 5 that is due 9/30/2015: broadband OMC contrast demonstration.  \nWhile the shaped pupil design developed during the  CGI  architecture  downselect  was  validated  in terms  of  both  mask  fabrication  and  testbed  performance,  the  HCIL  group  at  Princeton  University  produced an improved 'Shaped Pupil Lyot Coronagraph' (SPLC)  design  that  incorporates  a  Lyot  stop  along with the shaped pupil mask. This design improves the inner  working  angle  to  ~2.8 λ /D  thus  enhancing  the science  performance.  The  masks  for  this  SPLC  design  will  be  fabricated  and  demonstrated  on  the testbed in 2015. No fabrication process changes will be necessary to produce SPLC masks compared to the 1 st generation WFIRST-AFTA CGI SPC masks.", 'Hybrid Lyot Coronagraph Status 3.4.2.3': "The Hybrid Lyot Coronagraph is the other OMC operating mode. The main HLC starlight suppression component is a focal plane occulting mask with optimally shaped metal disc and dielectric layer profiles, as described in §2.4.3.6. The metal disc reflects the majority  of  the  incoming  on-axis  starlight  toward  the LOWFS reimaging optics, while the transmitted starlight  is  diffracted  to  be  blocked  by  a  Lyot  stop  in  a  \ndownstream  pupil  plane.  At  the  same  time,  slightly off-axis  planet  light  is  passed  through  the  Lyot  stop and transmitted to the imaging detector.  \nA band-limited Hybrid Lyot coronagraph has previously  demonstrated  the  best  reported  laboratory contrast results with an unobscured pupil (Lawson et al.  2013),  exceeding  10 -9 in  a  10%  band  at  ~3 λ /D working angle. These coronagraph designs used linear occulting masks to create a one-dimensional (and one-sided  due  to  the  use  of  1  DM)  dark  hole.  The WFIRST-AFTA CGI HLC has a new design capable of achieving  high  broadband  contrast  with  the WFIRST-AFTA  telescope's  obscured  pupil  in  the presence of realistic observatory jitter. Since the initial WFIRST  HLC  design  was  presented  during  the downselect  process  in  2013,  design  revisions,  consisting  of  optimizing  both  the  occulting  mask  profile and initial deformable mirror settings, resulted in significant  improvements  to  the  predicted  contrast  performance at small inner working angles with realistic LOS jitter. At the same time, the profiles of metal and dielectric  layers  were  simplified  to  make  the  mask fabrication less challenging. For the first time, circular HLC occulting masks were successfully fabricated at JPL's  MicroDevices  Lab  and  extensively  characterized, as shown in Figure 3-39.  \nThe  HLC  starlight  suppression  performance  is currently being validated in a dedicated testbed, with work  progressing  toward  Milestone  4  in  2015.  The HLC testbed has included, from the start, two 48x48  \nAOX  DMs  baselined  for  the  flight  instrument. It is also important to point out that for the  first  time  the  HLC  occulting  mask  has been designed to not only work as the coronagraph  occulter  in  transmission,  but  also as the Zernike LOWFS mask in reflection.", 'PIAACMC Status 3.4.2.4': "The backup Phased-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC)  architecture  is  based  on  the concept  of  apodizing  the  telescope  pupil using reflections  from  two  carefully  shaped  \n<!-- image -->  \nFigure 3-39: The HLC occulting mask imaged with (a) a differential interference contrast microscope and (b) an atomic force microscope (the central portion of the mask).  \n<!-- image -->  \naspheric mirrors (Guyon et al. 2005). The design variation proposed for the WFIRST-AFTA CGI combines PIAA  mirrors  with  a  milder  profile  and  a  focal  plane phase  mask.  The  PIAACMC  concept  promised  the smallest inner working angle, and was selected as the backup technology to OMC. In July of 2014, the 2 nd generation PIAACMC design was delivered featuring 1  deformable  mirror,  for  a  1-sided  dark  hole,  and  a simplified optical layout different from the OMC. While the PIAA mirror design was more benign than those already demonstrated under TDEMs, a new and untested component was the focal plane mask, which in the updated PIAACMC design became reflective and divided  into  35  rings  with  >1000  azimuthal  zones  of varying  heights.  Fabrication  and  characterization  of this  PIAACMC  mask  and  demonstration  through modeling that its fabrication quality is consistent with achieving the required contrast was required to pass milestone 3 in December of 2014. Using nanofabrication  at  JPL's  MDL and an extensive suite of characterization  equipment  consisting  of  optical,  atomic force,  and  scanning  electron  microscopes  (Figure 3-40), it was shown that the PIAACMC mask quality is sufficient  to  meet  milestone  3.  A  PIAA mirror design  \n<!-- image -->  \n<!-- image -->  \nFigure 3-40:  A PIAACMC reflective focal plane  mask  imaged with (a) an interferometric optical microscope (for larger features), (b) an atomic force microscope image (for fine features), and (c) a scanning electron microscope (for zone transitions).  \n<!-- image -->  \nupdate  and  tolerancing,  followed  by  the  mirror  procurement  and  testbed  validation,  are  the  next PIAACMC development steps for FY 2015-2016.", 'Low-Order  Wavefront  Sensing  and  Con3.4.2.5 trol': 'To  achieve  the  required  coronagraph  performance in a realistic space environment, a Low-Order Wavefront Sensing and Control (LOWFS/C) subsystem  is  necessary.  This  subsystem  provides  sensing and suppression of spacecraft LOS pointing drift and jitter  as  well  as  low-order  wavefront  errors  driven  by changes in thermal loading of the telescope.  \nThe  LOWFS/C performance will  be  initially  validated  in  a  dedicated  LOWFS/C  testbed,  before  its components  are  integrated  into  the  dynamic  OMC testbed. This demonstration will include the OTA simulator (a miniature version of the WFIRST-AFTA telescope) that generates realistic pointing jitter and loworder wavefront errors, as well as LOWFS/C components  and  algorithms  that  provide  sensing  and closed-loop  suppression  of  these  wavefront  disturbances  to  the  levels  that  enable  each  coronagraph mode to  meet  its  science  requirements.  Sensing  in-  \nformation  can  also  be  used  on the  ground  for  PSF  subtraction and  data  editing.  Closed  loop control  will  suppress  the  pointing  jitter  and  drift  using  a  Fast Steering Mirror (FSM) with ~50 Hz control bandwidth.  \nThe  sensor  uses  starlight discarded  by  the  coronagraph after it  is  reflected  from a common  location  for  both  OMC technologies  -  a  focal  plane with  HLC  occulters  and  SPC field stops. The selected  \nFigure 3-41: (a) A 48x48 PMN deformable mirror with 24 flex ribbon and connectors, (b) a new generation 128 channel, non-multiplexed, DM driver board.  \n<!-- image -->  \nLOWFS  architecture  and  recent  progress  are de-scribed in detail in §3.4.1.3 .  \nThe LOWFS/HLC mask shown in Figure 3-39 already  underwent  initial  testing  in  the  LOWFS  lab.  A calibrated PZT tilt mirror was used to test the sensitivity. These early lab tests have demonstrated that the LOWFS sensor has high sensitivity and is capable of measuring  the  sub  milli-arcsecond  tilt  needed  for meeting Coronagraph Milestone 6, as shown in Figure  3-35.  The  test  image  and  the  LOWFS  signals closely matched the model predictions, limited by the laboratory  air  turbulence.  The  complete  LOWFS/C validation testing will take place in 2015 in a vacuum chamber followed by the integration of LOWFS/C into the dynamic coronagraphic testbed.', 'Deformable Mirror 3.4.2.6': 'The WFIRST-AFTA coronagraph instrument has baselined the monolithic PMN (Lead Magnesium Niobate)  Deformable  Mirror  (DM)  technology  developed by AOA Xinetics (AOX) (Wirth et al. 2013). JPL has a long  history  of  working  with  AOX  to  develop  large format,  small  actuator  pitch  PMN  DMs  for  highcontrast imaging. Such deformable mirrors were used in  the  highest  contrast  testbed  demonstrations  of  all Lyot-type coronagraphs: HLC, SPC, PIAA, and Vector Vortex  (Lawson  et  al.  2013).  Two  48x48,  monolithic PMN DMs were manufactured by Xinetics for the first time and delivered to JPL in 2009 (Figure 3-41a) with the specifications listed in Table 3-12.  \nOne of these two DMs passed a random vibration  test  with  an  overall  level  of  10.8  g  rms  in  2012. This test level was based on a survey of random vibration proto-flight test levels for 10 relevant JPL missions. Both DMs are currently being used in the static HLC  testbed.  New  48x48  DMs  are  currently  being  \nfabricated  at  AOX,  with  one  of  them  slated  to  go through thermal cycling qualification testing.  \nRecently,  a  new  generation  of  DM  driving  electronics for the HCIT has been designed and fabricated to move from multiplexed to non-multiplexed drivers (Figure 3-41b). This change is aimed at eliminating the stroke drift experienced by actuators with lower parallel resistance during multiplexing.', '3.4.3 Integration & Test': 'The coronagraph instrument integration and test flow has been carefully developed by considering the following:  (1)  optical  and  mechanical  interfaces  for ease of verification; (2) parallel development and verification  of  key  sub-assemblies;  (3)  key  performance verification  at  the  instrument  level  and  minimizing payload level I&T efforts. Coronagraph optics can be divided  into  two  categories:  (1)  passive  optics  that form a diffraction-limited beam with the primary, secondary, tertiary, and collimating mirrors; and (2) active optics  that  suppress  starlight  for  planet  imaging  and spectroscopic  characterizations.  Figure  3-42  shows key optical and mechanical interfaces.  \nThe coronagraph integration  and  test  (I&T)  flow is shown in Figure 3-43. First the passive optics, such as the fold mirror assembly and the tertiary/collimator sub-bench, are built and tested. They will be delivered to  the  telescope  vendor  early  to  be  integrated  and tested with the telescope primary and secondary mirrors.  This  allows  early  verification  of  the  telescope and  its  wavefront  quality  to  the  coronagraph  instrument.  \nIn  the  meantime,  the  coronagraph  sub-bench  is integrated  and  tested.  First  the  active  components (DMs, detectors and actuators) are fully tested. Then the  optical  bench  is  assembled  and  aligned,  with  a possible  seating  shake  and  subsequent  alignment  \nTable 3-12: The WFIRST-AFTA coronagraph baseline deformable mirror specifications.  \ncheck/adjustment. In parallel, the electronics  are  assembled and fully bench tested. Next the electronics are  integrated  with  the  optical  bench,  and  full  functional and performance testing is done in vacuum. It may be possible to do some testing in air, using short integration  times  to  avoid  detector  saturation.  Once functionality and performance have been verified, the full instrument assembly can be completed. EMI/EMC testing  follows,  with  any  necessary  modifications  to the  electronics  or  shielding.  Then  the  thermal  blankets  are  installed,  followed  by  mass  properties  and dynamics  testing.  After  a  functional  test,  the  instrument  is  placed  in  a  vacuum  chamber  for  bake  out, thermal  cycling,  and  thermal  balance  tests.  Finally, the full functional and performance testing is done in vacuum with cooled detectors.', '3.4.4 Development Schedule': 'The coronagraph instrument development schedule is divided into three key sections. The technology  development  section  (TRL-5  and  TRL-6)  will demonstrate the system level at TRL-5 in the relevant environment,  using  the  HCIT  under  vacuum  and  an OTA  simulator  to  mimic  the  telescope  jitter  and thermal drift. Key assemblies such as the DM and ultra-low noise detector will also be developed to retire risk  early  during  the  technology  phase.  We  plan  to elevate the DM and detector TRL to 6 before the formulation phase.  \nThe next section is the design reference mission development  and  risk  reduction  activities  section. During  the  pre-formulation  phase,  significant  resources  are  invested  in  the  early  design  of  a  reference flight instrument. Multiple design cycles are performed to refine the design. During these design cycles,  a  full  physics-based,  end-to-end  coronagraph model has been developed that can be used for instrument  performance  predictions  and  simulations. This physics-based model will help with design trades during  the  formulation  phase.  During  this  phase,  a number of engineering risk reduction activities will be performed,  e.g.,  prototyping  the  precision  mask changer mechanism and the deformable mirror driver electronics. The focus will be on mechanism stability and  repeatability  for  the  high-precision  mask  alignment (shaped pupil and hybrid-Lyot), and flight parts, packaging and cabling for DM electronics. These efforts during the pre-formulation phase will help reduce technical  and  schedule  risks  during  the  implementation phase.  \nThe final schedule section covers Phase A/B/C/D.  The  coronagraph  instrument  schedule  includes 12 months to complete the conceptual design and  12  months  to  complete  the  preliminary  design during formulation. 40.5 months are budgeted for the final  design,  fabrication,  integration,  and  test  of  the coronagraph  instrument.  These  durations  are  standard for an instrument of this size and complexity. After  \ninstrument delivery to the payload, additional time is also  budgeted  for  abbreviated  end-to-end  performance tests at the payload level (see §3.7).  \nThe  HCIT  will  be  converted  into  a  coronagraph systems  testbed  after  the  technology  demonstration phase. The coronagraph systems testbed will be upgraded when new hardware, such as prototypes, engineering  development  units,  engineering  models, etc.,  is  available.  It  will  be  used  for  early  flight  software development during the formulation phase. The coronagraph  systems  testbed  can  be  used  during phase E to support science operations and possible new algorithm development.  \nFigure 3-42: The key coronagraph instrument sub-assemblies are shown. The fold mirror assembly in the left red box is separate from the instrument itself and is separately mounted to the instrument carrier. The Tertiary & Collimator sub-bench (highlighted in the left yellow box) will be tested with the telescope primary and secondary mirrors early. The two yellow areas are two separate sub-benches to be developed in parallel.  \n<!-- image -->  \nCorrected, 0.021, P-V  \nFigure 3-43: The Coronagraph instrument Integration and Test flow chart.  \n<!-- image -->', '3.5 Fine Guidance System': "The FGS function for WFIRST-AFTA is provided by tracking guide stars using the science focal plane of  the  wide-field  channel  in  its  imaging  mode  (the spectroscopy mode is discussed at the end of §3.5). One  Guide  Window  (GW)  containing  a  pre-selected guide star is tracked on each of the wide-field channel focal plane's 18 H4RG SCAs using its standard single GW output channel. The horizontal and vertical (h/v) motion  of  the  centroid  of  each  star's  position  is  determined  in  the  wide-field  instrument's  ICDH,  and provided to the S/C ACS system with a lag time of no more than one GW update cycle. On each SCA, the readout of its GW (16 x 16 pixels in size while observing)  is  interleaved  with  the  uninterrupted  readout  of 128 lines of science image data (Science Outputs and the  GW  Output  cannot  be  active  at  the  same  time given  the  current  H4RG  design),  resulting  in  a  GW update rate of 5.86 Hz, and a Science Image frame time of 5.46 s. ACS simulations have indicated that a ≥ 4 Hz update rate is very comfortable for meeting the ACS slow drift pointing control requirement of 14 mas rms/axis.  The  interleaving  of  the  GW  readouts  only increases Science Image frame time by ~3.5% (5.28 s  to  5.46  s),  with  minimal  read  noise  implications. Other choices are possible, but for this design reference mission concept the GW size and Science Image interleaving implementation provides a good balance between GW and Science Image update rates.  \nOperationally,  all  science  survey  pointing  positions are uploaded from the ground, and each pointing includes a row/column position on each SCA identifying where the GW star (12<H\\_AB<17 magnitudes acceptable) for that SCA will be found. The slew from one  FGS  controlled  pointing  position  to  the  next  is made under star tracker and gyro control, and a 64 x 64  pixel  Acquisition  GW  size  is  temporarily  used  to ensure  that  the  GW  star  selected  on  each  SCA  is within that initial GW given the star tracker/gyro pointing accuracy. Simulations indicate that guide star acquisitions will require only one GW update, and after the  overall  pointing  error  drops  below  100  mas  all GWs will return to their observing mode size of 16 x 16 pixels.  \nThis FGS concept as implemented on WFIRSTAFTA is very robust in terms of both redundancy and scientific utility. As few as 4 of the 18 FGS GWs that are  available  are  needed  for  the  ACS  to  meet  its pointing  requirements,  so  there  is  substantial  tolerance to any issue (e.g. the SCA reset at the start of an observation) that might interfere with the acquisi-  \ntion or quality of a GW on multiple SCAs. From a science perspective, though non-common path pointing drifts will need to be considered for coronagraph and wide-field  IFU  pointings,  wide-field  channel  observations  will  be  immune  to  this  concern  since  its  focal plane provides the FGS star images, a risk reduction consideration for WL survey imaging. Even more critically,  all  GW  star  images  are  sent  to  the  ground, providing PSF variation tracking at ~6 Hz across the wide-field channel focal plane, data valuable for validating  the  accuracy  of  WL  galaxy  shape  measurements.  Guiding  during  GRS  observations  is  more challenging due to the use of dispersed star images, as h/v motion must be derived from the cross dispersion and bandpass cutoff edges of the spectral continua of bright stars. FGS performance is being evaluated relative to the mildly relaxed GRS pointing stability  requirements  (~20  mas  rms/axis)  for  stars  of magnitude  HAB=12.5  and  brighter  (the  probability  of ≥ 3 such stars in the FoV at the North Galactic pole is >95%), for update rates of 2 Hz and 4 Hz.", '3.6 Spacecraft': "The  WFIRST-AFTA  spacecraft  has  been  designed to provide all the resources necessary to support  the  payload  in  geosynchronous  orbit  using  mature and proven technology. The design is based on the  Solar  Dynamics  Observatory  (SDO)  spacecraft, which was designed, manufactured, integrated,  tested, and qualified at GSFC and is currently operating in  geosynchronous  orbit,  as  well  as  other  recent GSFC developed spacecraft like the Global Precipitation Measurement (GPM). The spacecraft bus design provides cross strapping and/or redundancy for a single-fault tolerant design.  \nStructures  and  Thermal : The  spacecraft  bus design  features  two  decks  stiffened  by  six  gussets and faced with module support plates all composed of aluminum  honeycomb  panels  with  M55J  composite facesheets and sized to meet minimum launch vehicle  frequency  requirements  while  minimizing  the spacecraft  structure  mass.  The  spacecraft  bus  provides the interfaces to the payload and the launch vehicle,  transferring  payload  loads  through  the  instrument  carrier  struts,  through  the  spacecraft  gussets and  into  the  payload  attach  fitting  (PAF);  see  Table 3-13  for  the  Observatory  mass  breakdown.  The spacecraft upper deck provides shear support of the bus,  while  also  resisting  bending.  The  propulsion  \nsubsystem is supported inside the bus on the lower deck, which also provides the interface from the gussets to the PAF.  \nThe  spacecraft  structure  includes  an  instrument carrier  that  is  the  primary  metering  structure  for  the payload. The instrument carrier is a composite truss structure  that  provides  opto-mechanical  support  for both  the  telescope  and  instruments,  provides  mechanical  latches,  with  design  heritage  from  HST,  to interface  the  instrument  modules  to  the  carrier,  contains  harness  to  route  power  and  data  between  the spacecraft and the instrument modules, and provides thermal  isolation  between  the  two  instrument  volumes. The telescope mounts directly to the instrument  carrier  via  bipods  that  attach  to  the existing telescope main mount interface. The telescope  outer  barrel  assembly  mounts  directly  to the spacecraft top deck via bipods, so that there is no direct load path from the outer barrel to the telescope or instrument optical systems.  \nThe  bus  also  supports  a  multi-panel  solar  array/sunshield to prevent the Sun from illuminating the instrument carrier, the telescope outer barrel past the secondary mirror, and the instrument radiators during science  observations  at  roll  angles  up  to  15 ϒ (see Figure 3-44). The side panels are stowed for launch and  are  released  on-orbit  to  maximize  the  area available for generating electrical power.  \nThe  spacecraft  design  features  6  serviceable modules  containing  spacecraft,  wide-field,  or  telescope electronics. These modules are designed to be robotically serviceable, enabling refurbishment or upgrades  to  the  observatory  by  replacing  individual modules. Each of the spacecraft modules includes a  \nTable 3-13: Observatory mass breakdown  \nFigure 3-44: The spacecraft bus with solar array/sunshield  showing  serviceable  modules  (both  the sunshield  side  panels  and  the  high  gain  antenna  are shown in launch configuration). The serviceable modules house spacecraft, wide-field and telescope electronics.  \n<!-- image -->  \nkinematic Module Restraint System (MRS) based on the  Multimission  Modular  Spacecraft  (MMS)  design, which was proven during the on-orbit module change out of the Solar Maximum Repair Mission. This MRS includes  a  beam  interfacing  to  kinematic  constraints on  the  top  of  each  module  and  an  accompanying floating nut/ACME threaded fastener on the bottom of each module. These module interfaces can be robotically  engaged  and  disengaged,  providing  a  simple, repeatable  mechanical  interface  to  the  spacecraft structure. The modules also include a grapple fixture to  enable  removal  of  the  modules.  The  expected docking interface with the robotic servicer is a standard  Marman  band  interface.  Docking  to  the  existing launch vehicle payload adapter fitting allows sufficient reach for the robotic servicer to remove and replace the spacecraft modules.  \nEach  module  contains  a  set  of  connectors  with alignment features to allow 'blind mating' of the module harness connectors to connectors on the harness internal  to  the  spacecraft  bus  connecting  between modules and to the payload. This electrical interface  \nhas  been  demonstrated  on  the  HST  radial  instruments.  \nThe  electronics  are  mounted  on  the  outboard panel of each of the modules with doublers used as needed for thermal conductivity. The spacecraft coldbiased  thermal  design  maintains  the  spacecraft  and payload electronics within their operational limits  using surface coatings, heaters and radiators.  \nElectrical Power : The  electrical  power  subsystem uses a direct energy transfer design, using heritage designs from the recent GPM mission, to provide regulated  power  to  the  Observatory.  Three,  bodymounted solar  array  panels  provide  the  observatory power. The solar array is sized to provide full observatory  power  (3200  W)  at  end  of  life  with  2  strings failed at the worst case observing angles of 36° pitch and 15° roll with 30% power margin. The solar array relies  on  multi-junction,  gallium  arsenide  solar  cells with at least 29.5% efficiency to provide Observatory power. To minimize thermal backload from the array to the instruments, the backside of the array is insulated and optical solar reflectors are interspersed between the solar  cells  to  cool  the  array.  An  internally redundant power supply electronics box controls the distribution  of  power,  providing  unregulated  28  Vdc power to the spacecraft and payload, provides solar array power management, and controls battery charging.  The  baselined  geosynchronous  orbit  has  two eclipse  seasons  of  ~23  days  per  year  with  a  maximum eclipse period of 72 minutes. Three 80 A-hr batteries  provide  power  to  all  Observatory  loads  during the maximum eclipse duration.  \nCommunications : The  communication  subsystem design leverages the SDO design to provide high reliability, continuous data downlink from the geosynchronous orbit.  S-band  transponders  receive  ground commands and send real-time housekeeping telemetry to the ground via 2 omni-directional antennas. The high  rate  science  downlink  uses  two  dedicated  Kaband transmitters,  each  with  a  0.75  m  gimbaled  antenna, to continuously downlink science data without interrupting science operations. The Ka-band modulator has been updated from the SDO design and is capable  of  downlinking  at  a  data  rate  of  1.2  Gbps, providing  50%  margin  to  the  baseline  science  data rate of 600 Mbps. A prototype of the updated Ka-band modulator  is  currently  being  assembled  and  will  be available for testing in early 2015.  \nCommand & Data Handling : The  internally  redundant  command  and  data  handling  (C&DH)  subsystem hosts the spacecraft flight software, provides on-board real time and stored commanding, receives payload and spacecraft housekeeping data, and provides  fault  management  for  spacecraft  health  and safety as well as safing for the payload, when necessary.  The  observatory  uses  a  MIL-STD-1553B  command/telemetry bus and uses SpaceWire for the high rate  science  data.  The  C&DH  provides  the  interface between the instruments high rate science data and the  Ka-band  system  and  formats  and  encodes  the instrument  science  data  for  downlink.  With  both  the wide-field and coronagraph instruments operating, the C&DH  will  interleave  this  data  onto  the  Ka-band downlink. Due to the direct, continuous science data downlink,  no  science  data  recorder  is  required  for WFIRST-AFTA.  The  C&DH  also  provides  the  interface  to  the  S-band  transponders,  performing  command decoding and distribution as well as encoding for S-band downlink.  \nPropulsion : The propulsion subsystem is a simple  mono-propellant  design  in  blow  down  mode  and uses  an  SDO  heritage  design.  A  single  fuel  tank stores  the  high-purity  hydrazine  fuel  and  nitrogen pressurant and mounts to the spacecraft lower deck. Eight  22  N  (5  lbf)  attitude  control  subsystem  (ACS) thrusters  adjust  for  launch  vehicle  dispersions,  provide  east-west  stationkeeping,  provide  momentum management and allow for disposal at the end of mission life.  \nAttitude Control : The attitude control subsystem provides three-axis control of the spacecraft and uses data from the inertial reference unit, star trackers, and the  payload  FGS  to  meet  the  pointing  control  and stability  requirements.  The  internally  redundant  inertial  reference  unit  provides  precise  rate  measurements to support slew and settle operations. The star trackers  (3  for  2  redundant)  are  mounted  on  the  instrument carrier so they are directly related to the instrument  pointing.  The  star  trackers  are  used  for coarsely pointing to within 3 arcsec RMS per axis of a target. After that, the FGS takes over to meet the fine pointing requirements for revisits and relative offsets (see §3.4.4). A set of four 75 N-m-s reaction wheels is used for slewing as well as momentum storage. The wheels  are  mounted  to  and  passively  isolated  from the spacecraft lower deck to attenuate high-frequency  \nwheel-induced  disturbances.  The  ACS  thrusters  are used to desaturate the wheels to manage momentum buildup. The internally redundant Mechanism and Attitude  Control  Electronics  (MACE)  box  controls  the attitude  control  subsystem  and  provides  an  independent  safe  hold  capability  using  coarse  sun  sensors and reaction wheels, which keeps the observatory thermally-safe, power-positive and protects the instruments  from  direct  sunlight.  The  MACE  controls the  fine  pointing  of  the  observatory  based  on  the guide star centroids provided by the wide-field instrument C&DH. The MACE also deploys the solar array side panels and the high gain antennas and controls the gimbals for the high gain antennas.", '3.7 Payload and Observatory Integration & Test': 'Integration  and  test  (I&T)  activities  for  WFIRSTAFTA occur in two phases, Payload I&T and Observatory I&T. During Payload I&T, the Telescope, WideField  Instrument,  Coronagraph  Instrument  and  Instrument  Carrier  will  be  integrated  together  and  the optical  performance  of  the  payload  will  be  verified. For  the  wide-field  instrument,  the  optical  test  is  a high-fidelity  end-to-end  measurement  of  wavefront  \nerror  and  photometric  throughput.  For  the  coronagraph instrument, it is an interface test with a performance  health  check  at  a  single  wavelength.  As shown in Figure 3-45, deliverables to the effort are:  \n- ∞ The Telescope, including the Outer Barrel Assembly (OBA), the Forward Optic Assembly (FOA), and the Telescope Electronics\n- ∞ The Instrument Carrier\n- ∞ The Coronagraph Instrument (CGI) Optics Package and Fold Mirror Assembly (FMA)\n- ∞ The Wide-Field Instrument Cold Sensing Module and the Warm Electronics, including the Instrument Command and Data Handling Electronics (ICDH), Focal Plane Electronics (FPE) and the Mechanism Control Electronics (MCE)  \nAt delivery to Payload I&T, these assemblies will have already been fully qualified against the required environmental  tests,  will  have  been  verified  to  meet performance requirements and will have demonstrated  compliance  with  internal  optical  alignment  budgets.  \nFigure 3-46 shows the Payload I&T flow, includ-  \nFigure 3-45: Assemblies delivered to payload I&T.  \n<!-- image -->  \nFigure 3-46: Payload integration and test flow, including build-up of the payload and the key optical tests.  \n<!-- image -->  \ning the build-up of the Payload as well as the critical optical  tests  that  occur  between  Payload  elements. Prior  to  the  start  of  Payload  I&T,  instrument  surrogates are delivered to the Telescope development at the  Exelis  facility  to  enable  optical  interface  verification  and  measurement  of  Telescope  wavefront  error (WFE). The WFI team provides a high-fidelity optical verification  unit  (OVU);  the  CGI  team  provides  their flight  FMA  and  flight  Collimator  Sub-Bench, which is temporarily  separated  from  the  CGI  optics  package; and the Spacecraft team provides an IC Simulator.  \nWhile the WFI and CGI continue their flight developments,  the  build-up  of  the  Payload  starts  with the delivery of the Telescope and Telescope Electronics,  the  flight  IC  from  the  Spacecraft  team  and  the flight  CGI  FMA  to  the  Payload  team  in  the  Goddard Spacecraft  Systems  Development  and  Integration Facility (SSDIF). These assemblies are mechanically integrated  together  and  aligned.  After  thermal  closeouts  are  completed,  the  partial  Payload  assembly  is put in the Space Environment Simulator (SES) chamber to check out the optical test setup needed for the later Payload end-to-end (ETE) test.  \nPayload  integration  resumes  in  the  SSDIF  with successive deliveries of the flight CGI and flight WFI. Each instrument is mechanically and electrically integrated to the Payload. Final ambient operation is confirmed  with  functional  testing  of  the  electronics  and detector aliveness tests.  \nAfter  thermal  closeouts,  the  Payload  is  returned to the SES for Payload Optical ETE testing. This test consists of four optical test setups:  \n- ∞ Primary Mirror (PM) Center of Curvature (CoC) test to track PM sag due to gravity, the largest error source;\n- ∞ WFI Half Pass test to replicate Instrument-level results and track WFI alignment separately;\n- ∞ Payload ETE test to verify WFI+Telescope WFE under flight-like conditions; and\n- ∞ CGI ETE test to check Coronagraph alignment to Telescope and verify CGI+Telescope WFE at one wavelength.  \nFigure 3-47: Payload in the Space Environment Simulator chamber in the payload optical end to end test configuration. Thermal shrouds are not shown.  \n<!-- image -->  \nFigure 3-47 shows the green ray trace of the PM CoC test (converging above the auto-collimating flat) and  the  overlapping  red  ray  traces  of  the  WFI  halfpass and Payload ETE tests. The challenge of testing through gravity-induced aberration is solved by characterizing  mirror  sag  in  lower  assembly-level  tests and  by  using  focus-diverse  wavefront  sensing  with phase retrieval at the Payload level.  \nObservatory  I&T  begins  after  the  completion  of Payload Optical ETE testing when the integrated Payload assembly is delivered to the spacecraft and the two  are  mechanically  and  electrically  integrated  together. First motion tests of the solar array/sunshield and high gain antenna boom release mechanisms are performed  and  the  baseline  Comprehensive  Performance  Test  (CPT)  is  run  to  verify  full  Observatory electrical performance across all interfaces. The CPT is  performed  before  and  after  all  major  Observatory environmental  activities.  After  the  baseline  Observatory  performance is verified,  the  Observatory  is  subjected to a series of environmental tests to verify performance during and after exposure to the predicted launch  and  on-orbit  environments.  Electromagnetic Interference  and  Compatibility  testing  will  verify  that all Observatory functions are self compatible, i.e. they do  not  create  an  electromagnetic  interference  that disturbs  another  element.  The  Observatory  is  next subjected  to  vibration  and  acoustic  testing  to  verify structural integrity against the simulated launch envi-  \nronment.  A  launch  vehicle  interface  deployment  test is  also  performed  to  demonstrate  compatibility  with the  mechanical  shock  environment  produced  when the  Observatory  separates  from  the  launch  vehicle. Finally,  the  Observatory  moves  back  to  the  SES chamber for Observatory thermal balance and vacuum testing. The thermal balance test is performed to allow  correlation  of  the  thermal  models  for  final  onorbit temperature predictions while the thermal vacuum testing cycles the Observatory between its worstcase  temperature  extremes  to  verify  performance across the operational temperature range. After thermal testing, the Observatory is shipped to the launch site for final preparations prior to launch.', '3.8 Integrated Modeling/Mission Performance': 'Integrated  modeling  as  realized  on  WFIRST combines structural, thermal, optical, and control systems models to provide Observatory level optical performance  assessments  of  major  design  configurations.  These  assessments  are  typically  WFE  and/or LOS absolute/stability predictions at an interface defined  by  Science  (e.g.  WFI  and  CGI)  or  Spacecraft (e.g. star tracker platform) instrumentation teams.  \nThese  Observatory  IM-provided  input  datasets enable  detailed  science  performance  simulations  of key  WFIRST  science  surveys  (e.g.  coronagraphy, galaxy redshifts,  galaxy  shapes,  SNe luminosity, microlensing,  etc.)  to  be  performed,  determining  margins on key survey requirements (e.g. imaging mode PSF ellipticity  stability  for  WFI,  contrast  and  speckle noise  for  CGI)  that  when  combined  with  sky  model assumptions can be used to estimate science survey returns (see Figure 3-48).', '3.8.1 Integrated Modeling Inputs': "Structural, thermal, optical, controls, and systems leads  from  each  of  the  major  Observatory  Flight Segments (S/C, Telescope, WFI, and CGI) join with the  Study  Office  IM  discipline  and  analysis  leads  to form  the  Observatory  IM  team.  This  team  structure has  matured  dramatically  over  the  last  year,  and  is key to the high quality of the results being produced.  \nThe  major  tools  used  are  Thermal  Desktop v5.6+,  SINDA  v5.6+,  MSC/Nastran  v2008,  Zemax, SigFit, Code V, and the DOCS Toolbox. Linear Optical Models (LOMs) are generated internally by the IM team to the specifications of the Instrument teams to determine  WFE/LOS  sensitivities  to  both  rigid  body motions and figure changes of optical elements. The DOCS  Toolbox  is  used  to  assess  optical  defor-  \nFigure 3-48: The integrated modeling process assesses WFE and LOS stability at defined instrument interfaces to enable detailed science performance simulations for each science program.  \n<!-- image -->  \nmation/motion impacts using the LOM sensitivities. It is particularly valuable to have two independent optical  performance  assessment  techniques  available, SigFit and LOM/DOCS. They are used to cross-check each other's optical predicts, with SigFit also providing  high  spatial  frequency  information  useful  in  the evaluation of optical mount designs.  \nEach of the IM Flight Segment teams (S/C, Telescope,  CGI,  and  WFI)  provides  the  IM  team  with structural  and  thermal  models  meeting  the  Math Model  Guidelines  document  requirements.  These models are integrated by the IM team to form the Observatory  Structural/Thermal/Optical  (STOP)  and  Jitter models.  \nThe STOP model assesses the optical response of the Observatory to environmental changes that result in thermal/gravitational/moisture disturbances (e.g. gravity  release,  temperature  changes  from ground  to  orbit,  orbital/attitude-driven  temperature fluctuations, and long term moisture desorption), and includes  the  effects  of  both  rigid  body  motions  and figure changes of optical elements.  \nThe Jitter model is built in two steps. The Observatory Modal Structural Model is built first. It includes D-struts to isolate the Payload from S/C disturbances, includes  an  open  OBA  door  and  two  deployed  high gain antennas (HGAs), has passive vibration isolation for  the  reaction  wheel  assemblies  (RWAs),  and  predicts  modes  out  to  300  Hz.  Prior  to  the  final  modal analysis run, an on-orbit thermal profile is applied to the structural model to set grid point temperatures so that  temperature  dependent  material  properties  will reflect orbital conditions.  \nIn the second step, the modal results are used to construct  a  MatLab  Reduced  Dynamics  Response Model with 0.25% damping. Disturbance sources are applied  to  this  model,  and  the  rigid-body  motions  of the  optical  elements  (figure  distortions  at  high  frequencies  are  not  significant)  are  convolved  with  the LOM to estimate the resulting WFE/LOS instabilities.  \nAs a reference point,  the  Observatory  structural model element count is as high as the Global Precipitation  Measurement  (GPM)  Observatory  and  Solar Dynamics Observatory (SDO) structural models were  \nat  CDR.  Models  of  this  detail  are  needed  due  to WFIRST-AFTA's  large  mirrors  and  tight  WFE/LOS requirements, yet  they  are  agile  enough  to  allow  for reasonably short analysis cycles once the Observatory model is created (~100 STOP solutions from 3 orbit/attitude cases in 1+ weeks).  \nModeling Uncertainty Factors (MUF's) are multiplicative factors applied to the analysis results to account for model prediction uncertainties. A x2 factor is currently  applied  to  the  STOP  optical  element  grid point motion predictions, a value which will decline as models are test-correlated and when statistical models are run. For Jitter predictions, the MUF value increases  with  frequency  due  to  higher  modal  prediction uncertainties. For the current Observatory configuration, a MUF of x2.04 is used below 20 Hz, with this value  increasing  linearly  to  x4.13  at  40  Hz  and  remaining fixed at that value for higher frequencies. The values  used  reflect  the  use  of  some  disturbance models  that  have  been  validated  at  the  component level. Note that the Telescope model used in the current IM analysis has been modally correlated, but no credit has yet been taken for this in the Jitter MUF.  \nFor  STOP,  two  orbit/attitude  slew  cases  were analyzed. A WFI Worst Slew case (Beta = 11° orbit) where the Observatory was stable in a Hot Case attitude (pitched 36° away from the Sun and rolled about the LOS 15°, with Azimuth angle chosen to place the normal to the WFI Optical Bench radiator in the orbit plane), and then the Observatory was instantaneously slewed to a Cold Case attitude (pitched 36° towards the Sun, rolled 15° about the LOS, with Azimuth angle chosen to place the radiator normal 48° out of the orbit  plane).  This  is  an  extremely  demanding  case, selected  from  a  triaged  set  of  orbital  cases  from  an earlier but similar configuration primarily based on selecting  the  attitudes  that  produced  the  hottest  and coldest WFI optical bench temperatures.  \nA  Coronagraph  representative  'Day  in  the  Life' slew sequence designated 'OS3' was defined by the CGI team and is a series of 4 pointings (at a calibration star spectrally similar to the eventual target star, then at a bright star to quickly create a dark hole, then at the target star (which has a planet), and then back to the original calibration star). A Beta = 42° orbit was chosen,  with  the  time  of  year  selected  to  maximize the absorbed solar flux delta resulting from the modest pitch variations (~8°) associated with this pointing sequence.  \nAn additional thermal disturbance that is common to  both  slew cases is the initial cooldown from room  \ntemperature (293 K) to orbital temperatures. The first STOP solution time step of each slew case was arbitrarily used as the reference temperature at which the initial  commissioning  adjustments  of  the  Telescope Secondary  Mirror  (SM)  and  any  instrument-internal (i.e.  the  WFI  F2  fold-flat  mirror)  optical  alignment mechanisms are made. One SM setting is expected to  apply  to  all  four  WFIRST  Science  optical  paths, since it is intended to optimize Telescope focus, and this was confirmed in the current IM analyses with the CGI and WF Channel ideal SM refocus motions (for the same WFI worst slew case initial time step) differing  only  by  0.3  um  in  the  despace  (focus)  direction. During flight, these initial settings (both SM focus and any  instrument-internal  focus  settings)  will  be  made prior to the initiation of Science Operations, and modifications  are  only  expected  to  be  necessary  in  response to long term temperature or moisture desorption drifts.  \nPre-launch  alignment  offsets  designed  to  have the  Wide-Field  Channel  mirrors  cool  into  alignment after launch are considered in the IM simulation of the WFI commissioning process, but CGI and IFU optical paths  are  assumed  to  be  ideally  aligned  prior  to launch and do not yet take advantage of pre-launch offsets.  \nFor  Jitter,  RWA,  HGA,  and  WFI  cryocooler  disturbance  sources  are  all  independently  evaluated. Four  standard  (not  fine-balanced)  Honeywell  HR1475 wheels (LDCM heritage) are the basis for the RWA disturbances,  including  sub-super  harmonics  from  a Honeywell-supplied  bearing  model.  Four  HGA  stepper motors (SDO, GPM, and LDCM heritage) are the basis  for  the  HGA  pointing  disturbances.  The  HGA actuator  design  includes  microstepping  and  low  detent  features  to  reduce  disturbances,  and  passive HGA boom damping. A linearized model of actuator stiffness is included in the structural model.  \nThe  reverse  Brayton  Cycle  cryocooler  (design down-scaled from HST/NICMOS) disturbances are so low that they cannot be measured during normal operation  (pointing  jitter  due  to  the  cryocooler  was  not detected  during  HST/NICMOS  observations).  The power  spectral  density  disturbance  input  is  scaled from  vibrations  that  can  be  measured  during  initial cooldown, and a MUF of x10 is applied to these estimated  values.  To  be  conservative,  the  same  cryocooler disturbances are input at its compressor and both the Wide-Field and IFU Channel focal planes.", '3.8.2 Integrated Modeling Outputs': "ement grid point motions predicted at each time step.  \nThe integrated modeling process was first developed  and  run  for  the  wide-field  instrument  after  the 2013  WFIRST  SDT  report.  With  the  decision  to  include  the  coronagraph  as  a  baseline  instrument  on WFIRST-AFTA,  the  coronagraph  instrument's  structural, thermal, and optical models have been incorporated into this process. The integrated model results presented below focus on the wide-field instrument's critical imaging mode, but a full set of STOP and Jitter optical  stability  outputs  (WFE  and  LOS)  have  been generated  for  the  current  design  for  the  Wide-Field Imaging Mode (WIM), Wide-Field Spectroscopy Mode (WSM), IFU, and CGI optical paths, and are the basis for  the  Preliminary  Performance  Simulation  Results presented in §3.8.3.", 'STOP Optical Processing/Outputs for WFI 3.8.2.1 and CGI': "For WFI STOP, after an initial SigFit/LOM WFE cross-check for WIM and WSM using a 1 K bulk temperature  change,  the  WFI  Worst  Slew  case  (see §3.8.1) was run in both WIM and WSM configurations (WIM  with  a  filter  in  the  WF  Channel  beam  path, WSM with  the  grism  disperser  there,  and  with  CGI and  IFU  optical  paths  always  being  available).  The slew case was modeled for 32 time steps with 1 hour between each time step, covering 6 hours before the slew from the hot to the cold attitude, and 24 hours after, with the x2 MUF being applied to the optical el-  \nTelescope  SM  correction  (tip/tilt/focus  available, but only focus adjustment used) was applied to optimize WFE at the WF Channel WIM exit pupil, as previously discussed.  \nWF Channel F2 alignment correction (tip/tilt/focus all  used)  was  then  performed  considering  all  optical motions/deformations  along  the  WF  Channel  WIM optical path. The F2 focus adjust was an iterative procedure,  with  the  optical  motions  resulting  from  the cooldown from the ground alignment temperature of 293 K to the initially  analyzed  time  step  being  compensated, as planned, by ground alignment offsets to ensure  that  the  cooldown  optical  error  budget  was met  (this  eventually  required  that  82%  of  the cooldown  optical  element  rigid  body  motions  be  removed by the ground alignment offset, a reasonable value, with no figure compensation being required).  \nLOM  sensitivities  were  then  applied  to  optical grid  point  motions  at  each  time  step  to  estimate  the effects  on  WFE  and  LOS  stability.  These  WFE/LOS predictions were compared to specifications to assess preliminary  margins  (see  Table  3-14  for  the  WIM margins summary for STOP/Jitter).  \nThe  CGI  STOP  processing  sequence  was  very similar,  the  major  differences  being  the  use  of  the OS3 slew case (see §3.8.1) to define the analysis orbit/attitude  scenario,  the  use  of  the  WIM  T2  position (no  special  T2  adjustment  for  the  coronagraph)  and the fact that no pre-launch alignment offsets were in-  \nTable 3-14: Wide-field Imaging Mode integrated modeling results, with Modeling Uncertainty Factors included (x2 for STOP and x2-x4 for Jitter), show large STOP margins even for a demanding WFI worst case slew and good jitter margins for all major Observatory vibration sources. Note: 18 SCAs are included in the Wide-Field Channel STOP performance assessment; one central focal plane field point is used for the Wide-Field Channel Jitter assessment; HGA jitter responses are average values, with peaks to be assessed in the next design iteration.  \nluded. WFE (at the fast steering mirror) and LOS (at the first focus) were assessed following cooldown and at each of 42 output time steps (5000 seconds apart) that spanned the OS3 observing sequence. The LOM sensitivities were applied to the optical motions (and to the deformations of the PM and SM only) at each output time step to generate the WFE and LOS predicts as a function of time for delivery to the coronagraph team.  \nDetailed optical predicts based on cooldown and the above observing sequences have been generated for all optical paths and will be provided as inputs to all  WFIRST science survey teams to aid in their detailed Performance  Simulations.  Two  preliminary post-processing  assessments  based  on  the  current STOP optical predicts are included in §3.8.3, the first addressing  WIM  PSF  ellipticity  stability  during  the WFI Worst Slew case (critical to weak lensing's galaxy  shape  survey),  and  the  second  addressing  the contrast achieved by the coronagraph during the OS3 slew case (critical to its ability to detect planets).", 'Jitter Optical Processing/Outputs for WFI 3.8.2.2 and CGI': 'The Jitter processing is more simple than STOP processing as the disturbance sources are applied to the Observatory structure and the resulting rigid body optical  motions  (no  figure  changes)  are  directly  assessed using LOM optical sensitivities for each optical path. As previously noted, preliminary results/margins relative  to  the  WFIRST  2013  SDT  Report  Jitter  requirements  are  shown  for  the  WIM  configuration  in Table 3-14. Detailed Jitter optical predicts have been generated for all optical paths and will be provided as inputs to all WFIRST science survey teams to aid in their detailed performance simulations (current results have been provided to the coronagraph team).', 'Wide-Field  Science  Performance  Simula3.8.3.1 tions': 'A  key  performance  parameter  for  the  weak lensing shape measurement is the knowledge of the ellipticity  of  the  Point  Spread  Function  (PSF)  in  the presence of thermal drifts when the Wide-Field Channel is in its WIM configuration and making WL imaging observations. The PSF is fit with a Gaussian:  \n𝑊 𝑥 , 𝑦 = 𝐴 ! exp ! ! ! ! ! ! , 𝑥 = 𝑥 -𝑥 ! 𝑦 -𝑦 ! , 𝑀 ! ! = 𝑀 !! 𝑀 !" 𝑀 !" 𝑀 !!  \nand the ellipticities are calculated as:  \n𝑒 ! = 𝑀 !! -𝑀 !! / 𝑀 !! + 𝑀 !! 𝑒 ! = 2 𝑀 !" / 𝑀 !! + 𝑀 !!  \nThe April 2013 WFIRST SDT report established a PSF ellipticity knowledge requirement of better than 4.7  x  10 -4 .  Demonstrating  PSF  ellipticity  stability  at that level over a WL imaging observation would greatly facilitate meeting this requirement. Initial analysis of the WFE results indicates that even during the worst case  WFI  slew,  as  previously  described,  with  a  x2 MUF  applied,  order  of  magnitude  ellipticity  stability margins are predicted over the full WF Channel focal plane  (see  Figure  3-49).  Having  large  positive  margins  for  this  demanding  slew  case  is  extremely  encouraging,  as  it  suggests  that  we  can  design  the weak  lensing  observing  strategy  (perhaps  the  most demanding  WFI-based  survey)  without  needing  to make slew size a primary scheduling constraint.', 'Coronagraph Science Performance Simu3.8.3.2 lations': "For the coronagraph, contrast and speckle-noise sensitivities to temperature and vibration disturbances are key parameters. The IM team has developed stability  predictions  for  the  wavefront  error,  due  to  both types of disturbances as evaluated at the fast steering mirror  located  at  the  exit  pupil.  The  CGI  team  has generated  preliminary  science  performance  simulation predicts based on those predictions as described below. For science performance, different aspects of the  contrast  are  of  interest,  with  the  two  most  important parameters being:  \n- 1. The mean contrast 𝐶 over the dark hole (DH)\n- 2. The (spatial) standard deviation of the postprocessed image, 𝜎 !!  \nSince the coronagraph alone can't produce a sufficient dark hole due to the wavefront error induced by imperfections in  the  optics,  it  must  use  actively  controlled  deformable  mirrors  to  correct  the  wavefront errors to create the dark hole. The net contrast performance  of  the  WFIRST-AFTA  system  is  thus  dependent  on  both  the  coronagraph  optics  and  the wavefront  control  system,  and  it  must  be  predicted using end-to-end modeling that incorporates both.  \nAfter  science  yield,  the  most  important  operational  performance  requirement  is  the  efficiency  of reaching a dark hole. Dark hole acquisition is an iterative process that takes place while the instrument ob-  \n/  \nnm  \n-0.02  \n-0.04  \nWFIRST-AFTA 0  1  2  3  4  5  6  7  8  9  10111213141516171819202122232425262728293031  \nInitial State  \nFigure 3-49: Plot of delta ellipticity over a weak lensing observation with time steps of 3600 seconds after a slew at hour 7. Δ e1 ≤ 3.3 x 10 -5 / 184 sec provides 14.2x margin on 4.7 x 10 -4 and Δ e2 ≤ 4.1 x 10 -5 / 184 sec provides 11.5x margin on 4.7 x 10 -4 . The lines represent the center field point of each of the 18 detectors and a point for the FoV center.  \n<!-- image -->  \n<!-- image -->  \nInitial State  \nTime (Hours)  \nserves a bright star near the science star. The field at the focal plane is sensed, and a revised DM solution to  eliminate  the  remaining  light  in  the  dark  hole  is computed  and  commanded.  In  successive  iterations the light level drops and the time to estimate the field grows accordingly. The presence of incoherent light, such as from the zodi background, and detector noise can  further  lengthen  the  time  to  achieve  the  necessary signal-to-noise ratio (SNR).  \nThe  formation  of  speckles  in  the  dark  hole  is modeled by a diffraction model. The performance of each  WFIRST-AFTA  coronagraph  mode  is  derived from intensive numerical simulations of the combined telescope + coronagraph system. This involves calculating the propagation of a wavefront through the optics  and  accounting  for  diffraction  from  obscurations and  scattering  from  hypothetical  surface  fabrication errors. The freely and publicly-available PROPER optical  propagation  library  (Krist  2007)  is  used  for  this propagation.  PROPER  includes  routines  to  perform near and far field propagation, create complex apertures,  generate  low  and  high  order  synthetic  aberrations, and model a deformable mirror with measured actuator influence functions. PROPER is available for IDL (Interactive Data Language) and is being ported  \nto Matlab. The PROPER library has been verified for coronagraphic modeling in NASA Technology Demonstrations for Exoplanet Missions (TDEM) studies  (Krist  et  al.  2011,  2012a,  2012b)  and  validated against  results  from  the  High  Contrast  Imaging Testbed (HCIT) at JPL (Sidick et al. 2013). Some coronagraphs had particular components that could not be  well  represented  directly  with  PROPER  routines and  thus  required  custom  procedures  (e.g.,  high sampling  for  the  small  focal  plane  mask  used  by PIAACMC).  \nPROPER is used to model a realistically aberrated WFIRST-AFTA system, including deformable mirrors. By itself, PROPER only represents the output of the system and does not perform any wavefront control.  That  is  accomplished  by  using  custom  software that implemented the Electric Field Conjugation (EFC) wavefront control algorithm (Give'on et al. 2007). The aberrated wavefront for the system is computed using PROPER and then EFC is used to determine the deformable  mirror  settings  to  suppress  the  scattered light (this is an iterative process due to the nonlinear nature of the propagation). After the dark hole around the  star  is  created,  jitter  is  included  by  propagating multiple  small  telescope  pointing  offsets  through  the  \nmodel.  The  end-to-end  modeling  procedure  used  is the same as was used in the WFIRST-AFTA coronagraph  design  downselect  process  described  in  Krist (2014).  \nThe  full  performance  model  includes  the  STOP model that gives the wavefront errors at the pupil located  at  the  CGI  fast  steering  mirror  along  with  the PROPER model that starts at this point and predicts speckles in the coronagraph image plane. As of this report we have begun using this model to assess the coronagraph  performance  in  one  key  respect:  the stability  of  the  speckles  in  the  presence  of  thermal variations resulting from normal operations on orbit.  \nSTOP  modeling  of  a  realistic  observation  sequence was conducted to evaluate the wavefront stability  and its  effect  on  coronagraphic performance. A bright  star  ( β Ursae  Majoris)  was  imaged  over  6.1 hours and then the telescope was slewed to the science target, a star with known radial-velocity-detected exoplanets (47 Ursae Majoris), for 22.3 hours of exposures. To optimize the thermal stability of the Payload during the scenario, a set of modest thermal accommodations  (an  MLI  radiation  shield  to  block  the view of the IC to the MLI on the back of the Solar Array panels, MLI closure of the small gaps between the Solar  Array  panels,  and  fixed  temperatures  for  the bipods running from the IC to the Telescope and the S/C) were added to the thermal analysis. The wavefront variations at each 5000 second time step due to the structural and optical deformations caused by the thermal  changes  were  computed  and  input  to  the  \nPROPER coronagraph model to generate the corresponding dark hole images, with planets added to 47 UMa.  A  realistic  model  of  the  low-order  wavefront sensing and control system (LOWFS/C) was included to correct for wavefront variations.  \nAs shown in Figure 3-50, in the unprocessed image (left), only the brightest planet can be seen with any confidence against the background scattered light speckles. Subtracting the β UMa image from the 47 UMa one significantly reduces the speckles and clearly  reveals  the  three  simulated  planets  with  contrasts of  ~1x10 -9 .  This  level  of  speckle  suppression  is  only achievable  because  the  wavefront  remained  stable (to within tens of picometers) during the observations of both stars, thanks to the thermal stability of the system and the use of LOWFS/C. Based on the encouraging performance shown in the contrast predictions, the  next  design  iteration  will  incorporate  design  features  to  provide  a  more  thermally  stable  instrument carrier.", '3.8.4 Summary and Future Plans': "The  initial  IM  results  based  on  the  Observatory configuration described in this report indicate that the Observatory design is performing well and has positive margins relative to the WFI's WIM and WSM optical  requirements  as  currently  understood.  WFI  IFU channel WFE/LOS predicts have been completed and will  be  used  to  assess  its  preliminary  performance margins  and  to  refine  requirements.  The  detailed evaluation of contrast and speckle noise performance  \nFigure 3-50: Simulated coronagraphic images of 47 UMa using the Hybrid Lyot Coronagraph in broadband light ( λ = 523 - 578 nm). On the left is the unprocessed image (sum of all images of the star taken during the STOP model time series), expressed in terms of equivalent contrast relative to the star. On the right is the absolute difference between the 47 UMa and β UMa images in which the background speckles are largely subtracted to reveal planets (the planet contrasts and distances from the field center are indicated).  \n<!-- image -->  \nby the CGI team using the IM-supplied STOP and Jitter  data  will  continue,  with  the  results  presented  in §3.8.3.2 being a major step forward in substantiating the  feasibility  of  incorporating  a  coronagraph  on WFIRST-AFTA. These data results inform the understanding  of  current  margins  and  provide  insight  into future design trades.  \nThe current IM cycle has continued the maturation that has been seen in previous iterations. All four optical  paths  are  now  being  modeled.  Math  Model Guidelines have been established to ease the integration  of  the  S/C,  Telescope,  CGI,  and  WFI  structural and thermal models to form the Observatory IM model.  SigFit  and  LOM  optical  cross-checks  have  been implemented (both before and after the STOP runs). WFI cooldown offsets have been analyzed along with sequential  Telescope  and  WF  Channel  refocusing. HGA design, modeling and analysis has been greatly refined. An interface for delivering WFE and Jitter optical results to the CGI team has been developed and will provide an excellent frame of reference as we engage  with  other  science  survey  simulation  teams  to understand the optical data deliveries that will enable their  work.  There  has  not  been  space  in  this  short summary  to  address  the  ACS  pointing  control  work that  is  ongoing,  but  per  the  STOP  LOS  line  item  in Table 3-14  the  pointing  stability  margins  under  ACS control  are  substantial,  and  future  work  will  involve considering  possible  interfaces  to  the  fast  steering mirror function that is provided in the CGI.  \nAccurate, timely, team-oriented, and wellconfigured integrated modeling is essential to providing the optical performance feedback needed to support  both  trade  evaluations/closures  in  the  next  design  cycle,  as  well  as,  science  survey  simulations aimed at validating key requirements flowdowns. The progress made in the current IM iteration has been a big  step  towards  realizing  an  IM  process  that  responds to those challenges.", '3.9 Ground System': 'The  WFIRST-AFTA  Ground  System  comprises three  main  elements:  1)  the  facilities  used  for space/ground  communications  and  orbit  determination, 2) the Mission Operations Center (MOC) and 3) the  Science  Operations  Center  (SOC),  including  the facilities  for  science  observation  planning,  science and  instrument  operations,  and  ground  data  processing and archiving. For each element, existing facilities and infrastructure will be leveraged to provide the  maximum  possible  cost  savings  and  operational efficiencies.  The  functions  to  be  performed  by  the ground  system  and  the  associated  terminology  are shown in Figure 3-51.  \nTwo dedicated 18 m dual Ka and S-band antennas located in White Sands, NM are used for spacecraft tracking, commanding and data receipt. The antennas  are  separated  by  ~3  miles  to  minimize  the chance  of  weather  events  interrupting  the  downlink. The two ground stations are within the beam width of the  Ka-band  antenna  on  the  spacecraft  so  both  receive  the  downlinked  data  simultaneously.  Three  18 m  antenna  ground  stations  are  currently  in  use  at White Sands, one is dedicated to the Lunar Recon-', 'Mission$Opera2ons$': '- ¥ Spacecraft (S/C) and instrument health and safety monitoring\n- ¥ Real time and stored command load generation\n- ¥ Perform command uplink & telemetry downlink\n- ¥ S/C subsystem trending and analysis\n- ¥ Perform S/C simulations using vendor testbed\n- ¥ Support S/C FSW maintenance\n- ¥ Perform Level 0 Processing\n- ¥ Distribute Level 0 data\n- ¥ Archive Level 0 & engineering data\n- ¥ Mission Planning and Scheduling\n- ¥ Perform commissioning planning and execution\n- ¥ Generate orbital planning products & perform momentum management\n- ¥ Ground System monitoring\n- ¥ Anomaly Resolution & Safemode Recovery', 'Instrument$Opera2ons/Support$': '- ¥ Maintain instrument test beds\n- ¥ Support commissioning planning/execution\n- ¥ Perform instrument FSW maintenance\n- ¥ Perform instrument/telescope calibration\n- ¥ Generate instrument command loads\n- ¥ Perform instrument anomaly resolution', 'Science$Support$': '- ¥ Perform Science planning & scheduling\n- ¥ Support Mission Planning & Scheduling\n- ¥ Support commissioning planning/execution\n- ¥ Support Science Teams\n- ¥ Develop algorithms for data processing\n- ¥ Support instrument & telescope calibration\n- ¥ Support Participating Scientists (GOÕs)', 'Public$Outreach$': '- ¥ Perform public outreach activities for public and astronomical community  \nFigure 3-51: WFIRST Ground System functions and associated terminology.', 'Space/Ground$Communica2ons$ $&$Orbit$Determina2on$': '- ¥ S/C tracking & orbit determination\n- ¥ Command transmission\n- ¥ Data receipt', 'Data$Processing$Pipeline$': '- ¥ Develop and maintain pipeline architecture and standards !\n- ¥ Develop and maintain data processing pipeline\n- ¥ Ingest Level 0 data\n- ¥ Perform Level 1-3 data processing\n- ¥ Transfer Level 0-3 data  \n!', 'Data$Archive$': '- ¥ Ingest and archive level 0-3 data products\n- ¥ Ingest and archive higher level data products\n- ¥ Manage proprietary data periods\n- ¥ Provide data search and access tools\n- ¥ Interoperate with other archives !  \nnaissance  Orbiter  (LRO)  and  two  are  dedicated  to SDO.  The  two  SDO  antennas  may  be  available  for WFIRST-AFTA,  depending  on  how  long  beyond 2015,  the  end  of  the  baseline  5-year  mission,  SDO operates. The antenna dedicated to LRO is expected to be available for WFIRST-AFTA as LRO is currently in  its  extended  mission  phase.  The  WFIRST-AFTA development cost assumes that one new ground station will be built with one of the three existing ground stations available as the WFIRST backup. The White Sands ground stations interface with the MOC for all commanding and telemetry. Tracking data is sent to the GSFC Flight Dynamics Facility (FDF).  \nThe MOC performs spacecraft, telescope and instrument  health  &  safety  monitoring,  real-time  and stored  command  load  generation,  command  uplink and telemetry downlink, spacecraft subsystem trending & analysis, spacecraft anomaly  resolution, safemode  recovery,  level  0  data  processing,  and transmission  of  science  and  engineering  data  to  the science and instrument facilities. The MOC performs Mission-level Planning and Scheduling. With continuous downlink access, operations and communication scheduling  complexity  is  reduced  and  DSN  opera-  \n!', 'Science Center Activities': '<!-- image -->  \nShort-term Observatory Scheduling  \nand Planning  \nMonitor Science Program Execution  \nFigure 3-52: Proposed assignment of ground system tasks to Mission, Science, and Instrument Operations Centers and the Science Teams.  \n<!-- image -->  \ntions are eliminated.  \nThe SOC science and instrument divisions maintain  instrument test beds, perform instrument & telescope  calibrations,  assist  in  the  resolution  of  instrument  anomalies,  perform  instrument  flight  software maintenance,  and  generate  instrument  command loads.  \nThe SOC is also responsible for science planning &  scheduling,  supporting  mission  planning  activities carried out by the MOC, running the Guest Investigator (GI) and Guest Observer (GO) Programs, providing Science Team, GI, and GO support, and performing  public  outreach  activities  for  the  public  and  the astronomical  community.  Data  handling  responsibilities of the SOC involve ingesting Level 0 science and engineering data from the MOC and performing Level 1-3 data processing for the Science Teams and GO community  and  transmitting  these  calibrated  data  to the archive, which will hold all science and engineering  data  from  the  mission.  Data  search  and  access tools are provided to the science community that enable  efficient  searches  and  delivery  of  archival  data  \nthat  ensure  interoperability  with  NASA  data  archives and the Virtual Astronomical Observatory.  \nSeveral dedicated Science Teams will be funded over the prime phase of the mission to work with the WFIRST Project, Science Centers and broader astronomical  community  on  the  definition,  execution,  and analysis  of  the  primary  dark  energy,  exoplanet,  and NIR  survey  observing  programs.  In  this  period,  the GO/GI program provides funding for analysis of public data  and  for  pointed  observations  selected  competitively. Operations costs and grants for the GO/GI program in the primary mission are fully included in the lifecycle costs.  \nThe  proposed  assignment  of  ground  system tasks  to  the  Mission,  Science,  and  Instrument Operations  Centers  and  to  the  Science  Teams  are shown in Figure 3-52.', '3.10 Concept of Operations': "We  have  constructed  an  existence  proof  of  a possible WFIRST-AFTA observing sequence. This is only  an  existence  proof:  the  actual  observing schedule  will  be  determined  at  a  time  closer  to launch. Its purpose is to demonstrate that an observing  plan  meeting  WFIRST-AFTA  science  objectives  is  possible  with  the  reference  hardware and orbit.  \nFor  the  'existence  proof'  exercise,  the  following constraints were assumed:  \n- ∞ The total available observing time is 6 years, assuming  a  start  of  science  operations  on October 31, 2024.\n- ∞ The orbit is a circular geosynchronous orbit with a mean longitude of 105 ϒ W. It has initial  inclination  28.5 ϒ and  RAAN  228 ϒ .  Over the  course  of  the  mission,  Sun,  Moon,  and Earth asphericity perturbations cause the orbit to precess to inclination 26.4 ϒ and RAAN 187.6 ϒ . The initial inclination is driven by the latitude  of  the  launch  site,  and  the  initial RAAN is chosen to provide optimal geometry for the science programs.\n- ∞ The supernova program is carried out over a period of 2 years, with a 26% duty cycle. The SN  observations  require  0.53  years  of  live time  plus  0.10  years  of  overhead.  The  SN field  is  located  in  a  region  near  an  ecliptic pole so that there are no annual cutouts due to  Sun  avoidance  and  no  monthly  cutouts due to Moon avoidance, and must have E(B -V)<0.02. The notional field chosen is centered at b = -34°, l = 261°.\n- ∞ The microlensing program is carried out during six ~ 2.4 month 'seasons' when the Galactic bulge is in the field of regard. In order to  measure  the  stellar  microlensing  curve, we require observations over the full season, except  for  interruptions  of  ~5  days  each month when the Moon passes near the Galactic  bulge.  To  provide  a  time  baseline  for lens-source relative motion studies, 3 microlensing seasons are scheduled at the beginning of the mission and 3 are at the end.\n- ∞ The HLS program requires imaging in multiple filters as well as counter-dispersed spectroscopy  (dispersion  in  both  the  north  and south  directions).  With  prism  dispersion  in  \nonly  one  direction  relative  to  the  spacecraft and  a  constraint  to  point  the  solar  array/sunshield toward the Sun, counterdispersion  requires  two  visits  ~6  months apart (or N years + ~6 months), with the telescope pointed 'forward' in the Earth's orbit in one case and 'reverse' in the other. Other drivers on the HLS program are to: (i) reduce zodiacal background [all observations are at <2x the background at the ecliptic poles]; (ii) contain  the  HLS  within  the  LSST  footprint; and  (iii)  make  as  much  of  the  footprint  as possible visible from telescopes in both hemispheres.  Since  the  zodiacal  background  is highest  in  the  Ecliptic,  these  drivers  compete. For this exercise, we have prioritized (i) and (ii),  and  done  the  best  possible  on  (iii). Galactic  dust  columns  are  E(B -V)<0.02 (median)  and  E(B -V)<0.04  (95 th percentile) according to the Schlegel et al. (1998) map. Of the HLS footprint, 72% is north of declination 40 °S and 44% is north of 30 °S.  \n- ∞ The  coronagraph  program  is  assigned  1 year of total observation time, notionally broken into 26 blocks of 2 weeks each. These blocks are required to avoid the GEO eclipse seasons.\n- ∞ The GO program uses time not allocated to other  programs,  and  has  a  requirement  of ≥ 1.25  years.  All  celestial  objects  must  be accessible at some point during the GO period.  \nThe  time  not  allocated  to  strategic  programs  is 1.33  years.  All  programs  were  required  to  operate within the Sun angle constraints (line-of-sight to Sun angle  54-126°  and  roll  ±15°)  to  provide  adequate power  and  stray  light  control,  and  stray  light  constraints  were  enforced  for  both  the  Earth  and  the Moon.  The  existence  proof  observing  sequence  is shown in Figure 3-53.", 'High-Latitude Survey': "The high-latitude survey is performed in 4 filters (Y, J, H, and F184) and the grism. For each filter, a sequence of 3 or 4 images is acquired via small-step dithers  (roughly ¼ SCA  horizontally  and  vertically simultaneously) to cover chip gaps (see Figure 3-54). The observatory then slews 1 field height and repeats the pattern. A sequence of strips along the sky is ac-  \nFigure 3-53: The example WFIRST-AFTA observing sequence. Each vertical stripe denotes a 5-day period, and the 6-year mission proceeds from left to right. The microlensing seasons (magenta) and coronagraph blocks (gray) are indicated, as are eclipse seasons (white rectangles at top). The supernova survey (blue) uses portions of the telescope time for 2 years. High-latitude imaging (red) and spectroscopy (yellow) are interspersed.  \n<!-- image -->  \nuired in this way. A second pass over each field is acquired a half integer number of years later, to provide full sensitivity, Nyquist sampling (for J and redder bands), and to aid in the self-calibration solution. For calibration  purposes,  the  second  pass  is  rolled  relative to the first pass to provide repeat observations of stars at all pairs of positions on the focal plane. The repeat passes are distributed throughout the mission so  that  long-term  drifts  in  the  calibration  can  be tracked and removed. The grism mode uses a similar pattern,  except  that  4  passes  with  2  small-step  dithered positions each are performed, so that WFIRST obtains  grism  spectra  at  4  roll  angles.  Two  of  these are  scheduled  in  the  'leading'  geometry  relative  to Earth's orbit and two in the 'trailing' geometry, so that both  northward  and  southward  dispersion  directions are obtained. This improves the wavelength determination of emission lines, since the offset of the emission  line  centroid  relative  to  the  continuum  centroid (used as a reference in slitless spectroscopy) is suppressed as a source of systematic error.  \nThe HLS covers 2227 deg 2 (defined by at least 3 observations per filter, including the grism; the bounding box is 2279 deg 2 ) and uses 2.01 years (including overheads).  The  example  observing  sequence  is based  not  on  analytic  estimates  of  coverage  rates, but on actual analysis of individual pointings, includ-  \nFigure 3-54: Example of the sequence of observations for the high-latitude survey in H-band. The observatory first  performs  a  sequence  of  4  small-step  dithers  to cover the chip gaps (yellow). This pattern is repeated to  cover  the sky (red). A half-integer number of years later,  the  observatory  returns  to  perform  a  second pass over the  field  (blue)  at  a  general  angle.  The  second pass enables internal relative  calibration  via  repeat observations of stars at all pairs of positions on the  focal  plane,  as  well  as  monitoring  of  long-term drifts.  \n<!-- image -->  \ning the effects of field distortions on the tiling solution, the  slew  and  settle  times  to  the  next  field  (including slews  on  all  3  axes,  the  reaction  wheel  torque  and angular  momentum  allocations,  and  the  observatory moment of  inertia  tensor).  The  HLS  footprint  is  displayed in Figure 3-55. All HLS science forecasts assume that  3.3%  of  the  observations  are  lost  due  to miscellaneous factors and are not recovered.  \nThe  exposure  times  in  the  high-latitude  survey are 32 frames (173.5 s) or 64 frames (347.1 s) for the imaging and spectroscopy exposures, respectively.", 'Microlensing': "WFIRST  carries  out  its  microlensing  program during  72-day  'seasons'  when  the  Galactic  Bulge  is between 54 ϒ and 126 ϒ from the Sun (hence accessible  with  WFIRST).  Each  season  is  interrupted  only when  the  Moon  passes  near  the  Galactic  Bulge, which occurs for ~5 days each month in geosynchronous orbit. The 6 microlensing seasons have a total length of 0.98 years (1.18 years of Sun angle accessibility  for  6  seasons,  minus  a  total  of  0.20  years  of lunar interruptions). The microlensing footprint is displayed  in  Figure  3-55  and  in  more  detail  in  Figure 2-29.  \nThe initial RAAN of the orbit is chosen to place the  orbit  normal  within  48 ϒ of  the  Galactic  Bulge, thereby guaranteeing 24-hour coverage of the Bulge region with no daily Earth viewing cutouts. The orbit  \nremains  favorably  oriented  for  microlensing  for  12 years following launch, and is thus acceptable for the 6-year primary mission.  \nThe microlensing program observes 10 fields in the Galactic Bulge (although the final number and selection  are  still  being  optimized).  Most  observations are  carried  out  in  the  wide  (W149)  filter,  cycling through  each  field  in  sequence  with  52  s  observations.  Every  12  hours,  a  cycle  (one  observation  of each field) will be carried out with a bluer filter (Z087) and a longer exposure time (290 s) to provide color information  on  microlensed  sources.  Because  of  the layout of the detectors in the focal plane, ~85% of the survey footprint is observed for the full time while the remaining 15% is observed only in either the Spring or Fall seasons.", 'Supernovae': "The  time  allocated  to  the  supernova  search  in this 'existence proof' operations plan is a total of approximately six months. The plan is to run the supernova survey for a 2-year period, using a 30-hour visit every 5 days for a total of 146 visits. The strategy is to use the Wide-Field Imager in two filter bands to discover the supernovae and to use the IFU spectrometer to take spectra to identify and type the supernova candidates, to obtain points on the light curves, take a deep  spectrum  near  peak  brightness  for  redshift measurements and to measure detailed spectral fea-  \nFigure 3-55: The footprint observed during the WFIRST-AFTA DRM. The red area indicates the high-latitude survey. The magenta spot indicates the microlensing fields. The blue spots denote the proposed supernova survey fields.  \n<!-- image -->  \ntures, and to take galaxy reference spectra of the host galaxy after the supernovae have faded to a negligible level to allow galaxy background light subtraction from each light curve point.  \nSince the number of supernovae per square degree  increases  significantly  with  redshift  due  to  the volume effect,  the  plan  is  to  carry  out  the  survey  in three tiers, searching larger areas at lower redshifts, all near the ecliptic pole to minimize interference from the Sun and the Moon:  \n- ∞ Low z (z < 0.4) search 27.44 deg 2\n- ∞ Mid z (z < 0.8) search 8.96 deg 2\n- ∞ High z (z < 1.7) search 5.04 deg 2  \nWith an imager field 6 H4RG detectors wide and 3 detectors high, the 5.04 deg 2 search area would be 3  fields  wide  and  6  fields  high,  making  the  area  18 detectors  wide  and  18  detectors  high.  Similarly  the 8.96  deg 2 area  would  be  4  fields  wide  and  8  fields high for 24 by 24 detectors, and the 27.44 deg 2 area would be 7 fields wide and 14 fields high for 42 by 42 detectors. More elaborate cadences and tilings could be implemented with for example different cadences for  the  search  for  the  different  redshift  ranges.  The exposure times for the search are designed to be able to  be  sensitive  to  supernovae  12  days  before  peak brightness.  The  proposed  supernova  fields  are  displayed in Figure 3-55.  \nThe  spectroscopic  observations  in  this  plan  will be designed to observe one supernova at a time, using the IFU. The exposure time is tailored to achieve the desired S/N ratio on the individual target supernovae,  with  the  longest  exposure  times  used  for  the z~1.7 SNe.  \nEach 30-hour visit will on average be used as follows:  \n- ∞ Imaging for discovery 8 hours\n- ∞ Supernovae ID and typing 5 hours\n- ∞ Lightcurves 7 hours\n- ∞\n- Deep Spectra 7 hours\n- ∞\n- Galaxy Reference 3 hours  \nThere  are  some  subtleties  to  the  schedule  that will  be  worked  out  in  more  detail  when  the  final  observing program is selected. A supernova will have to be followed for about 35 rest frame days past discovery to obtain its light curve. Thus out of the 146 visits over  the  two  years  the  discovery  search  will  be  run  \nonly  for  the  first  132  visits,  leaving  the  last  70  days (depending on the redshift) for light curve follow up.  \nThe  galaxy  reference  spectrum  will  have  to  be taken  approximately  one  year  after  the  peak  brightness of the supernova to make sure that the supernova light  has  faded  to  a  negligible  level.  Thus  for  the first  year  of  the  survey  galaxy  reference  spectra  will not be taken, using only 27 hours per visit. During the second year galaxy reference spectra will be taken for the supernovae discovered during the first year, using all  30  hours  per  visit.  Time  for  the  galaxy  reference spectra  for  the  supernova  discovered  during  the  second year, roughly 3 hours every 5 days, will have to be  allocated  during  the  third  year,  using  the  time saved during the first year. This time does not have to be exactly 3 hours every 5 days but can be scheduled to minimize the impact on the third year program.  \nThe example observing plan includes overheads and the brief (~3 hr) cutouts each day when the supernova fields are near the Earth. It currently schedules  the  reference  spectra  with  the  5-day-cadence supernova visits, which is not realistic for supernovae observed in the second year; it is expected that incorporating this correctly will make the scheduling easier since reference spectra can be scheduled at times of lower demand by other programs.", 'Coronagraph': 'The  initial  observations  will  focus  on  discovery and  characterization  of  planets  near  the  target  star. When a previously known or unknown planet is detected, additional observations will be made for longer time  periods  with  full  spectral  resolution  for  planet characterization.  A  typical  scenario  for  characterization of a planet will unfold as follows. For a given target  star,  the  coronagraph  will  first  acquire  and  observe a relatively bright nearby star in order to generate the dark hole. If the bright stars are taken from the roughly 100 brightest stars in the sky, then on average  any  given  target  star  will  have  one  such  bright star  within  approximately  20  degrees  of  it.  Once  the dark hole is achieved, the telescope will slew to the science  target.  The  deformable  mirror  configuration will be held constant to that generated from the bright star.  The  target  stars  have  a  median  brightness  of /u1D449 ∼ 6 mag. Full  spectroscopic  characterization  of  the planet  will  take  place  sequentially  in  the  three,  18% wide  IFS  spectral  bands.  Finally,  the  telescope  will slew to a calibration star for speckle characterization. The calibration star is chosen to be spectrally compa-  \nble to the science target. The required observation time for this observational scenario depends strongly on the coronagraph performance parameters and the actual planet contrast. Analysis was carried out to estimate  the  observation  time.  A  10 -8 instrument  contrast  and  a  10 -9 planet  contrast  were  assumed.  The design has 10% overall throughput to the image plane and 6% throughput to the IFS detector (including reflection losses) in the entire annulus around the target star. Assumptions include the very low noise EMCCD detector.  \nFigure  3-56  shows  a  schematic  of  the  coronagraph observation scenario. In a representative scenario, the bright, target and calibration stars would be beta Ursa Major, 47 Ursa Major and 61 Ursa Major, respectively. The slew, thermal settling, and acquisition of each of the three stars requires roughly twelve hours.  The  dark  hole  generation  on  the  bright  star takes  place  within  6  hours.  Spectroscopy  covering 600-970 nm in 3 sequential 18% bands takes approximately 20 hours. The total time required to complete the entire representative scenario is two days.', 'Slew and Settle Operations': 'As a survey mission, the slew and settle time of the  observatory  is  a  key  performance  characteristic. We have allocated a maximum of 40 N . m/s  angular momentum for slews, with the remainder of the reaction  wheel  capacity  reserved  for  angular  momentum storage. This enables the most frequent steps (including all microlensing steps, as well as the small dithers and 1-field steps in the HLS) to be torque-limited.  \nSlew and settle performance has been estimated by  time-domain  simulation.  The  pointing  profile  was  \nFigure  3-57:  Settling  times  for  short  FoV  slews  (0.8 deg) are typically between 4 and 6 sec, with a few outliers up to 8.25 sec.  \n<!-- image -->  \nFigure 3-56: Scenario for a typical known planet characterization observation.  \n<!-- image -->  \ncomposed of  490  gap-filling  slews  (small  dithers)  of 0.025 deg in Y and Z, 84 short FoV (field steps) of 0.8 deg,  and  13  tile-sized  row  slews  of  5.5  deg.  This proof-of-concept profile differs from the latest survey profile described in earlier paragraphs, but does provide a representative sample of slew lengths to use in the coverage rate estimates quoted above.  \nThe  slews  followed  a  torque-limited  profile, shaped  at  the  ends  to  avoid  excitation  of  structural oscillatory  modes.  Assuming  the  mass  properties from an early observatory design iteration:  \n- ∞ Gap-filling  slews  require  11.25  sec  for  the slew, and <6.25 sec to settle.\n- ∞ Short  FoV  slews  require  50.25  sec  for  the slew,  and  <8.25  sec  to  settle  (see  Figure 3-57)\n- ∞ Row slews require 132 sec for the slew, and <13.0 sec to settle.  \nAll times have been re-scaled to the current moment of inertia tensor (plus margin) for the operations concept presented here.  \nOnce the observatory has settled, a full frame of the  H4RG-10s  (~5.5  s)  is  acquired  in  reset/read mode, then sampling begins for the next exposure.  \nOverall observation efficiency is most sensitive to slew/settle performance of the most numerous slews: the gap-filling slews (HLS) and short FoV slews (microlensing). As the design matures, efforts to achieve high  efficiency  will  focus  on  maintaining  the  level  of slew/settle  performance  presented  here,  and  in choosing efficient survey tiling strategies.', '3.11 Cost & Schedule': "interface demands on the observatory.  \nThe  WFIRST-AFTA  configuration  in  this  study report  builds  on  the  past  WFIRST configurations, as well as earlier JDEM mission design concepts. These encompass  the  JDEM-Omega  configuration  submitted  to  Astro2010,  through  the  WFIRST design reference  missions  developed  in  collaboration  with  the WFIRST  Science  Definition  Team  (November  2010 thru July 2012), and more recently with the WFIRST Science  Definition  Team  (October  2013  to  January 2015).  The  current  WFIRST-AFTA  design  reference mission incorporates the use of an existing 2.4-meter aperture  telescope  with  a  wide-field  infrared  instrument to meet the science objectives of the 2010 Decadal  Survey.  The  most  significant  improvement  of this payload combination over earlier smaller aperture WFIRST and JDEM designs, was the incorporation of considerably  finer  plate  scale  into  the  wide-field  instrument, opening up game-changing Guest Observer and Guest Investigator science opportunities, in addition  to  the  baseline  dark  energy  and  exoplanet  science prescribed in the Decadal Report  \nIn  addition,  a  coronagraph  has  been  added  to this  WFIRST  payload  baseline  as  a  technology demonstration  for  high  contrast  exoplanet  imaging. The  baselined  Occulting  Mask  Coronagraph  (OMC) incorporates  both  Shaped-Pupil  and  Hybrid  Lyot  occulting techniques into the coronagraph design. These techniques were selected for their technical maturity  and  due  to  the  fact  that  they  place  less  stringent  \nThe  development  phase  for  this  WFIRST-AFTA baseline  is  82  months,  from  preliminary  design through  launch  (phase  B/C/D).  This  development phase is preceded by a formulation phase (Phase A, nominally  12  months)  and  several  years  of  preformulation studies, many of which have already taken place. The observing phase (Phase E) of the mission is baselined and costed for six years. The development  schedule  is  shown  in  Figure  3-58.  Slightly over seven months of funded schedule reserve is included in the development.  \nThe WFIRST-AFTA design reference mission utilizes the 2.4-meter aperture telescope that was fabricated for another flight program, but subsequently not flown. The telescope optics and all of the supporting structure has been fabricated and integrated. The actuators  will  be  rebuilt  to  the  design  of  the  original hardware and the telescope control electronics design leverages existing electronics boards from Exelis' inventory of commercial flight hardware to bring the telescope  to  full  flight  configuration.  The  availability  of this  telescope  hardware  eliminates  this  critical  piece of the payload from getting on the mission critical path and simplifies  the  number  of  trades  that  need  to  be performed by establishing interfaces early. The early delivery of the telescope enables more extensive payload test opportunities (telescope + wide-field), including  the  certification  of  critical  payload-level  Ground Support  Equipment.  The  WFIRST-AFTA  wide-field", 'WFIRST Development Schedule': '<!-- image -->  \nFigure 3-58: The 82 month WFIRST-AFTA development schedule includes slightly over seven months of funded schedule reserve.  \ninstrument has incorporated some simplifications as a result  of  the  larger  aperture  2.4  m  telescope.  The wide-field  instrument  utilizes  two  optical  channels,  a simplification from earlier concepts. A single element wheel is accommodated by the use of a grism for the galaxy redshift survey. The wide-field focal plane has eighteen detectors, one-half the number of detectors of some earlier design reference missions. The widefield  instrument  incorporates  the  addition  of  an  Integral Field Unit; however, electrically this capability is essentially  a  nineteenth  detector  and  electronics channel.  The  optics  for  the  IFU  are  small  and  high TRL.  \nThe  build-up  and  integration  philosophy  of  the WFIRST-AFTA  observatory  is  based  on  the  wellestablished  practice  of  building  small  assemblies  of hardware, thoroughly testing them under appropriate flight  environments,  and  then  moving  on  to  the  next higher level of integration with those assemblies. The WFIRST-AFTA telescope and instrument will be developed and individually qualified to meet mission environments. The critical path of the mission is through the development of the wide-field instrument. The instrument is qualified prior to integration with the telescope.  Following  ambient  checkout,  the  entire  payload is tested at temperature and vacuum at GSFC to verify the end-to-end  optical performance.  The spacecraft is then integrated to the payload, and tested in ambient. Following a successful ambient checkout, a complete observatory environmental test phase is  performed. Upon successful completion of the observatory environmental test program, the observatory  is  readied  for  shipment  to  the  KSC,  where  the launch campaign is conducted.  \nThe  parallel  build-up  of  all  of  the  mission  elements  allows  substantial  integration  activity  to  occur simultaneously, increasing the likelihood of schedule success. The early delivery of the telescope will allow the  use  of  the  telescope  for  early  instrument  optical checkout including ground support equipment, allowing the retirement of integration risk even earlier in the program.  Because  all  of  the  major  elements  of  the observatory  (telescope,  instrument,  and  spacecraft) are  located  at  GSFC  over  2 ½ years  before  the planned launch, there is considerable flexibility in optimizing  the  schedule  to  compensate  for  variation  in flight element delivery dates, should workarounds be necessary. Over the 2 ½ year I&T period, the Project will have flexibility to reorder the I&T work flow to take advantage  of  earlier  deliveries  or  to  accommodate later  ones.  Should  instrument  or  telescope  schedule  \nchallenges  arise  there  are  options  to  mitigate  the schedule  impacts  by  reallocating  the  payload  level environmental  test  period.  Should  instrument  or spacecraft challenges arise, there are options to modify  the workflow and pull other tasks forward to minimize risk and maintain schedule. The payload design includes  access  to  the  instrument  volume  when  attached to the spacecraft, allowing late access to the instruments  during  observatory  I&T.  The  WFIRSTAFTA observatory I&T flow is very achievable, given the  planned  schedule  reserve  and  the  opportunities available for workaround.  \nFifty-five  months  are  allocated  to  complete  the wide-field instrument, from the start of preliminary design,  through  the  delivery  of  the  instrument,  not  including  funded  schedule  reserve.  The  coronagraph delivers two months before the wide-field instrument. The  overall 82-month  observatory development schedule includes slightly over seven months of funded schedule reserve, further increasing the likelihood of executing the plan.  \nEarly  interface  testing  between  the  observatory and  ground  system  is  performed  to  verify  performance and mitigate risks to launch readiness. Prior to payload  integration,  interface  testing  between  the spacecraft and the ground system is performed. Immediately following payload integration to the spacecraft,  end-to-end  tests  are  performed,  including  the payload elements. These tests are performed numerous times prior to launch to ensure compatibility of all interfaces  and  readiness  of  the  complete  mission team.  \nSeveral NIR survey mission concepts have been costed  by  the  Study  Office  over  the  past  six  years, and  many  of  these  have  been  validated  with  independent cost estimates requested by NASA HQ. These have tracked very closely, including the independent  cost  estimate  performed  as  part  of  the  Decadal Survey.  The  current  design  reference  mission  is uniquely different in  that  it  also  includes  the  coronagraph  technology  demonstration.  HQ  has  directed that  the  coronagraph  will  impose  no  driving  requirements on WFIRST, and during development the coronagraph  implementation  will  be  treated  as  a  technology  demonstration.  These  two  points  are  critical, as they ensure that the coronagraph will not jeopardize the mission critical path and put at risk the science mandated  by  the  Decadal  Survey.  However  it  does allow exoplanet high contrast imaging to take a huge leap forward in technological evolution with a modest additional budgetary investment, because of the fortu-  \nitous timing of the WFIRST survey mission, along with the maturation of the high contrast imaging technologies.  No  other  approach  offers  such  a  highly  leveraged advancement in aerospace coronagraphic technology advancement.  \nThe life cycle cost estimate for the current baseline (with coronagraph) is in process and is being developed using the same techniques (grassroots, parametric, and analogy) that have been applied to previous  cost  estimates.  Project  Management,  Systems Engineering,  Mission  Assurance,  and  Integration  & Test, are estimated using a grassroots approach and validated against analogous missions. Pre- and Postlaunch  Science  will  be  projected  based  on  the  expected size of the WFIRST Science Announcement of Opportunity  (AO).  This  estimate  will  include  support for the AO-selected science teams in the mission development phase as well as the 6 years of operations. Additional  funds  for  the  Guest  Observer  and  Guest Investigator Program are included in the Science estimate. The payload and spacecraft will be estimated primarily using parametric estimates, with the exception that the telescope estimates rely on historical estimates to cost the overall telescope effort. The parametric  estimates  will  be  constructed  using  master equipment lists (MELs) and historical cost databases and are adjusted for mass and complexity factors.  \nThe  WFIRST-AFTA  design  reference  mission has an implementation strategy that is low risk, proven and amenable to workarounds. The early delivery of the telescope due to its unique nature, allows for a payload and observatory I&T program that will have the ability to retire risk early and affords the flexibility to  adapt  to  changes  should  development  problems arise. The current WFIRST design reference mission is executable and delivers the #1 ranked science defined  in  New  Worlds  New  Horizons,  while  providing an unprecedented Guest Investigator/Guest Observer capability and an extraordinary opportunity in spacebased high contrast exoplanet imaging.', '4.1 Data Rights Considerations': "The clear trend in the astronomical community during  the  past  decade  has  been  a  move  away  from  sequestered access to telescope resources in the form of guaranteed time and proprietary data rights. For facilities that are primarily intended for guest observer use, this approach held sway for NASA's Great Observatories. Hubble, Spitzer, and Chandra, for example, all had a one year default proprietary period for their  General Observer  data.  However,  these  policies  were  not  applied  for  some  types  of  programs.  In  particular,  data sets  of  general  use  to  the  broad  community,  such  as the Hubble Deep Field, many Hubble Treasury projects, and Spitzer Legacy observations are released with no proprietary  period.  Large  programs  (e.g.,  Spitzer GO programs over 500 hours) often waived any proprietary period. During its extended mission, Spitzer projects for over  100  hours  had  a  zero  default  proprietary  period with an optional maximum of 90 days.  \nInterestingly,  an  inquiry  into  time-to-publication  for various proprietary period models revealed there is no strong correlation between proprietary data periods and promptness of publication. This would seem to indicate that the cessation of proprietary rights does not provide a  motivator  to  prompt  publishing.  Further,  the  willingness of teams to waive proprietary periods on large investigations  points  to  an  underlying  situation  wherein the value of a period of prior planning and preparation is more important than the value of a period of restricted data access.  \nMore  recently,  the  Fermi/LAT  instrument,  which provides a large area imaging capability for general astrophysics,  used  a  data  policy  with  a  one  year  postlaunch  proprietary  period  for  the  instrument  team,  but then  all  data  after  the  first  anniversary  are  available immediately upon processing. The quantitative question to ask is then what the post-launch proprietary period is for,  and  therefore  how  long  it  should  be.  This  can  be answered when considering whom the proprietary period serves.  \nThe WFIRST SDT subscribes to a broad open data / open skies policy, whereby all researchers across the world will have equal access to all data in the archive. As a general principle, this ensures maximal utilization of this publicly funded science mission. To quote from the New Worlds,  New  Horizons Decadal  Survey,  'the principle  of  open  skies  is  compatible  with  the  guiding principle of maximizing  future  scientific  progress' (NWNH,  p.85).  It  allows  for  competition  within  the  \ncommunity, which is a widely recognized means to ensuring the highest level of scientific merit. Open competition implies that pre-launch products such as science data simulations and analysis algorithms will be made available  to  the  community  to  enable  the  broadest reach of scientists to use the data from WFIRST for a wide range of science investigations.  \nFor WFIRST's major surveys (the HLS, supernova, and microlensing surveys), it is expected that Science Investigation Teams (SITs) will be funded to work with the WFIRST Project Office, Science Operations Center (SOC), and the broader astronomical community to develop  the  operational  planning,  science  simulations, and analysis software development (see § 3.1 0). These teams will be well prepared for analyzing survey data, and their algorithms and data products would be made public along with those provided by the WFIRST SOC.  \nGiven that the instrument/science teams have significant knowledge and experience with WFIRST by the end  of  in-orbit  checkout,  it  would  not  substantially  diminish their  competitive  advantage  to  allow  for  a  zero proprietary  period  for  all  WFIRST  data  in  the  archive. This is a policy consistent with that being implemented for LSST; the preface to the LSST Science Book states 'the LSST project will deliver fully calibrated survey data to … the public with no proprietary period' (p. 9). The time to enter data into the archive needs to be prompt in  order  to  facilitate  rapid  follow-up  observations,  but this  time  may  be  level-dependent.  NASA  categorizes the most basic data as Level 0: unprocessed instrument data, where only artifacts of communication have been removed. The first astronomically useful data are likely to be Level 1B: reconstructed, unprocessed instrument data  with  instrument  and  radiometric  calibrations  applied. The data manipulation required to ready data to this level is relatively modest, and is done with the bestavailable  calibrations  at  the  time  of  production.  This level  of  processing  and  release  is  appropriate  for WFIRST, enabling the SOC to produce transient alerts and to archive the raw images for the community to do near-real-time analysis. For the LSST, where transient alerts are also an important element of the science, the total time for this stage (i.e., from data storage to L1B availability) is 60 seconds ( LSST Science Book ,  2009, Section 2, p.39;  \nhttp://www.lsst.org/files/docs/sciencebook/SB\\_2.pdf).  \nFollowing  this  lead,  prompt  release  in  the  archive  of WFIRST L1B data products would maximize the output of time-domain astronomy from WFIRST, including the great  number  of  supernova  and  microlensing  events. Eventually, science data are processed to Level 3: im-  \naging  data  have  been  extensively  calibrated  and  coadded to provide deep images and/or spectra, and other science data products (often catalogs) are produced. It  is  reasonable for this greater effort to have a longer timeline  for  release.  Many of the high-level  data  products (e.g., basic source catalogs with source classifications)  could  and  should  be  released  to  the  public  on rapid timescales (3 months or less). A longer time period can be adopted for releases of specialized high-level survey products that require more intensive processing and meticulous analyses.  \nWFIRST  archival  data  are  of  substantial  value, both  to  provide  for  General  Investigator  (GI)  science and to enable competing teams to address the key science investigations of the mission. For example, a meritorious  external  team  wishing  to  conduct  microlensing investigations  using  the  WFIRST  data  should  be  supported to do so, even though there would be a competitively  selected  SIT  responsible  for  working  with  the WFIRST Project and SOC on the design and execution of a microlensing survey. This approach would yield the best  science  outcome  through  multiple  independent and  competing  groups  analyzing  the  same  data.  In  a no-proprietary-period  approach,  both  teams  should  be funded. The SDT does not support a policy wherein a single team selected early in the mission lifetime would be  forever  without  viable  competition  for  the  analysis and publication of results with the WFIRST data. To this end,  we  suggest  that  the  WFIRST  project  conduct  a competition roughly two years prior to launch that would select  teams  to  conduct  compelling  science  investigations  using  the  already-planned  WFIRST  survey  data. The  SDT  also  assumes  there  will  be  at  least  annual calls  for  Guest  Observer  (GO),  GI  and  Theory  proposals,  to  allow  responsiveness  to  the  latest  scientific developments and insights. This approach should provide a level of support and sufficient timescale to permit the selected teams to be in a position to conduct these investigations as soon as WFIRST data become available,  thereby  reducing  the  discrepancy  in  preparation between the initially-selected  WFIRST science investigation teams and the newer teams.", '4.2 Science Team Selection Considerations': "As no formal decision for the WFIRST acquisition strategy  has  been  made,  there  remains  the  possibility of a few different approaches to selecting the SITs. Key in these options is whether there is a hardware contribution related to instrumentation that is a portion of the SIT  selection.  Note  that  in  all  options  the  role  of  the WFIRST  SOC  will  need  to  be  factored  in  when  as-  \nsessing the optimal strategy. While the SITs have the goal  of  achieving  specific  science  outcomes,  the WFIRST SOC and Project have as top goals optimizing the  overall  scientific  productivity  of  the  mission  by  the entire astronomical community. We consider three options here as representative of the range of paths that could be explored.  \nIn  the  first  option,  a  NASA  Announcement  of  Opportunity (AO) is released to solicit proposals for providing  a  flight  instrument  along  with  scientists  including one or more members of the SIT. For WFIRST, the two instruments would thus result in two groups from which members would be drawn to comprise the SIT,  along with a number of Project Scientists, representatives of international participants, and others. Since WFIRST is a mission comprised predominantly of well-defined observations (e.g., Planck) rather than a general observer capability (e.g., Spitzer), the key focus of the two SITs would necessarily be on these high priority astronomical  observations.  To  combine  the  selection  of  the  instrument and its SIT would be to merge the instrumentbuilding  team  with  the  astronomical  observation  team. This approach would not permit making a selection independently on the instrument-building and astronomical observation experience and techniques of competing groups.  \nA second option to consider would solicit members for a Science Working Group (SWG) with relevant and broad experience to provide oversight and counsel on the direction and progress of the WFIRST development. Prior  to  launch,  a  separate  solicitation  would  result  in selecting a number of science investigations to produce the required WFIRST science outcomes defined by the Decadal Survey, including measurements of dark energy  and  dark  matter,  the  production  of  a  large  infrared survey  for  archival  purposes,  exoplanet  microlensing study,  and  the  demonstration  of  coronagraphy  for  observations of debris disks and exoplanets. The selected SWG would therefore resemble the present SDT, and would  have  no  hardware  deliverable  and  no  defined science investigations to conduct. This approach could provide a prompt initiation of the SWG, and because of its  advisory  nature  could  remain  dynamic,  with  members  assigned  for  a  term  and  being  replaced  by  new members throughout the duration. However, it does divorce  the  SWG  from  the  teams  who  must  eventually conduct the Decadal-prioritized science; this will result in  a  set  of  instrumentation  and  an  operational  design that was not optimized for the selected science investigations.  However,  this  approach  does  not  reflect  the role of the WFIRST SOC staff, who would already bring  \nextensive  experience  in  optimizing  science  from  the WFIRST mission.  \nA third approach would be a scenario where NASA acquires  the  instruments  separately  from  the  science investigations.  For  the  science  investigations,  multiple teams  would  be  selected  to  address  the  science  outcomes  listed  in  the  previous  paragraph.  These  SITs could  be  selected  by  NASA  Research  Announcement (NRA) rather than by AO, and could be selected both sooner  and  more  quickly  as  a  result.  The  individual SITs  would  be  tasked  with  conducting  the  Decadalprioritized  science,  and  would  be  responsible  for  addressing, in collaboration with the WFIRST Project and SOC, a significant amount of work during the course of WFIRST's mission lifecycle. Initially, during the formulation  period,  this  would  consist  primarily  of  science  requirements definition and flowdown, and could also involve early science observations using other facilities to promote the development of these requirements or other related future activities (cf. Appendix G). During mission  development,  each  SIT  would  be  responsible  for the production and dissemination of high fidelity science data simulations, which serve both to inform the broader community of the output of WFIRST and to provide the  WFIRST SOC with flight-like  data  products  to  run through the archive pipeline. The SITs would participate with the SOC in conducting data challenges to promote end-to-end evaluation of WFIRST operations and analysis. Nearing the time of WFIRST launch, the SIT activities  would  then  trend  toward  participation  in  detailed observation  planning  and  in-orbit  checkout  planning. During  the  initial  verification  and  checkout  period,  the SIT would work with the SOC to process the early data and to freshen the survey execution plans. Once formal survey operations begin, the SITs would each then be tasked with conducting the necessary analysis and calibration  to  realize  the  final  science  outcome  that  was their responsibility.  \nTo  form  the  mission  SWG,  each  SIT,  instrument team,  and  international  partner  would  contribute  one member in addition to the project team and SOC members. A number of interdisciplinary scientists would also be  appointed,  in  part  to  represent  the  interests  of  the broader  scientific  community, à  propos the  guest  observer program. This SWG, numbering in the neighborhood of 15 members, would then feature representation for  both  the  science  outcomes  and  the  instrument builds, but would not conflate the membership and selection  of  the  two.  It  would  provide  representation  for each  of  the  science  investigations,  for  the  instrument teams, for the broader community, and for international  \npartners.  \nIn this third option, the hardware deliverables of the instruments would be acquired via independent means, and  would  be  executed  accordingly.  There  would  be close connections between the SITs and the scientists and  engineers  working  on  the  instruments  and  at  the SOC:  at  first  through  requirements  definition,  then through data simulations, subsequently during integration  and  testing  analysis,  and  finally  through  on-orbit calibration.  In  this  fashion,  the  SITs  would  serve  as  a body of  instrument  scientists  for  the  hardware  without having been selected specifically for their knowledge of instrumentation; scientists with that expertise would be selected with the instrument build, and will also be contributed by the SOC.  \nOne  potential  disadvantage  with  the  above  approaches is that  SWG  membership tends to be either static, where individuals selected near the beginning of the mission lifecycle remain in their designated role until the end of the mission, or tends to be dynamic, where individuals who help to conceive of the mission design are  not  necessarily  those  who  eventually  execute  the mission  observations  and  analysis.  Both  of  these  extremes  have  obvious  undesirable  downsides.  To  mitigate this, the third option could employ a mix of strategies.  A  SIT  that  is  selected  near  the  beginning  of  the mission for, e.g., a five-year term would then be reconsidered halfway through mission development for either re-competition or continuation. The interdisciplinary scientist  positions  could  be  provided  a  shorter  term,  as their  deliverables  are  less  concrete,  and  can  be  competed multiple times over the mission lifecycle. This approach should permit a consistent infusion of new people  and  new  ideas  into  the  project,  while  some  of  the people  (in  particular,  the  instrument  teams)  would  be engaged for the longer term. Establishing an additional external  Advisory  or  Users  Committee  with  rotating membership might also be considered.  \nIn  all  three  of  the  scenarios  described  above,  the SITs would work in close collaboration with the SOC to execute  the  primary  science  components  of  the WFIRST  mission.  In  this  scenario,  the  SIT  members work with the WFIRST SOC to test and verify the performance  of  the  two  key  science  instruments  prior  to launch, although with some differences of responsibilities  depending  on  the  role  of  the  SIT  with  regards  to instrument  production.  After  launch,  the  SITs  and  the SOC work in partnership to ensure the surveys are executed efficiently and that a vibrant GO program is enabled as a key component of the WFIRST mission. The SITs  and  SOC  work  to  deliver  promptly  to  the  global  \nastronomical  community  a  broad  range  of  high-level science products to maximize WFIRST science and to ensure the instruments are performing at their peak capabilities.  The  SITs  would,  as  befits  their  charter,  be amply  funded  to  carry  out  the  advanced  analyses needed  to  extract  the  top-level  scientific  objectives  of the  primary  surveys.  The  SITs  would  have  the  advantage of significant funding and an intimate knowledge of the instrument performance, gleaned during  their  participation  in  the  preflight  integration  and testing  of  the  science  instruments,  that  will  ensure completion  of  the  necessary  science  outcomes.  However,  the  community  at  large  would  be  enabled,  and ideally well funded, to perform similar studies using the reduced data  in  the  public  archive  in  order  to  provide essential cross-checks of results and to foster new ideas  for  extracting  the  key  constraints  on  dark  energy, dark  matter,  and  the  properties  of  exoplanets.  This broad  participation  enabled  by  a  well  calibrated  and well  documented archive built by a collaborative effort of the SITs and SOC staff will ensure that the WFIRST mission is regarded by the entire astronomy community as a key asset for all of astrophysics and not an expensive  experiment  being  run  by  a  small  fraction  of  the community.  \nRegardless of which approach is eventually taken, the principle guiding the selection of the Science Working  Group  should be one in which scientists are competitively  selected  for  science  investigations.  The  SDT suggests that a rigorous tasking for these scientists will ensure  robust  involvement  of  these  scientists  and  will provide for a healthy and deep involvement in all phases  of  mission  development.  Their  tasks  would  include collaboration with the WFIRST Project and SOC on science requirements flowdown, preparatory observations, data simulation, operations planning, data analysis, and publication.  This  is  essentially  the  task  in  option  three above,  but  could  be  employed  with  more  or  less  emphasis in the other two options.  \nAs recommended in §4.1, the SDT envisions a data rights model where a near-zero proprietary period is invoked  for  all  WFIRST  observations  following  in-orbit checkout.  Scientists  associated  with  the  project  would be  provided  incentive  via  direct  support  for  their  programmatic  activities,  not  guaranteed  time.  In  keeping with this, there would be no reserved observations catalog  requiring  that  the  GO  program  avoid  observing  in any of the fields selected for the surveys. The SDT did consider models of proprietary access for SWG members, but found no justification that satisfied the rigor of maximizing science results; instead, the justification for  \nsuch proprietary access was typically to provide for incentives/rewards for the years of effort those individuals contribute to the success of the WFIRST mission.  \nGiven the above, the SWG and the SITs would be entirely  populated  by  members  with  significant  funded work necessary for the success of the WFIRST mission in all phases. Specifically, the statement of work would include collaboration with the WFIRST Project and SOC on:  \n- ·  Phase A/B: science requirements flowdown\n- ·  Phase C/D: simulated data flow; training sets; preparatory observations; algorithm preparation\n- ·  Phase D/E: operations planning; pipeline validation\n- ·  Phase E: data analysis; calibration/trending → science outcomes  \nA decision on the details underlying these broad tasks which are best performed at the project level, which are best performed by the SOC, which are best performed by the science teams, and what the interfaces are - will depend on the nature of the selection of the SITs and the  roles  of  the  WFIRST  Project  and  SOC.  The  SITs should be provided support, including funding for salary time for the PI and Co-Is, and additionally for such staff and  postdocs  as  are  necessary  to  conduct  detailed modeling  and  analyses.  The  funding  level  would  be modest early on, increasing pre-launch to a level sufficient  to  carry  out  the  major  science  investigations  incumbent upon WFIRST.", '5 PATH FORWARD': 'This report marks the completion of the 2014 SDT and Project Office work on the WFIRST-AFTA mission. NASA will use this material and ongoing costing studies of the mission to decide on the path toward further development.  There  are  a  number  of  activities  that  are important  for  future  science  teams  to  undertake.  The following tasks are recommended for study in the coming two years:', 'A. Optimization of the Reference Design': '- ∞ Study  possible  GO  and  GI  program  examples and how they fit in the observing program. The deep supernova fields, parallel coronagraph observations, and possible "deep drilling" GO programs  will  also  be  valuable  as  calibration  data sets.  Determine  quantitatively  which  science programs  and  calibrations  could  be  undertaken with the same data sets.\n- ∞ Optimize  the  filter  set  and  grism  bandpass across the WFIRST science program. The optimization may be a function of the telescope temperature  if  at  the  time  of  the  study  a  final  temperature  has  not  been  selected.  As  part  of  this optimization, there should be a call for community input.\n- ∞ Perform further  investigations  of  the  IFU  instrumentation (e.g.  a  data  cube  simulator)  and  science (GO program capabilities and use for calibration of redshift distributions).\n- ∞ Develop a more detailed operations concept for the supernova program, including the science return for alternate observing strategies.\n- ∞ Explore non-exoplanet science cases for the coronagraph and its associated instruments (AGN, high  spatial  resolution  visible  imaging,  evolved stars, etc.)\n- ∞ Perform analysis to improve predictions of microlensing  event  rates,  and  conduct  a  detailed  assessment of microlensing event parameter estimation (see Appendix K).\n- ∞ Continue to track the science impact of engineering  trades  (in  e.g.  momentum  management, communications,  detector  specifications...)  as the need arises.\n- ∞ Study the advantages and disadvantages of going  to  L2  (versus  the  inclined  geosynchronous orbit  baseline)  for  science  yield  and  the  cost,  \nrisk, and complexity of the mission (see Appendix C).', 'B. Systematic Error Control': '- ∞ Assess  the  relative  photometric  calibration  of the wide-field instrument. Determine via simulation  the  extent  to  which  HLS  observations enable  this  calibration  internally,  and  investigate the impact of color terms, nonlinearities, persistence, background/thermal  variations, and secular degradation (e.g. coatings) on the calibration solution. Also determine the extent to which the microlensing data and deep WFI imaging in parallel with the coronagraph could be  used  to  improve  or  cross-check  this  solution.\n- ∞ Characterize  anticipated  astrometric  performance of the wide-field channel. Estimate the extent  to  which  the  distortion  map  and  plate scale  can  be  measured  internally  to  WFIRST observations,  and  assess  the  impact  of  nonlinearities, time dependence of the optical parameters, chromatic terms, and small-scale irregularities on the astrometric performance of the HLS and on pointed GO observations.\n- ∞ Develop photometric and astrometric systematic  error  budgets  (e.g.  PSDs)  for  the  microlensing program. Connect these requirements to  the  output  of  the  integrated  modeling  and assess performance and margin.\n- ∞ Build  a  calibration  strategy  and  an  absolute calibration error budget, including covariances between  wavelengths,  for  the  IFU  and  compare  it  to  preliminary  supernova  program  requirements.  Study  the  ability  to  cross-check this  solution  for  the  IFU  against  observations with the wide-field instrument.\n- ∞ As  a  result  of  the  above  studies  determine what,  if  any,  hardware  modifications  are  required  to  meet  the  systematic  error  requirements  of  the  dark  energy  and  microlensing programs.\n- C. Synergies with Other Observatories\n- ∞ Survey the need for precursor observations for microlensing (see Appendix G), for low redshift supernovae, and for radial  velocity  studies  of exoplanet coronagraph targets.  \n- ∞ Study opportunities for joint  observations and requirements  for  joint  analyses  (including software requirements) with Euclid, LSST and other ground telescopes.\n- D. Coronagraph\n- ∞ Develop  a  more  detailed  coronagraph  DRM model, including: the most recent estimates of performance  and  exposure  times,  a  search strategy for finding new planets, statistical information about extrasolar planet populations, expected preparatory information from Doppler surveys, and post-processing capabilities.\n- ∞ Perform a deeper investigation of coronagraph polarization,  including  polarization  effects  of the telescope, science gains from polarization measurements,  and  relative  benefits  of  alternative polarization analyzer modules, and operational aspects.\n- ∞ Assist with development of a wavefront control algorithm technology development plan including  quantitative  milestones  on,  e.g.,  convergence rate vs. star brightness, joint estimation algorithms that continuously update wavefront solutions to distinguish planets from speckles.\n- ∞ Determine  pre-flight  and  in-flight  calibration requirements for the coronagraph.\n- ∞ Study  and  analyze  techniques  for  removing residual star light in coronagraph images and spectra in order to optimize sensitivity for detecting planets and circumstellar dust.\n- E. Policy Issues\n- ∞ Consider  various  topics  related  to  foreign  involvement  in  WFIRST  through  discussions with foreign members of the SDT.', '6 CONCLUSION': "The  WFIRST-AFTA  mission  is  highly  compelling and is found in the current study to be feasible and affordable.  It  will  revolutionize  our  understanding  of  the expansion  of  the  universe,  the  birth  and  evolution  of galaxies, and the formation and atmospheric composition of exoplanets. It has significantly enhanced performance compared to previous configurations and compared to the Astro2010 requirements, as concluded by the 2014 NRC review panel. The larger mirror gives finer imaging and improved sensitivity making the mission more powerful and more complementary to LSST and Euclid.  In  addition,  JWST  will  greatly  benefit  from WFIRST's discovery of interesting objects in the widefield  survey.  The  coronagraph  enables  rich  scientific return at much lower cost than a dedicated smaller coronagraphic telescope mission, enabling the first images and spectra of exoplanets like those in our solar system and of dust disks around nearby stars. The future conceptual design work described in §5 will further refine  the  observatory  and  its  performance,  enabling  a faster and lower-risk development.", 'Appendix A Impact of Telescope Temperature': "In  order  to  reduce  risk,  the  WFIRST-AFTA  SDT has baselined a telescope operating temperature of 282 K, within the currently qualified range of the telescope. This section considers the impact of the 282 K baseline, relative to the 270 K operating temperature in the 2013 SDT  report.  Attention  is  focused  on  the  wide-field  instrument because the coronagraph operates out to only 1 ∝ m and hence is not sensitive to the telescope thermal background.  \nAn assessment of the wide-field channel sensitivity was carried out using the following assumptions:  \n- ∞ Telescope  temperatures  of  270  K  and  282  K  are assessed. The telescope was qualified to operate down to 277K.\n- ∞ The  standard  detector  read  noise  model  is  used: one sample every 5.423 s (100 kHz readout, using 32 channels of the H4RG-10 device, including the interlaced guide window). Read noise is assumed to  be  at  the  requirement  level  of  20  e -per  CDS, with a correlated noise floor of 5 e -RMS. The super-Poisson variance in sample-up-the-ramp mode (1.2x in the limit of many samples) is included. Detector  dark  current  (excluding  telescope  and  instrument thermal backgrounds allocated separately) is 0.015 e -/pix/s.\n- ∞ The equivalent emissivity per surface of the primary  and  secondary  mirrors  is  0.025.  This  includes the  emissivity  of  the  protected  silver  coating (0.017), a 2% contamination allowance distributed evenly among the optical surfaces, and 30% additional margin.\n- ∞ For  thermal  calculations  +2  K  was  applied  to  the telescope temperature, e.g. the '282 K' is actually evaluated at 284 K. This factor is intended to account for several miscellaneous effects that will increase  the  thermal  backgrounds  in  WFIRST  beyond the formal thermal emission in a rectangular filter. For example, a Δλ / λ = 0.05 width trapezoidshaped cutoff is equivalent to an increase in temperature  of  +0.65  K,  and  a  variation  of σ T  =  1  K RMS results in  an  effective  emission  temperature increase of +0.037 K relative to the mean temperature of the mirror due to the nonlinearity of the intensity-temperature  relation  for  an  emissive  surface.\n- ∞ Because WFIRST-AFTA uses 2.5 ∝ m cutoff detectors, a warm telescope creates an additional thermal background due to filter red-leak (or imperfect  \n- out-of-band  rejection:  a  small  fraction  of  the  telescope  thermal  radiation  near  2.5 ∝ m  penetrates the  filter).  An  out-of-band  transmission  of ≤ 0.01% for all filters is assumed.\n- ∞ In  the  F184  filter,  microlensing-wide  filter,  and grism modes, a full pupil mask is included. A pupil mask was not included for the H band in the 270 K baseline, but is included at 282 K. In the other filters, the emissivity from the secondary mirror support tubes and central baffle are included.\n- ∞ Zodiacal backgrounds are taken to be 1.40x, 1.60x, and 1.76x the annual mean at the ecliptic poles for the grism, Y/J/H filters, and F184 filter respectively. (For the grism, this is the mean sky brightness in the  HLS;  for  the  filters,  this  is  the  75 th percentile sky brightness, as described in the main report.)\n- ∞ Field dependence of the filter bandpass is not yet included.  It  will  result  in  higher  telescope  thermal emission in the center of the field of view and lower thermal emission near the edges. This variation in thermal background is estimated to be 20% peakto-valley.\n- ∞ The  coronagraph  has  an  internal  operating  temperature  of  290  K,  warmer  than  the  telescope. Thus it emits thermal radiation that can reflect off the secondary mirror and enter the WFI. In the H, F184,  and  W149  filters  it  is  blocked  by  the  pupil mask. In the bluer filters with no pupil mask, some of this radiation can in principle reach the WFI detectors  due  to  nonzero  out-of-band filter  transmission, but this is negligible compared to the thermal emission  from  the  telescope  central  baffle  (the small  solid  angle  of  the  coronagraph  more  than compensates  for  the  higher  surface  brightness  at 290  K  vs.  282  K).  Thus  the  coronagraph  thermal emission was not included.", 'A.1. HLS Spectroscopic Survey': 'The 2013 baseline grism survey wavelength range was 1.35-1.95 ∝ m (270 K). Given the increased thermal backgrounds at 282 K, the wavelength range has been  reduced  to  1.35-1.89 ∝ m.  At  270  K  and λ max=1.95 ∝ m, the thermal background was estimated at 0.17 e -/pix/s (versus 0.49 e -/pix/s for the sky), whereas at 282 K and λ max=1.89 ∝ m the backgrounds include 0.27 e -/pix/s (thermal) and 0.45 e -/pix/s (sky).  \nThe yield of H α detections at 7 σ in the HLS spectroscopic survey is 7344 gal/deg 2 at 282 K, versus 8363 gal/deg 2 at  270  K.  Figure  A-1  shows  the  redshift  \nFigure A-1: The redshift distribution of the spectroscopic H α galaxy sample at 270 K and at 282 K. Note the cutoff at z=1.88 due to the reduced wavelength range at 282 K.  \n<!-- image -->  \ndistribution  of  the  spectroscopic  H α galaxy  sample  at 270K and 282K.', 'A.2. HLS Imaging Survey': 'The impact of the 282 K baseline temperature on the sensitivity of the HLS imaging survey is described in Table  A-1.  Both  depths  (point  source  sensitivity)  and WL galaxy yields are shown. Overall the penalties as-  \nTable  A-1:  Properties  of  the  HLS  imaging  survey  and their dependence on telescope temperature. The penalties  for  the  282  K  telescope  temperature  for  imaging depth  and  WL  galaxy  yield  are  shown  in  the  last  two rows. Calculations in this table are at the nominal number  of exposures; HLS forecasts in the main text take into  account the full distribution of the number of exposures.  \nsociated with 282 K operation are mild: in H band we lose 0.07 mag of depth and 6% of the source galaxies. The F184 band (the reddest) suffers the greatest degradation,  but  the  loss  of  depth  is  still  only  0.28  mag, with an 18% reduction in the number of WL galaxies.  \nExtended  source  sensitivity  is  worse  than  point source  sensitivity  by  the  amount  shown  in  Table  A-1 (for an exponential profile source with a half light radius of  0.3  arcsec).  This  factor  is  independent  of  the  telescope temperature.  \nThe loss of only 0.28 mag of depth in F184 when going from 270 K to 282 K may seem counterintuitive since the telescope thermal emission (which is brighter than the zodiacal emission) increases by a factor of 3x. It  is  therefore instructive to review the intermediate results  of  the  exposure  time  calculator  (ETC)  to  understand why only a modest degradation is predicted. The most important contributions to the noise budget in the HLS are sky (zodiacal) background, thermal emission, and read noise. In a 32 frame exposure (173.5 s), the zodiacal background is 65 e -/pix,  compared to thermal emission of 66 e -/pix (270 K) or 207 e -/pix (282 K). The read noise for 32 frames is 10 e -RMS (variance of 100 sq.  e -/pix),  dominated  by  the  CDS  noise.  These  numbers  alone  would  predict  a  degradation  of  a  factor  of 372/231 in variance when going from 270 K to 282 K, or 0.26  mag  in  depth.  The  more  complete  calculation  in the  ETC  finds  a  degradation  of  0.28  mag.  Note  that even at 282 K, thermal emission contributes only 58% of the total noise budget.', 'A.3. Deeper Imaging Modes': 'Many  GO  programs  will  require  deeper  imaging than is planned for the HLS, and consequently the impact of telescope temperature is greater for these observations. This impact is shown in Figure A-2 for the H and F184 filters (the two most strongly impacted). The time penalty in F184 for the warmer telescope is 1.5x at 26 mag AB (0.2 mag deeper than the HLS), 2.0x at 27 mag AB, and 2.1x at 28 mag AB. Even at 28 mag AB depth, the time penalty in the bluer bands is small: 11% in H and 6% in J.', 'A.4. Microlensing': 'The  microlensing  survey  uses  primarily  the  wide filter (W149), which due to the cutoff at 2 ∝ m admits a significant  thermal  background.  However, since microlensing observations are performed close to the ecliptic, the sky background is also higher. At the midpoint of a microlensing season, the zodiacal count rate is 3.28 e -/pix/s, in comparison to the thermal emission count rate  \nFigure A-2: The exposure time required to reach a given depth in the H and F184 filters. The zodiacal brightness is taken  to  be  that  at  median  conditions  (30 ϒ ecliptic  latitude and at quadrature). The total time is split into 5 dithered sub-exposures; depths beyond 28.5 mag AB would likely be split into more sub-exposures due to the cosmic ray rate in GEO.  \n<!-- image -->  \nof  1.21  e -/pix/s  (at  282  K)  or  0.39  e -/pix/s  (at  270  K). The thermal rate, while significant, is not dominant even at  the  higher  temperature.  The  distribution  of  starlight count rates is shown in Figure A-3, and it is seen that starlight  is  dominant  over  zodiacal  and  thermal  emission in almost all pixels. The median starlight count rate is 12.06 e -/pix/s, which corresponds to a 2.6% degradation of the Poisson error bar in going from 270 K to 282 K.  The  degradation  due  to  the  higher  thermal  background is worse for fainter pixels, e.g. at the 10 th percentile  brightness  the  degradation  worsens  to  5.0%, and at the 1 st percentile brightness it worsens to 6.6%. Given  this  very  minor  degradation  in  the  photometric uncertainties in the microlensing fields, the higher operating  temperature  will  have  negligible  impact  on  the WFIRST-AFTA microlensing program.', 'A.5. Integral Field Channel': 'The  integral  field  channel  produces  independent spectra  for  each  segment  of  the  image  slicer  at  the spectrograph entrance. The telescope thermal emission is therefore dispersed, and will increase the background only  in  the  last  few  pixels  of  each  spectrum.  This  will not  have  a  significant  impact  on  the  supernova  program.  \nFigure  A-3:  The  simulated  distribution  of  count  rates from starlight + zodiacal background in the microlensing fields.  Colors  indicate  fields  at  different  Galactic  latitudes; the yellow curve is the mean over all fields simulated.  \n<!-- image -->  \n<!-- image -->  \nAppendix B Scientific Synergies between WFIRST-AFTA and JWST', 'http://wfirst.gsfc.nasa.gov/': 'WFIRST observations will be synergistic with other major astronomical facilities planned for the next decade. The WFIRST science program has many unique aspects that will enhance the science return from upcoming space missions including JWST and Euclid, wide imaging and spectroscopic surveys being undertaken by Subaru, and ambitious upcoming ground based facilities including LSST and multiple 30 meter telescopes. In this appendix, we include a  few  of  the  science  opportunities  enabled  by  such  synergistic  observations.  These ideas  were  submitted  to  the WFIRST SDT by members of the astronomical community.  \nJason Rhodes (JPL), Jason Kalirai (STScI), Eric Gawiser (Rutgers) jason.d.rhodes@jpl.nasa.gov', 'Science Investigations:': '- 1. Studies of the earliest galaxies (Dan Coe and Larry Bradley)\n- § Large solid angle survey with WFIRST-AFTA to discover the most luminous sources at 10<z<20 using the Lyman break drop-out technique that is used by HST to discover z>11 galaxies.\n- § JWST NIRSPEC and MIRI detailed spectroscopy enabled by the discovery with WFIRST-AFTA of sufficiently bright sources yields clues to ionization, metal growth, and possibly masses of these infant galaxies.\n- 2. Finding the first stars via high-z pair instability supernovae (Massimo Stiavelli)\n- § Discovery of PISN from zero metallicity first generation stars at z>10 to explore the first generation of stars, their initial mass function, and the initial enrichment of the ISM.\n- § PISN have 1-2 year timescales and would be observable with WFIRST-AFTA to z~15-20. Their expected source density of 1-2 per square degree requires WFIRST-AFTA for discovery and JWST to determine the properties of their host galaxies. Working in the infrared, WFIRST-AFTA will (post-SWIFT), have an unparalleled capability to discover rare z>6 sources (e.g. GRBs and supernovae) due to the ultraviolet opacity of the IGM prior to reionization.\n- 3. Probing dark matter via lensed QSOs (Tommaso Treu)\n- § Measurement of dark matter sub-halos down to 10 6 MSun will test CDM versus self-interacting or warm dark matter models.\n- § WFIRST-AFTA has the unique capability to discovery 1000s of quad lensed QSOs in a large solid angle sky survey which requires HST resolution. JWST/MIRI is then required to measure flux ratios of the lensed sources at mid infrared wavelengths to avoid stellar microlensing.\n- 4. Progenitors of supernovae and other highly variable objects (Knox Long)\n- § Within 50 Mpc, where significant resolution is possible to identify individual stars or their environments, we expect 50 core collapse SN and 15 SN1a per year.\n- § JWST follow-up of these nearby supernovae will be significantly enhanced if pre-detonation images permit the identification of the type of progenitor star. WFIRST-AFTA surveys at HST resolution over a broad range of wavelengths provide pre-detonation images of nearby galaxies.  \n- 5. Globular clusters in nearby galaxies (Paul Goudfrooij)\n- § Massive star clusters trace early star formation history and galaxy assembly.\n- § Wide Field, high resolution and sensitive NIR photometry is required to select samples outside the local group. JWST/NIRSPEC MOS spectroscopy is required to obtain metallicities to derive star formation timescales.\n- 6. AGB stars and dust production in the local volume (Martha Boyer & Karl Gordon)\n- § AGB stars are major producers of dust, especially carbon, in the ISM. Understanding both the mechanisms of dust production and its implications for the infrared properties of galaxies requires improved understanding of this short lived phase of stellar evolution.\n- § Wide field near infrared observations with WFIRST-AFTA will establish a sample of AGB stars suitable for detailed follow-up with spectroscopy and longer wavelength observations using JWST.\n- 7. Galactic streams in nearby galaxies (Harry Ferguson)\n- § Tidal streams from the merging of dwarf galaxies into nearby large galaxies provide clues to the assembly history of these galaxies and a key test of CDM models.\n- § WFIRST-AFTA has the unique capability to discover and map streams surrounding ~100 massive galaxies within 5 Mpc. JWST will then provide the deepest imaging and infrared spectroscopy to yield constraints on the ages, kinematics, and chemical abundances of the streams via observations of individual stars.\n- 8. Simultaneous observations of exoplanets with WFIRST-AFTA and JWST (Marshall Perrin)\n- § The inclusion of a white light coronagraphic instrument with an integral field spectrometer on WFIRST-AFTA opens the possibility of simultaneous observations with the JWST coronagraphs to achieve broader spectral coverage.\n- § Studies of exoplanet atmospheres, indications of weather and seasonal variations, and (with the inclusion of a polarimeter capability within the WFIRST-AFTA coronagraph), detailed measurements of scattered light from circumstellar dust in exoplanetary systems will be possible.\n- 9. Resolved Studies of Galaxy Formation (Jason Kalirai)\n- § Measuring the surface brightness, abundance gradient, velocity dispersion, star formation history, and substructure in the halos of nearby Milky Way type galaxies provides a view into their formation history, and an input to test models of galaxy formation.\n- § Observations with WFIRST-AFTA will reveal starcount maps for nearby galaxies, and can be used to locate a pristine population of halo stars. Follow up observations with JWST can be used to directly measure turnoff ages and ground based 30-meter telescopes to measure stellar velocities.', '1. Studies of the earliest galaxies (Dan Coe and Larry Bradley)': "The first galaxies likely formed ~ 100 - 400 Myr after the Big Bang (z ~ 11 - 30) contributing to reionization and the end of the 'dark ages', a process likely complete by ~ 900 Myr (z ~ 6). The nature of these early galaxies and the degree to which they contributed to reionization are the current frontier outstanding questions of extragalactic astronomy. The Hubble and Spitzer Space Telescopes have yielded candidates with robust photometric redshifts as distant as z ~ 10.8 or 420 Myr (Coe13) and perhaps z ~ 11.9 (Ellis13, though the authors urge caution due to the singleband detection). The former is gravitationally lensed into multiple images, the brightest magnified by a factor of ~8 to AB mag 25.9, enabling more detailed follow-up study. Significant samples of high-redshift candidates have been discovered back to ~600 Myr after the Big Bang (~100 candidates at z ~ 8: Bradley12, Oesch12, Ellis13). Deep Hubble imaging has yielded the fainter, more numerous population, while wider, shallower Hubble surveys as well as very wide field (~square degree) ground-based surveys have discovered the rarer relatively brighter galaxies. No survey has yet achieved the area, depth, and wavelength coverage required to yield significant numbers of z > 9 galaxies within the universe's first 500 Myr.  \nThe  wide  and  deep  near-IR  survey made  possible  by  NRO  WFIRSTAFTA will transform our understanding  of  the  early  universe  by  yielding ~100,000 high-redshift (7.5 < z < 15) candidates bright enough (AB mag < 26) for follow-up study, that could allow  for  detailed  stellar  population studies,  metallicities,  and  kinematics with  the  James  Webb  Space  Telescope  and  large  ground-based  telescopes.  The  figure  at  right  shows  a range of  expectations  for  cumulative (in  redshift)  numbers  of  high-redshift galaxies  in  a  2,000  square  degree survey.  This  is  based  on  current measurements  at  z  ~  8  (Bradley12) extrapolated  to  higher  redshifts  both optimistically and pessimistically  \n<!-- image -->  \nbased on constraints from the handful of ~8 current z > 9 candidates (Bouwens11, Zheng12, Coe13, Bouwens13, Ellis13, Oesch13). Contributions from gravitationally lensed galaxies are estimated by roughly assuming one strongly lensing cluster per square degree and adopting an average lens model from the CLASH multi-cycle treasury program (Postman12). Most ten-sigma detections (green) will be properly identified, but pushing down to five-sigma detections will result in >50% incompleteness relative to the numbers shown in gray. Key questions to be addressed by these observations are: (1) how rapidly did early galaxies build up; (2) what was their contribution to reionization; (3) were early galaxies primarily composed of pristine Population III stars?", '2. Finding the first stars via high-z pair instability supernovae (PISN) (Massimo Stiavelli)': "A central goal of the JWST mission is the observation of the first stars and galaxies. Actually observing a single population III star may be possible when it dies as a pair-instability supernova. Such supernovae are very luminous but also very rare. WFIRST-AFTA provides the most viable means of discovering such objects as this requires deep large area near infrared surveys with high angular resolution and good photometric precision over long timescales. JWST would then provide detail studies of both the SN and its host galaxy.  \nPresent day star formation mechanisms rely upon gas cooling via metals and dust to condense gas into stars. As these heavy elements originated in the first generation of stars (Population III) stars, those stars are expected to have formed via different and very uncertain mechanisms which likely resulted in a relatively higher proportion of very high mass stars. Such stars can end their lives as Pair Instability SuperNovae (PISN) with extremely high luminosities that visibly brighten their host galaxies. At z>10, time dilation will make these SN visible for periods of several years requiring long term (but infrequent) monitoring with deep images to discover PISN.  \nPISN have been discussed by Weinmann and Lilly 2005 (ApJ, 624, 526). They find SN rates in the range 0.2-4 sq deg per year at redshift 15-25. These rates are in some sense even an upper limit for the following reasons: (1) recent studies have found even lower masses for Pop III stars largely due to some evidence for fragmentation. If the mass function extends down to few tens of solar masses and at the same time the upper mass cutoff goes down to 300 MSun or even much lower, the range of masses giving rise to PISN shrinks and they become even rarer. (2) The full impact of negative feedback (especially radiative but also chemical, i.e., if there is enrichment you don't form Pop IIIs) have been underestimated until the last 5 years or so (e.g. Trenti and Stiavelli 2009, ApJ, 694, 879). There is a lot of uncertainty on Pop III from H2 and even higher uncertainty on those from atomic H. While 2 PISN per sq deg per year is a moderately optimistic but not unreasonable rate if fragmentation is rare, it would be hard to sustain that rate with the amount of fragmentation that some are finding now.", '3. Probing dark matter via lensed QSOs (Tommaso Treu)': "Measuring the mass function of subhalos down to small masses (e.g. 1x10 6 MSun) is a unique test of cold dark matter and of the nature of dark matter in particular. The CDM mass function is supposed to be a power law rising as M -1.9 until Earth-like masses. A generic feature of self interacting dark matter and warm dark matter is to introduce a lower mass cutoff. Current limits set that cutoff at somewhere below 1x10 9 MSun. We know from MW problems that there is a shortage of luminous satellites at those masses, but that's never going to be conclusive because subhalos can only be detected with traditional methods if they host stars.  \nOne powerful way to detect subhalos independent of their stellar content is via the study of large samples of strong gravitational lenses, in particular the so-called flux ratio anomalies (see Treu 2010, ARA&A, 48, 87 and references therein). Small masses located in projection near the four images of quadruply-lensed quasars cause a strong distortion of the magnification and therefore alter the flux ratio. However, anomalous flux ratio can also be caused by stellar microlensing if the source is too small. The only way to avoid microlensing is to go to wavelengths such as mid-IR where  the  lensed  quasar  emission  is  sufficiently  extended.  Large  sample  of  thousands  of  lenses  are  needed  to achieve sensitivity down to 1x10 6 -1x10 7 solar masses required to probe the nature of dark matter. Unfortunately, at the moment only 3 dozen quads are known, and only a handful of those are bright enough at mid-IR to be observable from the ground (e.g., Chiba et al. 2005, ApJ, 627, 53). JWST-MIRI is so powerful that it will be able to observe any quad discovered in the next decade with integration times of order seconds to minutes. However, JWST will be limited for this application by the number of known quads. Ground based surveys before JWST launches will probably discover of order 100 quads, still short of the number require to fully realize its potential as a dark matter experiment.  \nDiscovering thousands of quads will require a close to full sky survey at HST-like resolution (Oguri & Marshall, 2010, MNRAS, 405, 2709), i.e. WFIRST-AFTA. The ability to resolve and therefore discover quads is a very strong function of resolution and therefore WFIRST-AFTA will be unmatched in its ability to find them. Of course if WFIRST-AFTA comes after JWST, those will not be available for mid-IR follow-up at JWST resolution.", '4. The progenitors of SNe and other highly variable objects (Knox Long)': "JWST will carry out detailed studies of SNe in nearby galaxies, particularly since its IR capability will allow it to probe the late phases of a SN explosion to determine the nature and distribution of the ejecta and to understand the conditions in SNe that lead to dust creation (see, e.g. Barlow 2009). However, a crucial aspect of understanding SNe is to connect a SN explosion to its progenitor star. The combination of WFIRST-AFTA and JWST are crucial to rapid progress in this area.  \nThe importance of high quality imagery for the advancement of this subject has been made clear with HST. Indeed, some HST imagery exists for about 25% of the SNe (and luminous blue variable outburst) exploding in galaxies within  28 Mpc (Smart et al 2009). (Over about a decade, 50% of the SNe actually occurred in galaxies that were observed with HST, half occurred outside HST's small FOV) HST images have resulted in the identification of at least 4 progenitors, including discovery of the binary progenitor for SN1993J (Maund et al 2004) and enabled studies of the local stellar  populations in the remainder. As a result, we know that the most common type of core collapse SNe (type II-p) arise from red supergiants and that the minimum and maximum masses for these SNe is about 8 Msol and 17 Msol (Smart et al. 2009).  \nBut WFIRST-AFTA, with its large FOV, will do much better. For example, it would be quite straightforward to create a uniform treasure archive of nearby galaxies at distances within, say 50 Mpc, that extended out well beyond the D25 contours. About 50 core collapse SNe and about 15 Ia SNe are expected in this volume every year. It would also be possible with a little effort to survey larger galaxies, up to and including M31 and M33. Not only would this enable some of the science associated with the PHAT multi-cycle treasury program of M31 (which an allocation of 830 orbits with HST covers only a portion of the galaxy), but it would also ensure that when the next SN goes off in one of these galaxies, that pre-exposure images would be able to identify the progenitor down to (depending on crowding) a mass of about 3.5 MSun (Dalcanton 2012). One could also imagine shallower surveys to map the entirety of the SMC or LMC down to considerably lower mass limits.  \nFurthermore, the needs for pre-explosion images are not just limited to the progenitors of SNe, but includes a wider range  of  other  objects:  the  Eta  Car-like  explosions  of  luminous  blue  variables,  supernova  imposters,  such  as SN2008S and optical transients such as those seen in M85 and NGC300. All of these objects are likely candidates for JWST observations. JWST would be used not only for spectroscopic observations during the explosion that would characterize the SNR, but, if the WFIRST-AFTA mission were complete, would carry out the NIR imagery after the SN had faded to find out which object had been disrupted as a result of the SN explosion.  \nReferences: (1) Barlow, M. J. 2009, Prospects for Studies of Stellar Evolution and Stellar Death in the JWST Era, in Astrophysics in the Next Decade, Astrophysics and Space Science Proceedings. ISBN 978-1-4020-9456-9. Springer Netherlands, 2009, p. 247  \n- 5. Near-field cosmology and galaxy evolution using globular clusters in nearby galaxies (Paul Goudfrooij)  \nThe increasing realization that the study of star clusters has direct relevance for the basic processes involved in how galaxies assemble and evolve over time has placed this field at the forefront of extragalactic research in recent years. A fundamental, yet unresolved, question in the formation of early-type galaxies is the assembly and chemical enrichment histories of their 'halo' and 'bulge' components which are represented by the metal-poor and metal-rich GC subpopulations,  respectively.  Working  together,  WFIRST-AFTA  and  JWST  can  make  unprecedented  progress  in solving this question.  \n- a) Globular Clusters as Fossil Records of the Formation History of Galaxies  \nStar formation plays a central role in the evolution of galaxies and of the Universe as a whole. Studies of star-forming regions in the local universe have shown that star formation typically occurs in a clustered fashion. Building a coherent picture of how star clusters form and evolve is therefore critical to our overall understanding of the star formation process. Most star clusters disrupt within a few Gyr after they form, building up the field star population in the process. However, the most massive and dense star clusters remain bound and survive for a Hubble time. These globular  clusters  (GCs)  constitute  luminous  compact  sources  that  can  be  observed  out  to  distances  of  several  tens  of megaparsecs. Furthermore, star clusters represent the best known approximations of a 'simple stellar population', i.e., a coeval population of stars with a single metallicity, whereas the field stars in galaxies typically constitute a mixture  of  populations.  Thus,  studies  of  GC  systems  can  constrain  the distribution of  stellar  ages  and  metallicities whereas measurements of the integrated light of galaxies can only provide luminosity-weighted averages of these key quantities. Consequently, GCs represent invaluable probes of the star formation rate and chemical enrichment occurring during the main star formation epochs within their host galaxy's assembly history (see, e.g., review of Brodie & Strader 2006).  \nThe study of extragalactic GCs was revolutionized by the Hubble Space Telescope (HST). The main reason for this is that the size of GCs is well-matched to diffraction-limited optical imaging with a 2-m class telescope: a typical GC half-light radius of ~3 pc at a distance of 15 Mpc corresponds to 0.05 arcsec on the sky, which is roughly the diffraction  limit  (and  detector  pixel  size)  for  HST  at  600  nm.  This  yields  very  high  quality  photometry  of  GCs  relative  to ground-based imaging by beating down the high galaxy surface brightness in the central regions of galaxies. Furthermore, it also allows robust measurements of globular cluster radii, and hence of their dynamical status.  \nNotwithstanding the important progress that HST imaging has facilitated in this field, there is one critical property of GC systems that HST imaging cannot address well. GC systems around massive nearby early-type galaxies extend far into the galaxy halos, covering several tens of arcminutes on the sky (e.g., Goudfrooij et al. 2001; Zepf 2005), while the FOV of HST images is only 3.3 × 3.3 arcmin 2 . This is illustrated in Figure 1. Obviously, wide fields of view (> 20' per axis) are required to accurately determine total properties of GC systems (e.g., total numbers of clusters per unit galaxy luminosity, color or metallicity distributions, trends with galactocentric distance). Furthermore, the faint outer halos of galaxies are thought to hold unique clues regarding the early assembly history of galaxies, and bright GCs constitute one of the very few probes that can be studied at high S/N in these environments.  \nFigure 1: R-band KPNO 4-m/MOSAIC image of the giant elliptical galaxy NGC 4472 in the Virgo cluster of galaxies, covering a 36' × 36' FOV. Footprints of available HST/ACS and HST/WFPC2 images are drawn in red and blue, respectively. Globular cluster candidates from Rhode & Zepf (2001) are indicated as green dots. Note the small fraction of globular cluster candidates covered by HST images, implying the need for large and uncertain extrapolations when trying to extend conclusions from the HST studies to the full systems of globular clusters. Figure taken from Zepf (2005).  \n<!-- image -->  \nAppendix B: Scientific Synergies between WFIRST-AFTA and JWST  \nb) New Constraints on the History of Star Formation and Chemical Enrichment of Early-Type Galaxies  \nA key discovery of HST studies of GC systems of luminous galaxies was that their optical color distributions are typically bimodal (e.g., Kundu & Whitmore 2001; Peng et al. 2006). Figure 2 shows an example. Follow-up spectroscopy of bright GCs using 10-m-class telescopes indicated that both ''blue'' and ''red'' populations are typically old (age > 8 Gyr), implying that the color bimodality is mainly due to differences in metallicity (e.g., Puzia et al. 2005). In broad terms, the metal-rich GC population features colors, metallicities, radial distributions, and kinematics that are consistent with those of the spheroidal ('bulge') component of early-type galaxies. In contrast, the metal-poor GC population has a much more radially extended distribution, and is likely physically associated with metal-poor stellar halos such as those found around the Milky Way and M31 (e.g., Bassino et al. 2006; Goudfrooij et al. 2007; Peng et al. 2008).  \nFigure 2: g -z color distribution of globular clusters in the massive elliptical galaxy M87 from Peng et al. (2006). Note the obvious color bimodality, which has been confirmed to be mainly due to differences in metallicity, and which is common among massive earlytype galaxies in the local universe.  \n<!-- image -->  \nThe bimodality in optical colors of GCs constitutes one of the clearest signs that star formation in luminous early-type galaxies must have been episodic. However, we emphasize that the optical color distributions do not significantly constrain when these events occurred, or in what order. This is because optical colors alone cannot generally distinguish  between  different  combinations  of  age  and  metallicity  (the  ''age-metallicity  degeneracy'').  A  general  understanding of the age and metallicity distributions of GC systems requires braking this degeneracy. There are two primary and complementary ways to do this.  \n(1) The combination of optical and near-IR photometry .  The main power of this method (using color-color diagrams) is the ability to identify age differences (of order 25% for high-quality data), due to the fact that near-IR colors are primarily sensitive to metallicity while optical colors (e.g., r-z ) are sensitive to both age and metallicity. This approach resulted in the identification of substantial populations of intermediate-age metal-rich GCs in the inner regions of several early-type galaxies (Goudfrooij et al. 2001; Puzia et al. 2002; Hempel et al. 2007; Georgiev et al. 2012). The current limitation of this method is twofold. While HST has a powerful near-IR channel in its WFC3 instrument, its use is limited to the innermost regions of  nearby  galaxies  due  to  its  relatively  small  footprint  of  2' × 2'  (cf.  Fig.  1 above). The NIRCam instrument to be installed on the 6.5-m James Webb Space Telescope (JWST) will reach 2 mag fainter than HST in a given integration time, but its footprint is similarly small. Conversely, while near-IR imaging instruments with reasonably large fields of view are starting to become available on large ground-based telescopes (e.g., 7.5' × 7.5' for HAWK-I on the VLT), contamination of GC candidate samples by compact background galaxies is a major concern for ground-based spatial resolution (see, e.g., Rhode & Zepf 2001). As demonstrated by HST, imaging at 0.1 arcsec resolution effectively eliminates this concern due to the marginally resolved nature of GCs (cf. Section 1). Thus, the study of galaxy formation and evolution by means of accurate GC photometry will benefit tremendously from space-based wide-field imaging in the 0.6 - 2 μ m range. A relatively simple multi-chip Optical-NIR camera installed on one of the two 2.4-m NRO telescopes would be ideal for this (and many other) purpose(s). Their fast (f/1.2) primary mirror could easily yield a useful field of view of hundreds of square arcminutes per exposure at a resolution of 0.1 arcsec, providing accurate photometry of virtually all GCs associated with nearby galaxies with very little contamination. Such an instrument would not only place crucial constraints on the assembly history of massive  \nearly-type galaxies, it would also allow the selection of the best targets for follow-up multi-object spectroscopy to infer their chemical enrichment history (see below).  \n(2) Follow -up Space-Based Multi-Object Spectroscopy . The main strength of this technique lies in the presence of intrinsically strong absorption lines of several key elements in the 0.7 - 2.5 µ m region (e.g., O, Mg, Al, Si, Ca, Fe), which facilitates accurate determinations of overall metallicities and element abundance ratios that can be used to infer typical timescales of star formation (e.g., Valenti et al. 2011). Currently, this technique is only available from the ground and is therefore significantly hampered by the high surface brightness of the diffuse light of the inner regions of the host galaxies. In practice, this limits the application of this technique currently to the outer regions of galaxies. This has caused a general lack of crucial spectroscopic information for the metal-rich GCs, which are located mainly in the inner regions. While future developments in the area of adaptive optics systems on large telescopes will enable high spatial resolution imaging and spectroscopy from the ground, they will do so only over a small (< 1') FOV which is not useful for spectroscopy of extragalactic GCs. This science can however be expected to advance dramatically with the advent of NIRSpec on the JWST with its multi-slit array and high-efficiency medium-resolution gratings.", 'References': 'Betoule et al. 2014: arXiv:1401.4064  \nBildsten et al. 2007: ApJ, 662, L95  \nChiba et al. 2005: ApJ, 627, 53  \nCollett et al. 2013: MNRAS 432, 679  \nCunha et al. 2012: MNRAS 423, 909  \nDas, Errard, & Spergel 2013: arXiv:1311.2338  \nDe Putter, Takada, Dore 2013: arXiv:1308.6070  \nFerguson et al. white paper:  \nhttps://www.lsstcorp.org/sites/default/files/WP/Ferguson-galaxies-02.pdf  \nGavazzi et al. 2008:ApJ, 677, 1046  \nGawiser et al. white paper:  \nhttps://www.lsstcorp.org/sites/default/files/WP/Gawiser-ultradeep-extragalactic-01.pdf  \nGehrels et al. 2014, arXiv:1411.0313  \nGreene et al. 2013: ApJ 776, 64  \nIvezic et al. 2014: arXiv:0805.2366  \nJoachimi & Schneider 2010: A&A, 517, A4  \nJoyce, Jain, Khoury & Trodden 2014: arXiv:1407.0059  \nKasliwal & Nissanke 2014: ApJ 789 L5  \nKulkarni 2005: astro-ph/0510256  \nLaureijs et al. 2011: arXiv:1110.3193  \nLi & Paczynski 1998: ApJ, 507, L59  \nNewman 2008: ApJ, 684, 88  \nNewman et al. 2013: 1309.5384  \nNierenberg et al. 2014: MNRAS, 442, 2434  \nOguri & Marshall 2010: MNRAS, 405, 2579  \nRefsdal 1964: MNRAS 128, 307  \nRossi et al. 2007: arXiv:0711.4096  \nSuyu et al. 2014: ApJ 788, L35  \nReyes et al. 2008: I MNRAS, 390, 1157  \nTreu 2010: ARA&A, 48, 87-125  \nWeinberg et at 2013: Phys. Reports, 05, 001', '6. AGB stars and dust production in the local volume (Martha Boyer & Karl Gordon)': "When low- to intermediate-mass stars (0.8 < M < 8 MSun) begin to ascend the asymptotic giant branch (AGB), pulsations levitate material from the stellar surface and provide density enhancements and shocks, encouraging dust formation and re-processing (e.g., Bowen 1998; van Loon et al. 2008). This dust is subsequently released to the interstellar medium via a strong stellar wind driven mainly by radiation pressure on the grains. The composition of the dust depends on the atmospheric chemistry (the abundance of carbon relative to oxygen) which is altered by dredging up newly formed carbon to the surface of the star (the 3rd dredge-up; Iben & Renzini 1983). The efficiency of the 3rd dredge up (which depends on the stellar mass) and the initial metallicity of the star determine whether or not a star will ultimately become a carbon star, with metal-poor stars becoming carbon-rich more easily owing to a lack of oxygen available to tie up the newly dredged-up carbon into CO molecules.  \nWhile all stars between 0.8 and 8 solar masses will pass through the AGB phase, the phase itself is short, making AGB stars rare. Despite this, they may be among the most important contributors of dust in galaxies. The most significant known dust producers are AGB stars and supernovae (SNe) and it is unclear which dominate the dust production in the Universe since the dust-production rate from SNe is highly uncertain. However, even if assuming the most generous estimates for SNe dust production, the AGB stars come out as at least equally important over the lifetime of galaxies like the Magellanic Clouds (e.g., Matsuura et al. 2009; Boyer et al. 2012). AGB stars are certainly the most important contributors of carbon dust, as their total dust input is dominated by the carbon stars and SNe are thought to produce mainly silicates.  \nThe infrared flux of galaxies is often used to infer the total masses and star formation rates of galaxies. Since AGB stars  are  among  the  brightest  sources  and  radiate  strongly  from  1-20  microns,  they  can  significantly  affect  these measurements. In the Magellanic Clouds, AGB stars account for up to 30% of the 3-4 micron flux, despite being < 5% of stellar population (Melbourne & Boyer 2013). Without accounting for the AGB stars, stellar masses measured in the near-IR could be biased too high, especially in galaxies with large intermediate-aged populations.  \nDespite their importance, very little is known about the details of the evolution and dust production in AGB stars. AGB stars in galaxies more distant than the Magellanic Clouds have been difficult to observe at IR wavelengths owing to limits in sensitivity and resolution, leaving us with observations of a handful of stars in a random smattering of nearby galaxies. In the Magellanic Clouds, the Spitzer SAGE programs (Gordon et al. 2011; Meixner et al. 2006) have provided an incredible wealth of new information about AGB stars with their fully complete photometric catalogs in the IR, but IRS spectra was limited to only the brightest AGB stars even in these nearby galaxies. AGB stars in the Milky Way have been difficult to identify, leaving us with samples biased towards only the most extreme examples. Optical surveys do not suffice for AGB observations, as up to 60% of a galaxy's AGB population can be obscured by circumstellar dust (Boyer et al. 2009).  \nThe James Webb Space Telescope will go a long way towards understanding these important stars owing to its incredible sensitivity in the IR. For the first time, whole populations of AGB stars can be observed both photometrically and spectroscopically in the IR within the complete suite of galaxy environments available in the Local Volume, potentially  shifting  our  understanding of AGB stars and AGB dust production in profound ways. Since the lifetime of JWST is limited, it is crucial that we identify AGB stars in the Local Volume before, or at least in tandem with the JWST mission so that IR spectra can be obtained for an unbiased sample of stars. The most efficient way to identify AGB stars is to use near-IR photometry since the spectral energy distributions of most AGB stars peak from 1-3 microns, and since circumstellar dust does not obscure the stars at these wavelengths in the vast majority of cases (95% of the AGB stars in the LMC are detected in the K-band with 2MASS data).  \nNear-IR photometry also has the potential to separate carbon-rich from oxygen-rich AGB stars, depending on the exact filters chosen. This is due to molecular absorption in AGB atmospheres (e.g., TiO, CN, C2) in the 0.5-2 micron region. The J-K color successfully separates C from O stars in the Magellanic Clouds with 85% confidence (Riebel et al. 2012), allowing for the construction of a representative and un-biased sample of sources for follow-up spectrosco-  \npy. The near-IR wide filters on HST/WFC3, on the other hand, do not separate C-rich from O-rich stars, making it difficult to calibrate stellar evolution models.  \nWith filters similar to 2MASS J, H, and K, and with resolution and sensitivity similar to HST, WFIRST-AFTA could identify all AGB stars of interest within the Local Volume, allowing for the most efficient usage of JWST.", 'References:': 'Bowen, G. H. 1988, ApJ, 329, 299 Boyer, M. et al. 2012, ApJ, 748, 40 Boyer, M. et al. 2009, ApJ, 697, 1993 Gordon, K. et al. 2011, AJ, 142, 102 Iben, I., Jr. & Renzini, A. 1983, ARA&A, 21, 271a Matsuura, M. et al. 2009, MNRAS, 396, 918 Meixner, M. et al. 2006, AJ, 132, 2268 Melbourne, J. & Boyer, M. 2013, ApJ, 764, 30 Riebel, D. et. al. 2012, ApJ, 753, 71 van Loon, J. Th. et al. 2008, A&A, 487, 1055', '7. Galactic streams in nearby galaxies (Harry Ferguson)': "Figure 1: Simulations of tidal streams around a z=0 elliptical galaxy; colors code stellar age (from Bournaud 2010 ASPC, 423, 177).  \n<!-- image -->  \nWFIRST-AFTA's wide-field capabilities, low background, and high spatial resolution will  revolutionize  the  study  of streams of stars around nearby galaxies, formed by the tidal destruction of infalling dwarf galaxies. Outside of the Local  Group,  these  streams  are  typically  below  the  surface-brightness  limits  for  detection  from  ground-based  telescopes, but can be revealed with high-resolution observations, where individual RGB stars can be distinguished from background galaxies. Numerical simulations of galaxy formation suggest that there are streams around every L* galaxy.  \nThe TRGB absolute magnitude is MJ = -5.67-0.31[Fe/H] (Valenti 2004, MNRAS, 354, 815). With observing times of an hour or two per galaxy, WFIRST-AFTA can detect streams down to TRGB + 3 mag around all the 100 most massive galaxies within 5 Mpc. With observing times per galaxy of 10-100 hours, WFIRST-AFTA can detect streams in galaxies to the distance of the Virgo cluster. WFIRST-AFTA will provide breakthrough statistics on the number and morphology of the streams and the colors of their stars. The dissolution of dwarf galaxies in the halos of massive galaxies depends sensitively on (1) their dark-matter contents, (2) star-formation and feedback in the dwarf galaxies before they enter the massive halo and (3) interaction of the gas in the dwarf galaxies with the gas in the more massive halo. Item (1) is a fundamental assumption of LCDM models, but is currently hard to reconcile with all of the observed properties of satellite dwarf galaxies. Items (2) and (3) are very poorly constrained in galaxy-formation models; they provide the wiggle room for LCDM to survive the current discrepancies. So observations of streams will be very im-  \nportant. The same observations, of course, will pick up low-surface-brightness dwarf galaxies, which will also be important.  \nJWST does not have the field of view to carryout out such imaging studies, but has the spectroscopic sensitivity to follow up these observations. A rough rule of thumb is that JWST NIRSpec can obtain an R=100 spectrum of any star detected by WFIRST-AFTA, with the same exposure time that WFIRST-AFTA used to detect the star. This will improve  the  constraints  on  the  metallicities  of  the  streams,  and,  by  doing  so,  help  to  constrain  the  ages  of  the streams. At higher resolution, R=2700, JWST, with observing times of 10-100 hours for galaxies within 5 Mpc, can obtain kinematics and more precise chemical abundance measures of individual elements. Phase-space densities of the streams will provide strong constraints on the mass and shape of the parent dark-matter halo (e.g. Penarrubia et al. 2006, ApJ, 245, 240), and may also allow tests of alternative models of gravity (e.g. Kesden 2009, Phys Rev. D. 80, 83530.)  \nThe combination of JWST and WFIRST-AFTA greatly exceeds the individual contribution of each mission. WFIRSTAFTA is the finder scope. It obtains broad-brush statistics on the prevalence of streams. JWST probes the details that are necessary to really constrain the physics.", '8. Simultaneous observations of exoplanets with WFIRST-AFTA and JWST (Marshall Perrin)': 'Motivated by recent dramatic growth in studies of exoplanets, there is significant community interest in support of including a very high contrast coronagraphic camera as a second science instrument alongside the wide-field instrument on WFIRST-AFTA . Such a coronagraph would operate at contrasts up to 1e9 in visible light (likely at least 0.61 micron total range with instantaneous spectral coverage ~ 10-20%, observed with an integral spectrograph with resolution R~50-100). This would enable low-resolution imaging spectrophotometry of Jupiter-mass planets around nearby stars, as well as extremely sensitive observations of scattered light from circumstellar dust. The inner working angle of this coronagraph would be well matched to JWST\'s coronagraphs, of order 0.2", with the smaller telescope diameter being offset by the shorter operating wavelengths.  \nWe highlight here three specific areas of synergy between an WFIRST-AFTA coronagraph and the coronagraphs on JWST: (a) broad spectral coverage studies of atmospheric properties and chemistry in exoplanets, (b) the exciting possibility of time domain observations of weather or seasonal changes in exoplanetary atmospheres, which could benefit substantially from simultaneous operation of the two observatories, and (c) characterization of the complete range of bodies in nearby systems, including dusty debris belts and analogs to the still-poorly-understood Fomalhaut b.', 'a) Understanding Exoplanet Atmospheres.': "Brown dwarfs and giant planets have atmospheric (photospheric) properties that change dramatically as they cool over time, due to complex processes such as cloud formation and on-equilibrium atmospheric chemistries that are not yet well understood (e.g. Fortney & Nettelmann 2010). While sample sizes remain small, initial indications from e.g. the HR 8799 planets and 2M1207 suggest that planetary-mass companions have colors distinctly different from brown dwarfs, hinting at significantly different physics. The complexity of atmospheric chemistries imprints itself in atmospheric spectra in a variety of ways, including for instance absorption and scattering features from clouds of H2O and NH3, and also the effects of high altitude photochemical hazes (e.g. Cahoy et al. 2010). In the case of Jupiter, such photochemical hazes are one of the dominant contributors to atmospheric opacities, causing its overall reddish color (cf. Marley et al. 1999). Unlike transiting planets, directly imaged planets are (at least potentially) accessible to spectral characterization across a broad range of wavelengths spanning the bulk of their spectral energy distributions, offering a path to interrogate atmospheric properties through observations in both scattered light and thermal emission. Current spectral models for exoplanet atmospheres are subject to degeneracies when fitting only nearinfrared  data; optical  spectrophotometry  (0.6-1.0  microns)  can  break  these  degeneracies  and  aid  in  unambiguous retrieval  of  atmospheric  parameters.  For  instance,  a  Cycle  19  HST  program  (PI:  Barman)  has  recently  obtained WFC3 0.9 µ m observations of HR 8799 to allow robust tests of cloud models that are not possible on the basis of near-IR data alone. The combination of a high contrast optical coronagraph on WFIRST-AFTA with the near- to midinfrared  capabilities  of  JWST  would  enable  extending  such  studies  to  the  large  sample  sizes  needed  to  robustly characterize extrasolar planet populations.  \nAdvanced adaptive optics systems on ground-based 8-10 m (and potentially larger) telescopes will likely be competitive with JWST's contrast performance at near-IR wavelengths (1-2 microns), but atmospheric effects will in general prevent very high contrast (1e9 or better) observations from the ground, and will certainly preclude such observations at wavelengths substantially less than a micron even on timescales of 10-20 years from now. A very high contrast coronagraph in space is the only route to such data.", 'b) Weather and Seasons on Exoplanets': 'In addition to characterizing the bulk properties of exoplanets, we seek to understand them as dynamical systems, worlds in their own right. In several cases for close-in transiting planets, time-resolved observations have enabled a rough mapping of variations in brightness and temperature across their surfaces, providing insights into global circulation  and  weather  patterns (e.g.  Knutson  et  al.  2009,  2011;  Cowan  et  al.  2009). Likewise,  observations  of  brown  \ndwarfs in the field indicate that substantial fraction (perhaps 10-20%) show variability on short time scales indicative of weather (Radigan et al. 2011); in some case the variability is as high as 25% in the J band. Initial models suggest that this variability can be explained by patchy clear regions in an otherwise cloudy atmosphere, possibly indicating holes or breaks in the cloud layer. (Radigan et al. 2012)  \nRecent modeling has shown that appears feasible to extend this technique of time-resolved mapping to direct imaging observations, and use the rotational modulation of exoplanets to recover their properties, including potentially surface  properties,  cloud  cover  variations  and  weather.  See  Kostov  &  Apai  2012  for  a  detailed  discussion,  and  also Cowan and Strait 2013. These will be technically challenging observations but the potential payoff is large. This technique  would  strongly  benefit  from  simultaneous  studies  with  both  JWST  and  WFIRST-AFTA  to  allow  multiwavelength characterization of any variations and better wavelength coverage to discern spectral signatures of spectral components. While additional study of optimal observing techniques is needed, initial simulations suggest greater modulation at shorter wavelengths (Kostov & Apai 2012), indicating that WFIRST-AFTA can be a key contributor here. Because of the time variability of these effects, simultaneous observations are required with both telescopes if broad spectral models are to be fit.  \nDepending on mission lifetimes, it may also be possible to observe seasonal changes. For instance, over the years of the  Cassini  mission  to  Saturn,  we  have  witnessed  the  seasonal  transformation  of  the  northern  hemisphere from pale blue to straw yellow (and the inverse in the southern hemisphere), believed to be driven by haze production due to increased ultraviolet illumination with the changing angle of incidence of sunlight. The potential extended mission lifetimes of JWST or WFIRST-AFTA are comparable to a significant fraction of an orbital period for Jovian planets on 3-5 AU orbits. Maximizing the temporal overlap between the two missions might improve our ability to detect such seasonal changes.  \n- c) Studies of Planetary System Architectures as traced by Small Bodies  \nA coronagraphic instrument on WFIRST-AFTA could also potentially provide polarimetric measurements of light scattering from both planets and circumstellar dust - crucial because JWST lacks any polarimetry capabilities whatsoever. (In fact, several of the leading coronagraph concepts require polarization beam splitting for optimal operation, for instance the vector vortex coronagraph, so polarimetric capabilities may arise naturally as an inherent part of the starlight suppression methods.) Studies of solar system planets and theoretical modeling of exoplanets have demonstrated that polarimetry is a key diagnostic for assessing the presence of clouds or hazes in planetary atmospheres, so polarimetry could help with the above mentioned studies. But moreover, measurements of polarization can provide key constraints on dust grain properties in circumstellar disks (e.g. Graham et al. 2007, Perrin et al. 2009). When combined with observations of dust thermal emission in the mid-infrared with JWST and submillimeter with ALMA, scattered light imaging and polarimetry will enable comprehensive characterization of grain distributions, and therefore constraints on parent planetesimal populations in nearby debris disks.  \nConsider also the case of Fomalhaut b (Kalas et al. 2008), now confirmed by recent STIS coronagraphy to definitely be a physical companion on a disk-crossing-orbit, but whose physical nature remains very unclear. It has been suggested to possibly be a dust cloud from a recent collision of two KBO-type objects, or perhaps a giant planet surrounded by a swarm of moonlets in a collisional grinding process (See Currie et al. 2012 and Galicher et al. 2012). Having found one such object already with HST, it seems likely that further examples exist and may be found by JWST. Combined optical and infrared measurements, especially with optical polarimetry, would be a compelling tool to determine the physical nature of Fomalhaut b and similar objects. (Indeed, if the ACS HRC coronagraph was still operational, it would today be near mandatory to obtain ACS polarimetry of Fomalhaut b). Because JWST lacks polarimetric capabilities, a WFIRST-AFTA coronagraph including polarimetry would provide an extremely valuable adjunct capability that would enhance our ability to characterize small bodies and dust grains. When combined with infrared observations of giant planets and their atmospheres, JWST and WFIRST-AFTA together hold the potential to achieve comprehensive understanding of nearby planetary systems spanning from giant planets to asteroid and debris belts.', '9. Resolved studies of galaxy formation (Jason Kalirai)': "The detailed study of nearby galaxies can impact our fundamental knowledge of the processes that shape the formation and assembly of galaxies. The signatures of early accretion events can be directly seen in the halos of galaxies, where recent star formation is non-existent and stellar orbital time scales are of order the Hubble time. Perhaps the best example of a fully resolved spiral galaxy's halo is that of M31, as shown in the Figure below (McConnachie et al. 2009). From this star count map, we can measure the surface brightness profile, the level of substructure, and the abundance gradient of the stellar halo, and directly compare these signatures to those predicted in modern Nbody simulations of galaxy formation (e.g., Bullock & Johnston 2005).  \n<!-- image -->  \nUnlike our map of M31, most nearby galaxies contain a patchwork of high precision data, often focused on the visible bulge and disk. Improving this situation is difficult since it requires a telescope with  \n- 1.) high throughput to measure the stellar tracers in old stellar population, red giants, out to several Mpc,\n- 2.) high resolution to provide robust morphological separation between faint extragalactic contaminants and stars in the sparse halos,\n- 3.) wide field of view to probe stellar distributions to out beyond 100 kpc in a limited number of pointings  \nWFIRST-AFTA satisfies all of these requirements. With a modest investment of telescope time of about 1 month, WFIRST-AFTA can survey several magnitudes of the red giant branch in 100 of the closest galaxies over their complete spatial extents. Such a survey would provide the means to study the diversity of stellar halos in detail, and to correlate their properties with galaxy size, luminosity, environment, and other factors.  \nDespite this wealth of new information, WFIRST-AFTA, like Hubble, will be limited to measuring direct ages for old stellar populations to galaxies within the Local Group. The main-sequence turnoff in a 13 Gyr population is too faint to measure with a 2.4 meter telescope beyond the distance of Andromeda. JWST's NIRCam and NIRISS instruments  \ncan easily do this, out to several Mpc. However, blind pencil beams will run the risk of encountering recent accretion events and therefore not revealing the age of the oldest component of the galaxy, and so the JWST observations need WFIRST-AFTA to establish the spatial maps beforehand. The JWST observations can be then fine tuned to explore quiescent areas of the stellar halos, with the appropriate density to reveal robust star formation histories.  \nTaken together,  the  combination  of  star  formation  histories  (JWST),  level  of  substructure  (WFIRST-AFTA),  abundance gradients (WFIRST-AFTA and JWST), surface brightness profiles (WFIRST-AFTA) and velocity dispersions (30-meter) could be established for a dozen galaxies, and would provide an unprecedented data set to test N-body models of galaxy formation and evolution.", 'Appendix C Orbit Discussion (L2 vs. GEO)': "The  baseline  orbit  for  WFIRST-AFTA  is  a  28.5° circular  inclined  geosynchronous  orbit  with  an  initial RAAN of 228 ϒ . 1 However, all of the core WFIRST science programs are possible at either GEO or in a halo orbit around the Sun-Earth L2 Lagrange point; the SDT has deliberately avoided writing requirements that could not  be  met  at  either  location.  The  Observatory  design would also be similar at L2, but there would be changes in some systems as noted below.  \nWhile  both  orbits  offer  a  viable  mission  concept, there are significant advantages and disadvantages to each choice. The Study Office and SDT intend to perform a more detailed assessment of the orbit trade in 2015.  This  will  include  quantitative  assessment  of  the science  performance  in  each  area,  cost  differences, and the relative risk of the GEO and L2 options. A highlevel discussion of the key factors at play in this trade is discussed below.  \nCommunications  and  Data  Rate: The  principal  advantage  of  the  baseline  GEO  orbit  is  that  it  enables WFIRST-AFTA to continuously downlink data to a dedicated  ground  station  enabling  a  much  higher  science data downlink rate.  \nFor an L2 mission, the Observatory communication and data system will need to move from this 'bent-pipe' downlink concept at GEO to a store-and-downlink approach with multiple science downlinks per day to the Deep Space Network (DSN). This will require the addition of a science data recorder to store large amounts of science data between contacts. The expected number  of  contacts  per  day,  the  duration  of  each  contact, and the requirement to be able to miss at least one contact (which will happen occasionally) will drive the size of the recorder. Although the WFIRST-AFTA communication system is capable of downlinking 300 Mbps from L2,  the  DSN  is  currently  limited  to  data  rates  of  150 Mbps. These factors necessitate the science data volume be reduced by some combination of compression and less frequent sampling of the data. There is additional  complexity  in  planning  and  scheduling  the  communications between the ground and the Observatory  \nat  L2  that  does  not  exist  in  GEO  with  a  continuous communications  link.  The  impact  of  this  to  operations staffing will be assessed as part of the trade study.  \nFrom the science point of view, the higher data rate in  GEO  means  that  much  more  detailed  information from the NIR detectors can be downlinked (every 1 or 2 samples of each pixel), versus L2 where only summary information is available (slopes in each exposure, plus quality  flags  and  the  full  samples  from  a  small  subsample of the pixels  to  study  the  effects  of  the  rampfitting  algorithms).  The  availability  of  this  information reduces risk in the dark energy analysis, since it enables  additional  internal  cross-checks  (e.g.  first  versus second  half  of  each  exposure).  This  information  also provides  additional  diagnostics  of  subtle  detector  effects and the propagation of pointing drifts through the ramp-fitting algorithm.  \nThe high data rate will also transmit information on microlensing  sources  that  change  brightness  significantly during a 50-second integration (although we expect significant improvement for only a small fraction of the planetary events; note that the 15-minute observing cadence  was  chosen  for  measurement  of  the  finite source size effects).  For  similar  reasons,  the  handling of  moving  objects  by  the  analysis  pipelines  is  simpler with the data rate in GEO.  \nThe  continuous  communications  in  GEO  also  allows  immediate  access  to  WFIRST-AFTA  data,  which would  enable  real-time  alerts  of  events  detected  by WFIRST-AFTA to be sent to other telescopes. However, there are few anticipated planetary events for which observations  from  other  telescopes  will  be  useful  for measuring microlensing parallax or possibly other science  goals.  Some  of  the  brighter  events  can  be  observed from ground-based telescopes, but the optimal strategy  may  be  to  simply  observe  all  the  WFIRSTAFTA  exoplanet  survey  fields  from  the  ground.  Realtime  alerts  might  be  useful  for  follow-up  observations from larger, narrow-field telescopes, like JWST or 8m+ ground-based telescopes. JWST is unlikely to be able to respond more quickly than about 48 hours to alerts, so there will be little advantage for the GEO orbit, but there might be some advantage with the GEO orbit for follow-up  observations  from  ground-based  telescopes. However,  the  science  return  of  such  observations  is likely  to  depend  on  developments  in  adaptive  optics systems  in  the  next  decade,  and  no  study  of  the  science return of such a program has been performed.  \nObserving Constraints: In  addition  to  the  Sun  angle constraints,  which  are  the  same  at  GEO  and  at  L2,  \nWFIRST-AFTA  suffers  from  additional  observing  constraints  in  GEO  due  to  the  Earth  and  the  Moon.  The scheduling  of  observations  is  thus  more  complex  and less efficient at GEO than at L2.  \nDue to Sun constraints, the microlensing fields are available during two ~72 day 'seasons' each year, centered in March and September. At L2, these fields are available  with  no  interruptions  throughout  the  whole season.  In  GEO,  there  is  a  cutout  of  4-5  days  once each  month  as  the  Moon  passes  near  the  Galactic Bulge. 2 This means that to achieve the same total duration of the microlensing program, ~1 extra season must be allocated for a GEO mission versus an L2 mission. This  allocation  may  impact  some  GO  programs  that need to observe near the Galactic Bulge.  \nThe  dark  energy  programs  are  less  affected  by these constraints.  The  supernova fields are located at high ecliptic latitude for year-round visibility (for either a GEO or L2 mission), and hence have no Moon cutouts; depending  on  final  placement  there  may  be  a  daily Earth  cutout,  but  there  is  no  requirement  to  schedule them at a particular time of day. The principal effect of GEO observing constraints on the dark energy program is  that  the  telescope  must  move  from  field  to  field  to avoid the Earth, making several large (tens of degrees) steps each day. These inefficiencies have been incorporated  in  our  forecasts.  However,  the  increased  efficiency at L2 would be minor (of order several percent).  \nThe coronagraph program is the most strongly impacted by GEO observing constraints. The Moon is not an  issue,  since  coronagraph  observations  can  be scheduled  at  a  time  of  month  when  the  Moon  is  not near  the  target.  However,  66.5%  of  the  sky  (a  'band' around  the  WFIRST-AFTA  orbit)  suffers  a  daily  Earth viewing cutout of duration ranging from 0 to 5.6 hours. This band precesses, but still 59% of the sky is within the  daily  cutout  band  throughout  the  duration  of  the primary  mission.  For  coronagraph  targets  within  this band, WFIRST-AFTA would have to 'nod' off the target and return after the Earth has moved out of the way. At L2, these complex and inefficient operations would not be necessary.  \nThe scheduling software used for the GEO baseline in this report has also been run successfully for an  \nL2 orbit. A detailed optimization of both mission profiles, incorporating  ongoing  improvements  in  the  fidelity  of the slew modeling, will provide a quantitative basis for this trade.  \nThermal and Mechanical Disturbances: The  Observatory has been found to meet thermal and jitter stability  requirements in GEO with large margins. However, the  improved  thermal  stability  of  the  L2  environment (without  variable  thermal  loading  from  the  Earth)  and reduction  of  HGA  stepping  disturbances  are  expected to  result  in  further  increase  in  margins  relative  to  the requirements  of  the  weak  lensing  and  coronagraph programs. These improvements in stability would simplify  the  science  analysis  and  improve  the  science team's ability  to  simultaneously  solve  for  any  unanticipated sources of systematic error.  \nDue to the design of the science programs (particularly  the  pseudo-random dither strategy recommended for  microlensing),  the  predictable  daily  effective  plate scale  changes  in  GEO  due  to  relativistic  aberration have no impact.  \nInstrument  Sensitivity: The  principal  backgrounds (zodiacal light, read noise, dark current, and telescope thermal  emission)  and  hence  instrument  sensitivities are  nearly  identical  at  GEO  or  L2.  Earthshine  is  a source of  background in  GEO but not at L2; however analysis has shown that WFIRST-AFTA already meets its  Earthshine  requirement  of  <10%  of  the  zodiacal background in GEO with large margins, so the effect of eliminating it is small.  \nIonizing Radiation: Both GEO and L2 experience the flux of cosmic ray protons and heavy ions, but GEO is within  the  Earth's  trapped  electron  belt.  Thus  in  the baseline  GEO  orbit,  a  significant  amount  of  radiation shielding is required around the wide-field focal planes to  meet  our  preliminary  charged  particle  flux  requirement of ≤ 15/cm 2 /s  (versus 5/cm 2 /s  at  L2).  This  shielding  could  be  reduced  due  to  the  lower  radiation  environment at L2.  \nFor  the  short  HLS  imaging  exposures,  pixels  'recovered' by flagging the cosmic ray in the full ramp data are affected by increased read noise, and hence do not  have  the  full  sensitivity  of  an  uncorrupted  pixel. Thus the lower  cosmic  ray  rate  at  L2  results  in  fewer lost pixels. Preliminary estimates suggest a minor (4%) increase in the number of weak lensing source galaxies at L2, relative to the numbers quoted in this report. The risk of degradation of the WFI science programs if the  \nnumber of affected pixels per ionizing particle is greater than expected, or due to temporal variability in the electron flux, would be lower at L2.  \nMicrolensing  Parallax: Both  the  GEO  and  L2  orbits offer  opportunities  for  microlensing  parallax  measurements.  The  most  useful  measurements  are  likely  to ones that can give mass estimates for very short duration  microlensing  events,  likely  due  to  free-floating planets, because it is otherwise quite difficult to determine lens masses for these events. While it is possible to  measure  the  microlensing  parallax  effect  for  some events from the GEO orbit (Gould 2013), a more promising  method  is  probably  to  do  simultaneous  observations from the ground and WFIRST-AFTA (Gould et al. 2003). Only the brighter events can be observed from the  ground,  but  high  precision  measurements  are  not needed  to  get  interesting  constraints  on  free-floating planet lens masses. While detailed state-of-the-art calculations of this question have not yet been performed, it  seems likely that the L2 orbit is somewhat better for the  estimation  of  free-floating  planet  masses  with  the microlensing parallax effect.  \nLaunch  Vehicle  and  Propulsion: For  this  DRM,  the Delta IV Heavy launch vehicle was baselined. This vehicle enables either a GEO or L2 mission with healthy mass margins.  \nThe  Delta  IV  Heavy  has  the  capability  to  lift  the Observatory  directly  to  the  circular  inclined  geosynchronous  orbit,  which  allowed  the  simplification  of  the Observatory  propulsion  system  from  a  large  bipropellant system (needed to circularize from GTO and baselined in 2013) to a much smaller mono-propellant system.  A  mono-propellant  propulsion  system  is  also required  for  an  L2  configuration;  however,  a  flight  dynamics analysis will need to be performed to determine the Δ V  required  for  any  course  corrections  to  L2,  for orbit  insertion,  and  station-keeping.  It  is  expected  that the fuel required to meet these Δ V requirements will be larger than for the GEO configuration.  \nAnother factor in the trade study is the requirement to make the Observatory compatible with servicing by a robotic servicer. Early in the trade study, a location for servicing  the  Observatory  will  need  to  be  determined, with options including L2 or at an intermediate location, such  as  an  Earth-Moon  Lagrange  point.  The  trade study will assess implications to the Observatory design for servicing at either location.  \nStructures: In  general,  the  baseline  Observatory  mechanical and thermal design supports an L2 configuration, but some updates may be required for an L2 configuration.  \nCryocooler: A mechanical cryocooler is required for a GEO  mission  using  the  2.5 μ m-cutoff  detectors  (the most  mature)  since  with  the  thermal  loading  from  the Earth the ~90 K operating temperature is not achievable with a passive radiator. Studies have shown that the requirements  of  the  WFIRST  observing  programs  do not  allow  us  to  keep  the  radiator  continuously  pointed away from the Earth in GEO (the strategy usually employed by survey missions in Sun-synchronous orbit).  \nPassive  cooling  using  large  radiators  was  the baseline  for  past  WFIRST  DRMs  at  L2.  However,  a large radiator may have some implications for servicing the wide-field instrument. More study will be required to assess whether a cryocooler is required at L2.  \nAlthough  the  WFIRST-AFTA  DRM  was  designed for a 28.5° inclined geosynchronous orbit, the design of the Observatory for an L2 mission would be very similar.  A  detailed  trade  study,  considering  the  factors above,  to  assess  the  impacts  to  the  WFIRST-AFTA DRM will be performed in 2015. The resulting modifications to the DRM will be costed by the Project to understand the total cost delta for an L2 configuration.  \n<!-- image -->  \nAppendix D GO and GI One Page Science Ideas", 'Abstract': 'Among    the    many    disciplines    of    astronomy    expected    to    benefit    from    the    upcoming    Wide--Field    InfraRed Space     Telescope     (WFIRST)     mission     will     be     Solar     System     science.          This     white     paper     explores     potential WFIRST    observations    of    Solar    System    targets,    focusing    on    giant    planet    investigations    as    an    example,    and discusses    special    software    and    operations    implementations    that    would    be    of    particular    use    to    the    Solar System    community.', 'WFIRST:    Continuation    of    the    Hubble    Space    Telescope    Legacy': "With     anticipated     spatial     and     spectral     resolution     comparable     to     Hubble     Space     Telescope     (HST)'s     Wide Field    Camera    3,    WFIRST    will    be    seen,    in    multiple    ways,    as    a    continuation    of    HST--quality    observations    in the     visible     and     near--infrared     parts     of     the     spectrum.        The     contributions     of     WFIRST     to     Solar     System science     will     be     will     be     significant,     as     proven     by     HST's     legacy.          In     the     broader     picture,     WFIRST's capabilities    will    allow    it    to    serve    a    role    similar    to    that    of    HST    in    publicity,    education,    and    public    outreach, providing     high--quality     imagery     of     various     objects     in     the     visible,     portraying     them     as     the     human     eyes would    see    them.        WFIRST    can    also    capture    stunning,    newsworthy    phenomena    such    as    erupting    storms, impact    events,    and    photogenic    satellite    transits.        However,    there    are    myriad    ways    in    which    WFIRST    will uniquely    contribute    to    scientific    investigations    as    well.", "WFIRST's    Potential    Contributions    to    Giant--Planet    Science": 'The    visible    and    near--infrared    spectra    of    the    four    giant    planets    --    Jupiter,    Saturn,    Uranus,    and    Neptune    -are     dominated     by     the     signature     of     methane,     which     varies     in     absorption     strength     by     several     orders     of magnitude.        Because    of    this,    different    parts    of    this    spectral    range    probe    a    wide    variety    of    depths    in    the atmospheres of these planets, especially when combined with center--to--limb comparisons. Observations     at     different     wavelengths     will     reveal     the     altitudes     and     optical     properties     of     the     upper tropospheric    cloud    layers    on    these    planets,    and    how    they    vary    with    location.        These    conclusions    will    in turn    have    significant    implications    for    our    understanding    of    chemistry,    thermodynamics,    and    circulation on    these    planets.  \nRecent    findings    on    Uranus    and    Neptune    have    shown    that    the    upper    tropospheric    methane    abundance varies     with     latitude     (unlike     on     Jupiter     and     Saturn)     (Sromovsky     et     al.     2014, Icarus 238,     137--155; Karkoschka     and     Tomasko     2010, Icarus 205,     2,     674--694).          Comparison     with     nearby     hydrogen     lines     will enable     determination     of     the     methane     abundance     across     the     disks     of     these     planets     for     accurate interpretation    of     the     methane     opacity,     as     well     as     clarifying     the     extent     of     this     abundance     variation.          In addition     to     determining     the     abundance     variation     to     greater     precision,     further     investigation     will     reveal the    depth    to    which    these    variations    persist,    and    whether    they    evolve    over    time    --    all    three    items    of    great interest    to    modelers    of    the    Uranian    and    Neptunian    atmospheres.', 'Importance    of    Time--Domain    Science': 'While    observations    with    the    Hubble    Space    Telescope    have    already    enabled    much    of    the    above    analysis, it     must     be     remembered     that     many     of     these     discoveries     have     been     made     through     observing     transient events     that     evolve     in     timescales     of     weeks     to     months,     and     capturing     future     events     of     different     types should    bring    further    progress.        We    emphasize    that    the    planets    are    not    static    objects;    these    time--domain', 'WFIRST    Guest    Investigator    (GI)    and    General    Observer    (GO)    Science    Cases': "studies     are     critically     important     because     they     are     one     of     the     main     drivers     of     new     discoveries     in     solar system    science    today.        With    Jupiter    and    Saturn,    we    have    seen    dramatic    atmospheric    changes    such    as    the disappearance    of    Jupiter's    south    equatorial    belt;    the    ongoing    shrinking    of    Jupiter's    Great    Red    Spot;    the development,    evolution,    and    dissipation    of    immense    Saturnian    storms    in    1990--1991    and    2010--2011;    and intermittent    and    yet    intense    storm    activities    on    Uranus.        The    orbital    periods    of    Uranus    and    Neptune    are long     enough     that     seasonal     change     on     these     planets     is     not     well     understood,     and     ongoing     observations will     be     critical     as     the     seasons     proceed,     both     to     discover     new     development     and     to     maintain     a     suitable temporal    baseline    of    observations.", 'WFIRST    Sensitivity:    Critical    to    Small    Body    Observations': 'The     Hubble     Space     Telescope     has     been     employed     in     successful     campaigns     to     discover     new     satellites around     the     giant     planets     as     well     as     Kuiper     Belt     objects     (e.g.,     Showalter     et     al.     2013,     DPS     meeting     #45, #206.01;     Showalter     et     al.     2012,     IAU     Circ.,     9253,     1).          As     the     retrieval     techniques     continue     to     improve, WFIRST    will    likely    be    able    to    discover    further    new    satellites    and    KBOs.        In    addition    to    new    discoveries, WFIRST     will     enable     further     investigations     of     known     small     objects     whose     orbital     elements     are     poorly constrained.', 'WFIRST:    Complementing    JWST    Capabilities': "WFIRST     will     also     be     valuable     when     used     to     complement     other     datasets.          For     example,     the     upcoming James    Webb    Space    Telescope    (JWST)    will    set    the    new    standard    for    near--    and    mid--infrared    observations; however,    the     JWST's     missions     exclude     many     solar     system     science     topics.          For     example,     Mars,     Jupiter, and    Saturn    will    not    be    observable    over    JWST's    full    spectral    range    because    those    targets    are    too    bright and     saturate     JWST     pixels     even     with     the     shortest     possible     exposure.          Furthermore,     JWST     may     observe Solar    System    targets    only    at    solar    elongation    angles    between    85°    and    135°,    typically    granting    two    50--day windows    per    year.         Should     a     time--sensitive     event     such     as     an     impact     or     sudden     storm     occur     when     the body    in    question    is    outside    of    JWST's    field    of    regard,    other    facilities    such    as    WFIRST    will    be    able    to    step forward.", 'Solar    System    Observation    Requirements': 'There    are    two    special    requirements    of    WFIRST    implementation    that    would    be    of    unique    importance    to Solar System     observations:     tracking     and     targeting     of     moving     objects,     time--critical observation scheduling.', 'Moving    Object    Targeting    and    Tracking': 'Because     targets     in     the     Solar     System     are     constantly     moving     with     respect     to     the     background     sky,     the ability    observe    moving    targets    will    be    essential.        The    maximum    movement    rates    of    several    Solar    System targets    are    given    in    the    table    below;    if    such    rates    are    unachievable    with    WFIRST,    the    target    movement rates    may    be    lowered    at    the    expense    of    freedom    in    scheduling.        It    must    also    be    noted    that    more    swiftly moving    targets    may    also    be    desired,    such    as    comets    and    near--Earth    asteroids.        Additionally,    since    Solar System     targets     do     not     have     fixed     locations,     observers     would     appreciate     a     system     pipeline     that     could recognize     the     names     of     Solar     System     targets     and     determine     their     ephemerides,     rather     than     requiring target    positions    to    be    supplied    by    the    user.  \nTable    1:    Maximum    Tracking    Rate    Necessary    for    Observing    Solar    System    Targets', 'Time--Critical    Observation    Scheduling': "Lastly,    it    must    be    mentioned    that    time--sensitive    events    are    not    uncommon    in    Solar    System    astronomy. Some    events    may    be    anticipated,    such    as    close    approaches    by    asteroids,    optimal    observing    geometry    for the     giant     planets'     ring     systems,     and     mutual     events     among     satellites.          Observing     plans     must     be     able     to request    such    time    constraints.        Other    time--sensitive    events    have    little    advance    warning,    such    as    sudden changes     in     comet     outgassing,     meteorological     events     in     planetary     atmospheres,     and     witnessing     the aftermath     of     impact     events.          The     ability     to     conduct     target--of--opportunity     considerations     will     be     of immense    value    in    such    scenarios.", 'Background': "Within     the     next     decade,     ground--based     gravitational     wave     (GW)     detectors     are     expected     to routinely    detect    the    mergers    of    binary    compact    objects    (neutron    stars    and    black    holes).    The    NS-NS    and    NS--BH    mergers    contain    ultra--dense    (>10 14 g/cm 3 )    matter    and    hence    provide    a    laboratory for some     of     the     most     extreme     astrophysical     processes     in     the     Universe.     Electromagnetic observations,     sensitive     to     the     composition     and     thermodynamic     state     of     the     matter,     will     be required     to     complement    the     GW    signal,     which     constrain     the     NS     and     BH     masses.     Except     in     the lucky    case    of    a    gamma    ray    burst    that    happens    to    be    beamed    toward    us,    we    will    have    to    rely    on isotropic     electromagnetic     counterparts.     Tidal     debris     or     accretion     disk     winds     are     expected     to expel     neutron--rich     material     from     the     merger     resulting     in     an     isotropic     radioactivity--powered remnant.     Dubbed     'kilonova',     the     counterparts     should     be     detectable     in     the     optical/NIR     with durations    of    order    days    and    luminosities    of    order    10 40 -10 42 erg/s.    Follow--up    of    binary    mergers will    be    challenging:    GW    detectors    lack    intrinsic    angular    resolution,    and    simultaneous    fitting    of    an event    in    several    detectors    can    only    localize    a    source    to    an    error    ellipse    of    a    few    to    hundreds    of deg 2 .     This     ellipse     will     contain     not     just     the     binary     merger     counterpart,     but     also     many     unrelated 'false     positive'     transients.     The     eventual     goal     is     to     obtain     not     just     a     detection,     but     also     a     light curve    and    spectroscopy    to    constrain    the    velocity,    opacity,    and    composition    of    the    debris.", 'WFIRST': 'Theoretical     predictions     for     the     counterpart     suggest     that     the     emission     peaks     in     the     NIR     due     to opacity    considerations    (Barnes    and    Kasen    2013).    Hence,    the    exquisite    wide--field    mapping    speed, red    sensitivity    and    rapid    response    capability    of    WFIRST    in    geosynchronous    orbit    are    well--suited to this     search.     Specifically,     we     suggest     following     up     binaries     localized     within     6     deg 2 and detection    S/N>12    by    a    network    of    5    GW    detectors.    During    a    5--year    mission,    we    expect    ~30    such binaries    within    the    WFIRST    field    of    regard    at    a    median    distance    of    230    Mpc    (Nissanke,    Kasliwal and    Georgieva    2012).    At    this    distance,    a    depth    of    HAB=24.6    mag    corresponds    to    MH,AB=-12.2    or λLλ = 6×10 39 erg/s.     The     rate     of     NS--NS     mergers     is     currently     uncertain     by     1-2     orders     of magnitude:    the    follow--up    strategy    and    criteria    for    a     ToO     trigger     will     be     adjusted     based     on     the actual    event    rate.    One    possible    follow--up    plan,    requiring    a    total    of    27    hours    per    binary    (including overheads),     would     involve     2     filter     (J+H     to     mag     24.6     AB     at     S/N=10)     and     grism     (S/N=5     per synthetic    R=30    element    at    HAB=22)    observations    of    the    entire    error    ellipse    as    quickly    as    possible. After    this,    we    envision    imaging    mode    (J+H)    revisits    at    4    epochs    from    t    ~    1-30    days,    and    a    later reference    epoch.    Once    the    counterpart    candidate    list    is    reduced    to    ≤10    candidates    based    on    the grism     spectrum     and     the     photometric     evolution,     we     would     use     the     IFU     to     acquire     a     high     S/N spectrum    (S/N=5    per    synthetic    R=30    element    at    mag    24.9    AB).', 'Key    Requirements': 'Image    Quality -    the    information    density    in    best    possible    image    quality    enables    lens    modeling; coupled    flexion    and    weak    lensing    measurements    at    larges    scales    also    demand    good    IQ Grism -    for    redshifts;    ground--based    spectroscopy    will    complement    in    wavelength    coverage Field    of    View -    A    wide--area    survey    -    i.e.    the    HLS    --        is    required    to    identify    these    rare    populations. Single--shot    wide    FOV    also    uniquely    enables    mass    probe    of    massive    haloes    over    full    radial    range Wavelength    Coverage -    multi--band    imaging,    with    broadest    possible    coverage,    maximizes    lens-modeling    return,    and    enables    best    photo--zs    for    weak    lensing    reconstructions.  \nhttp://adsabs.harvard.edu/abs/2008ApJS..176...19F  \nhttp://adsabs.harvard.edu/abs/2014ApJ...783..138G', 'The    Investigation': 'There    are    two    components    to    this    investigation:    completing    the    low--mass    population    of    young    nearby associations     and     finding     new     associations.     The     first     part     involves     imaging     known     nearby     associations: the β Pictoris     moving     group,     the ε and η Chamaeleontis     clusters,     the     TW     Hya     association     itself,     the Tuc/Hor,    Columba,    AB    Doradus,    and    Argus    Associations.    These    all    range    in    ages    from    5    to    50    Myrs.    For the    second    component,    we    will    select    known    isolated    young    stars    to    search    for    low--mass    stars    with    their know    space     motions.     Determining    membership    to    the    association    requires     determination    of    the    UVW velocity     components     and     medium     resolution     spectroscopy     to     search     for     youth     indicators.     The     2.4m WFIRST     will     be     able     to     detect     all     the     Y0     (MH=20     mag,     Kirkpatrick     et     al.     2012)     dwarfs     within     100     pc (mH(AB) ≈ 26.3    mag).        The    role    of    WFIRST    is    to    determine    proper    motions    of    very    low--mass    objects    (best done    in     the     NIR,     where     they     are     brightest)     in     an     efficient     way,     given     its     large     field     of     view.          Repeated visits    (at    least    three    and    preferably    five)    and    ground--based    spectroscopic    follow--up    will    be    necessary.  \nFig.    1:    Left:    Nearby    southern    young    associations.    Right:    CMD    diagram    for    associations    nearby    the    sun.    From Zuckerman    &    Song    (2004)  \n<!-- image -->', 'Exoplanet    Spectroscopy    with    WFIRST': "Provided     a     low--resolution     spectroscopic     capability     is     incorporated     into     the     final     design,     NRO     WFIRST could     be     used     without     serious     modification     for     spectroscopy     of     transiting     exoplanets.     Exoplanet atmospheres    could    be    studied    both    in    transmission    and    in    emission,    and    the    effective    wavelength    range (.7    to    2    microns)    of    NRO    WFIRST    is    well--matched    to    the    most    interesting    molecular    signatures    we    expect to    see    in    hot--Jupiter--like    atmospheres.    Key    diagnostic    molecules    would    include    water,    methane,    carbon dioxide,    and    carbon    monoxide,    which    are    particularly    important    for    investigating    atmospheric    radiation balance,    temperature    structure,    equilibrium/nonequilibrium    chemistry,    and    photochemical    processes.  \nExoplanet     spectroscopy     can     be     carried     out     with     either     a     slit     or     a     slitless     system.          A     slitless     system necessarily    entails    some    risk    of    spectral    contamination    by    other    sources    in    the    field,    but    in    most    cases this    could    be    overcome    if    the    spacecraft    has    some    degree    of    rotational    freedom.        For    a    traditional    slit,    to avoid     jitter--induced,     time--variable     slit     losses,     exoplanet     spectroscopy     would     benefit     from     using     a     slit many    times    wider    than    the    FWHM    of    the    spatial    PSF.    While    the    critical    information    is    contained    in    the time     domain     rather     than     the     spatial     domain,     an     integral     field     unit     would     also     be     suited     to     exoplanet spectroscopy,    provided    that    pointing--induced    'slit    losses'    can    be    minimized.    The    optimal    system    would again    use    fibers,    lenslets,    or    image    slicers    whose    elements    subtend    an    area    several    times    larger    than    the spatial    PSF.  \nSince     the     primary     molecular     bandheads     are     quite     broad,     high     spectral     resolution     is     not     required, particularly    for    an    initial    survey.    The    low    resolution,    R    =    75    grism    considered    in    DRM1    for    would    be    more than    adequate.        By    obtaining    spectra    over    multiple    eclipses,    WFIRST    can    build    up    signal--to--noise    ratio    for the    faintest    or    most    interesting    sources,    or    search    for    variations    in    composition,    temperature    structure, or    other    signs    of    global    climate    change.  \nSystematics     will     be     dominated     by     pointing     performance     and     detector     stability.     With     the     large     field     of view     available,     pointing     drifts     can     be     very     accurately     determined     in     post--processing     using     the     many thousands     of     other     sources     in     the     field.     Without     any     design     optimizations     specific     to     exoplanet observations,    HST    and    Spitzer    have    both    demonstrated    that,    with    suitable    calibration    and    decorrelation techniques,    systematics    can    be    brought    down    to    a    level    of    30--70    ppm    (Demory    et    al.,    2011,    A&A,    544, 113,    Todory    et    al.    2012,    ApJ,    746,    111).  \nSome    of    the    brightest    exoplanet    spectroscopy    candidates    will    saturate    NIRSpec    and    thus    be    essentially unobservable     with     JWST.     If     NRO     WFIRST     includes     the     higher     resolution,     R=600     prism     for     the     galaxy redshift     survey     in     DRM1,     then     WFIRST     will     in     principle     be     capable     of     obtaining     exoplanet     spectra     for targets        ~1.6    magnitudes    brighter    than    JWST.    In    the    post--HST    era,    WFIRST    may    become    our    only    means for obtaining     high--precision,     space--based     spectra     for     such     objects     in     this     particularly     interesting wavelength    range.  \nAngelle    Tanner    (MSU),    at876@msstate.edu  \nDavid    Bennett    (U    Notre    Dame)", 'Kernel--phase    on    NRO    telescope': 'A     space--borne    telescope    is    the    ideal    observatory    for    the    study    of    cool    dwarfs    and    their    companions    in the    near--to--mid    IR.    Ground    based    observations    of    such    objects    indeed    typically    require    Laser    Guide    Star Adaptive     Optics     (LGSAO)     observations,     which     do     not     exhibit     satisfactory     performance     yet;     and     the detection    limits    are    strongly    limited    by    the    background,    beyond    the    K--band.  \nThe     self--calibration     properties     of     Kernel--phase     enable     detection     of     companions     and     high--precision relative     astrometry     in     a     regime     of     angular     separation     (<     100     mas     in     the     near--IR)     that     currently     eludes any     other     imaging     technique.     Repeated     observations     allow     to     fully     characterize     orbital     parameters, which     combined     with     RV     or     wide     field     astrometry,     provide     high     precision     dynamical     masses     of     these otherwise    elusive    objects    (e.g.    Martinache    et    al,    2007,    ApJ,    661,    496;    Martinache    et    al,    2009,    ApJ,    695, 1183).  \nThe application     of     the technique     is however     not restricted     to     nearby     low--mass     stars.     Any     observation usually performed     with     high--performance     AO,     for instance,     resolved     observations     of     the     Galactic     center could    benefit    from    Kernel--phase.', 'Key    requirements': 'Sampling:     PSF     should     be     Nyquist     sampled     at     the shortest    wavelength    of    interest  \nWavefront     quality:     Strehl     better     than     50     %     at     the shortest    wavelength    of    interest  \nExample    of    NICMOS    Ker--phase    super--resolution    (64    milli-arc        second    separation)    discovery    around    the    nearby    L-Dwarf    2M    2351--2537    (Pope    et    al,    2013).  \n<!-- image -->', 'Detecting    Neutron    Stars    and    Black    Holes    through    Astrometric    Microlensing': 'Stars     with     initial     masses     of ∼ 8-20     M ⊙ are     expected     to     end     their     lives     as     NSs,     and     those     with greater     masses     as     BHs     (Heger     et     al.     2003).     As     much     as     10%     of     the     total     mass     of     our     Galaxy should    be    in    the    form    of    NSs    and    BHs    (Oslowski    et    al.    2008).    However,    a    vast    majority    of    stellar remnants     are     expected     to     be     single,     either     primordially     or     due     to     disruption     of     binaries     by supernova     (SN)     explosions     (Agol     &     Kamionkowski     2002).     Such     isolated     massive     remnants     are extremely    difficult    to     detect     directly,     and     in     fact     no     isolated     BH     has     ever     been     unambiguously found    within    our    Galaxy.    Mass    measurements    of    NSs    and    BHs    mostly    come    from    observations    of binary    systems    which    show    NS    masses    to    be    concentrated    around    1.4M ⊙ ,     and    BH    masses    to    be a     narrow     Gaussian     at     7.8     ±     1.2     M ⊙ (Ozel     et     al.     2010).     However,     theoretical     models     (Fryer     & Kalogera     2001)     predict     that     the compact--remnant     distribution     should     be     a     continuous distribution     from     1.2     to     15M ⊙ . The     discrepancy     between     the     observed     and     predicted     mass distribution     of     BHs     is     generally     attributed     to     the     fact     that,     BHs     in     binaries     are     a     biased     and minority    sample.    What    is    missing    is    an    unbiased    mass    distribution    for    isolated    stellar    remnants.  \nAstrometric    Microlensing: Isolated    stellar    remnants    can    be    detected    through    microlensing.    The microlensing    survey    programs    such    as    OGLE    and         MOA          have     so     far     detected     more     than     8000 microlensing     events.     If     stellar     remnants     constitute     a     few     percent     of     the     total     mass,     many     of these     observed     microlensing     events     must     be     due     to     stellar     remnants.     However,     microlensing light    curves    are    degenerate    with    respect    to    the    mass,    velocity    and    distance    of    the    lens.        A    route to    resolving    these    degeneracies    arises    from    the    fact    that    microlensing,    in    addition    to    amplifying the     brightness     of     the     source,     produces     a     small     shift     in     its     position     (Dominik     and     Sahu,     2000). Thus    if    high--precision    astrometry    is    added    to    the    photometry,    the    deflection    of    the    source    image can     be     measured,     and     thus     the     mass     of     the     lens     determined     unambiguously.     The     sizes     of     the astrometric    shifts,    however,    are    such that    they    require    a    2m--class    space    based    telescope.  \nWFIRST/NRO: Astrometric     precisions     of     order     300     microarcsec     have     been     achieved     with HST/WFC3,     so     we     expect     that     a     similar     astrometric     precision     is     achievable     with     NRO.     The maximum    astrometric    deflection    caused    by    a    0.5    M ⊙ lens    at    2    kpc    is    400 ∝ as    (see    Figure    1).    This implies    that    NRO    can    measure    the    astrometric    deflection    caused    by    almost    all    NSs    and    BHs.  \nIn order     to     unambiguously     measure     the     mass     of     the     lens,     the     remaining     quantity     to     be determined     is     the     distance     to     the     lens.     Fortunately,     the     timescales     of     microlensing     events caused    by    NSs    and    BHs    are    long    (    >30    days),    so    photometric    observations    of    these    events    with NRO        will    provide    clear    measurements    of    the    parallax    distances.  \nFrom     our     HST     observations     towards     the     galactic     bulge,     we     estimate     that     NRO     will     enable monitoring     of     about     20     million     stars     towards     the     Galactic     bulge     in     a     single     pointing,     covering about    0.25    square    degrees.    By    monitoring    10    fields    in    the    Galactic    bulge,    200    million    stars    can    be easily    monitored    continuously.    Since    the    optical    depth    towards    the    Galactic    bulge    is    about    3    * 10(--6),     this     will     lead     to     the     detection     of     600     microlensing     events     at     any     given     time,     and     5000 events     per     year.     Taking     the     current     statistics     of     microlensing     events,     about     10%     of     them     (500 events)    are    expected    to    have    TE    >    30    days,    and    at    least    three    dozen    of    them    are    expected    to    be due     to     NSs     and     BHs.     Observations     taken     over     5     years     will     lead     to     the     detection     and     mass measurement    of    well    over    100    NSs    and    BHs.    These    measurements    will    provide    (i)    constraints    on SN/GRB    explosion    mechanisms    that    produce    NSs    and    BHs,    and    (ii)    a    quantitative    estimate    of    the mass    content    in    the    form    of    stellar    remnants.  \nScott    Gaudi    (OSU),    gaudi@astronomy.ohio--state.edu,    Matthew    Penny    (OSU),    Naoteru    Gouda (NAOJ),    Yoshiyuki    Yamada    (Kyoto    U.)', 'WFIRST--AFTA': "WFIRST--AFTA    will    enable    high--precision     proper     motion     measurements     and     parallaxes    to     essentially     all the    ~56    million    bulge    and    foreground    disk    stars    in    the    ~2.8    square    degree    microlensing    survey    field--of-view     with     magnitudes     of     HAB<21.6.          For     the     exoplanet     survey,     WFIRST--AFTA     will     achieve     photometric precisions     of     ~1.2%     per     52s     observation     for     stars     with     HAB<21.6.     Assuming     a     resulting     astrometric precision     of     a σ AST ~ 2 mas     per     observation     (i.e., σ AST ~ FWHM/SNR~0.14' ✕ 0.012~1.7     mas),     and N~33,000    observations,    the    final    mission    uncertainty    on    the    measured    proper    motions    over    a    T~5    year baseline    will    be σ ∝∝ ~    (12/N) 1/2 ( σ AST/T)    ~    0.01    mas/yr. The    typical    proper    motion    of    a    star    in    the    bulge    is ∝ ~100     km/s/(8000     pc)     ~     3     mas/year,     and     thus     individual     stellar     proper     motions     will     be     measured     to ~0.3%.              Similarly,     the     fractional     uncertainty     on     the     parallax     of     a     star     in     the     bulge     will     be σ \\_ Π / Π ~     ( σ \\_AST/ Π )(2/N) 1/2 ~     10%,     where Π ~     1/8     mas     is     the     typical     parallax    of     a     star     in     the     bulge.     Note     that    these estimates    assume    that    systematic    uncertainties    can    be    controlled    to    better    than    ~0.01    mas,    or    1/1000 th of     a     pixel.     Because     these     observations     will     be     taken     in     the     NIR,     they     will     reach     below     the     bulge     MS turnoff     and     will     be     relatively     unaffected     by     extinction.     The     occasional     observations     in     bluer     filters     will help     distinguish     between     bulge     and     disk     populations.          With     these     measurements,     AFTA--WFIRST     will provide    unprecedented    measurements    of    the    kinematics    and    structure    of    the    bulge.  \n<!-- image -->  \n<!-- image -->", 'Detecting    ultra--faint    galaxies    with    WFIRST': 'Detecting    ultra--faint    galaxies    throughout    the    full    Milky    Way    volume    requires    imaging    down    to    the    main sequence     turnoff     at     300     kpc     (Walsh     et     al.     2008),     corresponding     to     roughly     r     =     27     mag.               High     spatial resolution     is     critical,     as     background     galaxies     which     are     otherwise     unresolved     from     the     ground,     vastly overwhelm     the     number     of     stars     at     these     magnitudes.               Star--galaxy     separation     will     severely     limit     the number    of    distant    Milky    Way    satellites    found    in    ground--based    surveys.        A    deep    wide--field    WFIRST    survey would    allow    an    unprecedented    search    for    the    faintest    dwarfs    to    the    outer    limit    of    the    Milky    Way    halo.', 'Characterizing    ultra--faint    galaxies    with    WFIRST': 'In    addition    to    finding    ultra--faint    galaxies,    WFIRST    is    well    positioned    to    characterize    these    galaxies.            High-precision     photometry     of     the     stellar     main--sequence     turnoff     will     yield     accurate     ages     for     these     systems which     appear     to     have     exclusively     old     stars     (e.g.,     Brown     et     al     2012).        Furthermore     80     microarc/year proper    motions    will    allow    *internal*    measurements    of    motion    in    these    systems,    allowing        estimates    of dark    matter    mass    and    density    (i.e.,    <2    km/s    for    50    stars    @    100    kpc,    in    3    years).  \nDepth    -        Deep    point    sources    imaging    to    the    main sequence    turnoff    at    300    kpc    (mr    ~    27)  \nFOV            -        Wide    field    imaging    (1000+    sq    deg)  \nto    cover    large    volume    of    Milky    Way    halo  \nCadence    -    Repeat    observations    for    proper    motions  \nCaption:            The    luminosity    function    of    known Milky    Way    satellites    (red)    as    a    function    of luminosity.            Green    and    blue    curves    are    the predicted    satellite    numbers    based    on different    assumptions    for    incompleteness (taken    from    Tollerud    et    al.    2008).  \nAppendix D: GO and GI One Page Science Ideas  \n<!-- image -->  \nAlis    J.    Deason    (UCSC)    alis@ucolick.org;    Kathryn    V.    Johnston    (Columbia); David    N.    Spergel    (Princeton    University);    Jay    Anderson    (STScI)', 'Galaxy    Evolution    from    Resolved    Stellar    Populations:    Halo    Age Distributions    of    the    Local    Volume': "Background : Large     galaxies     like     the     Milky     Way     are     formed     hierarchically     through     dozens     of satellite     accretion     events     that     not     only     build     up     the     stellar     halo,     but     also     contribute     to     the evolution     of     the     galaxy     as     a     whole.     Statistical     studies     comparing     satellite     and     field     dwarfs indicate    that    star    formation    is    quenched    early    in    the    accretion    process    (e.g.,    Geha    et    al.    2012). Thus,    the    youngest    stars    in    a    satellite    can    be    used    to    date    the    initial    infall    of    that    satellite    into    its parent     halo.     Asymptotic     giant     branch     (AGB)     stars     are     prime     tracers     of     these     accreted populations    as     they     are     present     in     stellar     populations     over     a     wide     range     of     ages     (4     Myr     to     10 Gyr).    As    shown    in    Figure    1    for    the    LMC,    the    NIR    magnitude    and    color    of    an    AGB    star    is    strongly dependent     on     its     age.     The     NIR     CMD     is     therefore     an     ideal     tool     for     quantifying     the     stellar     age distribution    of    nearby    galaxy    halos.  \nWFIRST:    Observational    programs    of    this    nature    are    difficult    to    carry    out    from    the    ground    and    to date    this    technique    has    only    been    applied    to    the    SMC,    LMC    and,    as    a    pencil--beam    survey    in    M31. With     WFIRST,     however,     it     is     feasible     to     explore     the     halo     age     distribution     in     a     representative sample    of    nearby    galaxies    to    complement    Hubble    and    Spitzer    Legacy    programs    (LVLS,    ANGST), that     have     observed    recent    and    old    star    formation    tracers    in    all    galaxies    within    3.5    Mpc    and    all S/Irr    within    11    Mpc.    Further,    WFIRST    will    allow    an    expansion    beyond    existing    HST    NIR    imaging    to obtain    full    spatial    coverage    of    the    M31    disk,    bulge    and    halo.    Key    questions    addressed    by    these observations     will     be:     (1)     what     is     a     'typical'     galaxy's     accretion     history?     (2)     over     what     physical scales    does    satellite    accretion    vs in--situ star    formation    dominate?    and    (3)    is    the    age    distribution smooth    or    discontinuous,    and    what    does    this    imply    about    the    typical    progenitor    over    time?", 'WFIRST:': "The    main    factor    limiting    stellar    population    studies    is    angular    resolution.        With    ground--based    telescopes, light     from     individual     stars     is     blended     together,     prohibiting     the     study     of     stars     beyond     the     Local     Group. While     adaptive     optics     can     alleviate     this     problem,     stellar     population     studies     require     a     level     of photometric    accuracy    and    stability    that    cannot    yet    be    achieved    routinely    for    long    integrations    over    large fields     of     view.          In     contrast,     the     superb     resolution     and     stability     available     with     a     2.4m     space--based telescope    allows    individual    red    giant    stars    to    be    resolved    at    distances    out    to    ~5    Mpc    in    the    main    body    of galaxies,    or    out    to    even    larger    distances    in    low    surface    brightness    regions    (halos,    intercluster    light,    dwarf galaxies,     etc).          High     luminosity     stars,     which     more     easily     rise     above     the     crowding     limit,     can     also     be detected    out    to    greater    than    ~10    Mpc,    allowing    the    detection    of    massive    main    sequence    stars,    blue    and red     supergiants,     and     AGB     stars.        WFIRST's     wavelength     coverage     is     optimized     for     the     cooler     of     these stars,    whose    bolometric    luminosity    peaks    longward    of    7000    Angstroms;    however,    many    hotter    stars    can be    sufficiently    luminous    to    still    be    detectable    at    WFIRST's    wavelengths.        The    near--IR    coverage    of    WFIRST also    minimizes    the    impact    of    dust    on    interpretations    of    CMDs.        Existing    studies    in    the    Magellanic    Clouds (Nikolaev    &    Weinberg    2000,    Boyer    et    al    2011)    have    demonstrated    that    there    would    be    significant    added value     if     WFIRST     detectors     were     sensitive     out     beyond     1.7     microns,     even     with     the     high     background expected    for    a    non--cryogenic    mission.", 'Resolving    Intracluster    Light    in    the    Virgo    Cluster': 'Intracluster     light     (ICL)     is     an     important     tracer     of     the     dynamical     state,     growth     history     and structural    composition    of    galaxy    clusters.    Relevant    observables    include    the    fractional    luminosity, radial    light    profile,    and    presence    of    substructure    in    the    ICL,    all    of    which    are    a    strong    function    of cluster    mass,    substructure,    and    dark    matter    distribution    (Krick,    Bernstein    &    Pimbblet    2006,    Krick &     Bernstein     2007,     Rudick     et     al.     2010,     Montes     &     Trujillo     2014).     Numerical     simulations     indicate that     the     ICL     in     clusters     accounts     for     anywhere    from    10%    to    70%    of    the    total    cluster    luminosity (Purcell     et     al.     2008,     Rudik     et     al.     2010,     Martel     et     al.     2012,     Contini     et     al.     2014),     though     this remains    largely    untested.  \nIn    spite    of    its    importance,    very    little    is    known    about    the    ICL.    It    is    notoriously    difficult    to    study    the ICL    by    direct    imaging,    since    even    the    brightest    components    of    the    ICL    have    surface    brightnesses around    B~28    mag/arcsec 2 (Mihos    et    al.    2005)    and    the    vast    majority    of    the    ICL    is    expected    to    be orders    of    magnitude    fainter    than    this.    The    fundamental    limits    to    low    surface    brightness    imaging are     set     by     control     of     systematics     (scattering,     detector     stability,     and     flat     fielding     errors),     so     the limiting    depth    for    ground--based    low    surface    brightness    imaging    (B~29.5    mag/arcsec 2 ;     see    Slater et    al    2009)    has    remained    fairly    near    the    detection    threshold    of    the    ICL    for    the    last    40    years.    New observational     techniques     for     low     surface     brightness     imaging     from     the     ground     (such     as     the Dragonfly    Telephoto    Array)    hold    some    promise    for    allowing    the    ICL    to    be    probed    to    around    B    ~ 32     mag/arcsec 2 from    the     ground    (Abraham    &    van    Dokkum    2014),    but    going    much    fainter    than this     will     likely     remain     challenging     even     a     decade     from     now.     The     most     powerful     technique     for investigating     the     ICL     in     very     nearby     clusters     will     therefore     be     to     forego     direct     imaging,     and     to instead    exploit    the    resolution    of    space--based    observatories    by    directly    resolving    the    ICL    into    its constituent    stars.    Pioneering    observations    with    HST    (Williams    et    al.    2007)    have    set    the    stage    for this    type    of    work,    but    truly    transformative    observations    require    the    coupling    of    high    resolution with    wide    areal    coverage.    As    a    result,    WFIRST    seems    set    to    make    important    contributions    to    this important    area    of    astrophysics.    We    can    best    illustrate    the    potential    of    WFIRST    by    showing    how    it might    be    used    study    the    ICL    in    the    Virgo    cluster.  \nTo    properly    populate    a    color--magnitude    diagram    we    seek    to    image    stars    two    magnitudes    below the    tip    of    the    red    giant    branch.    We    can    estimate    the    number    of    such    stars    in    the    Virgo    cluster    in two    ways:  \n- 1. Using    NGC2419    (a    very    compact    globular    cluster    which    has    a    mass    of    about    10 6 M ☉ and    about 5     million     solar     luminosities)     as     a     reference,     we     count     556     stars     within     2     mag     of     the     RGB     tip. From    this     we     expect     to     find     5.56     ×10 --4 detectable    stars    per    unit    solar    mass    in    a     low     metallicity old    stellar    population.    Assuming    Virgo    has    a    total    mass    of    3×10 14 M ☉ (Ferrarese    et    al.    2012),    and a     baryonic    M/L    of    100,    we    have    a    baryonic    mass    of    3×10 12 M ☉ .     If     10%     of     this    mass    is    in    the    ICL, we     have     3×10 11 M ☉ of     baryons     in     the     Virgo     ICL.     The     corresponding     number     of     detectable     stars within    two    magnitudes    of    the    tip    of    the    RGB    is    1.7    ×    10 8 stars.    This    suggests    something    like    100 million    detectable    stars    within    2    mag    of    the    RGB    tip    in    Virgo.    Spreading    these    over    100    sq.    deg (the     area     covered     by     the     Next     Generation     Virgo     Survey)     results     in     a     space     density     of     1.7×10 6 intracluster    stars    deg --2 ,    or    about    500,000    per    WFIRST    field.  \n2. An    alternative    approach    is    to    scale    from    the    work    of    Williams,    Ciardullo    et    al.    (2007), who     report     ~5000     intracluster     stars     in     a     deep     ACS     field     (with     a     field     of     view     of     11.39 arcmin 2 ).     Based     on     their     Figure     9,     the     tip     of     the     RGB     is     at     F814W     =     27     mag.     Their     data goes    down    to    about    F814W    =    29    mag    so    they    probe    about    2    mag    below    the    RGB    tip.    The space     density     of     intracluster     stars     in     this     paper     is     ~     450/arcmin 2 , corresponding     to 1.6×10 6 intracluster    stars        deg --2 ,    in    good    agreement    with    our    previous    estimate    of    about half    a    million    targets    per    WFIRST    field    within    two    magnitudes    of    the    RGB    tip.  \nThe     required     integration     time     can     be     determined     from     knowledge     of     the     absolute magnitude    of    the    tip    of    the    red    giant    branch.    Since    the    ICL    is    thought    to    be    comprised mainly     of     stripped     stars,     we     can     estimate     the     magnitude     of     the     RGB     as     a     function     of abundance    by    using    two    globular    clusters    with    different    metallicities,    namely    ω    Cen    at [M/H] ≃ --1.5    and    47    Tuc    at    [M/H] ≃ --0.6.    According    to    Bellazzini    et    al    (2004),    the    H--band AB    absolute    magnitude    of    the    RGB    tip    is    --4.55    +/--    0.18    for    ω    Cen    and    --4.94    +/--    0.18    for 47    Tuc.    At    the    distance    modulus    of    Virgo    (31.1)    stars    two    magnitudes    fainter    than    the    tip of    the    red    giant    branch    would    be    at    HAB=28.55    mag    based    on    a    ω    Cen    stellar    population, and    at    HAB=28.16    based    on    a    47    Tuc    stellar    population.    Taking    the    fainter    of    these    (to    be conservative)    the    HST/WFC3    exposure    time    calculator    indicates    that    S/N    =    5    at    HAB    =28.5 mag    would    be    achieved    in    about    54,000s    with    WFIRST.    A    similar    amount    of    time    would be    required    in    order    to    obtain    a    comparable    depth    in    at    least    one    other    band,    for    a    total of     ~100ks.     Covering     Virgo     in     its     entirety     is     out     of     the     question     (it     would     mean     360 WFIRST     pointings!),     but     an     ambitious     program     to     radially     sample     the     cluster     ICL     at several     positions     from     the     core     to     the     virial     radius     would     be     feasible.     This     would     be     a very    large    program,    but    the    legacy    value    would    be    enormous.  \nChris    Mihos    (mihos@case.edu)    and    Paul    Harding    (paul.harding@case.edu)', 'Introduction': 'The WFIRST high-latitude survey will provide a large and homogenous sample of faint galaxies selected at wavelengths that most accurately trace stellar mass. This data set will enable a wide range of studies of galaxy formation, mass assembly and star formation over the full galaxy-building epoch. The lowresolution spectroscopic capability offered by slitless grisms has been shown to be highly effective in selecting galaxies with well-determined redshifts and a range of star forming histories Ð from extreme starburst, to quenched galaxies and old passively evolving systems. The Giant Magellan Telescope and other extremely large telescopes on the ground can leverage this dataset by providing deep spectroscopy, diffraction-limited imaging at the 20 mas scale and spatially resolved 2-D spectroscopy with 20-100 mas sampling.', 'WFIRST/NRO': 'The     Hubble     Space     Telescope     has     shown     how     powerful     this     resolved     structural     approach     is     for understanding     galaxies.     Only     very     small     fields     have     been     observed     with     Hubble,     and     most     of     those within     the     observed     optical.     To     study     the     formation     of     galaxies     will     require     high     resolution     imaging     in the    near--infrared,    which    WFIRST/NRO    will    provide,    especially    if    a    large    2.4m    mirror    is    utilized.        This    will bring    the    pixel    size    down    to    0.13--0.11    arcsec,    allowing    us    to    perform    WFC3    type    surveys    over    at    least    a few    degrees,    which    will    be    much    larger    than    any    near    infrared    survey    of    this    type    for    distant    galaxies    yet performed.                This    will    allow    us    to    directly    measure    in    an    empirical    way    how    galaxies,    and    the    stars    within them,    assembled    over    most    of    cosmic    history    to    within    a    Billion    years    of    the    big    bang.  \n<!-- image -->  \nCaption:    How    infrared    light    (F160W)    shows    features    of    distant    galaxies    not    seen    in    optical light    (F775W)        (from    Kocevski    et    al.    2011)', 'Searching    for    Extreme    Shock--dominated    Galaxy    Systems    from    1    <    z    <    2': "Background:    The    importance    of    turbulence    and    shocks    at    heating    gas    in    galaxies    is    only    just    beginning    to emerge     through     both     visible     IFU     imaging     and     mid--IR     molecular     hydrogen     observations     of     collisional galaxies,    and    galaxies    with    powerful    AGN    winds.    Recent    models    of    fast    shocks    predict    optical    emission-line    ratios,    which    overlap    the    Low    Ionization    Nuclear    Emission    Line    (LINER)    region    of    the    traditional    BPT diagnostic    diagram    (Fig1a).        Amazingly    (Fig1b    &    c)    the    distinct    nature    of    shocked    gas    can    be    diagnosed even    when    H α and     [NII]    are    blended-as    in    the    case    of    a    low--res    GRISM    spectrometer.    Although    many LINERs    are    likely    to    be    heated    by    sub--Eddington    accretion    onto    a    black    hole,    there    are    clear    examples    of LINER     emission     where     galaxy--wide     shocks     strongly     dominate     the     optical     spectrum,     e.     g.     NGC     1266 (Alatalo    et    al.    2012),    or    the    giant    shocked    filament    in    Stephan's    Quintet    (Xu    et    al.    2003;    Appleton    et    al 2006).    The    shocks    may    suppress    star    formation,    as    in    the    case    of    some    radio    galaxies,    where    the    jet    may drive     the     heating     (Ogle     et     al     2010;     Nesvadba     et     al.     2011).     Even     old     radio     galaxies     may     still     show remnants     of     shocked     gas     (Buttiglione     2013).     Discovering     more     'pure--shock'     objects     at     higher     z,     will allow     us     to     investigate     places     in     the     universe     where     strong     turbulence     is     operating     to     quench     star formation.    Finding    'nascent'    pre--starforming    disks    in    a    highly    turbulent    phase    will    help    us    understand how    galaxy    disks    form    and    evolve    (e.    g.    in    cold    flows),    or    how    AGN    feedback    may    influence    galaxy    hosts.  \nWFIRST:    Large    galaxy    surveys    such    as    SDSS    and    BOSS    have    already    begun    to    turn    up    rare    objects    in    the correct     area     of     phase--space     in     the     local     (z     <     0.2)     universe     (see     comparison     of     Fig1a     with     b).     WFIRST's near--IR     GRISM     capability     will     allow     for     a     similar     exploration     at     much     higher     z,     where     turbulent     galaxy disks     may     be     more     common.     Assuming     a     GRISM     spectrograph     with     160     <     R     <     260     in     the     wavelength range    1.1    to    2    microns,    WFIRST    will    detect    galaxies    over    a    range    1    <    z    <    2    in    the    required    lines.    Because the     [OI]/H α ratio     is     so     extreme     in     pure     shocked     systems,     it     may     not     even     be     necessary     to     detect     the [OIII]     and     H β lines     to     form     a     sample     of     extreme     shock--dominated     systems.     Based     on     simulations     and studies    using    a    similar    GRISM    on    HST/WFC3    (WISP),    2000--3000    emission    line    galaxies/sq.    degree    would be     detectable     (>     1     x     10 --16 ergs/s/cm 2 )     over     the     required     range.     With     large     planned     deep     redshift     BAO surveys    envisaged    in    the    WFIRST    Interim    Report    covering    ~2000--3500    sq.    degree    of    sky/yr,    even    if    only 0.5%     of     all     emission--line     galaxies     are     shocked     galaxies     (probably     conservative     given     that     7%     of     SDSS galaxies    are    LINERs),    then    we    expect    to    find    tens    of    thousands    of    shocked    galaxies    over    a    few    years    of operation.    These    BAO    samples    will    allow    us    to    investigate    how    these    galaxies    change    with    redshift    and local     environment-for    example    are     they     correlated     with     galaxy     over--density     or     filaments?     Significant new     ancillary     data     sets     (e.     g.     deep     SKA--precursor     radio     galaxy     surveys)     will     also     be     available     then, allowing    for    smaller,    deeper,    targeted    GO    searches    of    specific    dense    proto--clusters,    or    quasar    environs.  \n<!-- image -->  \n<!-- image -->  \nFig.1a  Classical  BPT  diagram  showing  separation  of  LINERs  (7%)  from  Seyferts  and  SF  galaxies  (Kewley  et  al. 2006).  Fig1b.  Some  LINERS  may  be  created  in  high-speed  shocks  (Rich  et  al.  2012).  Models  show  range  of  shock velocities and mixing fractions with SF. Fig1c. Even when H α +[NII] is blended,  the shock models separate cleanly from the starburst sequence on the x-axis.  \n<!-- image -->  \nKey    Requirements        for    GRISM    Survey  \nDepth    :-    1--2    x10 --16 ergs    s --1 cm --2 detection    threshold;        Areal    coverage:--    2000--3000    deg 2 (BAO    type    planned    coverage) Spectral    Resolution    (R    >    150)    ;        Wavelength    Coverage    -    1.1--2 ∝ m  \nJulian    Merten,    Jason    Rhodes    (JPL    /    Caltech),    jmerten@caltech.edu", 'Characterizing    the    sources    responsible    for    Reionization': 'Star-forming     galaxies     are     likely     responsible     for     reionizing     the     Universe     by     z~6,     implying     that     a     high fraction    of    HI-ionizing    (Lyman    continuum;    LyC)    photons    escape    into    the    IGM.    Measurements    of    galaxies at    z<3.5    show    the    average    escape    fraction,    fesc,    to    be    very    low    or    undetected    at    all    redshifts . At    redshift z ∼ 3,    high    fesc    ( ≥ 50%)    have    been    reported    in    only    about    10%    of    LBGs    and    Lyα    emitters    though    significant mysteries    remain    for    even    these    few    detections    (fesc    >    unity,    and    unknown    numbers    of    interlopers).  \nCurrent     studies     suggest     that     fesc     may     evolve     with     redshift     (Figure     1)     and/or     be     higher     in     low     mass galaxies.    A    recent    study    of    the    radiation    transport    of    LyC    at    z=    3--6    in    galaxies    drawn    from    cosmological  \nSPH    simulations    predicted    substantial    LyC    (fesc    =820%)     emission     from     galaxies     with     halo     masses Mhalo     <~     10 10 M*,     but     little     or     nothing     from     more massive     systems.     In     addition,     fesc is found     to increase     with     decreasing     metallicity     and     SFR     both     of     which     are     thought     to     positively     correlate with    Mhalo.  \nThe     LyC     is     best     studied     at     z<3     (in     the     UV)     due     to the     increasing     opacity     of     the     IGM     to     LyC     photons higher     z.     However,     current     studies     are     severely limited    by    the    need    to    find    appropriate    analogs    to the    low    mass/metallicity    objects    that    are    the    likely sources    of    LyC    photons    during    Reionization.  \nFigure    1:    LyC/f1500    measurements    (versus    UV luminosity)    at    z    ~    1    and    z    ~    3    corrected    for    the average    IGM    attenuation    at    the    relevant wavelengths    (Siana    et    al.    2010).  \n<!-- image -->', 'Resolved    stellar    population    studies    in    z  2    SF    galaxies': "Observations    show    that    'normal'    SF    galaxies    were    in    place    at    z  0.5,    with    stellar    population    and scaling     relations     consistent     with     passive     evolution     into     the     stable     population     observed     locally. Looking     back     to     z     >     2,     dramatic     changes     appear.     Massive     star--forming     galaxies     along     the     so-called    main    sequence    at    these    epochs    tend    to    be    thick,    clumpy    disks,    forming    stars    at    rates    (100 M ⊙ /yr)    much    higher    than    is    observed    in    the    thin,    quiescent    disks    observed    at    z    <    0.5.  \nGravitational    instabilities    in    gas-rich    turbulent    disks    can    produce    dense    'clumps'    supported    by cold     streams     of     gas.          These     structures     could     eventually     migrate     into     a     bulge     component     over time scales < 10 dynamical     times,     or     <     0.5     Gyrs.     As the clumps     merge,     the     growing spheroid/bulge    will    have    a    stabilizing    effect    on    the    disk,    and    eventually    it    will    be    massive    enough (~20%     of     the     galaxy     stellar     mass)     to     prevent     further     fragmentation.     Constraining     this     self-regulating     process     requires     accurate     measurements     of     the     ages     of     both     the     clumps     and     the diffuse    stellar    component.  \nFigure 1: z =2.5 galaxy from Elmegreen et al. (2005). WFIRST+IFU will provide low resolution spectra over scales < 2Kpc, accurately allowing age-dating of the stellar population.  \n<!-- image -->", 'Near    Infrared    Counterparts    of    Elusive    Binary    Neutron    Star    Mergers': 'Mansi    Kasliwal    (Carnegie),    Samaya    Nissanke    (Caltech),    Christopher    Hirata    (Caltech)', 'Mike    Gladders    (The    University    of    Chicago),    gladders@oddjob.uchicago.edu Strong    Lensing': "Background:     Strong     lensing     of     distant     sources     (galaxies,     AGN,     SNe)     provides     deep     insight     into the distant universe.     The increased     S/N     from lensing magnification     allows     for     precise photometry    over    a    much    broader    range    of    wavelengths    than    would    otherwise    be    accessible,    for luminous     and     highly     magnified     sources.     At     the     same     time,     strong     lensing     allows     us     to     probe more    deeply    into    the    galaxy    LF    than    any    other    technique;    the    current    Hubble    Frontier    Fields    are designed    to    exploit    this    effect    in    the    reionization    epoch.    Strong    lensing    of    distant    galaxies    also provides    access    to    unique    spatial    scales;    at    Hubble--like    resolutions    structures    smaller    than    100 parsecs     can     be     resolved.     Strong     lensing     is     also     a     powerful     probe     of     the     mass     structure     of     the foreground    lenses,    allowing    tests    of     ΛCDM    predictions    of     halo     and     sub--halo     properties     and/or the    detailed    physics    operating    in    halo    cores    over    several    decades    of    halo    mass.    Strong    lensing    of variable    sources    also    allows    for    a    geometric    cosmological    test    through    time    delays.  \nWFIRST:     Currently,     the     total     number     of     known     strong     lenses     is     hundreds.     Efforts     to     exploit ground--based     surveys     (e.g.,     DES,     LSST)     will     increase     this     by     hundreds     more     to     perhaps     a thousand.    The    strong    lens    sample    in    the    COSMOS    HST    data    -    67    candidates    (Faure    et    al.    2008)    in 1.6    deg 2 of     imaging    comparable    in    depth    to    the    WFIRST    HLS    -    suggests    that    the    WFIRST    strong lens    sample    will    number    in    the    tens    of    thousands,    even    if    one    restricts    the    sample    to    the    10--20% of    such    candidate    systems    which    are    unambiguous    and    'interesting'    (i.e.    clearly    multiply--imaged, and     potentially     model--able).     Defining     this     sample     from     the     WFIRST     HLS     represents     a     fantastic opportunity     for     citizen     science.     Strong     lensing     is     visually     compelling     and     unique,     and     offers     a direct    connection    to    the    physics    of    General    Relatively    that    frames    modern    cosmology.  \nThe     bright     end     of     this     sample     will     have     redshifts     from     the     HLS     grism     data     -     on     order     of     a thousand    systems;    that    will    represent    an    order    of    magnitude    increase    in    arc    redshift    statistics, and     will     likely     not     be     challenged     by     ground--based     efforts     since     the     sky     density     of     systems     will still     be     such     that     there     is     little     multiplex     advantage     for     all     but     the     widest--field     spectrographs. WFIRST--quality    multi--band    imaging,    and    grism    spectroscopic    redshifts    will    yield    an    abundance    of systems    that    can    be    modeled    in    detail.    Likely    the    limiting    factor    will    be    people    and    not    data;    the current     approach     of     a     hand--tooled     model     for     each     system     will     have     to     be     automated     and refined    if    we    are    to    fully    exploit    the    strong    lens    data    that    WFIRST    will    yield.  \nThe    bulk    of    the    sample    will    not    have    redshifts;    statistical    analyses    will    dominate.    Detailed    image--  \nlevel    simulations    will    play    a    critical    role    in    defining    selection    functions.    One    unique    problem    will be     the     lack     of     source--plane     images     with     sufficient     resolution.     The     best     path     forward     will     be some    form    of    'complexification'    applied    to    WFIRST    imaging    (e.g.,    Groeneboom    &    Dahle    2014). Lensing    statistics    aside,    WFIRST    offers    a    truly    unique    opportunity    to    coherently    probe    the    mass structure    of    the    largest    halos    over    a    prodigious    radial    and    density    range.    In    pointed    GO    mode, we    will    be    able    to    study    massive    clusters    from    the    strong    lensing    core,    through    the    intermediate flexion    regime    and    out    to    the    weak    lensing    regime,    anchored    in    the    true    'field',    in    one    image.", 'Appendix E Pasadena  2014  Conference  Summary': "The Wide-Field  InfraRed  Surveys:  Science  and Techniques conference was held in Pasadena, CA on November  17-20,  2014.  At  least  220  scientists  from around  the  world  attended,  engaging  in  lively  discussions both in session and during the breaks. The success  of  the  conference  reflected  an  increasingly  engaged  and  supportive  community-at-large  looking  forward to WFIRST-AFTA and its science.  \nThe conference was intended as a forum for scientists to consider recent progress from missions such as Spitzer, Kepler, Hubble, Planck, WISE and Herschel, as it  affects  the  design and utilization of the next generation of space-based infrared surveys, including WFIRST. Invited  talks  exposed  the  participants  to  the capabilities currently envisaged for WFIRST-AFTA, and assessed  the  mission's  promise  in  the  context  of  the anticipated performance of Gaia, JWST and Euclid, as well  as  ground-based  surveys,  especially  LSST  and large-scale  radio  surveys  such  as  the  next  generation VLASS. Because of the wide range of topics addressed by future infrared survey missions, from dark energy to exoplanets, and because of the increasing importance of  additional  community-driven  science,  the  emphasis was on bringing together these many scientific constituencies  to  present  their  perspectives  and  inform  the trade studies currently being pursued by the WFIRSTAFTA Science Definition Team and Study Office. As the conference unfolded, WFIRST-AFTA was the clear focus for the 220 participants, of which 15% were based at non-US institutions.  \nThe  conference  was  mostly  convened  in  plenary sessions, with about 30% of the time spent in parallel sessions  that  addressed  Dark  Energy,  Exoplanets, Milky  Way  and  Local  Group,  and  Beyond  the  Local Group topics. Two panel discussions were held in plenary  session;  one  focused  on  the  placement  of  the high-latitude  survey  fields  in  view  of  existing  and planned surveys and optimizing the science yield in areas besides dark energy; the other explored anticipated Community  Research  Support  Needs  for  maximizing science return from the WFIRST-AFTA mission. A total of 120 talks were delivered, including a NASA HQ perspective delivered by Paul Hertz, Director of the Astrophysics Division at NASA HQ, via video link, and a set of  closing  remarks  by  Alan  Dressler.  The  conference website  contains  more  detail  about  the  program,  abstracts,  participants  and  organizers.  PDF  versions  of  \nthe  talks  are  also  available  from  the  same  website: http://conference.ipac.caltech.edu/wfirs2014/.  \nThe richness of the conference and of its multiple science threads makes it nearly impossible to provide a complete and balanced summary. The major themes of dark energy, exoplanet discovery and characterization, and Galactic and extragalactic astrophysics were dominant. The following paragraphs however sample some of the themes that were noteworthy for eliciting particular interest among participants, or which were novel or unanticipated.  \nAdditional  Bulge  Science:  There  was  much  interest  in the  potential  for  additional  science  possible  using  the data from the baseline microlensing survey of the Galactic Bulge. Talks by Andy Gould and Mike Rich highlighted a number of science pursuits made possible by the  exquisite  astrometric  and  photometric  accuracies possible  with  WFIRST-AFTA:  under  stellar  astrophysics,  parallax  and  proper  motion  studies,  ages  and [Fe/H]  estimates,  and  astroseismology  for  millions  to tens of millions of stars with WFIRST-AFTA. In addition to  studies  of  the  dynamics  and  subpopulations  in  the bulge  leading  to  better  understanding  of  its  assembly history,  the  survey  will  provide  a  sensitive  search  for isolated or paired low-mass Black Holes, neutron stars or  other  exotic  objects,  and  within  the  Solar  System, precision  orbits  and  binary  fraction  for  thousands  of Kuiper Belt Objects. It should be stressed that this was only a first look at the potential science yield from the microlensing survey.  \nExoplanet Science with WFIRST-AFTA: A wide variety of  exoplanet  science  topics  and  techniques  were  discussed in the plenary and parallel sessions. A plenary talk highlighted  how  WFIRST-AFTA's  microlensing census of planets around the snowline will be critical to testing  theories  of  planet  formation.  The  parallel  session on science addressed the current state of the art in microlensing;  coronagraphic  imaging  of  planets  and disks; and the need for a resolving power of R~70 for retrieval  of  atmospheric  properties  of  giant  planets. There was discussion of the potential of a starshade for WFIRST-AFTA in an L2 orbit to test technology and to increase the number of small planets accessible to the mission. Parallel sessions on science requirements and precursor  observations  addressed  the  importance  of: HST observing in the Bulge fields for initial characterization;  ground-based  microlensing  to  build  the  US community; radial velocity  programs and  Gaia  as providers of targets for the WFIRST-AFTA coronagraph.  \nGeneral  Investigator  and  General  Observer  Science: Discussions  during  the  conference  explored  how  science beyond the areas of dark energy and microlensing will  be  possible  with  WFIRST-AFTA.  Guest  Investigators will primarily exploit the data acquired for the microlensing  survey  or  the  main  dark  energy  high-latitude survey for other topics such as stellar astrophysics (see above)  or  galaxy  evolution.  Guest  Investigators  would propose to do unique or novel science with the existing survey  data,  potentially  making  available  special  tools or methods that could be distributed to the community. In  the  parallel  and  plenary  sessions,  participants  were eager to discuss the potential for the high-latitude survey to find extremely young galaxies at high-redshift (z > 5), track the assembly of galaxies at later times, understand how galaxy properties are influenced by environment, and how best to use the grism data and targeted GO programs to diagnose star-formation and galactic feedback over a wide range of cosmic time. There was also an interesting discussion on how to recognize and maximally exploit the large number of strong gravitational  lenses  expected  in  the  WFIRST-AFTA  database. Guest Observers would follow the traditional proposal  process  to  conduct  observations  with  WFIRSTAFTA separate from the main surveys, targeting for instance  galaxies  in  the  Local  Group,  or  specific  highredshift structures. Because both research approaches will  be supported by WFIRST-AFTA, the design of the main surveys should be cognizant of the archival value of the data.  \nFilter  Set  Options:  One  manifestation  of  the  robust community engagement in the WFIRST-AFTA mission is that many of the speakers addressing GI/GO science topics suggested that their research would benefit from tuning of the filter bandpasses. In many cases, the suggestion was to extend the wavelength coverage of the mission, either  redward to mitigate extinction or reach higher redshifts, or blueward for improved color discrimination for both stars and galaxies.  \nThe  Data  Volume  Challenge:  Conference  participants anticipated the shear volume and richness of the data expected  from  WFIRST-AFTA  as  a  new  qualitative challenge,  and  discussed  how  best  to  prepare  for  it. Early availability of simulated WFIRST-AFTA data was generally  acknowledged  as  critical  to  preparing  the community,  and  LSST  data  access  and  exploitation were also seen as contributing significantly to this preparation. Eventually, the archives built to serve WFIRST-  \nAFTA data will require massive power, as well as agility and flexibility  to  evolve  novel  tools  in  response  to  the needs of users extracting new science from huge data sets.", 'Appendix F Exoplanet Detectability with the WFIRST-AFTA Coronagraph': "The  Coronagraph  Instrument  (CGI)  on  WFIRSTAFTA will ultimately be judged on its scientific yield, that is,  its  ability  to  directly detect and spectrally characterize  planets  and disks around nearby stars. In this Appendix we outline the basis for estimating the expected CGI  science  yield  for  three  groups  of  targets,  known radial-velocity  (RV)  planets,  'new'  as-yet  unknown blind-search planets, and debris disks. We find that all three  groups can be detected in sufficient numbers to produce substantial advances in the science of nearby exoplanets and disks.", 'F.1. RV Catalog': 'The list  of  known  RV  planets  used  here  contains 528 targets. Most of these range in distance from about 1 - 600 pc, in mass from 3 - 6000 MEarth, and in semimajor axis from 0.04 - 10 AU. The radius of each planet is estimated by using an empirical relationship between mass  and  radius  based  on  those  planets  with  known values of each. The planet brightness is estimated for a visible  geometric albedo of 40%, a Lambert scattering function, a circular orbit, an orbital inclination of 60 degrees, and a mean anomaly of 70 degrees (i.e., slightly brighter than at maximum elongation, and slightly closer to the star). The star brightness is estimated on the basis of its visual magnitude and color. The ratio of planet to  star  brightness  is  called  the  contrast.  We  assume that the orbital period and phase are so well known that we can estimate the optimum calendar date on which to search for the planet. Even over a broad range of inclinations, with a current RV solution it is possible to determine a range of dates over which the planet will have best observability (typically between 60 and 90 degrees phase). The main remaining uncertainty is the position angle on the sky, which requires that the search range be able to cover 360-degrees of azimuth, either in one observation or in several sequential ones.', 'F.2. Science Yield Model': "The purpose of our science yield model is to predict the fraction of planet light incident on the telescope that is delivered to the focal plane detector, the shape of  that  spot  (the  point  spread  function,  PSF),  the  instrumental polarization distortion, the brightness of the background  diffracted  'speckles',  and  the  degree  to which  the  speckles  vary  with  time.  Our  science  yield model comprises four parts: an optical model, a coro-  \nnagraph  model,  a  detector  model,  and  a  telescope model.", 'F.2.1 Optical Model': "Our optical model is the standard 'PROPER' program written by John Krist and employed by him for all of the instrument performance calculations in this section.  PROPER  propagates  a  wavefront  through  all  of the telescope and CGI optical surfaces, in the near and far  fields,  using  Fourier-based  Fresnel  and  angular spectrum methods. For the purpose of calculating science yield, the key results from PROPER are the azimuth-averaged  contrast  values  of  the  background speckle field,  the  fraction  of  planet  light  in  the  core  of the PSF (here taken to be the area enclosed by the fullwidth at half-maximum, FWHM), all for each of two orthogonal linear polarizations, as a function of radial angle on the sky, for selected values of the RMS angular jitter  of  the  telescope  pointing  direction,  for  a  given power  spectral  density  (PSD)  of  polishing  errors  and amplitude errors on the telescope mirrors, and integrated  over  the  full  wavelength  band.  Polarization  is  accounted  for  by  noting  that  the  portion  of  the  incident wavefront  that  is  reflected  from  the  angle  mirrors  (including the primary mirror) will suffer a phase delay between  the  radial  and  tangential  components,  which  in turn  negatively  affects  the  coronagraph  performance. Therefore,  we  currently  plan  to  separate  the  x  and  y polarizations with a Wollaston prism placed just before the  direct-imaging  detector;  the  coronagraph  deformable mirror settings can then be tuned to optimize contrast  in  either  polarization.  The  spectrograph  may  use either a single fixed polarizer or none; simulations show the shaped pupil coronagraph is less sensitive to these low-order  differential  aberrations.  Thus  the  dark  hole will be achieved, and the science measurements taken, in  one of these polarizations, even though both polarizations will be separately recorded.", 'F.2.2 Coronagraph Model': 'Our coronagraph model is a mostly shared optical system  hosting  two  coronagraph  architectures  that were chosen as the prime instrument after a community-wide down-selection process in 2013, with a third architecture as a study-phase backup. The prime instruments are the Hybrid-Lyot Coronagraph (HLC) and the Shaped-Pupil  Coronagraph  (SPC);  the  backup  instrument  is  the  Phase-Induced  Amplitude  Apodization (PIAA)  coronagraph.  All  three  architectures  are  being developed  in  parallel  in  laboratories  for  the  WFIRST mission. Each uses a combination of phase and ampli-  \ntude  control  of  the  wavefront  in  the  pupil,  near-pupil, and image planes to achieve contrast values on the order of 10 -9 over a range of azimuthal and radial angles on the sky. The coronagraph systems feed both a direct imager and an Integral Field Spectrograph (IFS).', 'F.2.3 Detector Model': 'Our detector model is centered on the well-known Electron-Multiplying  CCD  (EMCCD)  from  e2v.  Model parameters include pixel size, wavelength dependence of quantum efficiency, and parameters for each of three read modes: ordinary CCD-type operation (zero gain), electron-multiplying  analog  operation,  and  electronmultiplying photon-counting operation. All three modes are accessible in flight, but for the present estimate we use  only  the  latter,  most  sensitive,  photon-counting mode. Key parameters of interest, as used in the current  simulations,  include  dark  current  (0.0005  electrons/sec per pixel), clock-induced charge (0.001 electrons per pixel per read), gain factor (500), read noise (16 electrons RMS per read), integration time per snapshot (100 sec), and cosmic-ray effects (not included in this estimate).', 'F.2.4 Telescope Model': 'Our telescope model includes the shape of the pupil  (including  the  central  obscuration  and  six  spider arms), the off-axis angle of the CGI, the mirror prescriptions,  the  model  Power  Spectral  Density  (PSD)  of phase and amplitude errors of the primary mirror (PM) and  secondary  mirror  (SM),  the  model  RMS  pointing jitter, the coating reflectivity as a function of wavelength, the  polarization  transformation  as  a  function  of  wavelength and position within the pupil, the powered optics between the PM/SM and the CGI, and the model wavefront  deformation  owing  to  thermal  changes  in  the shape and location of telescope mirrors as a function of pointing  angle,  recent  slew  angle  history,  Earth  shadowing, and orbit phase with respect to Earth.', 'F.2.5 Exoplanet Detection Model': 'The expected science yield of the CGI is estimated separately  for  each  coronagraph  architecture  as  follows. For each wavelength band we estimate the count rate of electrons, in the FWHM of the planet image, for the  given  radial  (sky)  location  of  the  planet,  using  the factors of transmission and image size as supplied by PROPER. We make this estimate for each of three values of RMS pointing jitter (0.4, 0.8, and 1.6 mas) and for two values of post-processing factor (1/10 and 1/30), where the latter parameter gives the factor by which we  \nexpect  to  reduce  the  RMS  spatial  variation  of  the speckle contrast (equal to the average contrast, owing to speckle statistics) by mathematical processing of the image data on the ground. We also estimate the noise associated with the detection of the planet image as the square root of the sum of the total electron count in the FWHM  of  the  image  (planet  counts,  speckle  counts, detector  counts,  and  zodiacal  background  and  foreground  counts,  all  increasing  with  time)  plus  the  fixed noise  floor  from  the  speckles  reduced  by  the  postproduction factor (not increasing with time).', 'F.3. RV Planet Yield Estimates': "We solve for the time required to achieve a signalto-noise  ratio  (SNR)  value  of  5.0.  Note  that  the  fixed noise floor makes the faintest planets undetectable regardless of integration time. This (assumed) fixed noise floor is therefore an important limitation on our ability to detect  planets.  A  key  focus  of  future  work  will  be  to substantiate and reduce this factor given more realistic simulations  of  the  telescope's  thermal  response.  The post-production factors are chosen based on our experience with subtracting PSFs from images from groundbased coronagraphs, as well as from images made by HST. A key focus of future work will be to substantiate and reduce this factor given more realistic simulations of the telescope's thermal response.  \nOnce this procedure is completed for a given spectral band, we repeat it for all bands, 5 bands for the direct imaging channel and 3 bands for the Integral Field Spectrograph (IFS). See Table F-2 for the parameters of  all  7  bands.  Typically  the  short-wavelength  bands produce the most detections. This is due to diffraction, which places the response window at smaller angles for shorter  wavelengths.  Since  planets  tend  to  cluster  at small  angular  separations,  more  are  captured  in  short bands.  \nFor  planets  that  are  detectable  (SNR  >  5),  we solve  for  the  integration  time  given  the  different  assumptions regarding telescope jitter and postproduction  factor.  Planets  that  are  detectable  within  a maximum integration (typically 1 day) are retained. Finally, we generate a graphical display of the results in the form of a plot of contrast as a function of separation angle for detectable planets, for each coronagraph architecture  and  spectral  band.  A  brief  summary  of  the overall performance of the three architectures is shown in  Table  F-1.  A  popular  way  to  indicate  the  angular range of a coronagraph is to give the inner and outer working  angle  (IWA,  OWA);  however,  these  numbers can  be  misleading  because  detection  is  not  a  simple  \nbinary  function  of  angle.  For  some  architectures  the contrast smoothly drops through the inner parts of the dark  region.  Instead,  we  show  a  practical  example  of the  range,  using  the  known  RV  planets,  in  columns  2 and 3, where the angular separation of the closest and farthest detectable planet from the parent star is listed. Likewise,  the  best  achievable  contrast  can  be  a  misleading value, as the contrast floors of the architectures here typically vary by a factor of about 100. Thus, we instead  use  a  common  example  target,  47  UMa  c, which has a planet/star contrast of 43 x10 -10 ,  and  can be detected by all three architectures in Table F-1. The table  gives  the  5-sigma  sensitivity  limit  (contrast  floor) for  each  example  and  the  integration  time.  It  is  clear from this  table  that  these  parameters  can  vary  over  a large range in a practical case, so the nominal criterion is not these performance parameters per se. Rather it is the  total  number  of  planets  that  can  be  detected,  as shown in Figure F-1, Figure F-2, and Figure F-3.  \nTable F-1: Representative values of the angular range of each coronagraph architecture, and expected values of planet contrast, 5-sigma floor contrast, and integration time  for SNR = 5 for a typical planet.  \nTable F-2: Science filter bands.  For each filter, the columns give the central wavelength, ratio of full-width at halfmaximum (FWHM) to central wavelength, nominal science purpose, polarization state, destination focal plane, and coronagraph architecture to be used for that filter and destination.  \nFigure F-1: Science imaging yield of known RV planets that are detectable with the HLC, in the 565-nm band (10%), for a single polarization  (triangles). The  short-dash line  (lower curve)  is  the  5-sigma speckle  noise  detection  floor  for  the case of a telescope pointing jitter of 0.4 mas RMS residual uncorrected angle and after a post-processing factor of 30 times reduction in the spatial rms speckle noise is applied. The upper long-dash line is similar for a pointing jitter of 1.6 mas and a post-processing factor of only 10. The HLC has a 360-degree azimuth field in a single snapshot. The actual detection sensitivity for a given exposure will also depend on Poisson photon noise as a function of stellar magnitude and integration time; the speckle level sets a floor. The inner and outer working angles are effectively set by the angle limits of these floors as plotted. The solid triangle symbols are detections that are expected to take less than one day each, for the worst-case floor (upper); the open triangles are the extra planets that are detectable for the best-case floor (lower). The dashed green line indicates the estimated contrast of a target zodi cloud that has 10 times more dust than the Solar System, with an estimated continuation into the Edgeworth-Kuiper belt at larger angles, for a target system at 10 pc. For the HLC case shown, we expect to detect about 16 RV planets (S/N=5) in a total integration time of 10 days in a single polarization in this band. Most planets will have an integration time of less than 1 day.  \n<!-- image -->  \nFigure F-2: Science imaging yield of RV planets with the SPC, otherwise the same as Figure F-1. Here the science yield is 13 RV-planet detections. Each of which could be done in less than a day if the position angle of the planet were known. However, because it is not known, and because the SPC can only observe an azimuth range of about 120 degrees per snapshot, it will take three such snapshots to cover the full azimuth range, and therefore the total observing time will be about 30 days. The azimuth range of each snapshot with the SPC is only 2 × 65 degrees, so 3  snapshots are required to cover the entire 360-degree azimuth range, when searching for a planet;  however once a planet is discovered, it can then choose the appropriate azimuthal orientation for subsequent snapshots, either to improve the SNR or to observe at a different wavelength. Another difference with respect to the HLC is that the SPC has a higher contrast floor, which reduces the number of detectable planets. A compensating factor is that the SPC is less sensitive to telescope jitter, which gives it a better performance margin in flight and potentially  higher  spectral  bandwidth. The baseline for WFIRST-AFTA is to use the HLC for initial discovery at short wavelength and the SPC for long-wavelength characterization.  \n<!-- image -->  \nFigure F-3: Science imaging yield of the backup architecture, the PIAA coronagraph. This architecture has the twin advantages of having a greater overall throughput as well as having a theoretically smaller inner working angle, allowing it to access considerably more planets close to their star. However an accompanying disadvantage is that it is more sensitive to telescope jitter, which with the adopted values of jitter produces higher 5-sigma floor contrasts, as indicated in the figure. Therefore many planets that were detected by a large contrast margin with the HLC or SPC, are now closer to the PIAA contrast limit, and will therefore require the best possible operating conditions (lowest jitter and most aggressive post-production factor). This version of PIAA also has only one deformable mirror, hence the azimuthal field is 180  degrees, so  two snapshots are required in order to fully  examine a new system. The higher throughput and smaller inner working angle result in a greater number of detectable RV planets, and at a faster rate per planet than for the HLC or SPC, but operating with a relatively smaller margin.  \n<!-- image -->", 'F.4. Detectability of Currently-Undiscovered Planets': 'Analysis of current Doppler data (Howard & Fulton 2014, see also Figure 2-49 in main text) shows that current Doppler surveys have limited sensitivity at the angular separations for which WFIRST-AFTA is sensitive; for  example,  the  50%  Doppler  completeness  level  for the median WFIRST-AFTA target that also has Doppler RV data is ~100 Earth masses at 1 AU, in comparison to  WFIRST-AFTA  which  could  detect  a  1-Earth  mass (or  radius)  planet  at  1  AU,  for  a  typical  orbital  inclination. Other surveys, and in particular data from the Kepler  spacecraft,  show  that  there  are  a  large  number  of planets below this size. For example, planets from 2-4 Earth radius may be the most common type of planet in the  universe  (Fressin  et  al.  2013).  Therefore,  we  also estimated the ability of the CGI to search for as-yet unknown exoplanets, including exoplanets discovered by a future precision RV program.', 'F.4.1 25-Star Survey': "The first evaluation is for a short program (25 stars, 50  days).  We  describe  here  a  preliminary  estimate  of the number of planets that could be seen for one particular extrapolation of the Kepler statistics. Fully evaluating the detection yield - e.g., determining the optimal strategy for revisiting a given star, the best use of partial RV coverage, etc. - will require the development of a complete coronagraph DRM in the next phase. Section  F.4.2  below  presents  an  analysis  of  an  extended mission with target optimization.  \nFor our analysis, the frequency of planets, in terms of planet radius and period, is estimated from an analysis of, and extrapolation from, the Kepler planet discoveries  (Traub  2015  in  prep).  To  do  this,  we  estimated Kepler's bias against small planets at long periods, owing to instrument noise and stellar faintness, and simulated the mission using this bias function. We hypothesized  that  the  period-radius  distribution  in  the  population can be approximated by a separable product of a broken power law in period times a broken power law in radius. We find that this distribution function can fit the observed data with a chi-square of about 2, over a factor of about 100 in period and 50 in radius. This analytic fit produces ~4 planets per star.  \nThe Turnbull catalog of stars out to 30 pc is used as a base sample, but trimmed to have a population of stars  that  is  close  to  the  Kepler  population  (although this last step seems to make essentially no difference to the result). We randomly assign planets to these nearby  \nstars  using  the  period-radius  probability  distribution from the Kepler catalog. We then use these results as an  input  catalog  to  the  same  program  that  is  used  to calculate  the  detectability  of  RV  planets.  We  position the planets at a near-optimal phase (as was done with the RV planets) for convenience in calculation. If these new planets are targeted based on future RV work this is  a  reasonable  assumption;  otherwise,  multiple  visits will be needed for WFIRST to discover planets that are close to the inner working angle and hence only visible for  a  fraction  of  their  orbit.  For  brighter  planets,  most can be detected in as few as 2 or 3 snapshots spaced by several months, though for the lowest-radius planets (which  are  typically  only  visible  at  small  separations) detection completeness will be lower.  \nUsing  this  distribution  we  simulated  a  random search  for  currently-unknown  planets  around  nearby stars.  The baseline search targeted 25 stars manually selected from the Turnbull catalog. Each star was visited  4  times  and  observed  for  0.5  days.  We  split  the planets into three groups: giant, sub-Neptunes, and super-Earths.  These groups are defined as follows. 'Super-Earths' are those with a radius between 0.5 and 2.0 times the Earth's radius and are assigned a geometric albedo of 20%. The sub-Neptune planets, very common in  the  Kepler population, are between 2 and 4 RE and are  assigned  a  geometric  albedo  of  40%.  The  giant planets, from 4 to 15 RE, are also given the same geometric albedo of 40%.  \nWe simulated both an optimistic performance case (0.4  mas jitter,  x30  speckle  suppression) and a pessimistic  case  (1.6  mas  jitter,  x10  speckle  suppression). The results are summarized in Table F-3. In this population,  giant  planets  are  relatively  rare,  and  hence  few are discovered. Note that the strategy has not been fully  optimized. Although the expected number of SuperEarths found is small, any such discovery would be of extraordinary value.  \nA longer survey would yield more planets, as would a  survey  that  is  optimized  using  techniques  such  as Savransky et al.  (2010)  and  Stark  et  al.  (2014),  or  as one that selects targets based on Doppler information, presence  of  other  planets,  etc.  In  these  cases, WFIRST-AFTA could expect a yield of ~3 planets in the 1-2 Earth-radius class, as well as a large population of Neptune or sub-Neptune planets.", 'F.4.2 Long-Term RV Monitoring': 'We know that the current population of known RV planets  in  the  WFIRST  range  is  incomplete;  new  RV discoveries  made  between  now  and  the  launch  of  \nTable  F-3:  Predicted  number  of  planets  discovered  in  a  50-day  blind  survey,  evaluated  for  an  optimistic  case (pointing jitter of 0.4 mas RMS after compensation by the coronagraph fast steering mirror and post-processing noise reduction factor of 30 times) and a pessimistic case (1.6 mas jitter and 10 times factor). This prediction is for a totally blind survey, with no foreknowledge of the target stars, however if RV results are available to guide the target selection and timing of observation, these rates could be dramatically increased.  \nWFIRST will increase the potential population of characterizable  planets.  We  expect  a  NASA-NSF-funded RV spectrometer to come online at the WIYN telescope on  Kitt  Peak  in  2016  and  for  it  to  be  dedicated  to searching  for  RV  planets  in  connection  with  new  missions,  including  WFIRST-AFTA.  We  model  the  expected yield of this work using the same Kepler-derived distribution function of planets described above, allowing for the expected capabilities of such an instrument, and submitting the RV-discovered planets to our model of  the  HLC  coronagraph  on  WFIRST-AFTA.  We  find that  12  of  these  new  planets  are  detectable  with WFIRST-AFTA with exposure times of <1 day (see Figure F-6).', 'F.4. 3 Deep Optimized New-Planet Search': "The  ability  to  discover  new  planets  in  the  case above is limited by the time available for the search. We simulated  an  extended  new-planet  search  using  techniques based on Savransky et al. (2010). This survey targets  46  stars,  selected  from  the  Turnbull  catalog through  an  algorithm  that  calculates  fractional  completeness  for  each  target  as  a  function  of  mass  and semi-major  axis  and  prioritizes  targets  based  on  the expected number of planet discoveries per target for a  \nKepler-based  exoplanet  distribution.  (This  analysis used a radius distribution based on Fressin et al. (2013) rather  than  Traub  2015,  but  the  two  distributions  are very similar over the range covered here.) This extended survey was allocated 180 days.  \nAlthough carrying out this survey completely blind would  require  180  days,  if  targets  can  be  prioritized based  on  additional  information  (presence  of  other planets,  weak  Doppler  signals,  stellar  properties)  it could be executed in significantly shorter time. A preliminary simulation indicates that this survey could obtain full  R=70  spectra  of  ~9  of  these  newly-discovered smaller  planets.  Final  evaluation  of  likely  planet  yield will require development of a full DRM in simulations  \nThus,  the  prospect  for  detecting  new  planets around the nearest stars is very promising. These detections by themselves are likely to lead to new science results.  Although  WFIRST-AFTA's  ability  to  characterize  the  smallest  planets  will  be  limited  -  most  will  be faint,  and  also  at  such  small  separations  they  will  be undetectable at longer wavelengths - these detections are also likely to provide known targets for a future mission dedicated to terrestrial habitable-zone planets.  \nTable F-4: Predicted number of planets discovered in a 180-day blind survey, otherwise as in Table F-3. The values in this table were estimated completely independently of those in Table F-3, so it is remarkable that the values for at least the Optimistic case are in reasonable accord.  In future work, these methods of estimation will be revised and reconciled to eliminate any remaining differences.  \nFigure F-4: (Upper left) Kepler planet detections are shown as a function of period in units of days (horizontal axis) and planet radius in units of Earth radii (vertical axis). (Bottom) The number of planets in each period bin is added up and displayed as blue points, with statistical error bars indicated. The red points are a model fit to the data, allowing for planets that are not seen because they do not transit their star, and also allowing for the reduced sensitivity of the Kepler mission at long periods and for small planets. (Right) The number of planets in each radius bin is projected (blue points), and the functional fit is shown by red points. The excellent functional fit to the observed number of planets is our basis for asserting that the model used here for the number of planets per star, as a function of period and radius, is well determined, and can be used to project the expected yield of new planets from the WFIRST-AFTA coronagraph.  \n<!-- image -->  \nFigure F-5: Distribution of the number of planets per star, per bin, as a function of period and radius, in the Kepler population, as seen through the filter of the Kepler mission (blue 'observed' points) and without any filtering (red 'population' points), as estimated from the observed Kepler planets in combination with a model of the transit probability and the instrument plus star noise. Kepler's total noise (star plus instrument) masks planets at long periods and small sizes, which leads to the gap between the two curves in each panel. The governing law assumed here is that the distribution function is the product of a period-dependent factor times a radius-dependent factor, an assumption that is borne out by the quality of the fits in Figure F-4.  \n<!-- image -->  \nFigure F-6: Same as Figure F-1 but with a simulated population of planets discovered through an extended WIYN RV survey plotted in red.  \n<!-- image -->", 'F.5. Mission Time Estimate': 'Starting  with  the  integration  times  for  RV  planets and new planets given above, we can make a zerothorder estimate of how the CGI could spend its one-year allocation of time on the WFIRST-AFTA mission. There are six main categories to consider: (1) RV planet images; (2)  RV planet spectra; (3) disk images; (4) new planet  searches;  (5)  GO  programs;  (6)  overhead.  A nominal  time  estimate  for  each  of  these  categories  is sketched below. Note that this is not a full DRM, merely a strawman allocation of coronagraph mission time.', 'F.5.1 Time  for  Photometric  Characterization  of Known RV Planets': 'The total time required for a first-time detection of an RV planet is mainly determined by just the integration time assuming that the planet is in an approximately  optimum  orbital  position,  plus  whatever  overhead  is needed to tune the dark hole on a brighter star. We can be relatively sure that we can predict the right time to observe  an  RV  planet  because  we  already  have  in hand  the  ephemeris  from  RV  observations,  with  only the inclination of the orbit and the position angle missing. For the current work, we assume a statistically average inclination of 60 degrees. For the HLC, with a full 360 degrees of azimuth in a single snapshot, only one snapshot  of  a  target  needs  to  be  taken.  Numerical simulations show that all of the RV planets can be detected on the first try if they are observed when they are in the orbital range from about 45 to 90 degrees, where 90 is  maximum elongation. This range occurs 25% of the time (45/180 = 0.25), allowing for orbital symmetry. Most RV periods are in the range of 2 to 10 years, so the time when a planet is in an optimum orbital window is  easily  predicted  beforehand,  particularly  as  ongoing Doppler  measurements  refine  the  orbital  solution.  So we start by assuming that we can detect 16 planets in 10 days of observing time, at 565 nm, in x-polarization, with  no  additional  searching  time.  We  add  10  days more for measuring the y-polarization. Add another 10 days  for  observing  the  same  planets  in  the  465  nm band, single polarization. Add another 10 days for the 660 band. All of these are in imaging mode. Simulations stand behind these time estimates. The total is 40 days for photometric characterization RV planets.', 'F.5.2 Time for Spectra of Known RV Planets': 'We  use  the  SPC  and  the  IFS  for  spectra  in  the 660, 770, and 890 nm bands, at a spectral resolution of about 70. Two factors govern the yield of spectra: first, the  inner  working  angle  moves  outward  as  the  wave-  \nlength increases, cutting off planets that are too close to their star; second, the quantum efficiency of the detector  decreases at longer wavelengths. The net result is that  we  expect  to  obtain  spectra  of  RV  planets  at  the rates of about 7 spectra in 38 days in the 660 nm band, 6  spectra  in  40  days  in  the  770  nm  band,  and  only  3 spectra in 20 days in the 890 nm band. All spectra will be in the unpolarized mode.', 'F.5.3 Time for Disk Images': "Disks will already be included in the search for RV planets, as we cannot avoid seeing whatever disks are already there, within the limits of our integrations time per target.  In Figure F-1, Figure F-2, and Figure F-3, we  indicate  by  a  dashed  green  line  the  approximate brightness  of  a  zodi  disk  like  the  Solar  System's,  but with  a  10-times  greater  particle  density,  for  a  Sun-like star at 10 pc. For the fixed solid-angle of a pixel in the focal  plane,  the  surface  brightness  of  a  disk  is  independent  of  target  distance,  but  the  angular  size  will scale  as  the  inverse  of  distance,  and  the  contrast  will increase linearly with distance. The green line is for a single PSF, so the signal from a distributed disk will be determined by the ensemble of PSFs across the disk, improving the detection threshold by a factor of several. Thus  we  expect  that  the  CGI  will  be  able  to  detect  a disk at roughly the 1-zodi level, given all these caveats. In addition to disks around RV targets, we may wish to look at a score or more of other targets, e.g., selected on  the  basis  of  infrared  observations,  or  as  a  control population  of  stars  without  Doppler  planets,  for  which we allocate an extra 10 days. The total is thus 10 dedicated days for disks.", 'F.5.4 Time for New Planet Searches': "For as-yet undiscovered ('new') planets, a precise estimate of search time requires a full DRM, which will be carried out in future phases. We initially allocate 50 days  for  this  search,  plus  20  days  for  acquisition/overhead/follow-up  of  candidate  planets.  As  discussed above, an extended 180-day search could significantly  increase yield, including time for spectrophotometric follow-up.", 'F.5.5 GO Program': 'The WFIRST mission allocates about 25% of the time  to  a  General  Observer  (GO)  program,  so  for  the CGI this is 91 days.', 'F.5.6 Overhead': 'We assume that we will need 1 day to set up the dark  hole  for  each  RV  planet  that  we  observe  for  the first  time. Then, for a given RV target, the subsequent observations in a different polarization and different filters  should  take  less  time  to  tune  the  dark  hole,  for which  we assume a quarter-day each for roughly 160 targetings. (We do not count here an estimated 5 days of  coronagraph  time  for  a  dedicated  checkout  period, which occurs before the official 6-year mission starts). This  leaves  us  with  a  grand  total  of  56  days  of  overhead, conservatively estimated.', 'F.5. 7 Total Time': 'Adding the above time allocations for the CGI, we find a total of 365 days required for the proposed program, as shown in Table F-5.  \nTable F-5: Time allocation and performance against requirements for the CGI, for each major category of observation. To be revised when detailed engineering overhead times are available, and a realistic DRM can be calculated.', 'Appendix G Precursor Observations': "The NASA Exoplanet Exploration Program Analysis Group (ExoPAG) recently completed a study entitled 'Preparing  for  the  WFIRST  Microlensing  Survey'  that identified  several  precursor  observation  programs  that will enable and enhance WFIRST microlensing science, and  reduce  the  mission's  scientific  risk  (Yee  et  al. 2014). The most important of these are:", '1. A Ground-Based, Near-IR, Microlensing Survey.': "- The near-IR microlensing rate as a function of Galactic position is a critical input for the selection of the  WFIRST-AFTA exoplanet fields and design of the survey strategy, but the microlensing rate has never  been  measured  in  the  IR.  Galactic  models are currently insufficient for accurate predictions of the  microlensing  lensing  rate  and  optical  microlensing  surveys  are  insensitive  to  microlensing  in the  higher  extinction  regions  closer  the  Galactic plane  where  the  microlensing  rate  is  expected  to be higher. Thus, a near-IR microlensing survey of the central Galactic bulge is needed.\n- 2. Hubble  Space  Telescope  Precursor  Observations. The  infrared  channel  of  HST's  Wide  Field Camera 3 camera provides images with similar angular resolution, pixel sampling and passbands to WFIRST-AFTA. Thus, it is the ideal instrument to provide  test  observations  for  development  of  the WFIRST-AFTA exoplanet microlensing survey photometry-astrometry  pipeline.  In  order  to  simulate both  the  photometric  and  astrometric  signals,  we will  need  well-dithered,  multi-epoch  data.  Optical and IR HST observations spanning the candidate WFIRST-AFTA  exoplanet  microlensing  fields  will provide  deep  color-magnitude  diagrams  that  can be combined with the IR microlensing rate measurements to build  Galactic  bulge  models  that  can be used to make accurate predictions of the microlensing rates. Optical HST observations of previous planetary microlensing events can be used to infer the distance to the host stars, and thus determine the  Galactic  distribution  of  planets,  which  will  in turn inform the choice of the WFIRST-AFTA target fields.  Finally,  WFIRST-AFTA  has  the  potential  of measuring astrometric microlensing for many of the faint planetary host stars and stellar remnants. This capability  could  be  enhanced  with  precursor  HST observations  of  a  large  fraction  of  the  WFIRSTAFTA exoplanet microlensing fields.  Observations of  the  exoplanet  microlensing  fields  will  provide long  timeline  baseline  data  for  testing  astrometric  \nmeasurements  from  WFIRST-AFTA  observations alone.  \n<!-- image -->  \nAppendix H LSST/Euclid/WFIRST U. Penn Report", 'Optimizing the Joint Science Return from LSST, Euclid and WFIRST': "January 30, 2015  \nB. Jain, 1 D. Spergel, 2 R. Bean, A. Connolly, I. Dell'antonio, E. Gawiser, N. Gehrels, L. Gladney, K. Heitmann, G. Helou, C. Hirata, S. Ho, ˇ Z. Ivezi'c, M. Jarvis, S. Kahn, J. Kalirai, A. Kim, R. Lupton, R. Mandelbaum, P. Marshall, J. A. Newman, M. Postman, J. Rhodes, M. A. Strauss, J. A. Tyson, W. M. Wood-Vasey", '1 Where will we be in 2024?': "Astronomy in 2024 should be very exciting! LSST and Euclid, which should each be in the midst of their deep surveys of the sky, will be joined by WFIRST. With higher resolution and sensitivities than previous astronomical survey instruments, they will reveal new insights into areas ranging from exoplanets to the nature of dark energy. At the same time, JWST will be staring deeper into the early universe than ever before. Advanced LIGO should be detecting frequent collisions between neutron stars. ALMA will be operating at all of its planned frequencies, and the new generation of very large optical ground based telescopes should be revolutionizing ground-based optical astronomy. In parallel, advances in computational capabilities should enable observers to better exploit these complex data sets and theorists to make detailed time-dependent three-dimensional models that can capture much of the physics needed to explain the new observations.  \nThe focus of this report is an exploration of some of the opportunities enabled by the combination of LSST, Euclid and WFIRST, the surveys that will be an essential part of the next decade's astronomy. The sum of these surveys has the potential to be significantly greater than the contributions of the individual parts. As is detailed in this report, the combination of these surveys should give us multi-wavelength highresolution images of galaxies and broadband data covering much of the stellar energy spectrum. These stellar and galactic data have the potential of yielding new insights into topics ranging from the formation history of the Milky Way to the mass of the neutrino. However, enabling the astronomy community to fully exploit this multi-instrument data set is a challenging technical task: for much of the science, we will need to combine the photometry across multiple wavelengths with varying spectral and spatial resolution. Coordination will be needed between the LSST, Euclid, and WFIRST projects in order to understand the trades between overlapping areal coverage, filter design, depth and cadence of the observations, and performance of the image analysis algorithms. We will need to provide these data to the community in a highly usable format. If we do not prepare the missions for this task in advance, we will limit their scientific return and increase the cost of the eventual effort of fully exploiting these data sets. The goal of this report is to identify some of the science enabled by the combined surveys and the key technical challenges in achieving the synergies.", '2 Background on missions': 'This section covers the science goals and technical overview of the three missions.', '2.1 WFIRST': "WFIRST is the top-ranked large space mission of the 2010 New Worlds New Horizon (NWNH) Decadal Survey. With the addition of a coronagraph, WFIRST would also satisfy the top ranked medium space priority of NWNH. The mission is designed to settle essential questions in dark energy, exoplanets, and infrared astrophysics. The mission will feature strategic key science programs plus a vigorous program of guest observations. A Science Definition Team and a Study Office at the Goddard Space Flight Center and Jet Propulsion Laboratory are studying the mission with reports 3 in 2013, 2014, and 2015.  \nWFIRST is now baselined with an existing 2.4 m telescope NASA acquired from the National Reconnaissance Office (NRO), a telescope that became available after the completion of NWNH. This configuration is referred to as WFIRST-AFTA (Astrophysics Focused Telescope Asset). The mission consists of telescope, spacecraft, a Wide-Field Instrument (WFI), an IFU spectrometer and a coronagraph instrument, which includes an IFS spectrometer. The WFI operates with multiple bands covering 0.7 to 2.0 micron band with extension to 2.4 microns under study. It has a filter wheel for multiband imaging and a grism for wide-field spectroscopy (R=550-800). The pixel scale is 0.11 arcsec, which fully samples the PSF at the H band. The IFU has a 3 arcsec FoV and R=75 resolution. The coronagraph operates in the visible 400 - 1000 nm band. It has a 2.5 arcsec FoV, 10 -9 effective contrast and 100-200 mas inner working angle. The IFS has R=70 resolution.  \nWFIRST will measure the expansion history of the Universe as a function of cosmic time and the growth rate of the large-scale structure of the Universe as a function of time to test the theory of general relativity on cosmological scales and to probe the nature of dark energy. It will employ five different techniques: supernovae, weak lensing, baryon acoustic oscillations (BAO), redshift space distortions (RSD), and clusters. With its 2.4-meter primary mirror, the mission will measure more than double the surface density of galaxies detected by the Euclid mission and push these measurements further in the NIR. This higher density will enable more detailed maps of the dark matter distribution, measurements not only of two-point statistics but also higher order statistics, and multiple tests of systematic dependance of cosmological parameters on galaxy properties. The NRC noted in its recent review 4 : 'For each of the cosmological probes described in NWNH, WFIRST/AFTA exceeds the goals set out in NWNH.'  \nFor exoplanets, WFIRST will complete the census of exoplanets begun by Kepler. It will make microlensing observations of the galactic bulge using the WFI to discover several thousand planets at the orbit of Earth and beyond and will be sensitive to planets as small as Mars. WFIRST's microlensing survey will have the unique capability to detect free-floating planets, thus, enabling astronomers to determine the efficiency of planet formation. The coronagraph will directly image and characterize tens of Uranus to Jupiter mass planets around nearby stars and study debris disks.  \nWFIRST will also be a worthy successor to the Hubble Space Telescope. With 200 times the field-ofview of HST, and the same size primary mirror, it will conduct a rich program of general astrophysics and reveal new insights and discoveries on scales ranging from the nearest stars to the most distant galaxies.  \nTable 1 gives the WFIRST capabilities for surveys and SN monitoring observations.  \nHigh Latitude Survey (HLS): The nominal HLS will be for 2 years with 1.3 years for imaging and 0.6 years for grism spectroscopy. The coverage will be 2200 deg 2 of high Galactic latitude sky within the LSST footprint. The imaging will have 2 passes over the survey footprint in each of the 4 imaging filters (J, H, F184 [for shapes] and Y [for photo-z's]). Data from LSST will be required to provide optical filters for  \nTable 1: WFIRST capabilities in a nominal ∼ 2 . 5 year dark energy survey  \nphoto-z determination. Each pass will include four 184 sec exposures in each filter (with five exposures in J band) with each exposure offset diagonally by slightly more than a detector chip gap. This pattern is repeated across the sky. The spectroscopic survey will have four passes total over the survey footprint with two 'leading' passes and two 'trailing' passes to enable the single grism to rotate relative to the sky. Each pass includes two 362 sec exposures with offset to cover chip gaps. The two 'leading' passes (and two 'trailing') are rotated from each other by ∼ 5 · . It is anticipated that the sky coverage of the HLS will be significantly expanded in the extended phase of the mission after the baseline first 6 years. WFIRST has no consumables that would prohibit a mission of 10 years or longer, and is being designed with serviceability in mind to enable the possibility of an even longer mission.  \nSupernova Survey: A six month SN Ia survey will employ a three-tier strategy so to track supernova over a wide range of redshifts:  \n- · Tier 1 for z < 0.4: 27.44 deg 2 Y=27.1, J= 27.5\n- · Tier 2 for z < 0.8: 8.96 deg 2 J=27.6, H= 28.1\n- · Tier 3 for z < 1.7: 5.04 deg 2 J=29.3, H=29.4  \nTier 3 is contained in Tier 2 and Tier 2 is contained in Tier 1. Each of these fields will be visited every 5 days over the 6 months of the SN survey. The imager is used for SN discovery and the IFU spectrometer is used to determine SN type, measure redshifts, and obtain lightcurves. Each set of observations will take a total of 30 hours of combined imaging and spectroscopy. The fields are located in low dust regions ≤ 20 · off an ecliptic pole. A final revisit for each target for spectroscopy will occur after the SN fades for galaxy subtraction.  \nGuest Observer Program: A significant amount of observing time will be awarded to the community through a peer-selected GO program. An example observing program prepared by the SDT has 25% of the baseline 6 years of the mission, or 1.5 years, for guest observations. Significantly more time would be awarded in an extended phase after the 6th year. The GO program is expected to cover broad areas of science from the solar system to Galactic studies to galaxies to cosmology. The April 2013 SDT study contains a rich set of ∼ 50 potential GO science programs that are uniquely enabled by WFIRST. Astronomical community members provided a wide-ranging set of one-page descriptions of different GO programs that highlight the tremendous potential of WFIRST to advance many of the key science questions formulated by the Decadal survey. An important contribution that would likely come from key projects in the GO program would be to have deep IR observations of selected few-square-degree fields. These ultra deep drilling fields could reach limits of J=30 AB.", '2.2 LSST': "The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field, ground-based facility designed to perform many repeated imaging observations of the entire southern hemisphere in six optical bands (u, g, r, i, z, y). The majority of the southern sky will be visited roughly 800 times over the ten-year duration of the mission. The resulting database will enable a wide array of diverse scientific investigations ranging from studies of moving objects in the solar system to the structure and evolution of the Universe as a whole (Ivezic et al 2014).  \nThe Observatory will be sited atop Cerro Pachon in Northern Chile, near the Gemini South and SOAR telescopes. The telescope incorporates a 3-mirror astigmatic optical design. Incident light is collected by the primary, which is an annulus with an outer diameter of 8.4 m, then reflected to a 3.4-m convex secondary, onto a 5-m concave tertiary, and finally into three refractive lenses in the camera. The total field of view is 9.6 deg 2 and the effective collecting aperture is 6.6 m in diameter. The design maintains a 0.2 arc-second system point spread function (PSF) across the entire spectral range of 320 nm to 1050 nm. The etendue (the product of collecting area and field of view) of the system is several times higher than that of any other previous facility.  \nThe telescope mount assembly is a compact, stiff structure with a high fundamental frequency that enables fast slew and settle. The camera contains a 3.2 Gigapixel focal plane array, comprised of roughly 200 4K × 4K CCD sensors with 10 µ m pixels. The sensors are deep depleted, back-illuminated devices with a highly segmented architecture that enables the entire array to be read out in 2 s or less.  \nFour major science themes have motivated the definition of science requirements for LSST:  \n- · Taking a census of moving objects in the solar system.\n- · Mapping the structure and evolution of the Milky Way.\n- · Exploring the transient optical sky.\n- · Determining the nature of dark energy and dark matter.  \nThese four themes stress the system in different ways. For the science of dark energy and dark matter, LSST data will enable a variety of complementary analyses, including measurements of cosmic shear power spectra, baryon acoustic oscillations, precision photometry of Type Ia supernovae, measurements of timedelays between the multiple images in strong lensing systems, and the statistics of clusters of galaxies. Collectively, these will result in substantial improvements in our constraints on the dark energy equation of state and the growth of structure in the Universe, among other parameters.  \nThe main fast-wide-deep survey will require 90% of the observing time and is designed to optimize the homogeneity of depth and number of visits. Each visit will comprise two back-to-back 15 second exposures and, as often as possible, each field will be observed twice per night, with visits separated by 15-60 minutes. Additional survey areas, including a region within 10 degrees of the northern ecliptic, the South Celestial Pole, and the Galactic Center will be surveyed with either a subset of the LSST filter complement or with fewer observations. The remaining 10% of the observing time will be used on mini-surveys that improve the scientific reach of the LSST. Examples of this include the 'Deep Drilling Fields' where each field receives approximately 40 hour-long sequences of 200 exposures. When all 40 sequences and the main survey visits are coadded, this would extend the depth of these fields to r ∼ 28 . The LSST has identified four distant extragalactic survey fields to observe as Deep Drilling Fields: Elias S1, XMM-LSS, Extended Chandra Deep Field-South, and COSMOS.  \nTable 2 gives the LSST baseline design and survey parameters  \nThe rapid cadence of the LSST will produce an enormous volume of data, roughly 15 Terabytes per night, leading to a total dataset over the ten years of operations of over a hundred Petabytes. Processing  \nTable 2: LSST Capabilities for the fast-wide-deep main survey  \nsuch a large dataset and archiving it in useful form for access by the community has been a major design consideration for the project. The data management system is configured in three layers: an infrastructure layer consisting of the computing, storage, and networking hardware and system software; a middleware layer, which handles distributed processing, data access, user interface, and system operations services; and an applications layer, which includes the data pipelines and products and the science data archives. There will be both a mountain summit and a base computing facility (located in La Serena, the city nearest the telescope site), as well as a central archive facility in the United States. The data will be transported over existing high-speed optical fiber links from South America to the U.S.  \nThe observing strategy for the LSST will be optimized to maximize observing efficiency by minimizing slew and other down time and by making appropriate choices of filter bands given the real-time weather conditions. The final cadence selection will be undertaken in consultation with the community. A prototype simulator has been developed to help evaluate this process, which will be transformed into a sophisticated observation scheduler. A prototype fast Monte Carlo optical ray trace code has also been developed to simulate real LSST images. This will be further developed to aid in testing science analysis codes. The LSST cadence will take into account the various science goals and can also be refined to improve the synergy with other datasets.  \nLSST anticipates first light in 2020 and the start of the 10-year survey in 2022. It is fully funded for construction as of the summer 2014.", '2.3 Euclid': "Euclid is a medium class mission within the European Space Agency's (ESA) 'Cosmic Vision' program 5 . Euclid was formally selected in 2011 and is currently on schedule for launch in 2020. After traveling to the L2 Lagrange point and a brief shakeout and calibration period, Euclid will undertake an approximately 6year survey aimed at 'mapping the geometry of the dark Universe.' Euclid will pursue four primary science objectives (Laureijs et al 2011):  \n- · Reach a dark energy FoM > 400 using only weak lensing and galaxy clustering; this roughly corresponds to 1% errors on w p and w a of 0.02 and 0.1, respectively.\n- · Measure γ , the exponent of the growth factor, with a 1 σ precision of < 0 . 02 , sufficient to distinguish General Relativity and a wide range of modified-gravity theories.  \n- · Test the Cold Dark Matter paradigm for hierarchical structure formation, and measure the sum of the neutrino masses with a 1 σ precision better than 0.03 eV.\n- · Constrain n s , the spectral index of the primordial power spectrum, to percent accuracy when combined with Planck, and to probe inflation models by measuring the non-Gaussianity of initial conditions parameterized by f NL to a 1 σ precision of ∼ 2.  \nEuclid is optimized for two primary cosmological probes: weak gravitational lensing and galaxy clustering (including BAO and RSD). Therefore, Euclid will measure both the expansion history of the Universe and the growth of structure. Euclid comprises a 1.2m Korsch 3 mirror anastigmatic telescope and two primary science instruments. The visible instrument (VIS) consists of 36 4k × 4k CCDs and will be used to take images in a single, wide (riz) filter for high precision weak lensing galaxy shape measurements. The light entering the telescope will be split via a dichroic to allow for simultaneous observations with the Near Infrared Spectrometer and Photometer (NISP), which will take 3 band imaging (Y, J, H) and grism spectroscopy in the 1-2 µ mwavelength range. The NISP imaging is aimed at producing high quality photometric redshifts when combined with ground-based optical data from a combination of telescopes in the southern and norther hemispheres and the spectroscopy is aimed at producing accurate maps of galaxy clustering over 2/3 of the age of the Universe. NISP will contain 16 H2RG 2k × 2k NIR detectors procured and characterized by NASA. Together, VIS and NISP will survey the darkest (least obscured by dust) 15,000 square degrees of the extragalactic sky, providing weak lensing shapes for over 1.5 billion galaxies and emission line spectra for several tens of millions of galaxies, while taking full advantage of the low systematics afforded by a space mission.  \nWhile the Euclid hardware and survey design are specifically optimized for dark energy studies, the images and catalogs will enable a wide range of ancillary science in cosmology, galaxy evolution, and other areas of astronomy and astrophysics. These data will be made publicly available both in Europe via ESA and The Euclid Consortium and in the US via the Euclid NASA Science Center at IPAC (ENSCI) after a brief proprietary period. Small areas of the Euclid survey (suitable for testing algorithms and pipelines but not large enough for cosmology) will be released at 14, 38, 62, and 74 months after survey operations start (these are referred to as 'quick releases'). The full survey data will be released in three stages: circa 2022, 2500 square degrees; circa 2025, 7500 square degrees; circa 2028, 15,000 square degrees.", '3 Enhanced science': "The main dark energy probes established over the last decade are described next in the context of the three missions. They are: Type Ia supernova, galaxy clustering (baryon acoustic oscillations and redshift space distortions), weak lensing, strong lensing and galaxy clusters. The biggest advantage from combining information from the three missions is in the mitigation of systematic errors, especially via redshift information. For the observational and theoretical issues underlying the discussion here we refer the reader to recent review articles in the literature (Weinberg et al 2013; Joyce et al 2014).  \nLSST, WFIRST and Euclid each have their own systematic errors, most of which are significantly reduced via the combination of the survey datasets. The systematic errors affecting each of the surveys individually arise from their incomplete wavelength coverage (creating photo-z systematics), their differences in imaging resolution and blending (creating shear systematics), or from different biases in galaxy sample selections. In most respects the surveys are complementary in the sense that one survey reduces or nearly eliminates a systematic in the other. To achieve this synergy requires some level of data sharing; we discuss below the cases where catalog level sharing of data is sufficient and others where it is essential to jointly process the pixel data from the surveys.  \nThis section describes each dark energy probe, with a focus on mitigation of systematics, and returns to photometric redshifts (photo-z's). The last three subsections are devoted to stellar science, galaxy and quasar science, and the variable universe.", '3.1 Weak lensing': "Acosmological weak lensing analysis in any of these surveys will use tomography, which involves dividing the galaxy sample into redshift slices and measuring both the auto-correlations of galaxies within slices and cross-correlations of galaxies in different slices. Tomography gives additional information about structure growth beyond a strictly 2D shear analysis. However, there are a number of requirements on the data for a tomographic weak lensing analysis to be successful. First, we require a good understanding of both additive and multiplicative bias in the shear estimates, including how they scale with redshift. Second, we require a strong understanding of photometric redshift bias and scatter. This is true in general, but it becomes even more important when trying to model theoretical uncertainties such as the intrinsic alignments of galaxy shapes with large-scale structure.  \nThere are a number of ways in which the weak lensing science from each of LSST, WFIRST and Euclid would benefit by sharing data with the other surveys and thus improving our understanding of shear estimates and/or the photometric redshift estimates. This data sharing may include catalog-level data or possibly image data. Although the latter would pose additional complications in terms of the data reprocessing required to appropriately incorporate both ground and space images, the gains may be worth the effort where confusion or image blending are severe.  \nThe main benefit to LSST from either WFIRST or Euclid will be in terms of the calibration of shear estimates. The space-based imaging will have much better resolution due to the much smaller PSF size. The shapes of galaxies measured from space images will suffer less from model bias and noise bias (at a fixed depth) than the shapes of the same galaxies measured from ground images. A comparison of the shear signal of the population of galaxies observed by both LSST and either Euclid or WFIRST can help quantify these possible systematic errors in the LSST estimates. While each survey will have its own independent scheme to correct for calibration biases, a cross-comparison of this sort can be used to validate those schemes. Any additional correction that is derived could then be extended to the rest of the LSST area where there is no such overlap. Note that such a comparison would use a matched sample of galaxies in LSST and one of the space-based surveys, but would not involve comparing per-galaxy shape estimates. With different effective resolution, wavelength, and possibly shear estimation methods, there is no reason to expect agreement in  \nper galaxy shears (even allowing for variation due to noise). Instead, such a comparison would utilize the reconstructed lensing shear fields from the different surveys. WFIRST may be more effective than Euclid for this purpose because its narrower passbands mean that it does not suffer from the wide-band chromatic PSF issue mentioned below.  \nAnother benefit to LSST relates to blended galaxies. The higher resolution space-based images make it easier to reliably identify blended galaxies than in ground-based images. The performance of deblending algorithm in LSST image processing pipeline can be significantly improved by providing higher-resolution space-based data because of order half of all observed galaxies will be significantly blended with another galaxy. With space-based catalogs, one can at least identify which objects are really multiple galaxies or galaxy-star blends and do forced fitting using the space-estimated positions. Euclid will be more effective than WFIRST for this purpose because its footprint has a greater overlap with that of LSST.  \nOne benefit to Euclid from combination with LSST relates to chromatic effects. The diffraction-limited PSF is wavelength dependent and therefore differs for stars and galaxies due to their different SEDs. Euclid's very wide band imaging means that with its optical imaging alone, it will not be able to correctly estimate the appropriate PSF for each galaxy. Multi-band photometry is required to correct for this effect. Without correctly accounting for the color-dependent PSF, the systematic will dominate Euclid's WL error budget, so LSST photometry will be very useful in reducing this systematic error. Note that LSST cannot help with chromatic effects involving color gradients within galaxies, for which higher resolution imaging data will be necessary to estimate corrections; but LSST can provide information about chromatic effects involving the average galaxy colors.  \nFinally, there are some shear systematics tests that can be done in a joint analysis but not in any one survey individually. For example, one route that has been proposed within surveys to mitigate additive shear systematics is to cross-correlate shear estimates in different bands or in different exposures rather than auto-correlate shear estimates. However, some sources of additive systematics may persist across bands or exposures, which would make them quite difficult to identify within the data from the survey alone. Indeed, in essentially every survey that has been used for weak lensing analysis to date, the preliminary results indicated some unforeseen systematics. Despite care taken in the design and planned operations of new surveys, we cannot reliably exclude the possibility of unforeseen systematics.  \nIn the case of these three surveys, the systematic errors from each survey are expected to be very different. Thus, cross-correlating the shear estimates from one survey with those of another should remove nearly all shear systematic error contributions, leaving only the true weak lensing signature. If this cross-correlation analysis reveals differences from the analysis within individual surveys, it could signal a problem that needs to be investigated and mitigated. Furthermore, the surveys have different redshift distributions for the lensed galaxies, so a joint cosmological analysis using data from two or more of them will be complementary. The joint analysis would also be better able to constrain nuisance parameters like intrinsic alignments and photometric redshift errors.  \nAs described below, the principal way in which Euclid and WFIRST would benefit from sharing information with LSST is in the photometric redshift catalog. Without this additional data, Euclid and WFIRST will not be able to complete their weak lensing science goals. LSST will also gain from the IR band photometry of WFIRST and Euclid in terms of photometric redshift determination.  \nThe easiest form of data sharing between surveys is if only catalog information is shared. For some of the gains mentioned above, this level of sharing is completely sufficient: cross-correlations and shear calibration, for example. The deblending improvements would require an iterative reprocessing of the data, using a space catalog as a prior and then reprocessing the LSST data with that extra information. A similar iterative reprocessing would be necessary for Euclid to properly account for its color-dependent PSF using the LSST SED estimates as a prior. For the photometric redshift improvement, one could just use the multiple catalogs, but to do it properly, it is important to have access to the pixel data from both experiments at once to properly estimate robust colors for each galaxy. It will be a significant technical challenge to  \ndevelop a framework that will work with the different kinds of image data in a coherent analysis.", '3.2 Large-scale structure': "Figure 1: The chart shows how the complementarity of LSST, Euclid and WFIRST contributes to significant improvement in constraints on cosmological parameters. As described in the text, the improved constraints on σ 8 come from the mitigation of intrinsic alignment and other systematics in weak lensing; the improved constraints on the sum of neutrino masses ∑ m ν (in eV) comes from the combination of the weak lensing, CMB convergence maps, and galaxy clustering, in particular by reducing the multiplicative bias in shear measurement. Note that the space based surveys are assumed to have used ground based photometry to obtain photo-z's.  \n<!-- image -->  \nMeasurements of large-scale structure probe dark energy via baryonic acoustic oscillation features in the galaxy power spectrum. In addition, the full shape and amplitude of the power spectrum measure the clustering of matter, if one can also measure the biasing of galaxies relative to the matter. This provides new avenues to measure the properties of dark energy and probe gravity.  \nThe upcoming generation of spectroscopic surveys will make detailed maps of the large-scale structure of the universe. DESI, PFS, Euclid and WFIRST will focus on measuring galaxy clustering by obtaining spectra of tens of millions of galaxies over redshift ranges from z ∼ 0 . 4 -3 . 5 . The surveys complement each other using a variety of spectral lines (H α , OII, CII) and galaxy types (ELG and LRGs) as tracers and through having distinct, but overlapping, redshift ranges. DESI and Euclid will be wider surveys, while PFS and WFIRST will go deeper on smaller areas of the sky.  \nThe combination of spectroscopic and lensing data enables a test of general relativity on cosmological scales. The spectroscopic data provides information about galaxy positions and motions determined inertial masses moving in the local gravitational potential. The imaging data, by contrast, shows the effect of space-time curvature on the trajectories of photons. If general relativity is the correct description of gravity then these will agree. Spectroscopic and photometric galaxy cluster surveys from WFIRST, LSST, Euclid and DESI, and others, and their cross-correlation with contemporary CMB polarization (CMB lensing) and temperature (CMB lensing and kinetic Sunyaev-Zel'dovich) data will provide coincident, complementary dynamical and weak lensing tests of gravity in halos two to three orders of magnitude more massive than the galaxies within them. Thus we expect powerful tests of gravity by a joint analysis of the three surveys.  \nWe study the complementarity of WFIRST, LSST and Euclid by forecasting constraints on matter clustering (we pick σ 8 for convenience, which is sensitive to dark energy and is partially degenerate with the  \nparameters, n s , Ω m ), and the sum of neutrino masses in the Universe. While we concentrate on these particular parameters, there are many other possibilities considered by the community.  \nFigure 1 shows constraints on σ 8 and the sum of neutrino masses Σ m ν from the three surveys individually and in combination. We include a CMB prior from Planck, and marginalize over cosmological (and galaxy bias) parameters when appropriate. For the space surveys we assume that photo-z's will be obtained with the aid of ground based data. WFIRST's densely sampled spectroscopic galaxies will provide a detailed characterization of filamentary structure that is complementary to the lensing measurements provided by imaging surveys. This allows us to understand one of the most elusive systematics in weak lensing surveys - the intrinsic alignment (IA) of galaxies. One can test and validate IA models and marginalize over the free parameters in specific models when we can have a 3D map of the universe via galaxy spectra. In LSST, the lensing sources spans a large redshift range between 0 and 3 and a large luminosity range. With WFIRST and Euclid, we will have spectroscopic sources spanning a large part of this redshift range, which enables a very good construction of filament map of the surveyed volume. WFIRST offers a much higher density of sources while LSST and Euclid will cover a much large area of sky. The joint analysis leads to significant improvement in the constraint on σ 8 , as shown on the left in Figure 1.  \nWe also consider the constraints on massive neutrinos which suppress the growth of structure below the free-streaming scale. The combination of WFIRST and Euclid's spectroscopic sample, along with CMB lensing convergence, can be used to calibrate the shear multiplicative bias in LSST sources. We follow Das, Evrard & Spergel (2013) in methodology and calculate the improvement in constraints first in the multiplicative bias in shear, and propagate this to the constraints on the sum of neutrino masses that relies on the large sky coverage of LSST. We assume that a Stage III level CMB convergence field will be available. We plot the improvement in Σ m ν on the right in Fig 1.", '3.3 Galaxy clusters': "LSST, Euclid and WFIRST will use galaxy clusters (primarily via gravitational lensing mass measurements) as part of their cosmological measurements. However, both for cosmology and the study of galaxy evolution in clusters, a joint analysis of the data can greatly improve the reach of each mission. Fundamentally, this is because each of the missions observes different aspects of the emission from clusters. LSST provides optical colors, useful for cluster identification via photometric redshifts, as well as (for group-scale structures) time delays for lensed objects. Euclid provides shallow NIR photometry and somewhat deeper NIR spectroscopy, as well as higher resolution optical imaging. WFIRST will provide much better resolution images and deep NIR photometry and spectroscopy over a smaller area than Euclid. Because of the complementarity of these measurements, combining the data has implications for cluster finding, redshift determination, mass measurement and calibration, and the study of galaxy evolution in clusters.  \nGalaxy cluster finding: Over the past decade, techniques have been developed that select galaxy groups and clusters very effectively by isolating overdensities simultaneously in projected position and color space (for example redMaPPer). These techniques have been optimized for optical wavelengths. LSST will be extremely efficient at finding groups and clusters of galaxies and estimating their redshifts (although eROSITA will also be an efficient cluster finder, the redshift information available from the LSST imaging will allow selection of samples at fixed redshift for study). Although redMaPPer is effective to z ∼ 1 , extending its redshift range will require infrared imaging, which would be provided by Euclid or WFIRST. Given that the number density of detected (as opposed to resolved) sources in LSST and WFIRST are going to be similar, and given the importance of consistent photometry measurements across bands, simultaneous measurements of the pixel data would yield more accurate selection of clusters.  \nRedshift Determination: As discussed below, the photo-z's of galaxies will be greatly improved by combining the optical and infrared imaging of the three missions. Thus, joint analysis of the LSST+WFIRST/Euclid data gives more accurate cluster sample selection, and allows accurate determination of the background  \ngalaxy redshift distribution, which is the largest single source of systematic uncertainty in determination of the mass function from weak lensing mass determinations.  \nStrong and Weak Lensing: Measuring the weak lensing shear requires high resolution imaging. WFIRST will be able to resolve many more galaxies than LSST, and as discussed above will aid the shear calibration of LSST. In addition, the conversion of shear to mass depends on redshift information. In this way, the combination of LSST, Euclid, and WFIRST data will provide much more accurate mass measurements than either will alone.  \nCluster arc tomography is greatly improved by the joint pixel-level analysis of LSST, Euclid and WFIRST data. For instance, WFIRST will have the angular resolution to discover ∼ 2000 strong lensing clusters in its survey footprint. However, most of the arcs will be too faint (and too low surface brightness) to have spectroscopic redshifts. By contrast, LSST will reach surface brightness limits ( > 28 . 7 Mag per square arcsecond) sufficient to detect the arcs and obtain photometric redshift estimates, but will not have the resolution to separate the arcs cleanly from the cluster galaxies in many cases. Thus, the measurement of the tomographic signal from multiple arc systems, which is a strong test of cosmology, will be much stronger from the joint analysis than from Euclid, WFIRST or LSST alone. Once again, the added value of the pixel data is great, because cluster cores are very dense environments and obtaining valid photometric redshifts will require use of the space-based imaging to disentangle the light contribution form the arcs and cluster galaxies.  \nSystematics: One of the sources of systematic uncertainty in weak lensing shear measurements from galaxy clusters comes from the blending of sources both with other sources and with cluster galaxies. The source-source blending is in many ways similar to that encountered in large-scale weak lensing measurements, but in clusters, there is an additional source of bias from blending with cluster galaxies. This is both radially dependent and (because cluster concentration evolves with redshift) redshift dependent, and directly affects the normalization of the cluster mass function. Using the WFIRST data to directly measure the deblending bias in the clusters in common between the two surveys would make it possible to correct for the bias.", '3.4 Supernovae': 'Each individual Type Ia supernova (SN Ia) is potentially a powerful probe of relative distance in the Universe. Thousands of them provide detailed information about the expansion history of the Universe, in particular allowing us to probe the accelerated expansion and the nature of dark energy. Hundreds of thousands of them will allow us to probe the nature of dark energy in different regions and environments. A set spanning the past 10 billion years of cosmic history will allow for a rich and powerful exploration of the nature of the expansion and more recent acceleration of the Universe and thus reveal key insights into the key constituents.  \nGround-based SN Ia searches have provided almost one thousand well-observed SNe Ia in 20 years of work. Increasingly powerful ground facilities will rapidly increase this number to thousands per year (e.g., Pan-STARRS, PTF and DES) and then hundreds of thousands per year in the era of LSST. For a smaller subset (hundreds) of these supernovae, even calibrated spectrophotometric time-series have been obtained (at the nearby SN Factory). However, the rest-frame emission of SNe Ia is line-blanketed at UV wavelengths. Thus, by z ∼ 1 their light has already redshifted out of the optical atmospheric window easily accessible from the ground. In addition, because the relative distances across redshifts are estimated based on relative flux differences across wavelength, accurate cross-wavelength calibration is critical to use supernovae to determine the properties of dark energy.  \nThe stability of WFIRST in space yields significant benefits in both wavelength coverage and flux calibration for thousands of SNe Ia/year from 0 . 1 < z < 1 . 7 . The accessibility of the ground allows for the large aperture and high-etendue of the LSST system that can observe 10,000s of SNe Ia per year from', '0 . 03 < z < 1 .': "Measuring distances from z ∼ 0 . 03 to z ∼ 1 . 7 will connect the era when dark energy first made its presence known, through the transition to an accelerating expansion, and up to the present day. These are the key redshifts over which we will discover hints to the underlying nature of dark energy, and the combination of the high-redshift reach and calibration of WFIRST and the huge numbers and volume coverage of LSST will yield a strong and powerful pairing for SN Cosmology.  \nThe key question for this work will be the control of systematic uncertainties as we explore a large span of time and changing populations of host-galaxy environments in which the supernovae are born. The combination of WFIRST, LSST, and other ground-based follow-up instruments will make possible unprecedented rich characterization of each supernova so that low- and high-redshift supernovae can be matched at a more detailed level than with the broad 'Type Ia' definition. For example, a time series of detailed spectrophotometry could be obtained for the same rest-wavelengths for every supernova.  \nModern SN distance analyses are already joint analyses. The current Hubble Diagrams are constructed from supernovae from different surveys (e.g., Betoule et al. 2014 combined the Supernova Legacy Survey (SNLS), SDSS Supernova Survey, and the current heterogeneous sample of nearby z < 0 . 05 SNeIa). But a true joint analysis should begin at the pixel level and take advantage of all the internal details about calibration and photometry within each survey. Specifically, when combining SNeIa from different data sources, a joint analysis is beneficial because of: 1. Consistent pixel-level analysis, in particular photometric extraction; and, 2. Deep cross-checks of photometric calibration not possible with just extracted SN light curves.  \nSupernova surveys have distinct science requirements both on supernova discovery and early classification, and on the quality of distance modulus and redshift determinations of discovered supernovae. Each science requirement propagates into hardware and survey requirements. Technical requirements for supernova discovery (e.g., large field of view, detection of new point sources) can have a more cost-effective ground-based solution, whereas requirements for photometry and spectroscopy (e.g., high signal-to-noise SN spectral features, infrared wavelength coverage) are only fulfilled with a space observatory. A case in point is the baseline WFIRST plan where an imaging survey is conducted to identify supernovae for targeted spectroscopic observations. The large field of view of LSST and the availability of SN photons detectable by LSST out to z = 1 . 2 should make the LSST the better instrument for SN discovery, especially at low redshifts where the angular density of potential host galaxies is low. Assuming the triggering logistics work, this might free up WFIRST to do what it is better at: obtaining supernova spectrophotometric time series.  \nIn addition, there is a benefit of observing the same SN with multiple overlapping surveys. Such observations provide:  \n- · Direct cross-instrumental calibration on the source of interest. (It is important to note, however, that this calibration is not the same as the cross-wavelength calibration that is required when comparing supernovae at very different wavelength.)\n- · Expanding observations of the wavelength/temporal range of the supernova.\n- · A quantitative assessment of systematic errors.  \nFinally, supernova cosmology analyses require a suite of external additional resources beyond the direct observations of high-redshift supernovae. Thus, planning for a joint LSST-WFIRST SN cosmology analysis will yield significant gains in combining resources to obtain external data and theory needs. Some key examples include:  \n- · Low-z SN set, including possible spectrophotometric time-series follow up.\n- · Fundamental flux calibrators (which can provide the cross-wavelength calibration that is required when comparing supernovae at very different wavelength).  \n- · High-resolution spectroscopy of host galaxies.\n- · Improved SN Ia theory and empirical modeling.", '3.5 Strong lensing': 'The LSST, Euclid and WFIRST datasets will be particularly complementary in the field of strong gravitational lensing. Galaxy-scale strong lenses can be used as probes of dark energy (via time delay distances or multiple source plane cosmography). The time delays between multiple images in a strong gravitational lens system depend, as a result of the lens geometry, on the underlying cosmology - primarily the Hubble constant but also, in large samples where internal degeneracy breaking is possible, the dark energy parameters. (Refsdal 1964, Suyu et al 2014). Lens systems with sources at multiple redshifts may also provide interesting and competitive constraints on cosmological parameters, via the ratio of distance ratios in each system.  \nStrong lenses also provide unique information about dark matter, via the central density profiles of halos on a range of scales, and the mass function of sub-galactic mass structures that cause measurable perturbations of well-resolved arcs and Einstein Rings. Both this science case and strong lensing cosmology will benefit greatly from the large samples of lenses detectable in these wide field imaging surveys; we sketch these cases out below in Section 4, and identify how high fidelity space-based imaging and spectroscopy will enable new measurements.', '3.6 Photometric redshifts': "Photometry provides an efficient way to estimate the physical properties of galaxies (i.e. their redshifts, spectral types, and luminosities) from a small set of observable parameters (e.g. magnitudes, colors, sizes, and clustering). LSST will depend on these photometric redshifts for all of its major probes of dark energy as it is infeasible to obtain spectroscopic redshifts for the bulk of objects in the LSST sample with any reasonable amount of telescope time. For the WFIRST and Euclid missions, three of the key applications will rely on photometric redshifts: measures of the mass power spectrum from analyses of the weak lensing of faint galaxies, breaking of the degeneracies between possible redshift solutions for galaxies exhibiting only a single emission line in grism spectroscopy, and the identification of high redshift Type Ia supernovae based on the photometric redshifts of their host galaxies. In addition, photometric redshifts will play a key role in much of the LSST, WFIRST, and Euclid extragalactic science where we wish to constrain how the demographics of galaxies change over time.  \nThe high efficiency of photometric redshifts comes at a cost. The primary features that enable photometric redshift estimation are the transitions of the Balmer (3650 ˚ A) and Lyman (912 ˚ A) breaks through a series of photometric filters. Uncertainties in isolating the position of the breaks due to the low spectral resolution of the photometry give rise to a scatter between photometric redshift estimates and the true redshifts of galaxies. Confusion between breaks (due to sparse spectral coverage and incomplete knowledge of the underlying spectral energy distributions) leads to catastrophic photo-z errors, as seen in Figure 2.  \nExisting studies have demonstrated that while photometric redshift accuracies of σ z ∼ 0 . 007(1 + z ) are possible for bright objects with many filters, uncertainties of σ z ∼ 0 . 05(1 + z ) are more typical when restricted to 5-6 bands of deep imaging. Catastrophic photometric redshift errors (where the difference between the photometric and spectroscopic redshifts, ∆ z , exceeds the 3 -σ statistical error) typically occur in well over 1% of cases. As the photo-z scatter and catastrophic failure rate increase, information is degraded and dark energy constraints will weaken. Furthermore, if there are nonnegligible ( > ∼ 0 . 2% ) systematic offsets in photo-z's or if the ∆ z distribution is mischaracterized, dark energy inference will be biased at levels comparable to or greater than expected random errors. As a result, careful calibration and validation of the photometric redshifts will be necessary for the LSST, WFIRST, and Euclid surveys.", '3.6.1 The impact of Euclid and WFIRST near-infrared data on LSST photometric redshifts': "The LSST filter system covers the u, g, r, i, z and y passbands, providing substantial leverage for redshift estimation from z = 0 to z > 6 . For the LSST 'gold' sample of galaxies, i < 25 . 3 , Figure 2 shows how the HLS for WFIRST, with four bands comparable in depth to the 10 year LSST survey, (i.e. 5 σ extended source depths of Y AB =25.6, J AB =25.7, H AB =25.7, and F184 AB =25.2), will significantly improve on the photometric redshift performance from LSST alone. For example, at redshifts z > 1 . 5 , where the Balmer break transitions out of the LSST y band and into the WFIRST and Euclid infrared bands, the inclusion of the WFIRST data results in a reduction in σ z by a factor of more than two ( 1 . 5 < z < 3 ), and a reduction in the fraction of catastrophic outliers to < 2% across the full redshift range. Euclid's three-band NIR photometry, while shallower, will have a much greater overlap with LSST and will also provide a quantitative improvement in LSST photo-z's. Combining the LSST, WFIRST and Euclid photometric data effectively will depend, however, on the details of the respective filter systems, their signal-to-noise, our ability to extract unbiased photometric measurements from extended sources (e.g. the deblending of sources using the higher spatial resolution of the WFIRST data), and the accuracy of the photometric calibration of the data both across the sky and between the near-infrared and optical passbands.  \nFigure 2: A comparison of the relative photometric redshift performance of the LSST optical filters (left panel) with a combination of LSST and WFIRST filters (right panel). The simulated data assumes a 10-year LSST survey and a 'gold sample' with i < 25 . 3 . The addition of high signal-to-noise infrared data from WFIRST reduces the scatter in the photometric redshifts by roughly a factor of two (at redshifts z > 1 . 5 ) and the number of catastrophic outliers by a factor of three. These simulations do not account for deblending errors or photometric calibration uncertainties, and assume complete knowledge of the underlying spectral energy distributions of galaxies as an ensemble.  \n<!-- image -->", '3.6.2 Mitigating systematics with WFIRST and Euclid spectroscopy': "The optimization of photometric redshift algorithms and the calibration of photometric redshift uncertainties both require spectroscopic samples of galaxies. If simple algorithms are used, more than 100 spectroscopic survey regions (of ∼ 0.25 deg 2 ) with at least 300-400 spectroscopic redshifts per region may be required to optimize a photometric redshift algorithm (whether by refining templates and photometric zero points or as input for machine learning algorithms) to ensure that their accuracy is not limited by sample variance in the spectroscopic training set (Cunha et al. 2012); with techniques that take this variance into account, 15-30 fields may be sufficient (Newman et al. 2014). An ideal training set would span the full range  \nLSST$&$WFIRST$Weak$Lensing$DETF$FoM$is$>1.6x$larger$  \nif$can$train$at$z>2$with$IFU$  \nA$bigger$issue$for$WFIRST$WL:  \n!J  \n$or$  \nH  \nHlimited$sample$skews$to$higher$z!  \nFigure 3: Predictions of the fraction of LSST weak lensing sample objects that would yield a secure (multiple-confirmed-feature) spectroscopic redshift, based either on 1440-second exposure time with WFIRST (colored regions) or 10 nights' open-shuttertime spectroscopy with the Subaru/PFS spectrograph (black curve) WFIRST IFU spectroscopy would provide training redshifts for objects at higher z than are easily accessible from the ground, particularly if read noise per pixel is small (the colored regions indicate a range of feasible scenarios). Longer exposure times (e.g., in supernova fields or by optimized dithering strategies) could enhance the success rate further.  \n<!-- image -->  \nof properties (including redshifts) of the galaxies to which photometric redshifts will be applied. To the degree to which we do not meet this goal, we can expect that photometric redshift errors will be degraded, weakening constraints on dark energy as well as other extragalactic science.  \nCurrent spectroscopic samples fare well; surveys to R = 24 . 1 or i = 22 . 5 (more than two magnitudes shallower than the LSST 'gold sample') with 8-10m telescopes have obtained > 99% secure redshifts for 21-60% of all targeted galaxies, and > 95% secure redshifts for 42-75% of the galaxies (incorrect redshift rates above 1% would lead to photo-z systematics that exceed LSST requirements). WFIRST spectroscopy can address these limitations in a number of ways. Depending on the final configuration and dithering strategy for WFIRST , an object in the LSST weak lensing sample will fall on the IFU field-of-view at least 10% (and up to ∼ 100% ) of the time. Most objects in this sample would yield a successful redshift with a ∼ 1440 sec exposure (see Figure 3). For an IFU with a 3' × 3' field-of-view, at least 10,000 spectra down to the LSST weak lensing depth, corresponding to roughly 20,000 down to the WFIRST limits, would be measured concurrently with the WFIRST HLS (with minimal impact from sample/cosmic variance). This spectroscopy would have very different incompleteness from ground-based samples, allowing a broader range of galaxies to have well-trained photometric redshifts, with accuracy limited by the imaging depth rather than our knowledge of galaxy SEDs.  \nIf our spectroscopic samples do not have a success rate approaching 100%, accurate characterization of photo-z errors (required for dark energy inference) is likely to instead be based on the cross-correlation between spectroscopic and photometric samples (cf. Newman 2008). To meet LSST calibration requirements, such an analysis will require secure ( < 1% incorrect) spectroscopic redshifts for ∼ 100 , 000 galaxies spanning the full redshift range of the photometric samples of interest and an area of at least a few hundred square degrees. Euclid and WFIRST grism spectroscopy will provide spectra for many millions of galaxies over wide areas (e.g., 2 × 10 7 galaxies in the WFIRST HLS). However, this spectroscopy will provide the highly secure, multiple-feature redshifts required for training and calibrating photo-z's in only very limited  \nredshift ranges. As a result, Euclid and WFIRST grism spectroscopy may contribute to photometric redshift calibration in combination with other datasets spanning the remaining redshift range (e.g., from DESI), but cannot solve this problem on their own.", '3.7 Stellar science': "New insights on stellar populations in the Milky Way and nearby galaxies depend critically on gains in photometric sensitivity and resolution. Thus far, the state of the art imaging surveys of our Galaxy have involved relatively modest tools with respect to today's capabilities. For example, the SDSS survey is both shallow and operates at low resolution, and IR surveys such as 2MASS and WISE are based on even smaller telescopes operating at even lower resolution.  \nThe combination of LSST, Euclid, WFIRST and Gaia will transform our view of the Milky Way and nearby galaxies. LSST will map 18,000 square degrees of the night sky every few days, across 6 visible light filters. The imaging depth of LSST will be over 100 times (5 magnitudes) deeper than SDSS, and at higher resolution. WFIRST will overlap some of the same footprint, but will also extend the spectral range of Milky Way surveys to near-infrared wavelengths at even higher spatial resolution (0.1 arcsecond pixels). Euclid provides much higher spatial resolution than LSST in the visible (aids deblending sources and crowded field photometry) and Gaia addresses the single biggest contribution to the error budget of most stellar population studies aimed at characterizing physical properties; knowledge of the distance of sources.  \nMuch of the stellar population science case for LSST (e.g., from the Science Book) overlaps that from WFIRST (e.g., the community science white papers in the 2013 WFIRST SDT report). These include studies of the initial mass function, star formation histories for Milky Way components, near field cosmology through deep imaging and proper motions of dwarf satellites, discovery and characterization of halo substructure in nearby galaxies, and more. Given the wavelength complementarity alone, most stellar population investigations will be aided by the panchromatic baseline of LSST (and Euclid) + WFIRST (e.g., interpreting SEDs into fundamental stellar properties, increasing the baseline for star formation history fits from multi-band color-magnitude diagrams, confirming memberships of very blue or red stars in either data set, etc.). However, the overall quality of all three data sets for general investigations can be greatly enhanced (and, in a uniform way) by jointly re-processing the pixel data sets for LSST, Euclid, and WFIRST.  \nTo highlight the technical requirements for this joint processing, we point to three LSST and WFIRST 'killer apps' in stellar population science,  \n- · Establishing and characterizing the complete spectrum of Milky Way satellites\n- · Testing halo formation models by measuring the shapes, substructure content, masses, and ages of a large set of stellar halos within 50 Mpc\n- · Measuring the star formation history, Galactic mass budget, and spatially and chemically-dependent IMF  \nIn each of these cases, LSST and Euclid have the advantage with respect to field of view (and cadence). WFIRST has the advantage of higher photometric sensitivity to red giant branch and low mass star tracers, and much higher resolution for star-galaxy separation in the IR. Joint processing of the three data sets offers the following rewards,  \n- 1. By using the WFIRST astrometry to deblend sources and feed new positions of stars to LSST (and to a lesser extent, Euclid), the LSST and Euclid photometry can be made to go deeper. In the actual processing, the pixels from LSST, Euclid and WFIRST would be analyzed simultaneously to detect and perform photometry on all detections in any of the more than dozen LSST+Euclid+WFIRST bandpasses.  \n- 2. WFIRST photometry alone will be critically insensitive to hot stars (e.g., white dwarfs in the Milky Way, horizontal branch stars in the Local Group). In most halo and sparse populations, these objects will be easily detected by LSST, and to a shallower depth, Euclid. Similar to 1.), the LSST photometry can be used to obtain new measurements in the WFIRST data set and to get an infrared color for these sources.\n- 3. As a result of the above, many more sources in the overlapping footprint of the three telescopes will have high-precision panchromatic photometry. This increased wavelength baseline will yield a much more accurate characterization of the underlying stellar populations (e.g., the sensitivity to age, reddening, and distance variations increases on this baseline). Note, this is different from matching LSST, Euclid, and WFIRST catalogs since the goal here is to detect sources that otherwise would not have been measured in one of the three data sets. The biggest gain in our interpretation of the stellar populations to derive physical properties will come from accurate distances to the stellar populations from Gaia. The different photometric sensitivities is not a concern here, since there are bright tracers in most populations that Gaia can target.\n- 4. The WFIRST morphological criteria of faint sources provides a crucial assessment of LSST's stargalaxy separation.  \nMany of these joint analyses can be done at the catalog level while others likely require working with the pixels from each of the surveys.", '3.8 Galaxy and quasar science': 'The WFIRST photometry will go to a similar depth (on an AB scale) as the full coadded LSST images. Euclid NIR data, while shallower, will overlap a much larger area of the LSST survey. Thus the combination of LSST, Euclid and WFIRST will give high S/N 9-band photometry stretching from 3000 ˚ A to 2 microns (a factor of six in wavelength, twice that of either WFIRST/Euclid or LSST alone) for the Gold sample ( i < 25 . 3 ) of hundreds of millions of galaxies. This broad wavelength coverage probes the SEDs of galaxies beyond 4000A to redshifts 3 and beyond, allowing detailed determination of star formation rates and stellar masses during the cosmic epoch when galaxies assembled most of their stars. (Unobscured) AGN will be identified both from their SEDs and from their variability in the repeat LSST imaging.  \nThe Hubble Space Telescope has been able to obtain comparably deep photometry over a similar wavelength range over tiny areas of sky; for example, the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) covers only 0 . 2 deg 2 , while WFIRST will cover an area ten thousand times larger. With this much larger sky coverage, the combination of LSST and WFIRST can explore the evolution of galaxy properties over this broad range of cosmic history.  \nThe weak lensing signature from individual galaxies is too small to be measured, but stacking analyses can be done in fine bins of stellar mass and redshift, exploring the relationship between dark matter halo mass, stellar populations, galaxy morphology, AGN activity and environments during the peak of galaxy assembly. The exquisite resolution of the WFIRST images will also allow the role of mergers in galaxy evolution to be quantified, with galaxy pairs separated by as little as 3 kpc discernible over essentially the entire redshift range.  \nThe multi-band photometry will allow both quasars and galaxies at much higher redshifts to be identified as well. Current studies with HST have allowed identification of a handful of galaxy candidates to redshift 8. WFIRST + LSST will expand these studies over 10,000 times the area, looking for objects that are dropouts in the u through y filters. The wide area is particularly important for discovering the rare most luminous objects at these redshifts, that can be followed up in detail with JWST and the next generation of ∼ 30-meter telescopes. The study of such objects probes the exit from the Dark Ages, as the intergalactic medium  \nbecame reionized. Understanding the formation of the first galaxies and the reionization process in detail requires putting these objects in their large-scale structure context, which is only possible with samples selected over large solid angles. In particular, the expanding bubbles by which reionization is thought to progress are thought to subtend tens of arcminutes on the sky, requiring wide-field samples to explore them.', '3.9 The variable universe': "Time domain astronomy encompasses an extremely varied suite of astrophysical topics, from the repeated pulsations of regular variable stars that serve as tracers of Galactic structure and cosmological distances (e.g. RRLyrae and Cepheids), to transient events that by their nature occur either unpredictably or only once (e.g. stellar flares, supernovae, tidal disruption events). As suggested by these examples, transients and variables occur both locally and at the most distant reaches of our universe, and so comprise a population with both a very high dynamic range in luminosity and a wide span of colors. Time domain astronomy is a rapidly growing field: the rich public dataset provided by LSST will enable a large part of the astronomy community to analyze observations of transient and/or variable objects. The potential synergies between LSST, Euclid and WFIRST are as compelling and varied as time domain astronomy itself, but here we highlight some compelling examples.  \nThe combined WFIRST, Euclid and LSST datasets would greatly facilitate the characterization and classification of transient and variable objects. One of the challenges imminent in the coming LSST era is the identification of samples of variable and transient events to be targeted for additional observations. From the transient side, the anticipated high volume of the LSST alert stream requires rapid triage of large numbers of events to identify the most important transients: those events which, if not pursued with followup observations immediately, will be opportunities lost forever. Furthermore, the high volume of events also necessitates the prioritization of the most compelling sources to followup, which in turn requires rapid characterization of an event (where characterization here is distinguished from actual classification into a known category of object). The WFIRST and Euclid datasets will assist with these challenges in a number of ways. First, the deep infrared observations will greatly assist in the identification of the 'foreground fog' of very red Galactic sources: low mass stars and brown dwarfs. While LSST's depth will identify many of these objects in quiescence, some percentage will escape even LSST on account of their very red colors and low luminosities. Therefore, flares on these objects may still create what appear to be cosmological transient events in spite of their local origin. The deep, panchromatic characterization of the static sky will enable the association of transient events with co-located sources, whether those sources are quiescent detections of the same source, or possible host galaxies of the event whose properties may give clues for a deeper understanding of those transients.  \nAs pointed out in the previous subsection on stellar science, the strength of the combined datasets goes far beyond matching the WFIRST, Euclid and LSST catalogues. Rather it increases the depth of the photometry by making it possible to detect sources that would otherwise not have been detected. The ability to identify (or rule out) infrared counterparts may also be helpful in confirming some of the most elusive transients. For example, potential electromagnetic counterparts to gravitational wave sources are expected by current models to emit their peak emission in near IR wavelengths. The association of any gravitational wave event detection with a known galaxy greatly reduces the search volume for EM counterparts to gravitational wave events, and the elimination of faint red background galaxies as putative associated transient kilonova emission will help confirm potential multi-messenger events.", '4 Coordinated observations': 'A significant fraction of WFIRST time will be devoted to a Guest Observer program. In this section of the report, we consider a number of potential GO programs that will likely follow-up on or extend LSST observations. While the GO programs will likely be selected by a future Time Allocation Committee (TAC), we will benefit by preparing for likely observing scenarios. Here, we consider three examples of joint LSST/WFIRST studies: WFIRST follow-up of strong lenses and lensed AGNs found in LSST, joint observations of deep drilling fields, and joint WFIRST/LSST searches for the afterglows of gravitational wave bursts.', '4.1 Measuring dark energy with strong lens time delays': 'As described in the previous section, time delays between multiply imaged sources are a powerful cosmological probe. LSST will enable time delay distance measurements towards hundreds of lensed AGN and supernovae (Oguri & Marshall 2010, LSST Science Book). The detection of candidate systems, which have image separations of just 1-3 arcseconds, and confirmation of them by lens modeling, depends critically on the quality and depth of the imaging data, suggesting that there is much to be gained by searching a combined LSST/Euclid/WFIRST imaging dataset. Measuring cosmological parameters with this sample will require high signal to noise ratio and high resolution imaging and spectroscopy of any Einstein Rings discovered in order to constrain the lens mass distributions. By integrating longer on the most interesting systems, WFIRST can achieve background source densities of over 200 sources/arcmin 2 , which will enable detailed weak lensing mass maps of these systems.  \nJoint analysis of all LSST and wide field infrared survey data will improve the completeness and purity of the lens searches in the following ways: 1) a combined catalog of LSST and space-detected objects will produce a more accurate initial list of target lenses, and 2) joint analysis of all the available cutout images will enable better lens modeling, leading to a much cleaner sample of candidates to be confirmed in the followup observations.  \nBeing able to model large proportions of the lens sample precisely with high resolution space-based imaging will enable the surveys themselves to constrain the structure and evolution of massive galaxies across a homogeneously-selected sample, providing important prior information needed by other cosmology probes.  \nThe joint optical and infrared photometry provided by LSST, Euclid and WFIRST will constrain the mass environments of the strong lenses (including the line of sight environment) by providing accurate photometric redshifts and stellar masses for all the relevant galaxies in the lightcone (e.g., Greene at al 2013, Collett et al 2013).', '4.2 Probing dark matter with grism spectroscopy of lensed AGN': 'Measuring the mass function of dark matter subhalos down to small masses (e.g., 10 6 solar masses) is a unique test of the CDM paradigm, and of the nature of dark matter in general. The CDM mass function is expected to be a power law rising as M -1 . 9 down to Earth-like masses, while a generic feature of selfinteracting dark matter and warm dark matter models is to introduce a lower mass cutoff. Current limits set that cutoff at somewhere below 10 9 M glyph[circledot] . We know from observations of the environs of the Milky Way that there is a shortage of luminous satellites at those masses, but this may be entirely due to the physics of star formation at the formation epochs of these satellites. Dark Milky Way satellites at lower masses may be detectable through their dynamical effects on tidal streams, but statistical studies of the one galaxy we live in will always carry high uncertainty.  \nA powerful way to detect subhalos independent of their stellar content and in external galaxies is via the study of large samples of strong gravitational lenses, in particular the so-called flux ratio anomalies (see Treu 2010, and references therein). Small masses located in projection near the four images of quadruplylensed quasars cause a strong distortion of the magnification and therefore alter the flux ratios. However, anomalous flux ratios can also be caused by stellar microlensing if the source is small enough. One solution is to observe the narrow line region emission lines, where the lensed quasar emission is sufficiently extended to be unaffected by microlensing. Large samples of thousands of lenses could achieve sensitivity down to 10 6 -10 7 solar masses required to probe the nature of Dark Matter. Unfortunately, at the moment only 3 dozen quads are known, and only a handful of those are bright enough to be observable from the ground (e.g. Chiba et al 2005).  \nDiscovering thousands of quads will require surveys covering thousands of square degrees at subarcsecond resolution (Oguri & Marshall 2010). Between them, Euclid, WFIRST and LSST should discover over 10,000 lensed AGN, one sixth of which will be quad systems. Euclid and WFIRST have the potential to observe of order a thousand of these quads spectroscopically themselves, using narrow near infrared emission lines to avoid the microlensing and enabling the wholesale application of the lens flux ratio experiment (Nierenberg et al. 2014).', '4.3 Deep drilling fields': "The LSST collaboration plans several 'deep drilling' fields. While this aspect of the LSST survey is still under design, the broad plan is to reach AB ≈ 28 in ugriz bands (and shallower in y ), which is comparable to the medium depth planned for the WFIRST SN survey (J=27.6 and H=28.1 over 8.96 deg 2 ). The WFIRST deep SN fields will be deeper with depths of J=29.3 and H=29.4 over 5.04 deg 2 . LSST has currently identified four selected fields, each with areas of 9.6 deg 2 : ELAIS S1, XMM-LSS, COSMOS, and Extended Chandra Deep Field South. With three days of observation per band, WFIRST can cover each of these deep fields to AB = 28.  \nThe goals of these fields (Gawiser et al., white paper; Ferguson et al., white paper) are to (1) Test and improve photometric redshifts critical for LSST Main Survey science. (2) Determine the flux distribution of galaxy populations dimmer than the Main Survey limit that contribute to clustering signals in the Main Survey due to lensing magnification. (3) Measure clustering for samples of galaxies and Active Galactic Nuclei (AGN) too faint to be detected in the Main Survey (4) Characterize ultra-faint supernova host galaxies. (5) Characterize variability-selected AGN host galaxies. (6) Identify of nearby isolated low-redshift dwarf galaxies via surface-brightness fluctuations. (7) Characterize of low-surface-brightness extended features around both nearby and distant galaxies. (8)Provide deep 'training sets', for characterizing completeness and bias of various types of galaxy measurements in the wide survey (e.g. photometry, morphology, stellar populations, photometric redshifts). All of these goals will be clearly enhanced by complementary data in the infrared. As already outlined in the report, infrared data will significantly improve the certainty of photoz's. WFIRST high spatial resolution will be particularly powerful in these deeper fields where confusion is likely to be significant. The deblending, color correction and morphology arguments in sec 3 apply even more strongly at the greater depth reached in these fields.  \nIndeed, WFIRST provides great synergy by providing a high-resolution detection image that will allow LSST to go past the ground-based confusion limit. This in turn will motivate LSST to go deeper in gri than currently planned for the Deep Drilling Fields; by matching the LSST Main Survey filter time distribution, LSST will reach deeper than AB ∼ 29 in these three filters rather than the current baseline of AB ∼ 28.5, providing a better match to the deepest WFIRST imaging.  \nIt is worth noting that the VISTA VIDEO deep NIR survey regions are located at the centers of the already-approved LSST DDFs, and these will generate initial spectroscopy and multi-wavelength coverage even before WFIRST launches, making them optimal regions for covering deeper in NIR. However, if  \nWFIRST is able to cover all (or most) of the 9.6 deg 2 LSST field-of-view, LSST can respond by skipping the significant fraction of time spent in y band in the current LSST 'near-uniform DDF' approach. Using WFIRST imaging in lieu of LSST imaging in y band (and possibly z band) also offers a big improvement in both resolution and depth, as LSST only reaches AB=28.0,27.0 in z and y in the 'near-uniform DDF' approach spending 60% of DDF observing time in those filters; significantly deeper ugri images could be obtained if this time is saved. Full areal coverage by WFIRST of as many LSST DDFs as possible, in zyJH , will motivate LSST to devote its observing time in those fields to the deepest possible ugri imaging, enabling a wide range of science with these 'ultra-deep drilling' fields.", '4.4 Coordinated supernovae observations': 'If the WFIRST SN medium and deep surveys target the same fields as one of the LSST deep drilling fields, then coordinated observations would yield 8 band supernova light curves. The WFIRST IFU measurements of these supernovae would yield a powerful training set that could greatly enhance the value of the large LSST SN sample. These coordinated observations would not require any increase in observing time by either project but would enhance the return of both sets of observations.', '4.5 Variable universe: follow-up on novel targets': "LSST's cadence and depth will allow it to discover new classes of variable objects and 'golden' transients, examples of known classes of objects that have nearly ideal properties for particular aspects of astronomical study. WFIRST's resolution, spectral coverage, and wavelength coverage will make it a premier facility for following up on some of these objects in the near infrared. Since studies of individual targets do not take advantage of WFIRST's large field of view, large ground-based telescopes with high quality adaptive optics will also be important tools for follow-up observation.  \nThere are a host of potential targets for follow-ups. Examples include:  \n- · 'Macronovae' produced by the coalescence of binary neutron stars (Li & Paczynski 1998, Kulkarni 2005, Bildsten et al. 2007). These explosive events likely peak in the near-infrared and would be potential targets for both WFIRST imaging and IFU follow-up.\n- · LSST and WFIRST will be our most powerful combination of telescopes for detecting afterglows of gravitational mergers (Kasliwal and Nissanke 2014; Gehrels et al. 2014). Given the LIGO's large error box for each event, there will be many variable objects found at the LSST/WFIRST depths, a program of joint monitoring (perhaps, combined with the deep field program described above) will enable a better characterization of the rich zoo of transients.\n- · Gamma Ray Bursts (Rossi et al. 2007).", '5 Data management and analysis challenges': 'The sections above make clear that in essentially every area of astronomy and cosmology, joint analysis of the LSST, WFIRST and Euclid data will provide significant benefits. These will be made possible by linking the data from the different surveys and providing a common access point for interrogating the data in a user-friendly way with the appropriate tools. This would enable scientists to explore connections between the data sets and stimulate novel community research leveraging the combined data. The publication of detailed, accurate documentation along with the cross-referencing and associated data releases would be the most effective way to encourage and support the community in pursuing such research. This section describes the issues involved in carrying out such a program for the photometry and simulations required to analyze and interpret the data.', '5.1 Multi-resolution photometry': "There are quite a few challenges to producing accurate, consistent photometry across different filters with widely different resolutions, as would be the situation for combining LSST data with either WFIRST or Euclid.  \nWe can assume that we will have a catalogue of the positions of objects detected in at least one band (including single-band detections in u or H), and that we know the PSF in each band. There are issues with respect to the chromatic effects within a single band as well as spatial variation of the PSF across the field of view, which are important, but we can neglect them for this discussion. We also assume that blending issues have been taken into account, so we have a set of pixels in each band that correspond to a single object.  \nFor point sources, photometry is relatively straightforward. Because all point sources have an identical profile (again, ignoring for now the spatial variation of the PSF) we may use any aperture to measure the relative flux of all point sources in an image (a PSF aperture is optimal). We may then estimate the image's zero-point which gives us total fluxes for all sources. We may repeat this in all the bands, resulting in a catalogue of fluxes and colors.  \nMeasuring the fluxes of galaxies is harder. It is not possible to simply measure the total flux in an aperture large enough to include the entire galaxy as the measurements are too noisy, and this is not even a well-defined concept. On the other hand, a small aperture measures a different fraction of the flux of different galaxies, so we cannot simply apply an aperture correction as in the stellar case. Even if a galaxy has the same profile in each band these fractions are different if the PSF is band-dependent; if the profiles vary the difficulties are multiplied.  \nIf we can model galaxies adequately, this alleviates the difficulties of flux measurement. The PSFconvolved model flux is a reasonable definition of the galaxy's total flux in each band. However using model-based photometry is not a panacea, as if the model must be correct. For example, choosing a model in one band and applying it in another will not yield the correct color for a galaxy with a red bulge and a blue disk, a scale length that's a function of band, spiral arms, HII regions, or any other kind of substructure with a different color from the overall galaxy light.  \nIf the seeing is (or can be made) the same in all bands we are allowed to choose a single model. The resulting fluxes are not the galaxy's total fluxes, as different components are not necessarily weighted correctly, but these 'consistent fluxes' do represent the fluxes of a certain sample of the galaxy's stellar population. However, degrading all bands to a lowest common denominator would destroy much of the extra information present in the higher-resolution space data. Determining the optimal way to estimate consistent fluxes while keeping as much of this high-resolution information as possible is still an open research question.  \nGiven the complexity of the problem of measuring galaxy photometry across a decade in wavelength with varying PSFs, there is no optimal approach. Different science questions will require different ways of combining the multi-color data.  \n- · Photometric Redshifts: We may use an object's total or consistent fluxes to find a location in multicolor space and hence its redshift probability function, p ( z ) . If p ( z ) is unimodal and sharp, the two estimators predict nearly the same photo-z. However, in general this will not be so and p ( z ) will be different for the two choices of flux.\n- · Choice of Galaxy Model: In the rest-frame optical, a simple Sersic or constrained bulge-disk model is probably sufficient to return reliable fluxes (such models down-weight the contribution from localized star-forming regions, changing p(z) at least in principle). However, modeling galaxies across the broad redshift range covered by WFIRST, Euclid, and LSST will likely require more complex models (including, for example, the uv-bright knots that contribute the bulk of the flux in the far-uv). Constraining these models is going to be hard; one approach would be to demand that all components have a consistent p ( z ) .\n- · Photometry of Blended Objects If our models indeed accurately describe our galaxies then the deblending problem is no different from the galaxy photometry problem; instead of fitting multiple components to a single galaxy we fit multiple components to multiple galaxies, relaxing but not abandoning the constraints on components' p ( z ) . In practice it is not clear how well this will work, and there are intermediate schemes (similar to the deblender used in SDSS) that fit simplified models to the ensemble of objects to assign the flux to the child objects and then proceed with photometry. This is an unsolved problem, but given the upcoming data, we will need to must significant progress in the coming years.", '5.2 Joint simulations': 'WFIRST, Euclid and LSST will generate a remarkable set of observations in the optical and near-infrared wavebands. Their cosmological interpretation, especially in combination, will be very powerful but also very challenging. Many systematic effects will have to be disentangled from fundamental physics to fully exploit the power of the measurements. Simulations of all aspects of the experiment - at the cosmological scale, of the instruments, and of the data processing and analysis software - are critical elements of the systematics mitigation program. Joint analyses of multiple surveys require these simulations to have consistent interfaces, to enable the same realizations of cosmological volumes or multi-wavelength simulated galaxies to be passed through instrument-specific simulators, and ultimately to ensure that the correct correlations and joint statistical properties are represented when mock analyses are performed on the simulated output catalogs.  \nWe focus here on the role of coordinated simulations in two areas cosmological simulations and instrument/pipeline simulations .', '5.2.1 Cosmological simulations': 'Cosmological simulations play key roles within the interpretation of large scale structure surveys: (i) they provide controlled testbeds for analysis pipelines and tools for survey design and optimization via sophisticated synthetic skies populated with galaxies targeted by the specific survey, (ii) they provide predictions for different fundamental physics effects, including dynamical dark energy, modified gravity, neutrinos, and non-trivial dark matter models, (iii) they provide modeling approaches for astrophysical systematics, including gas dynamics, star formation, and feedback effects, and (iv) they provide important information about the error estimates via covariance studies. We will briefly elaborate on the synergies between the simulation programs required for WFIRST and LSST in these four areas in the following.  \nSynthetic sky maps -Inorder to build synthetic sky maps for Euclid, WFIRST and LSST, large-volume N -body simulation with very high force and mass resolution are essential. Next, the simulations have to be  \npopulated with galaxies using sub-halo abundance matching or semi-analytic modeling techniques, tuned to match the observed population of galaxies. While the wavelength ranges of Euclid, WFIRST and LSST will be different, a common code infrastructure will be beneficial in some areas (e.g., in exploring model parameter space) and critical in others (e.g., simulating realistic merged multi wavelength catalogs).  \nPrecision predictions for fundamental cosmological statistics - The precision requirements for cosmological observables and the fundamental physics to be explored is very similar for Euclid, WFIRST and LSST and a joint program in this area would be very fruitful. Both surveys are promising observations of large scale structure measurements at the sub-percent level, a tremendous challenge for cosmological simulations. Besides the precision challenge, different fundamental physics effects have to be explored systematically for both surveys.  \nAstrophysical systematics - Some of the systematics that have to be accounted for to interpret the observations from Euclid, WFIRST and LSST are common, such as the effects of baryonic physics on the weak lensing shear power spectrum. Since the accuracy requirements are similar, a joint program would be beneficial to both surveys. However, there are significant differences because of the differing ground and space-based nature of the two programs, different instrumentation and associated wavebands, and different galaxy populations and densities. Nevertheless, the underlying sky catalogs can be generated from the same set of simulations.  \nCovariance matrices -Since the Euclid, WFIRST and LSST surveys will have overlapping volumes, combining cosmological constraints from their data sets will require understanding the full covariance matrix of all observables extracted from the data sets, using simulations of the entire relevant volume. While the accuracy requirements for these simulations are much less stringent than for other applications, the large number of simulations required will represent a computational challenge.', '5.2.2 Instrument and pipeline simulations': "Instrument and pipeline simulations are also a critical element of any precision large scale structure program: they inform the relationship between the astronomical 'scene' in the Universe and the catalogs, parameters, and other information that is recorded in the processed data. They also provide an opportunity to exercise the data reduction and analysis tools prior to first light. The instrument and pipeline tools must be considered together, since in a precision experiment the pipeline is an integral part of the measurement process. Unlike cosmological simulations, these tools are highly instrument-specific: for example, the atmosphere is only included for ground-based observations, the patterns of ghosts and diffraction features are completely different for the LSST, Euclid and WFIRST configurations, and internal optical effects, cross-talk, and readout artifacts are fundamentally different in silicon CCDs versus NIR arrays.  \nDespite the differences in instrument simulators, it is critical that they be able to take compatible input data. Precision measurements of galaxy clustering and weak lensing depend on not just counting objects and measuring shapes, but understanding selection biases, blending effects, and error distributions of measured parameters. The combination of WFIRST, Euclid and LSST data will be used to measure photometric redshifts, and for both object-by-object and statistical comparisons of number density and shear. Simulation of these applications requires that the same objects be fed through both pipelines, and hence that the input scene (simulated stars and galaxies) be consistent and have the proper correlations of object properties across wavebands. While proprietary pipelines do not need to be shared outside of the individual constortia, the inputs of these pipelines must remain compatible.", '6 Conclusion': 'The scientific opportunity offered by the combination of data from LSST, WFIRST and Euclid goes well beyond the science enabled by any one of the data sets alone. The range in wavelength, angular resolution and redshift coverage that these missions jointly span is remarkable. With major US investments in LSST and WFIRST, and partnership with ESA in Euclid, we have an outstanding scientific opportunity to carry out a combined analysis of these data sets. It is imperative for us to seize it, and together with our European colleagues, prepare for the defining cosmological pursuit of the 21st century.  \nThe main argument for conducting a single, high-quality reference co-analysis exercise and carefully documenting the results is the complexity and subtlety of systematics that define this co-analysis. Falling back on many small efforts by different teams in selected fields and for narrow goals will be inefficient, leading to significant duplication of effort.  \nFor much of the science, we will need to combine the photometry across multiple wavelengths with varying spectral and spatial resolution - a technical challenge. As described in Section 3, the joint analysis can be carried out in ways that have different computational demands. The most technically demanding joint analysis is to work with pixel level data of the entire area of overlap between the surveys. Many of the goals of a joint analysis require such a pixel-level analysis. If pixel-level joint analysis is not feasible, catalog-level analysis can still be beneficial, say to obtain calibrations of the lensing shear or the redshift distribution of galaxies. Hybrid efforts are also potentially useful, for example using catalog level information from space for deblending LSST galaxies, or using only a mutually agreed subset of the data for calibration purposes. However the full benefits of jointly analyzing any two of the surveys can be reaped only through pixel-level analysis.  \nThe resources required to achieve this additional science are outside of what is currently budgeted for LSST by NSF and DOE, and for WFIRST (or Euclid) by NASA. Funding for this science would most naturally emerge from coordination among all agencies involved, and would be closely orchestrated scientifically and programmatically to optimize science returns. A possible model would be to identify members of the science teams of each project who would work together on the joint analysis. The analysis team would ideally be coupled with an experienced science center acting as a focal point for the implementation, and simultaneously preparing the public release and documentation for broadest access by the community.', 'I.1. Introduction': 'Outside the US, there is strong interest in participating in the WFIRST-AFTA mission, as part of both the Coronagraph  Instrument  (CGI)  and  the  Wide-Field  Instrument (WFI). For the past year, scientists in Japan, Canada,  and  the  United  Kingdom  and  Europe  have been  having  scientist-to-scientist  discussions  with  colleagues  in  the  US  about  possible  modes  of  participation.  In  each  of  these  national  areas,  scientists  have come together to make informal suggestions for future participation  as  part  of  the  CGI  and  WFI.  These  are their statements of interest.', 'I.2. Japanese interest in CGI and WFI': 'WFIRST-AFTA provides unprecedented opportunities  in  the  many fields of astronomy and astrophysics, especially  for  precision  cosmology,  microlensing  and high-contrast  studies  of  exoplanets.  Deep  and  widefield  surveys  produce  magnificent  data  to  study  of  extragalactic  and  Galactic  sciences.  We  appreciate  the opportunity to have a representative in WFIRST-AFTA SDT  from  its  start  in  2013  under  the  agreement  of NASA/JAXA.  The  activity  is  well  supported  by  the Space Science Steering Committee of JAXA/ISAS and it is highly visible in Japanese astronomical community. WFIRST-AFTA indeed rouses great interests of Japanese astronomers in many fields from cosmology, galaxy  formation  and  evolution,  Galactic  bulge  science, astrometry,  exoplanets,  with  expertise  of  deep/wide surveys  and  high-contrast  imaging  so  far  conducted with Subaru Telescope as well as the microlensing observations with MOA telescopes. The Japanese activity of WFIRST-AFTA  Coronagraph  (WACO)  Working Group including the funds for preliminary Research and Developments  is  officially  supported  by  JAXA/ISAS Space Science Steering Committee. This activity will be enlarged to the WFIRST-AFTA Working Group so that future contributions in developing WFIRST-AFTA hardware/software as well as science cases in various fields from  exoplanets  to  cosmology  will  be  developed.  Following are the important items of WFIRST-AFTA project and  its  development  to  which  Japanese  astronomers can significantly contribute.', 'CGI (Japan)': "As hardware contributions, Japan has been developing  and  can  develop  instrumentation  that  could  im-  \nprove  the  science  yield  of  the  WFIRST-AFTA  coronagraph. One of the possible contributions is the polarization module in the coronagraph; Japan could furnish a polarization  module  and  insertion  mechanism  for  the OMC,  to  enhance  debris/protoplanetary  disk  science where  polarization  measurements  are  a  valuable  observing tool and allow better inner working angle than the  conventional PSF intensity subtraction. Other possible contributions include innovative masks and analysis  techniques  for  coronagraph.  Japan  has  developed innovative  mask  fabrication  techniques,  specifically photonic crystals and super ink-jet printing.  These are potential  risk-reduction  technologies  for  the  mission, and  the  masks  could  be  evaluated  on  the  vacuum testbeds for such optics at JAXA/ISAS. Japan has also developed  new  analysis  techniques  for  coronagraphs; these  include  calibration  methods  PSF  subtraction, Speckle Area Nulling (SAN) method as a dark-hole control  algorithm,  the  use  of  low  order  wavefront  sensor telemetry  for  PSF  reconstruction,  and  other  related analysis tools. Japan could also provide a module and insertion  mechanism,  using  transmissive  elements,  to be moved in or out of the OMC optical train with minimal impact on the overall design. Japan could provide a PIAA module using reflective elements, to be mounted on  the  back  side  of  the  OMC  optical  bench,  sharing much of the OMC's optical system. This module would be  optimized  for  operation  in  the  red  (0.6-1.0  micron) and  possibly  the  near-infrared  (0.6-1.6  micron).  This takes advantage of the better Inner Working Angle of a PIAA  design  (IWA~1.5  micron/D),  and  would  have comparable angular resolution to the OMC in the blue (IWA ~2.5 λ /D) analysis tools.", 'WFI (Japan)': "Coordinated ground-based observations: Coordinating ground-based wide-field and deep spectroscopy as well as deep optical imaging are important in maximizing the WFIRST-AFTA output. Deep spectroscopic data provides  unique  calibration  for  photometric  redshift which is essential in precision cosmology and study of structure  formation.  The  Hyper  Suprime-Cam  (HSC) and  Prime  Focus  Spectrograph  (PFS),  which  are  the new  wide-field  instruments  of  8-m  Subaru  Telescope, would complement the science of WFIRST-AFTA. The large-scale observation program with HSC is now ongoing and will be completed until around 2019. The HSC program  will  deliver  the  datasets  with  5  broad-bands (grizy) and several narrow-band filters over the sky area of 28 deg 2 (deep layer) and 3.5 deg 2 (ultradeep, includ-  \ning a narrow-band filter centered at 1µm). These multicolor  data  sets  that  will  be  available  well  before WFIRST-AFTA launch would be very complementary to the  WFIRST-AFTA  NIR  data.  The  similar-size  largescale  PFS  program  is  planned  to  start  from  around 2019 for 5 years duration. The combination of the Subaru aperture and the PFS's wide FoV and multiplex can deliver a unique spectroscopic data set of faint galaxies for calibrating photometric redshifts of the WFIRST/AFTA  weak  lensing  program  as  well  as  for better characterizing spectral energy distribution of galaxies  when  combined  with  WFIRST-AFTA  NIR  data. With support of the Subaru community, we are also interested  in  exploring  a  coordination  to  carry  out  additional  HSC  and/or  PFS  surveys  for  the  regions  in  the northern hemisphere that are needed for the WFIRSTAFTA, if necessary.  \nMicrolensing  /  Galactic  Bulge  Science: The  MOA collaboration  has  been  one  of  the  major  microlensing survey teams for more than 10 years, and their experiences can contribute to the analysis of the microlensing exoplanet  search  by  WFIRST-AFTA.  The  state-of-theart  difference  imaging  pipeline  and  fast  light-curve modeling  algorithm  can  be  adopted  to  maximize  the exoplanet yield from the massive datasets by WFIRSTAFTA. We are planning to conduct a precursor groundbased IR microlensing exoplanet survey by a dedicated 1.8m wide-field  telescope  in  Namibia.  This  survey  will directly  search for the best observational fields for the WFIRST-AFTA, i.e. the highest event rate, in the galactic bulge before the launch. After the launch, the simultaneous observations from this ground-based telescope and  WFIRST  enable  us  to  measure  the  mass  of  the planets by the parallax measurements. As for the galactic  bulge  science,  the  microlensing  event  rate  and  the timescale  distributions  can  be  used  to  constrain  the bulge model and we have many experiences on such studies.  The  high  precision  astrometry  measurements of  the  stars  in  the  galactic  bulge  fields  by  WFIRSTAFTA are powerful  tools  to  study  the  structure  of  the bulge and their formation and evolutional history. However,  a  high  precision  astrometry  is  mostly  systematic limited.  Significant  amount  of  efforts  for  studying  various  systematics  on  the  micro-arcsec  astrometry  has been invested by the Japanese planned IR astrometric satellite, JASMINE.  The  precursor  mission,  nanoJASMINE will be launched very soon and their experiences should be useful for the planning and the analysis of the astrometric measurements by WFIRST-AFTA.  \nMotohide Tamura (University of Tokyo/NAOJ), coordi- nator for CGI Takahiro Sumi (Osaka University) Masahito Takada (Kavli IPMU, University of Tokyo) Toru Yamada (Tohoku University), JAXA/ISAS repre- sentative for WFIRST-AFTA JAXA/ISAS WACO Working Group Japanese WFIRST-AFTA Research Group", 'I.3. Canadian interest in CGI and WFI': 'Introduction  -  WFIRST  in  the  context  of  strategic planning in Canada: Within  the  Canadian  astronomical community there is very strong interest in and support  for  WFIRST.  The  Canadian  Long-Range  Plan (LRP) for Astronomy of 2010 ranked both ground-based and  space-based  projects.  The  top  priority  for  space astronomy  was  the  recommendation  that  \'Canadian astronomers participate in a major wide-field Dark Energy  satellite  mission.  Joining  Euclid  or  WFIRST  as  a significant  partner  would  fulfill  this  recommendation, provided that we can (i) negotiate a partnership in the leading  mission,  and  (ii)  identify  a  contribution  to  the satellite  instrumentation.\'  Note  that  Euclid  has  proceeded without a Canadian contribution to instrumentation.  Furthermore,  WFIRST  in  its  current  2.4m  AFTA format,  offers  additional  science  opportunities  beyond the dark energy projects. In particular, the addition of a coronagraph module also allows for Canadian strengths in this area to be applied to WFIRST, as described below.  \nCanadian  science  interests  related  to  WFIRST  Wide-field imaging: Canada has traditional strength in wide-field  imaging  by  virtue  of  the  Canada-FranceHawaii Telescope (CFHT), and in particular Megacam, the  CFHT  Legacy  Survey  (CFTHLS)  and  the  CFHT Large Programs. The Supernova Legacy Survey, based on the CFHTLS-Deep, is the most advanced SN survey in the world at present. It is a joint project between Canadian and French astronomers. Similarly, the CFHTLenS  analysis  of  the  Wide  component  of  the CFHTLS  is  the  current  state-of-the-art  weak  lensing survey. Both of these programs have had a very significant  scientific  impact.  Participation  in  WFIRST  would allow  existing  team  members  and  their  students  and postdocs  to  apply  their  expertise  to  SN  and  weak lensing  surveys  of  the  2020s.  More  broadly,  the  25% GO time will also be of great interest to Canadian astronomers.  Finally,  as  described  below,  the  Canadian astronomical community has ample expertise in instru-  \nmentation  related  to  the  wide-field  imaging  module  of WFIRST.  \nCanadian science interests related to WFIRST Exoplanets: WFIRST is of great interest to the exoplanet community  in  Canada,  which  views  the  coronagraph instrument as a key stepping stone in the quest to directly image and characterize planetary systems similar to  our  own,  a  line  of  research  in  which  Canada  has been very interested, active, and has acquired internationally  recognized  expertise.  Participation  in  WFIRST would build upon the space science and space instrumentation expertise in the community developed in the context  of  the  FGS-NIRISS  instrument  for  the  Webb telescope. Indeed, the two main science drivers of the NIRISS instrument, \'the detection of first-light galaxies and characterization of exoplanets\' are intricately connected to the main science goals of WFIRST. In addition,  the  Canadian  community  has  invested  in  several ground-based exoplanet-focused enterprises, most notably  GPI  (high-contrast  exoplanet  imager  for  Gemini South), NFIRAOS/IRIS/PSI (near-infrared adaptive optics imaging instrument for the Thirty Meter Telescope), and  SPIRou  (radial-velocity  exoplanet  finder  spectrograph  for  CFHT),  which,  together  with  the  NIRISS  efforts,  will  help  set  the  stage  for  the  work  to  be  undertaken  with  the  WFIRST  coronagraph.  The  timeline  of WFIRST is perfect, as it would come right after these projects.  \nStatus of WFIRST instrumentation studies in Canada: Since late 2013, a Canadian astronomer (Hudson) has participated in the WFIRST-AFTA SDT, supported by  the  Canadian  Space  Agency (CSA). In 2014, CSA issued  an  RFI  on  potential  contributions  to  WFIRST. Based on the response to this RFI and the importance of WFIRST to the Canadian astronomical community as expressed  in  the  Long-Range  Plan,  CSA  issued  an RFP for two WFIRST studies, one for contributions to the WFI component, and the other for contributions to the  coronagraph.  Based  on  the  RFI  submissions  and other  considerations,  CSA  selected  the  following  instrumentation options for further study.  \nSummary: At the time of writing, these instrumentation studies  are  ongoing.  The  WFI  study  is  being  led  by COM DEV and the coronagraph study by ABB Canada. In  the  second phase of the studies, a subset of these options  will  be  studied  in  greater  detail.  CSA  also  issued  a  call  for  a  "Pool  of  Experts"  to  assist  with  the studies which received a strong response (over 20 Ca-  \nnadian  researchers).  The  studies  are  expected  to  be completed  by  mid-2015.  The  mid-term  review  of  the 2010 LRP is also underway and will update the recommendations of the Canadian LRP.  \nThe findings and recommendations of these studies will be used as a basis to solicit the necessary funding for a contribution to WFIRST (through the CSA). It is hoped  that,  through  these  efforts,  Canadian  astronomers will have the opportunity not only to collaborate on WFIRST instrumentation but also that Canadian astronomical community as a whole will be able to fully access  WFIRST  data  and  to  participate  in  WFIRST  science team membership.', 'WFI (Canada)': "Integral  Field  Unit  (IFU)  or  subsystem(s): Canada has  accumulated  ample  expertise  in  developing  nearinfrared  spectrographs,  including  an  IFU-based  one, which will be essential to making a contribution to the WFI  IFU  module.  Specific  examples  include:  (1)  the Wide Integral Field Infrared Spectrograph, which is an image  slicer-based  integral  field  spectrograph  in  the near-infrared waveband, similar to what has been envisioned for  the  IFU  module  of  WFIRST;  (2)  in  partnership with the NASA JWST team, leading the development of a near-infrared multi-object spectrograph using the  microshutter  array  for  ground-based  wide-field adaptive  optics  observations;  (3)  the  Near  Infrared Echelle Spectrograph for the Keck II telescope with the California  Institute  of  Technology;  and  (4)  the  calibration system for the near-infrared instruments and adaptive  optics  system  of  the  Thirty  Metre  Telescope. Through  these  projects,  by  developing  cutting-edge near-infrared  spectrographs,  most  of  the  expertise  required for developing the WFI IFU module is present in Canada.  \nPhotometric calibration (pre-flight ground or flight): Several  of  the  primary  science  goals  of  WFIRST,  including measurements of dark energy using type Ia supernovae, and minimization of bias (and of bias uncertainties)  in  photometric  redshifts  for  weak  lensing measurements, will be limited in precision by calibration uncertainties,  particularly  those  stemming  from  photometric calibration of the imager. Canadian expertise in multiple areas of calibration, including photometric calibration  via  traditional  techniques  of  determining  and utilizing stellar standards, as well as novel means such as  calibrating  stellar  standards  via  calibrated  artificial sources above the atmosphere, will be critical in mini-  \nmizing these limiting uncertainties and thus maximizing the scientific output of WFIRST.  \nFine Guidance System: Canada has provided the full fine-guide  capability  (hardware  and  software)  for  the FUSE and JWST missions, via CSA's aerospace contractors,  working  with  science  teams.  The  complex tradeoffs  between  sensitivity,  noise,  image  quality, wavelength, and guide star availability are well understood, as well as field recognition and target acquisition. Canada is in an excellent and experienced position to provide such capabilities for the WFIRST WFI.  \nWide-field imager: In addition to the possible contributions to WFIRST instruments described above, the Canadian  community  has  developed  a  concept  for  a UV/blue wide-field imager (CASTOR) that could significantly  enhance  the  scientific  reach  of  the  proposed WFIRST WFI survey.", 'CGI (Canada)': 'Integral Field Spectrograph (IFS): The proposed IFS unit  shares many similarities with the IFS successfully developed for the Gemini Planet Imager by Université de Montréal and Université Laval. Canadian space industry has both the technical expertise and the collaborative  experience  with  CSA  and  NASA  for  delivering such a science instrument.', 'EMCCD detector for the IFS and the imaging came-': 'ra : An  electron-multiplying  charge-coupled  device (EMCCD), effectively operating with zero noise, would be an excellent choice for the needed detectors. NuVu Cameras,  based  in  Montreal,  is  one  of  only  three groups in the world with the required expertise on the control  electronics  for  EMCCDs.  With  funding  from CSA, work is proceeding on qualifying these  cameras for space applications.  \nSubsystems: Coronagraph subsystems, more specifically, the coronagraph low-order wave front sensor and the  coronagraph  filters/masks  wheels.  There  is  excellent Canadian expertise in adaptive optics (Canada has led  or  is  an  important  contributor  to  the  facility-class Gemini/ALTAIR  system,  the  Gemini/GPI  and  the TMT/NFIRAOS)  as  well  as  in  building  wheel  mechanisms for space applications.  \nData  reduction  pipeline,  data  processing,  and  archiving: Canadian  astronomers  developed  the  image  \nprocessing algorithms that allowed the first direct imaging  detection  of  exoplanets  in  2008.  This  pioneering work  has  then  continued  with  the  development  of  the data  reduction  pipeline  for  the  Gemini  Planet  Imager. Both the WFI and coronagraph studies will also analyze options for data processing and archiving contributions. The Canadian Astronomy Data Centre has a long history  of  productive collaboration with NASA on HST data management.  CADC  also  archives  wide-field  images from CFHT as well as data from many other observatories,  so  there  are  clear  opportunities  to  enhance WFIRST science potential for the astronomical community.  \nMichael  Hudson,  University  of  Waterloo  (CSA  representative on SDT, coordinator for WFI and CGI) Roberto Abraham, University of Toronto Justin Albert, University of Victoria Loic Albert, Université de Montréal Étienne Artigau, Université de Montréal Pauline Barmby, Western University Pierre Bastien, Université de Montréal John Blakeslee, NRC-Herzberg J. Richard Bond, CITA/University of Toronto Colin Bradley, University of Victoria Raymond Carlberg, University of Toronto Patrick Coté, NRC-Herzberg Andrew Cumming, McGill University Rene Doyon, Université de Montréal Ray Jayawardhana, York University Gary Hinshaw, University of British Columbia John Hutchings, NRC-Herzberg David Lafrenière, Université de Montréal Jérome Maire, University of Toronto/Dunlap Institute Christian Marois, NRC-Herzberg Brenda Matthews, NRC-Herzberg Jaymie Matthews, University of British Columbia Alan McConnachie, NRC-Herzberg Kristen Menou, University of Toronto Stanimir Metchev, University of Western Ontario Dae-Sik Moon, University of Toronto Ralph Pudritz, McMaster University David Schade, NRC-Herzberg Simon Thibault, Université Laval Diana Valencia, University of Toronto Jean-Pierre Véran, NRC-Herzberg Yanqin Wu, University of Toronto', 'CGI (UK and Europe)': "In France, Paris Observatory (LESIA), Marseille laboratory  (LAM)  and  Nice  Observatory  (LAGRANGE) have been involved in coronagraphy and high contrast imaging for exoplanets and disks science. These activities  were  started  many  years  ago  for  both  groundbased and space projects.  \nLESIA/Paris Observatory (FR): LESIA has been working  on  the  concept  of  the  phase  mask  (Rouan  et  al. 2000). We  have  manufactured  coronagraphs  for NACO/VLT  (Boccaletti  et  al.  2004),  SPHERE/VLT (Boccaletti et al. 2008) and MIRI/JWST (Boccaletti et al. 2005, Baudoz et al. 2006, Boccaletti et al. 2014.). We have  led  the  Cosmic  Vision  proposal  to  ESA  in  2010 « SPICES », a small-scale version of WFIRST for spectro-polarimetric  analysis  of  giant  planet  (ultimately  Super-Earth) atmospheres (Boccaletti et al. 2012, Maire et al. 2012). Several observations of disks and exoplanets using  current  facilities  were  published  by  our  team (Boccaletti  et  al.  2009,  2012,  2013a,b,  Mazoyer  et  al. 2014,  Galicher  et  al.  2013,  2014)  or  in  collaboration (Lagrange  et  al.  2009,  2010,  2012,  Bonnefoy  et  al. 2011, 2013, Chauvin et al. 2012, Rameau et al. 2013). Recently,  we  have  been  developing  a  dedicated  high contrast  test  bench  (THD  bench)  to  study  under  the same  conditions  several  coronagraphs  and  postcoronagraphic  techniques,  individually  and  in  association.  The  main  post-coronagraphic  solution  we  have been working on is  the  Self  Coherent  Camera  (SCC), which uses the coherence of the stellar light to generate Fizeau fringes in the science focal plane and spatially encode  the  speckles  (Baudoz  et  al.  2006).  The  SCC can be used as a focal plane wavefront sensor for active correction on space-based and ground-based telescopes (Galicher et al. 2008, 2010, Baudoz et al. 2010, 2012, Mazoyer et al. 2013) and as a differential imaging technique  to  discriminate  the  planet  image  from  the stellar residuals (Baudoz et al. 2006, 2013, Galicher et al.  2007).  The  SCC  has  been  tested  in  the  laboratory with  several  types  of  coronagraphs:  Four  Quadrant phase  Mask  (Rouan  et  al.  2000),  Multi-stage  Four quadrant phase mask (Baudoz et al 2008, 2010, Galicher  et  al.  2011)  and  Dual  Zone  Phase  mask (Soummer et al. 2003, Delorme et al. 2014). Laboratory results  on  the  THD  bench  proved  that  the  SCC  could reach a contrast of a few 10 -8 for  all  of  these  coronagraphs  at  short  spectral  bandwidth  (Mazoyer  et  al. 2014) and that the contrast is slightly degraded (4x10 -8 )  \nfor larger bandwidth (up to 5%, Delorme in preparation) or  when  measuring  the  wavefront  errors  on  medium spectral bandwidth (10%, Delorme et al. 2014).  \nApart  from  these  developments  on  high  contrast imaging,  LESIA  and  the  Observatoire  de  Paris  have strong expertise in building instruments for space missions with for instance participations in Corot, ROSETTA, CASSINI, Gaia)  \nLAM  -  Marseille  (FR): LAM  is  a  leading  European space laboratory combining astrophysical research and instrument  development  for  large  ground-based  and space telescopes, with participation in large space missions (SOHO, Herschel, Corot, Galex, Rosetta, Euclid). The  laboratory  has  been  deeply  involved  in  the  high contrast imaging  instrument  VLT-SPHERE  (IRDIS camera, high quality aspherical mirrors and high speed WFS camera), developing a deep knowledge on highcontrast  imaging  and  spectrograph  systems  (Vigan  et al. 2013, Antichi et al. 2009). LAM has also a long expertise in phase mask coronagraphy (DZPM, Soummer et al. 2003, N'Diaye et al. 2010, 2012) and associated post  coronagraphic  wavefront sensing  (Vigan  et  al 2011, Dohlen et al. 2013, Paul et al. 2013, 2014). LAM is  specialized in manufacturing very-high quality optics (Hugot et al.  2012)  and  contributed  to  the  STScI  high contrast imaging bench (HiCAT - N'Diaye et al. 2014). LAM  has  an  excellent  knowledge  in  producing  active mirrors and wavefront sensing for space (MADRAS and RASCASSE projects, Laslandes et al. 2012, 2013), in close  collaboration  with  space  industry  (Thales  Alenia Space). On all these topics, LAM has a very strong collaboration with the French  aerospace  laboratory (ONERA). With the support of the French space agency (CNES), numerous PhD thesis are pursued or planned in collaboration with ONERA, LESIA and STScI.  \nLAM is equipped with several technology facilities, specially  conceived  for  the  assembly,  integration  and tests  of  future  space  instrumentation.  These  facilities also  include  MOEMS  cryogenic  test  bench  and  highcontrast imaging bench. LAM has also a deep expertise in detector technology and was at the origin of the spinoff  company  First  Light  Imaging  (FLI).  This  company (already under contract with JPL) manufactures cameras with high cadence and low noise designed for wavefront sensing. They are built around E2V CCDs and the company  would  be  able  to  provide  support  on  the test/design of the detector and the electronics in collaboration with UK (see below).  \nLAGRANGE/Nice  Observatory  (FR): LAGRANGE  is associated  to  the  development  of  SCExAO  at  Subaru (Martinache et al. 2014) and in particular of the Low order  wavefront  sensor  (Singh  et  al.  2014),  as  well  as new  techniques  for  wavefront  sensing  (Martinache 2013a,  Martinache  et  al.  2012)  and  postprocessing (Martinache  2013b).  LAGRANGE has expertise in  designing  coronagraphs  and  high  contrast  test  benches (Martinez et al. 2007, 2008, 2009, 2010, 2011, 2012).  \nFrench institutes could participate at scientific and instrumental levels. Importantly, CNES would be willing to support a small contribution if WFIRST got select and is already funding our laboratories for technological developments (THD bench for the SCC, space active optic and WFS benches). First of all, the Maire et al. analysis can be re-applied and extended further to the case of WFIRST-AFTA with the objective to evaluate the science cases (not just detection but rather performance in characterization).  We  can  also  participate  to  the  design/optimization of the instrument with emphasizes on the wavefront sensing and correction (low and high orders)  and  provide  very  specific  components  (optics, etc..).  The  various  benches  and  space  facilities  can come in support to other US facilities for testing some components. In addition, with our observational expertise (VLT, Subaru) we can contribute to the data reduction strategy/pipeline.  \nOther countries involved in SPICES have also expressed  interests:  Obs  Padova  Italy  for  the  design  of the IFS with expertise in SPHERE, Netherland for polarimetry.  \nFinally,  Airbus  Defence  &  Space  (Toulouse)  has participated in the SPICES study and might be able to contribute on the platform or telescope.  \nCEI-OU/MSSL-UCL: In the UK interests centre on the  CCDs  and  the  associated  detection  chain  camera system.  These  are  based  around  a  close  alliance  between CCD manufacturer e2v, the Centre for Electronic Imaging  at  the  Open  University  (CEI-OU)  and  the Mullard  Space  Science  Laboratory,  University  College London (MSSL-UCL).  \ne2v and CEI-OU have established a formal cooperative relationship, with e2v funding PhD studentships and postdoctoral fellowships at CEI-OU, and providing devices for analysis, characterisation and testing, particularly with respect to radiation damage for the space environment. Senior engineers interact with the CEI-OU team. e2v in turn benefit from this detailed evaluation of their devices, and are able to implement improvements in  both  manufacture and operation as a result. MSSL-  \nUCL have worked with e2v and CEI-OU in a number of projects,  providing  the  detection  chains  to  operate  the CCDs  and  provide  digital  outputs,  including  those  in Gaia,  Euclid and PLATO ,  all  of  which  have  massive CCD  focal  planes,  the  biggest  flown  in  any  spacescience  instrumentation.  MSSL-UCL  lead  the  VISible instrument,  one  of  the  two  instruments  on Euclid .  VIS has 36 4k x 4k CCDs, and 144 detection chains supported by 12 camera units with low noise and ultra-high stability,  and  with  sophisticated  readout  schemes  developed in consultation with CEI-OU to maximise resilience to radiation damage. In Gaia, CEI-OU worked with MSSL-UCL  to  space-qualify  EMCCDs  for  the  spectrometer instrument, in a large testing programme using 100 CCDs. In PLATO , MSSL-UCL is building the camera units for 128 large format CCDs, this time with 256 detection  chains  in  32  units.  Moreover,  CEI-OU  is  already  under  contract  with  the  WFIRST  team  for  EM CCD characterisation.  \nIoA, Cambridge: The IoA has a long-standing involvement in science teams for space-based coronagraphic imaging, primarily  through  its  expertise  in  debris  disks (e.g., Wyatt 2008, ARAA, 46), the circumstellar disks of asteroids and dust which will be characterized by such techniques and provide noise that may prevent detection  of  planets.  Science  team  membership  includes both  European  and  US  projects  (SPICES,  DDX, EXCEDE which is currently  receiving  NASA  Category III  Explorer  funding  for  technology  development  and maturation, and HOSTS - the NASA-funded LBTI project  to  characterise  the  exozodis  of  nearby  stars  in preparation  for  future  imaging  of  Earth-like  planets). The group at the IoA also has a strong heritage in the production of science data products from key high value missions.  It  has  recent  relative  heritage  in  delivering advanced high throughput processing chains for Gaia, and  is  leading  the  exoplanet  analysis  system  for PLATO.  It  provides  data  systems  for  a  number  of ground-based  surveys,  imaging  (VISTA,  VST)  and spectroscopic (VLT/FLAMES, Gaia-ESO Survey, 4MOST,  WEAVE  [includes  significant  IFS  components]). There is a strong focus on exoplanet synergies, with Gaia and PLATO being closely coupled, interfaces to  both  will  be  of  significant  value  in  the  analysis  of WFIRST coronagraphic data.  \nThis tight collaboration between manufacturers and scientific  institutes  provides  an  unparalleled  understanding  and  capability  of  optimisation  of  the  detector chain and of its performance in space, which would be of undoubted benefit to the two Coronagraph channels  \non  WFIRST.  While  science  groups  such  as  CEI  and MSSL are both enthusiastic and competent to contribute  to  the  Coronagraph,  UK  funding  will  require  the usual approvals from the UK Space Agency, involving, in  the  first  instance,  a  Statement  of  Interest  to  the UKSA  Space  Projects  Review  Panel,  and  would  be subject to strategic and financial considerations currently being explored by UK groups with UKSA.", 'WFI (UK and Europe)': "WFI will be the pre-eminent astronomical wide field  \ninfra-red imager in the short and medium term. It's no surprise  therefore  that  several  European  groups  are eager to participate in the instrument programme, in the ground  system  for  the  processing  of  the  data  from  it, and in scientific programmes of interest to them which would be most effectively pursued with the WFI. An involvement  would  be  informed  by  current  contributions to (among others) JWST NIRSpec/MIRI and Euclid . Consequently, groups in France, Germany, Italy, Spain and  the  UK  were  consulted,  coordinated  by  UK  interests, with the request to non-UK groups to consult within their own communities. The list included in France: le Fèvre (LAM), Mellier (IAP); in Germany: Bender (MPE), Rix  (MPIA);  in  Italy:  Cimatti  (Bologna),  Scaramella (Rome);  in  Spain:  Castander  (Barcelona);  and  in  the UK: Sharples (CfAI, Durham), Wright (UKATC), Davies (Oxford),  Nichol  (Portsmouth),  Cropper  (coordinator, MSSL-UCL). These interests are summarised below for those who have responded.  \nLAM: Instrumental interests in the WFI design, manufacturing, testing; the IFU spectrograph including slicer disperser and mechanical structure, and, more generally,  opto-mechanical  systems.  For  the  ground  system, they  have  expertise  in  deep  spectroscopy  surveys  for cosmology and galaxy evolution; IFU spectroscopy processing;  multi-wavelength  analysis  -  photometric  redshifts, SED fitting and spectral analysis. They are lead institute for the Euclid -NISP instrument, and contributed to  the Herschel SPIRE FTS. Facilities  include  a  90m 3 vacuum chamber which they use for NISP. They also developed to TRL6 an IFU spectrograph for the SNAP study with LBNL, with a 4' x 4' field of view and spectral resolving power of 100 - 300.  \nIAP: Interest  is  in  image  processing  and  automated quality control software development and in pipelining. IAP hosts the Terapix data centre for wide field visible (MegaCam  at  CFHT)  and  near  infrared  imagers  \n(VIRCAM  on  ESO/VISTA).  IAP  is  responsible  for  the VIS Organisation Unit in the Science Ground Segment of Euclid ,  of  the  VIS  component  of  the  Simulation  Organisation Unit and of the wide field ground based survey of the Euclid northern sky with MegaCam at CFHT. IAP currently hosts the Planck HFI data center, producing  the  official  releases  for  ESA.  IAP  is  also  strongly involved in the data processing and analysis pipelines of the JWST NIRSPEC instrument.  \nMPE: Depending  on  time  scales  and  support  by  the German  funding  agency  DLR,  MPE  could  envisage contributing  similar  components  as  for Euclid , i.e. lenses, mounts including tests etc.  \nICE, IFAE Barcelona, & CIEMAT, IFT Madrid: Interest is in possible participation in the WFI mechanics, electronics  and/or  control  software.  They  currently  are  responsible for the Filter Wheel Assembly of Euclid -NISP and  the  Simulations  Organization  Unit  in  the  Science Ground  Segment;  they  also  host  the Euclid Spanish Data Centre. Besides Euclid , they are currently involved in  several  ground-based  Dark  Energy  experiments  DES,  PAU,  DESI  -  in  which  they  participate  in  management, planning, instrumental development, software development  and  scientific  coordination  and  exploitation.  Their  scientific  interests  are  focused  on  Dark Energy related research.  \nCfAI  Durham: The  primary  interest  is  in  the  Integral Field Unit. Their relevant heritage is participation in the optical  &  opto-mechanical  design,  complete  optics manufacture and test and cryogenic testing and qualification  of  the JWST NIRSpec  IFU  under  contract  to Astrium  GmbH,  and  in  collaboration  with  SSTL.  Engineering, flight and flight spare models were successfully delivered to Astrium for integration into NIRSpec. They also performed the complete optical & opto-mechanical design,  optics  manufacture  and  metrology  and  subsystem  I&T  for  the  24  IFU  units  for  the  VLT-KMOS spectrograph.  Their  capabilities  include  optical  and opto-mechanical systems design, a fully equipped diamond machining and optical  metrology  facility  as  well as sub-system test and integration.  \nMSSL-UCL: The primary interest is in the potential WFI Calibration  Unit.  The  applicable  heritage  is  the JWST NIRSpec  Calibration  Unit  engineering,  flight  and  flight spare  models  provided  under  contract  to  Astrium GmbH. This unit  provided  11  bands  of  highly  uniform illumination  in  the  1-5 µ m range,  and  included  comb  \nfilters  for  the  wavelength calibration. MSSL has instruments in over 50 missions with NASA ( Cassini, Swift ), ESA, JAXA, USSR/Russia, China and India. Cryogenic missions  include ISO LWS, Herschel SPIRE, JWST NIRSpec, Gaia and Euclid (VIS  instrument  lead,  VIS scientist on Euclid Science Team; weak lensing science working  group  lead).  Their  scientific  interests  include galaxy  evolution  astrophysics  and  cosmology,  particularly weak lensing, via their Euclid roles.  \nICG Portsmouth: Interest  is  in  IFU  spectroscopy  processing, and then in scientific aspects concentrated in supernova classification and analysis; redshift determination  from  slitless  spectroscopy;  and  precision  large scale structure measurements. They developed the IFU data processing pipeline for SDSS MaNGA. They have significant  science  leadership  roles  in  DES,  SDSS, DESI  and Euclid (lead  of  galaxy  clustering  science working group and BAO scientist on the Euclid Science Team).  \nUKATC: Interests  are  in  opto-mechanical  aspects  of the  WFI  camera,  IFU,  mechanisms  and  potential  calibration sources. They have extensive expertise in cryogenic instrumentation for space ( JWST -MIRI lead institute) and ground (VLT-KMOS; SCUBA2).  \nOxford: Interest  is  in  designing,  building,  testing  and using IFUs, as well as red/infrared spectrograph design and  construction  (through  FMOS,  SWIFT  &  KMOS). They have delivered extensive scientific surveys based on  IFU  data  (SAURON  +  ATLAS-3D  +  SWIFT)  and have expertise in terms of handling IFU data and bringing  it  to  a  stage  ready  for  scientific  exploitation.  They are involved in SDSS MaNGA having fabricated the Vgroove blocks that hold the fibres in place at the spectrograph  slit.  Oxford  leads  the Euclid science  working group for supernovae.  \nEuropean  participation  could  be  through  an  ESA Mission  of  Opportunity,  or  via  bilaterals  between  national agencies and NASA. Initial discussions have taken  place  with  ESA  and  some  national  agencies,  and these  are  being  pursued  subsequent  to  the  WFIRST SDT Meeting on 20/21 Nov. An MoO with ESA would require  national  agency  sponsorship,  and  might  follow the precedent established with Euclid with a reciprocal involvement  by  European  scientists,  together  with  instrument  and  ground  system  roles.  Pending  further consultations,  expectations  should  be  maintained  at  a  \nrealistic  level,  and  will  be  dependent  on  the  outcomes from the recent ESA Ministerial.", 'CGI Contributors:': 'Anthony Boccaletti, LESIA - Paris Observatory, FR (co-  \nordinator for CGI) Pierre Baudoz, LESIA - Paris Observatory, FR Riccardo Caudi, Padova Observatory, IT Kjetil Dohlen, LAM - Marseille Observatory, FR Marc Ferrari, LAM - Marseille Observatory, FR Raphaël Galicher, LESIA - Paris Observatory, FR Jones Geraint, UCL, UK Raffaele Gratton, Padova Observatory, IT Andrew Holland, CEI Open University, UK Emmanuel Hugot, LAM - Marseille Observatory, FR Frantz Martinache, LAGRANGE - Nice Observatory, FR Patrice Martinez, LAGRANGE - Nice Observatory, FR Jean Schneider, LUTH - Paris Observatory, FR Arthur Vigan, LAM - Marseille Observatory, FR Mark Wyatt, Cambridge University, UK', 'WFI Contributors:': "Mark Cropper, Mullard Space Science Lab (MSSL), University College London, UK (coordinator for WFI) Ralf Bender, Max-Planck-Institut für extraterrestrische Physik (MPE), Germany Francisco Castander, Institut de Ciències de l'Espai (ICE), University of Barcelona, Spain Roger Davies, Oxford Astrophysics, Oxford University, UK Ignacio Ferreras, Mullard Space Science Lab (MSSL), University College London, UK Olivier le Fèvre, Laboratoire d'Astrophysique de Marseille (LAM), France Yannick Mellier, Institut Astrophysique de Paris (IAP), France Bob Nichol, Institute of Cosmology and Gravitation (ICG), University of Portsmouth, UK Ray Sharples, Centre for Advanced Instrumentation (CfAI), Durham University, UK  \nGillian Wright, United Kingdom Astronomy Technology  \nCentre (ATC), UK  \n<!-- image -->", 'LSST Cadence': 'The 2200 square degree HLS will need to be complemented by near UV and ground based photometry in order to provide photometric redshifts for  the  WFIRST-AFTA  weak lensing experiment. These photometric redshifts will of course be an important WFIRST-AFTA data product for a wide range of other science areas, especially in galaxy evolution and the study of high redshift and rare objects. The unprecedented combination of area and depth of the WFIRST-AFTA HLS creates a challenge in getting optical and near UV imaging to the depth required to produce quality photo-z\'s for the 50-60 lensed galaxies per square arcminute that WFIRST-AFTA will observe. As discussed in §2.2.3.4, the WFIRST-AFTA weak lensing analysis will likely require the full ten year LSST depth over the 2200 square degree HLS. It would be beneficial to both LSST and WFIRST-AFTA to reach this full depth over the area of the WFIRST-AFTA HLS on a time scale contemporary with the WFIRST-AFTA HLS, rather than waiting until the full LSST survey is completed in 2032.  \nBenefits to LSST. The combination of full-depth LSST data and WFIRST-AFTA HLS NIR data will provide the gold standard in photo-z\'s. Furthermore, WFIRST-AFTA grism observations over the same area will provide many millions of high quality slitless spectra and WFIRST-AFTA\'s IFU can be run in parallel with WFI observations to provide even higher precision spectra of faint galaxies (~20k to LSST depth and ~30k to WFIRST depth). Thus, the WFIRST-AFTA photometric data will  help  to  provide  better  LSST  photo-z\'s  for  their  analysis  but  WFIRST-AFTA  will  also  provide many of the spectra needed for a training set to calibrate the photo-z\'s for both missions. A further benefit to LSST might be the reduced need for LSST observations at the reddest end of the LSST wavelength range (the z and y filters), where both the atmosphere and the physics of CCDs make ground-based observations less efficient than what WFIRST-AFTA can achieve. Finally, the joint processing of LSST and WFIRST-AFTA data will provide better object deblending parameters than LSST can achieve alone; WFIRST-AFTA will be able to provide a morphological prior for the deblending of LSST images (see § 2.7.3).  \nCadence Suggestion. Given the aforementioned benefits to LSST and the requirement for deep optical photometry for WFIRST-AFTA, it would be beneficial for the entire HLS to lie within the LSST observing area and to complete LSST and WFIRST-AFTA surveys of that area on comparable time scales. While the development of an observation schedule for WFIRST-AFTA remains a task for the Project and selected Science Teams, the likely timelines of the two projects indicate that reaching the full WFIRST-AFTA depth over this area will require LSST to accelerate observations on that part of the sky. Since the HLS area is roughly 1/8 as large as the LSST "Main Survey" region, this could be achieved by devoting 1.25 years of LSST observations to the HLS area, assuming that it covers a wide enough range of Right Ascension. More practically, it could be achieved by devoting 25% of LSST observing time to this area during each of the first 5 years of the LSST survey, which doubles the time it would naturally be observed during those years at a modest reduction in coverage of the rest of the Main Survey area during that time period. As LSST and WFIRST progress, there is a mutual benefit in continuing discussions about the optimal joint observation schedule.  \nOther Cadence Issues . There are other observation cadence symmetries between WFIRST-AFTA and LSST. These lie in areas where time domain is a key issue such as supernova observations and exoplanet microlensing. It is also imperative to ensure that the deep fields for both observatories are coordinated. Synergies for panchromatic data sets in GO programs and high resolution imaging of stellar populations should also be explored.  \nIan$Dell\'Antonio,$Gillian$Wilson,$Tommaso$Treu$for$the$Cosmology$ISDT$(ian\\_dell\'antonio@brown.edu)$ WFIRST/TMT)Synergies:)Cosmology)and)Fundamental)Physics)  \n$  \nIn$the$past$10$years,$progress$in$cosmology$has$been$greatly$aided$by$the$synergy$between$groundHbased$ and$space$OIR$facilities$$(HST$and$Spitzer).$$One$need$only$think$of$the$measurement$of$the$acceleration$ (and$earlyHtime$deceleration)$of$the$Universe$that$has$been$possible$due$to$the$measurement$of$type$Ia$ supernovae$$(Perlmutter$&$Riess$1999;$Riess$et$al.$2004),$or$of$the$combined$use$of$groundHbased$and$ spaceHbased$weak$lensing$to$discover$and$characterize$\'bulletHlike\'$clusters$e.g,$Clowe$et$al$2006;$Dawson$ et$al.$2012.$$$In$many$cases,$the$groundHbased$telescopes,$with$their$larger$collecting$area$and$field$of$ view$have$served$as$discovery$telescopes$and$spectroscopic$engines,$and$spaceHbased$observatories$with$ their$superior$resolution$and$lower$sky$background$have$served$to$extend$the$redshift$range$to$higher$ redshift$and$provide$superior$resolution.$$  \n$  \nIn$ the$TMT/WFIRST$era,$this$synergy$will$continue,$this$time$relying$on$the$superior$area$coverage$and$ photometric$ stability$ of$ the$ spaceHbased$ WFIRST,$ combined$ with$ the$ greater$ resolution$ and$ broader$ wavelength$ coverage$ of$ TMT.$ $ Although$ other$ topics$ in$ cosmology$ will$ of$ course$ benefit$ from$ the$ synergistic$capabilities$of$TMT$and$WFIRST,$we$highlight$four$areas$that$will$greatly$benefit.$$They$are:$$ Cluster$ scale$ cosmology$ (tomography,$ mass$ function$ evolution$ and$ high$ redshift$ cluster$ formation);$ galaxyHscale$cosmography$(gravitational$time$delays);$$supernova$cosmology;$and$\'nearHfield\'$cosmology,$ in$particular$surveys$of$the$MW$satellites$to$understand$the$properties$of$dark$matter.$  \n$', 'Cluster$Scale$Cosmology$': '$  \nWFIRST$is$expected$to$discover$~40000$M>$10 14 $Msun$clusters$out$to$z~3$in$the$2000$deg 2 $area$of$the$highH latitude$ survey$ (WFIRSTHAFTA$Final$Report),$offering$new$possibilities$for$constraining$cosmology$using$ the$ positions$ of$ multiplyHimaged$ background$ sources$ using$ the$ soHcalled$ "strong$ gravitational$ lensing$ angular$diameter$cosmography"$technique.$The$positions$of$the$multiple$images$depend$on$the$lens$mass$ distribution.$ They$ also$depend$ on$ the$ angular$ diameter$ distance$ ratios$ between$ the$ lens,$ source,$ and$ observer,$ thereby$ encapsulate$ information$ about$ the$ underlying$ cosmology$ (Paczynski$ &$ Gorski$ 1981;$ Blandford$ &$ Narayan$ 1992;$ Link$ &$ Pierce$ 1998;$ Golse$ et$ al$ 2002)$ $ Recent$ feasibility$ studies$ have$ demonstrated$ the$ power$ of$ this$ method$ (Jullo$ et$ al$ 2011;$ D\'Aloisio$ &$ Natarajan$ 2011),$ which$ is$ independent$of$the$value$of$the$Hubble$parameter,$and$complementary$to$CMB$and$SNIa$techniques.$$ WFIRST$will$discover$samples$of$clusters$at$higher$redshift$than$e.g.,$DES,$LSST,$Euclid$enabling$a$longer$ redshift$lever$arm$for$measuring$the$time$evolution$of$the$dark$energy$equation$of$state.$$However,$TMT$ will$be$needed$to$follow$up$the$multiple$images$and$obtain$spectroscopic$redshifts$for$them.$$In$particular,$ the$ much$ higher$ resolution$ of$ TMT\'s$ IRIS$ imager$ (roughly$ 5$ times$ the$ resolution$ of$ the$ Frontier$ Field$ images,$ and$ more$ than$ 10$ times$ the$ resolution$ of$ WFIRST)$ will$ allow$ many$ more$ lensed$ pairs$ to$ be$ discovered$and$a$much$more$accurate$mass$model$to$be$constructed.$$$  \n$  \nWhile$mass$estimates$for$the$new$sample$of$WFIRST$clusters$will$be$able$to$be$determined$from$the$weak$ gravitational$lensing$signal,$there$will$be$a$bias$inherent$in$these$mass$estimates.$$This$is$because$to$relate$ the$lensing$signal$to$the$mass,$one$needs$to$determine$the$value$for$the$critical$surface$density,$which$ requires$ knowledge$ of$ the$ redshifts$ of$ the$ faint$ source$ galaxies.$ $ While$ the$ background$ redshift$ distribution$can$be$estimated$photometrically,$it$will$be$preferable$to$reduce$the$uncertainties$in$cluster$ masses$by$determining$the$redshift$distribution$spectroscopically.$$This$will$be$particularly$important$for$ the$higher$redshift$WFIRST$clusters$for$which$the$background$galaxies$will$be$faint,$their$source$density$ low,$and$the$clusterHtoHcluster$variation$high.$$While$the$redshifts$of$some$background$galaxies$will$be$ directly$determinable$by$WFIRST,$TMT$is$capable$of$reaching$much$deeper$flux$limits$than$WFIRST,$and$ will$ be$ able$ to$ determine$ spectroscopic$ redshifts$ for$ a$ much$ higher$ fraction$ of$ the$ background$ galaxy$ population.$  \n$  \n$', 'Galaxy$Scale$Cosmography$': "It$is$not$just$cluster$scale$lenses$that$benefit$greatly$from$the$synergy$between$WFIRST$and$TMT.$$Time$ delay$ measurements$ of$ galaxy$ scale$ strong$ gravitational$ lenses$ have$ become$ an$ important$ tool$ for$ cosmology$(e.g.$Suyu$et$al.$2013).$$In$particular,$the$combined$measurement$of$time$delays$of$multiplyH imaged$quasars,$the$redshifts$of$the$quasars$and$lens$galaxy$as$well$as$the$internal$lens$galaxy$dynamics$ and$ detailed$ images$ of$ the$ lensed$ quasar$ host$ galaxy$ are$ required$ for$ the$ tightest$ constraints$ on$ the$ evolution$of$the$scale$factor.$$The$combination$of$WFIRST$and$TMT$is$ideally$suited$for$this$task.$$While$ large$groundHbased$surveys$such$as$LSST$will$cover$more$sky,$the$majority$of$lensed$systems$are$expected$ to$have$small$Einstein$radii$(<0.5'),$and$these$will$be$underrepresented$in$the$LSST$sample.$$The$WFIRST$ high$ latitude$ survey$ will$ discover$ hundreds$ of$ galaxyHscale$ lensed$ AGN;$ although$ the$ cadence$ of$ the$ survey$is$unlikely$to$lead$to$time$delay$measurements,$these$will$be$obtained$from$the$LSST$time$series$ (using$high$resolution$images$to$deblend$the$ground$based$images;$Tewes$et$al.$2013;$Liao$et$al.$2014)$$or$ for$the$fainter$systems$with$WFIRST$GO$mode$or$more$likely$through$TMT$imaging$with$IRIS.$$Crucially,$the$ superior$ resolution$ of$ IRIS$ would$ allow$ precise$ mapping$ of$ the$ QSO$ centroids$ (with$ <50$ microarcsec$ positional$ uncertainty),$ as$ well$ as$ precise$ maps$ of$ the$ arcs$ from$ the$ background$ quasar$ host$ galaxy.$$ These$ are$ needed$ to$ tie$ down$ the$ mass$ model.$ $ In$ addition,$ IRIS's$ IFU$ would$ allow$ the$ lens$ galaxy$ kinematics$to$be$determined.$$$In$a$sample$of$>100$galaxy$lenses,$we$expect$to$also$find$multiply$lensed$ Supernovae.$$Lensed$Supernovae$provide$independent$tests$of$the$mass$model$via$the$measure$of$the$ absolute$ magnification$ at$ the$ position$ of$ each$ supernova$ image.$$TMT$ spectroscopy$ will$ be$ critical$ to$ establishing$the$supernova$type$and$redshift.$  \n$", 'Supernova$Cosmology$': 'Lensed$supernovae$are$not$the$only$type$of$supernova$for$which$the$combination$of$WFIRST$and$TMT$can$ provide$ the$ critical$ cosmological$ information.$ $ The$ WFIRST$ Supernova$ Survey$ will$ potentially$ detect$ supernovae$ out$ to$ z~4.$ $ $ However,$ obtaining$ spectra$ for$ the$ faintest$ ones$ will$ require$ better$ NIR$ sensitivity$ than$ is$ possible$ with$ the$ current$ generation$ of$ 10mHclass$ telescopes.$ $ $ AOHassisted$ spectroscopy$with$IRMS$on$TMT$would$be$the$ideal$instrument$to$characterize$the$supernova$spectrum$ and$ test$ for$ any$ evolutionary$ effects$ at$ these$ highest$ redshifts.$$$In$ this$ way,$ TMT$ spectroscopic$ observations$can$provide$support$for$WFIRST$lightcurve$measurements$of$distant$supernovae.$  \n$', 'Near$Field$Cosmology$': "Another$cosmological$puzzle$that$can$be$addressed$best$with$the$combination$of$TMT$and$WFIRST$is$the$ puzzle$of$the$dark$matter$content$of$the$Milky$Way$satellite$galaxies.$$The$dark$matter$profile$of$these$ galaxies$is$important$both$as$a$test$of$the$LCDM$model$which$predicts$the$existence$of$density$cusps$in$ these$dark$matter$dominated$systems$(see$for$example$the$review$by$Pontzen$&$Governato$2014),$and$ because$it$affects$the$predicted$rate$of$dark$matter$annihilation.$$Determining$the$annihilation$rate$(the$ so$ called$ 'J'$ factor)$ is$ critical$ in$ constraining$ the$ possible$ masses$ of$ thermal$ relic$ WIMPS$ (GeringerH Sameth$&$Koushiappas$2013).$$Assuming$that$part$of$the$high$galactic$latitude$survey$of$WFIRST$is$carried$ out$in$the$northern$galactic$cap,$then$these$dwarfs$will$most$likely$be$observed$by$WFIRST$as$a$matter$of$ course.$$If$not,$it$will$be$necessary$to$secure$pointed$observations$with$WFIRST$as$part$of$the$GO$program.$  \n$  \nMeasuring$ the$ density$ profile$ of$ the$ faint$ Milky$ Way$ halos$ is$ complicated$ by$ two$ factors.$ $ First,$ we$ typically$ only$ have$ radial$ velocities$ to$ work$ with$ to$ reconstruct$ the$ 3Hd$ dynamical$ profile.$ $ Strong$ constraints$ on$ the$ profile$ in$ this$ case$ can$ require$ thousands$ of$ radial$ velocities.$ $ For$ many$ of$ these$ systems,$ however,$ only$ tens$ or$ hundreds$ of$ stars$ have$ been$ identified.$ $ These$ closest$ (and$ thus$ most$ interesting$from$the$point$of$view$of$dark$matter$detection)$dwarfs$are$much$too$large$on$the$sky$for$ efficient$mapping$with$TMT's$imager$(or$with$HST).$$At$the$same$time,$the$photometric$precision$and$high$ resolution$of$a$space$based$imager$can$allow$a$much$cleaner$look$at$the$colorHmagnitude$diagram$for$ stars$in$the$dwarfs,$allowing$many$more$stars$to$be$identified$over$the$entire$tidal$radius$of$the$dwarfs.$$$$ Once$the$candidate$stars$are$identified,$radial$velocities$must$be$obtained.$$For$the$brighter$stars$currently$ targeted,$this$requires$8H10m$telescopes$(e.g.$Walker$2009).$$For$the$fainter$stars,$TMT$will$be$required.$  \nThe$superb$astrometric$precision$that$will$be$afforded$by$TMT$using$IRIS$opens$another$possibility,$that$of$ measuring$stellar$proper$motions$and$recovering$starHbyHstar$3Hd$proper$motions.$$Given$the$accuracy$of$ astrometric$precision$already$achieved$by$Keck's$AO$system,$and$the$astrometric$improvement$afforded$ by$the$smaller$diffraction$limit$of$TMT,$it$will$be$possible$to$make$30$microarcsec$accuracy$measurements$ of$ the$ stellar$ positions.$ By$ monitoring$ the$ dwarf$ galaxy$ stars$ over$ the$ period$ of$ three$ years,$ proper$ motions$with$uncertainties$of$~7km/s$can$be$achieved$for$a$dwarf$at$100$kpc$distance.$$With$the$3Hd$ motions,$the$largest$source$of$degeneracy$in$the$dynamical$model$is$removed,$and$the$uncertainty$on$the$ slope$of$the$density$profile$will$be$reduced$by$at$least$a$factor$of$5.$$$Combining$the$power$of$WFIRST$and$ TMT$ on$ the$ profiles$ of$ the$ dwarfs$ will$ reduce$ the$ uncertainty$ on$ the$ profile$ parameters$ for$ a$ fixed$ parametric$model$by$more$than$an$order$of$magnitude$and$help$resolve$the$core/cusp$problem$as$well$as$ severely$constraining$the$most$popular$models$of$dark$matter$(or$aiding$in$its$discovery!)$  \n$  \n$", 'Conclusive+Identification+of+Gravitational+Wave+Sources+ +': '(Masaomi(Tanaka,(NAOJ,(masaomi.tanaka@nao.ac.jp,( (  \nand(TMT(ISDT(for(Time>domain(science)(  \n(', 'Background(': 'WFIRST(and(LSST(were(the(two(highest(priority(space(and(groundEbased(missions(in(the(2010(Decadal( Survey.((The(primary(mission(of(both(facilities(is(to(carry(out(wideEfield(imaging(surveys(of(the(sky(in( multiple(bands;(these(surveys(will(enable(a(wide(range(of(science,(including(weak(lensing,(largeEscale( structure(in(the(distribution(of(galaxies,(supernovae,(the(evolution(of(galaxies,(and(stellar(populations.(( LSST(is(an(optical(telescope,(and(will(do(deep(repeated(broadEband(photometry;(the(nearEinfrared(and( spectroscopic( capabilities( of( WFIRST( will( allow( much( more( accurate( photometric( and( spectroscopic( galaxy(redshifts(in(regions(of(survey(overlap.((  \n(', 'WFIRST(&(TMT(': 'For(example,(if(WFIRST(perform(deep(NIR(survey((26(AB(mag/visit(for(>(10(deg^2),(more(than(10(superluminous( supernovae( can( be( detected( at( z>10( (Tanaka( et( al.( 2013,( MNRAS,( 435,( 2483).( Color( selection( will( give( reasonable(estimates(for(the(redshift(and(explosion(types.(However,(in(order(to(study(if(the(rate(of(such(special( types(of(supernovae(increase/decrease(relative(to(the(total(star(formation(rate,(which(gives(the(information(of( the( initial( mass( function,( spectroscopic( identification( for( at( least( some( subsamples( is( necessary.( Synergetic( spectroscopic( observations( with( TMT( MOBIE/IRIS( will( give( firm( identification( of( such( high>z( supernovae.( Especially(superluminous(supernovae(and(pair(instability(supernovae(have(characteristic(features(in(the(rest>UV( wavelengths((bright(continuum(and(metal(absorption,(respectively),(deep(optical(spectroscopy,(in(addition(to( low>resolution(NIR(spectroscopy(by(WFIRST,(is(essential(to(classify(these(types(of(high>z(supernovae.(  \n(  \n( 2486  \n(  \nFigure:( Brightness( of( superluminous( supernovae( as( a( function( of( redshift,( based(on(numerical(simulations(by(Moriya( et( al.( (2013,( MNRAS,( 428,( 1020).( Figure( from(Tanaka(et(al.(2013.(  \n<!-- image -->  \nFigure 2.  \nObserved peak magnitude of Model F1 (left) and SN 2008es (right) as a function of redshift. To detect SNe at  \nz>  \n10, the  \nare crucial. A typical limiting magnitude per visit with the planned wide-field NIR satellites is 24-26 mag (see Section 7). The faintest  \n(32 mag) corresponds to  \n∼  \n10  \n6  \ns integration with  \nJWST  \n.  \nM. Tanaka, T. J. Moriya and N. Yoshida  \n(  \nrate of SLSNe to be 2  \n10  \n-  \n7  \nMpc  \n-  \n3  \nyr  \n-  \n1  \nat  \nz  \nSFR density from Hopkins & Beacom (2006),  \n×  \n∼  \n2  \nLinhua Jiang (China)', 'Identification+of+First+Supernovae+ +': '(Masaomi(Tanaka,(NAOJ,(masaomi.tanaka@nao.ac.jp,( (  \nand(TMT(ISDT(for(Time>domain(science)(  \n(', 'High-redshift (z>6) Quasars and Cosmic Reionization': "High-redshift (z>6) quasars provide a powerful tool to study the early universe. They are essential in understanding black hole accretion, galaxy evolution, and the IGM state in the first billion years of cosmic time. In recent 15 years, more than 70 z>6 quasars has been discovered (See a series of papers by X. Fan, by L. Jiang, and by C. Willott). However, these quasars only represent the most luminous quasars at z>6 (brighter than the characteristic luminosity in  the  quasar  luminosity  function,  QLF).  The  combination  of  wfirst  and  tmt  will  allow  us  to  perform  a  systematic search/study of much fainter quasars at z>6.  \nWFIRST, especially WFIRST+LSST, will help us very efficiently select z>6 quasar candidates down to 25-26 AB mag (Y band). Relatively bright candidates (Y<22 AB mag) can be easily identified by 5m class telescopes. But identification of fainter candidates can be very difficult, or more precisely, expensive (the spatial density of these objects is very low so that it's impossible to observe >1 object in the same field with masks). Currently it takes the MMT (6.5m) about 15+ min to identify ~22 mag candidates (almost the faintest known so far) in the SDSS stripe 82. With the same int. time, Keck can reach ~23 mag, and TMT can reach ~24.5 mag. So for faint z>6 quasars, TMT is very efficient.  \nTwo main science cases from faint quasars: 1) allow us to study regular quasars (not super luminous ones) and black  holes  at  z>6,  including  emission  line  properties,  black  hole  masses,  host  galaxies,  dust  properties,  etc.  2) measure the QLF to the faint end, and determine total ionizing photons from quasars. We know that one key question is, what sources are responsible for cosmic (H) reionization. People have tentatively ruled out quasars due to their very low spatial density. However, the QLF in the bright end is very steep, meaning that if the turn over point in the QLF is very faint, the ionizing photons from the whole quasar population will increase dramatically. This can only be determined by deep spectroscopic survey of very faint quasars at z>6.  \nYue Shen (China)", 'High-z Quasar Demography in the Mass-Luminosity Plane': 'The growth of the earliest SMBHs (at z>6) is one of the least understood topics in high-z galaxy formation sciences. Demographic studies are traditionally based on the quasar luminosity function (LF). With the development of spectroscopic methods to estimate the mass of these high-z quasars (e.g., virial BH mass estimators), it is now possible to study the abundance of these quasars in the mass-luminosity plane (Shen & Kelly 2012, Kelly & Shen 2013). Unlike the 1D LF, the quasar mass-luminosity plane constrains both the current activity (instantaneous luminosity) and integrated accretion history (BH mass) for the population of high-z quasars. Thus the 2D M-L plane can be used to understand the emergence/growth of high-z quasars and the average evolution of their accretion rate, in a way that cannot be achieved by studying the LF alone (which loses information by projecting the 2D distribution function onto the luminosity axis). Current instrumentation is able to constrain the M-L plane of z~6 quasars down to H\\_ab~20 with dedicated NIR spectroscopic programs on 6-10m telescopes.  \nA wide-area survey of WFIRST will provide a large sample of z>6 quasars down to sufficiently faint luminosities, and start to unveil the progenitor population of the most massive z>6 quasars (with BH mass > a few 1d9 MSun) discovered today. By mapping the M-L plane from high-z till z~6 to these faint luminosities, we will be able to monitor the growth of these high-z quasars in "real time" (as the cosmic time span at these high redshifts is short), and truly understand how these SMBHs grow so rapidly at early times.  \nRequirements: A wide-area WFIRST/AFTA survey with grism spectroscopy for quasar confirmation. Expected quasar number density is ~100 per 1000 deg^2 down to H\\_ab<24 at z>7. This flux limit is ~ 3 mag fainter than the current limit with VISTA. TMT/IRMS follow-up can provide K-band spectra (covering restframe MgII at z~7 to use as the BH mass estimator) with sufficient quality to measure spectral properties (S/N>10 at K\\_ab~24 in 5-hr integration). A TMT program with tens of hrs will assemble a decent sample of more than tens of z~7 quasars with BH mass estimates down to K\\_ab~23, and map the distribution in the quasar M-L plane at z~7.', 'Key References': 'Shen, et al., 2014, ApJS, in press, 2014, arXiv1408.5970S Shen, et al., 2015, submitted Woo, et al., 2008, 2008ApJ...681..925W WFIRST-AFTA Final Report TMT instrument documentation  \nFigure 1. Composite spectrum of star forming galaxies selected with the WFC3 grism on HST and observed with the FIRE near-IR echelle on Magellan (Masters et al. 2014, ApJ, 785, 153).  \n<!-- image -->', 'Evolution of the BH Mass - Galaxy Scaling Relations': 'A key science case with TMT in the next decade is to measure the evolution of the BH mass - galaxy scaling rations up to high redshift. This measurement will help us understand the nature of the co-evolution of galaxies and SMBHs, and whether or not AGN feedback plays an important role in galaxy formation.  \nDynamical BH masses with spatially resolved spectroscopy are only possible at low-redshift (except maybe for 1d10 MSun BHs). Beyond z>0.3, the primary method to estimate SMBH masses is reverberation mapping (RM) and its derivative, single-epoch virial mass estimators. However, these techniques only apply to AGN/quasars, and measuring host  galaxy  properties  in  these  active  galaxies  are  notoriously  difficult.  For  host  luminosity  and  stellar  mass, WFIRST/AFTA, when combined with deep optical imaging from the ground or space, will provide superb image quality and depth that will yield excellent measurements for numerous quasar hosts up to z~3 and to very faint quasar luminosities. For (integrated) host stellar velocity dispersion, TMT/MOBIE/IRMS/IRIS can measure sigma\\_* to z~4 for large samples of quasars. Therefore with WFIRST+TMT, we will revolutionize this field by compiling host measurements for large quasar samples to much fainter luminosities and high redshifts.  \nTMT will be absolutely necessary to push on stellar velocity dispersion measurements in faint quasar hosts. Currently,  the  best quasar sample with host sigma\\_* measurements is achieved with the SDSS-RM program (Shen et al. 2014, 2015), which has a sample size of ~90 quasars, probes one mag fainter than the earlier Keck samples (Woo et al. 2008), and covers to z~1 with ~60 hrs of optical spectroscopy with the 2.5m SDSS telescope. With TMT, we will be able to probe yet another 1-2 magnitudes fainter with only 1 hr integration, and expand to higher redshift with NIR spectroscopy. Hence a program of tens of hrs on TMT will compile an unprecedented sample to study the evolution of the M-sigma relation. By the time TMT becomes a reality, we should have much improved BH mass estimators from dedicated RM programs (such as the SDSS-RM program).  \nRequirements: Targeting the SDSS-RM field (14:14:49.00 +53:05:00.0), which is a 7 deg^2 field within CFHT-LS W3 and fully covers the AGEIS field and the CFHT-LS D3 field. This field also coincides with the PanSTARRS 1 Medium Deep Survey field MD07, with hundreds of multi-band photometric epochs during 2010-2013. This SDSS-RM field is being regularly monitored with SDSS BOSS spectroscopy (30-60 total epochs, 2014-2017), ground-based optical imaging  (CFHT,  Bok,  etc.,  2014-),  NIR  imaging  (UKIRT),  Spitzer  (Cyc  11-12,  20-month  baseline),  and  XMM.  The SDSS-RM program monitors 849 quasars (0.1<z<4.5; to i<21.7) photometrically and spectroscopically in order to measure broad-line lags and RM BH masses for more than tens of quasars (potentially hundreds of RM measurements combined with the early PanSTARRS light curves), and deep spectroscopy for excellent single-epoch virial BH mass estimates for the full sample. The multi-wavelength synergy in this field will maximize quasar sciences (quasar variability, host galaxies, quasar absorption lines, etc.). WFIRST+TMT coverage of this field will further enhance the science yields on quasars and SMBHs.', 'Studies of Extreme Star Forming Galaxies': 'WFC3 on HST and powerful ground-based near-IR spectrographs have extended classical nebular spectroscopy to the epoch of galaxy building, 1.5 < z < 4. The WFC3 grisms have shown the power of slitless spectroscopy to reveal galaxies with high equivalent width emission lines and, hence, high specific star formation rates. The R ~ 200 spectra provided by WFC3 provide samples for further study with large ground based spectrographs at resolutions of a few thousand.  \n<!-- image -->  \nRest wavelength (A)  \nModerate resolution spectra obtained with sensitive spectrographs on the ground provide access to weak emission lines that are sensitive to abundances and physical conditions in the HII regions. Spectroscopy of moderate sized samples has revealed evolution in line ratios and the topology of the diagnostic  \nGMTO%Corporation%is%a%not/for/profit%organization%  \n626/204/0500%%  \nGMTO%Corporation%·%251%S.%Lake%Ave,%Suite%300%·%Pasadena,%CA%%91101%·%USA%  \n%  \ndiagrams (e.g. [NII]/H α vs. [OIII]/H β ). The origin of the anomalous line ratios is not well understood at this time.  \nFigure 2. Velocity field and dispersion map for a massive star-forming galaxy observed with an AO fed integral field spectrograph on the VLT (Genzel et al. 2006, Nature, 422 786).  \n<!-- image -->  \nSpatially resolved spectroscopy with integral field spectrographs is providing us with dynamical masses and resolved ionization maps of star forming galaxies. The combination of adaptive optics and IFU spectrographs on 6-10m telescopes allows us to probe galaxies on kpc scales. These observations, however, are photon-starved. The ELTs will have enough light grasp to enable 2-D spectroscopy of large samples of galaxies. At present we lack large and robust data sets of star forming galaxies with suitable guide stars for AO spectroscopy with high Strehl ratios. The WFIRST wide-field survey will provide a large enough sample that we will be able to select desirable combinations of galaxy properties and wavefront control stars for resolved spectroscopy on sub-kpc scales with adaptive optics.  \nThe James Webb Space Telescope will have a large impact in the study of star forming galaxies over a wide range of redshifts, but it will not provide samples as large as those resulting from the WFIRST survey. Rare objects, systems with extreme environments and, perhaps, pristine abundances, will be revealed in the large WFIRST survey date. Deep moderate-resolution spectroscopy with near-IR spectrographs on the GMT and other ELTs will provide a powerful combination for advancing our understanding of the star formation in galaxies at the peak of the galaxy building epoch.', 'Quenched and Passive Galaxies': 'One of the outstanding challenges in contemporary astrophysics is understanding the origin of the Hubble sequence and the bimodal galaxy distribution. Quenched systems, those galaxies in which star formation has abruptly ended, putting them on the path to the red sequence, are easily recognizable from their strong Balmer sequence absorption features. Adequate spectra, however, are only available from massive systems. WFIRST will sample large numbers of passive and quenched systems over a range of stellar masses. Efficient near-IR spectrographs on the ground can provide high quality spectra needed to derive precise ages and star formation histories.  \n<!-- image -->  \nFigure 3. (left) Gemini GNIRS Spectrum of a compact passive galaxy and the derived likelihood function for its velocity dispersion from van Dokkum et al. 2009, Nature, 406, 717. On the right we show a simulated spectrum with the GMT centered around the Ca II H&K features that provide most of the weight for the velocity dispersion. The GMT and other ELTs can be used to determine dynamical masses for passive galaxies and cluster cores revealed by the WFIRST widearea survey.  \n<!-- image -->  \nThe key to connecting theory and observation and improving our understanding of the growth of galaxies is accurate stellar masses. Velocity dispersions have been measured for a few compact passive galaxies, but only for those with stellar masses well beyond the knee of the mass function. The grism on WFIRST will reveal large numbers of systems suitable for high precision determinations of velocity dispersions with near-IR spectrometers on ELTs. GMTÕs red and near-IR spectrographs can play a key role in this area by tying down the dynamical masses of passive and quenched galaxies for with masses equal to, or less, than M * .  \nThe WFIRST wide-area survey will also produce large number of distant galaxy clusters and bound groups that are the sites of galaxy transformations. Red and near-IR spectrographs on the GMT can provide both velocity dispersions for individual galaxies and for groups of galaxies undergoing rapid evolution.', 'Summary': 'In addition to its core missions of BAO, weak lensing, and exoplanet science, WFIRST will provide a rich legacy of unparalleled data for studies of galaxy evolution. The GMT and other extremely large telescopes on the ground can leverage the powerful imaging and low-resolutions spectra produced by WFIRST by providing high-sensitivity intermediate resolution spectroscopy of faint galaxies, galaxy clusters and rapidly evolving groups.', 'Synergy Between WFIRST-AFTA and the Giant Magellan Telescope: Spectroscopic Probes of Reionization': "Steven L. Finkelstein (UT Austin)  \nThe reionization of the intergalactic medium (IGM) marks the last major phase transition in the Universe, and provides a key glimpse into the formation and evolution of the GLYPH<222>rst luminous sources after the Big Bang. By the middle of the next decade, a number of new facilities will be coming online, including the Giant Magellan Telescope (GMT), the Large Synoptic Survey Telescope (LSST), the Square Kilometer Array (SKA), and WFIRSTAFTA, which, when combined, will allow a detailed probe of the evolution of the neutral fraction in the IGM during reionization. Two highly complementary techniques available for probing reionization are faint Ly α spectroscopy and 21cm tomography. As Ly α photons are resonantly scattered by neutral hydrogen, Ly α emission e ff ectively maps ionized regions in the universe, escaping when the size of the ionized bubble allows the Hubble GLYPH<223>ow to redshift the photons away from resonance. The 21cm line observations, speciGLYPH<222>cally the highly sensitive observations to come from the Square Kilometer Array in the next decade, will provide high sensitivity, high resolution maps of the neutral gas in the IGM. This complementary view will provide some of the GLYPH<222>rst maps of the spatial distribution of reionization, further constraining the nature and distribution of the key ionizing sources.  \nTo understand the requirements, we need to make some assumptions on the scale. If we assume that the SKA has a resolution of 1 ' , a conservative assumption is that SKA observations will resolve neutral regions on linear scales of /greaterorsimilar 10 ' . This corresponds to a physical size of ∼ 3 Mpc at z = 8, comparable to the expected size of ionized bubbles in the early universe (e.g., Furlanetto 2006). This is also the size of the deepest HST survey GLYPH<222>elds (e.g, GOODS, CANDELS, etc.). Thus, to obtain a statistical sample of ionized and neutral regions, a much wider survey is needed. While JWST will have the capability of detecting galaxies over the key redshift range of 6 < z < 10, its GLYPH<222>eld-of-view is small, and thus multiple wide GLYPH<222>eld surveys ( /greatermuch 1 degree) are unlikely. The High Latitude Survey (HLS) component of WFIRST will image 2000 deg 2 to m AB ≈ 27 from 0.8 GLYPH<208> 2.0 θ m. When combined with LSSTGLYPH<213>s deep optical data, the WFIRST survey is su ffi cient to photometrically select galaxies at 6 < z < 12. In Table 1 I show the estimated numbers of 6 < z < 10 galaxies to be discovered in the WFIRST HLS survey at two di ff erent magnitude limits.  \nSpectroscopic followup of these WFIRST sources is necessary both to prove their validity, but also to obtain measurements of the Ly α emission strength to provide the counter-image to SKAGLYPH<213>s neutral hydrogen maps. Although the GMT has the smallest mirror of the three giant segmented mirror telescopes, it will have instruments with the largest GLYPH<222>eld-of-view. The GMT collaboration is currently exploring multiple options for near-infrared spectroscopy at GLYPH<222>rst light, including a single object cross-dispersed JHK spectrograph, and a multiobject 1-1.3 θm J -band spectrograph. The single-object spectrograph will be highly useful for observing the brightest (m AB < 25) galaxies, which, as shown in Table 1, have very small space densities, unsuitable for a multi-object spectrograph (MOS). These galaxies will also be easily observable by JWST , should these missions GLYPH<223>y simultaneously. However, the collecting area of the GMT is 11.5 × larger than JWST , allowing fainter spectroscopy. Though night sky lines will be present, the high-resolution (R ∼ 6000) of the instrument, and the faint inter-line sky background (Sullivan & Simcoe 2012), will result in such observations  \n1  \nbeing at least as e ffi cient, if not more so, than similar observations with JWST .  \nThe true synergy between the GMT and WFIRST is in multi-object spectroscopy. Observing several sources simultaneously with a 22m (e ff ective aperture) telescope will reach extremely faint GLYPH<223>ux levels for Ly α emission, even for the faintest galaxies in the WFIRST survey. The current MOS design has an 8 ' GLYPH<222>eld-of-view, perfectly suited to the expected angular size of ionized bubbles during reionization, and > 5 × larger in area than the equivalent spectrograph on JWST . As deep GMT observations will reach 5 σ line GLYPH<223>ux limits of a few × 10 -19 erg s -1 cm -2 , given the numbers in Table 1 a single GMT observation will observe ∼ 80 galaxies at 6 <z< 8 simultaneously to a rest-frame Ly α equivalent width of 5 GLYPH<251> A at the WFIRST magnitude limit.  \nSummary : The Giant Magellan telescope occupies a unique region of the aperture size GLYPH<208> GLYPH<222>eld-of-view parameter space amongst the next generation of telescopes. A deep GMT multi-object spectroscopic survey of WFIRST-identiGLYPH<222>ed high-redshift galaxies will allow the deepest, most detailed spatial maps of Ly α emission in the distant universe. Combining these luminous observations with observations of the GLYPH<210>dark sideGLYPH<211>, the 21cm H i maps from the SKA, will provide a complete view of the reionization history of the universe.  \nReferences: Bouwens et al. 2014, ApJ Submitted /diamondmath Finkelstein et al. 2014, ApJ Submitted /diamondmath Furlanetto 2006, New Astronomy Reviews, 50, 157 /diamondmath McLeod et al. 2014, MNRAS Submitted /diamondmath Sullivan & Simcoe 2012, PASP, 124, 1336  \nTable 1: z = 6GLYPH<208>8 Galaxies in the WFIRST-AFTA HLS Survey  \nThese numbers assume the luminosity function of Finkelstein et al. (2014) at z = 6GLYPH<208>8, McLeod et al. (2014) at z = 9, and Bouwens et al. (2014) at z = 10. We assume a volume probed by a 2000 deg 2 survey, with ∆ z = 1, with a selection completeness of 90%.  \n2", 'WFIRST and the Prime Focus Spectrograph': 'This white paper discusses the complementary nature of WFIRST with the Prime Focus Spectrograph (PFS), an upcoming multi-object spectrograph that will go on the Subaru telescope. With 2400 GLYPH<222>bers, PFS will be the most highly multiplexed spectrograph on an 8m class telescope. Combined with the very wide wavelength coverage from 0 glyph[triangleright] 38 -1 glyph[triangleright] 3 θ m, PFS is in a unique position as a spectroscopic survey machine that can strongly complement upcoming space missions such as WFIRST. This document explores some of the obvious possibilities for complementarity, but is by no means exhaustive.  \nPFS will be a facility instrument on Subaru. We are planning a Strategic Survey Proposal (SSP; Takada et al. 2014) with three pillars. A 1400 deg 2 survey of emission line galaxies has the primary goal of measuring the baryonic acoustic oscillations out to z ∼ 1 glyph[triangleright] 6 (check), a galactic archeology component will measure the kinematics and chemical abundances of stars in the halos of the Milky Way and Andromeda, and a 25 deg 2 galaxy evolution survey will study the evolution of continuum and emission-line selected galaxies from the GLYPH<222>rst galaxies at z ∼ 7 to the present. With three-GLYPH<222>ve hour integrations we expect to reach limiting continuum magnitudes of J = 23 glyph[triangleright] 5 mag and line GLYPH<223>uxes of ∼ 10 -17 erg/s/cm 2 in the NIR arm. The galaxy evolution survey will exploit grizy imaging from the ongoing HyperSuprime Camera survey (cite?) in four deep GLYPH<222>elds: eCOSMOS, XMM-LSS, DEEP2-3, and ELAIS-N1. The combination of the galaxy evolution survey with WFIRST data would be very powerful:  \n- ÷ WFIRSTwill provide rest-frame optical galaxy morphologies for the continuum-selected galaxies at 0 glyph[triangleright] 7 < z < 2 galaxies studied by PFS, allowing an unprecedented mapping between bulge growth, star formation rate, and galactic outGLYPH<223>ows that may GLYPH<222>nally address the mechanisms that shut o ff star formation in galaxies (Barro et al. 2013).\n- ÷ Galaxy-galaxy lensing measurements enabled by WFIRST will allow mapping of the average dark matter halo properties of z ∼ 1 glyph[triangleright] 5 -2 galaxies as a function of physical properties derived from the spectra (e.g., Leauthaud et al. 2012).\n- ÷ The integral-GLYPH<222>eld unit will measure stellar population gradients in some of our galaxies; these can be examined both as a function of the nuclear spectra (e.g., emission line ratios, absorption line outGLYPH<223>ows) and as a function of galaxy structure from the imaging.  \nIn the longer term, the wide wavelength coverage in the blue and high spectral resolution of PFS will provide an important counterpoint to the grism available on WFIRST.  \n- ÷ As emphasized by Newman et al. (2014), upcoming dark energy surveys place extremely stringent requirements on photometric redshifts. PFS is apparently the only instrument (prior to the 20m GMT) that has the combination of sensitivity and multiplexing needed to build up adequate photometric redshift training samples.\n- ÷ One might imagine performing a PFS survey over the HLS area to Y ∼ 22 AB mag over a couple of years to provide a high GLYPH<222>delity grid of spectroscopic redshifts for  \ncontinuum-selected galaxies down to , to try and understand the bias of the emissionline galaxies observable by the WFIRST grism. From such a survey, one could improve photometric redshifts through clustering (e.g., Newman et al.; Menard et al.) and do any number of exciting astrophysical experiments as well.  \n- ÷ PFS will also have a moderate resolution ( R ∼ 5000) red arm ideal for measuring individual stellar abundances (Kirby et al.). The combination of PFS spectroscopy and WFIRST imaging would make a very powerful combination for Local Group studies.  \nWeshould plan now to maximize the joint science returns between planned PFS and WFIRST surveys.  \nMichael(Strauss((Princeton(University),(strauss@astro.princeton.edu(', "Synergy'Between'LSST'and'WFIRST'": '(', 'WFIRST(': "The(spectroscopic(survey(of(WFIRST(will(allow(redshifts(to(be(measured(for(the(brighter(galaxies(in(the( survey(area.(((To(go(deeper(will(require(photometric(redshifts,(which(photometry(in(the(nearEinfrared( alone(will(not(allow.((LSST(will(survey(18,000(square(degrees(in(the(Southern(Hemisphere(in(six(filters( ( u,g,r,i,z,y )( to( a( pointEsource( depth( of( r ~27.5.(((The(overlap(with(WFIRST(should(be(several(thousand( square(degrees,(in(which(we(will(have(photometry(from(the( u Eband(to(H(or(K,(allowing(for(excellent( photometric( redshifts.( ( WFIRST( image( quality( will( allow( galaxy( shapes( to( be( measured( to( fainter( magnitudes(than(LSST(can(go;(combining(with(the(photometric(and(spectroscopic(redshifts(will(allow( much( enhanced( cosmic( shear( measurements( as( a( function( of( cosmic( time.( ( The( broad( wavelength( coverage(will(also(allow(accurate(estimates(of(star(formation(rates,(stellar(masses,(and(dust(content(for( galaxies(at(a(wide(range(of(redshifts,(as(well(as(for(stellar(populations(in(the(Milky(Way(through(SED( fitting.((The(multiEband(photometry(will(reveal(and(characterize(rare(populations(of(stars(and(galaxies,( including('dropouts'(at(high(redshift.((LSST(will(visit(any(given(point(on(the(sky(roughly(1000(times(over( ten(years,(giving(detailed(information(on(variability(and(proper(motions.((If(the(operations(of(WFIRST( and( LSST( overlap( in( time,( there( will( be( an( opportunity( for( combining( the( data( streams( to( look( for( variability(in(both.((LSST(discoveries(can(also(be(followed(up(by(WFIRST(in(its(GO(program.(  \n(", 'Key(Requirements(': 'Depth(-(To(match(the(photometric(S/N(in(J/H/K(for(galaxies(seen(in(LSST( Sky(Coverage(-((To(overlap(the(LSST(footprint(over(at(least(1000(square(degrees( Resolution(-(Approach(the(diffraction(limit(with(wellEsampled(images(to(measure(galaxy(shapes(( Grism(-(For(spectroscopic(redshifts(of(large(populations(of(galaxies.( Wavelength(Coverage(-(>2(NIR(filters(to(extend(the(galaxy(SEDs(to(beyond(the(observed(optical(( Data(Processing(-((Allow(joint(processing(with(LSST(data(to(put(photometric(measurements(on(a(  \ncommon(scale(to(optimize(matching(and(crossEcomparison(of(the(two(datasets.(  \n<!-- image -->  \n(  \n(  \n(  \n(  \nA(realization(of(the(sky(coverage(of(LSST(in(the(rE band,(represented(in(Equatorial(coordinates.(( The(color(represents(the(number(of(visits(across( the(sky(in(a(simulation(of(LSST(operations:(low( Galactic(latitudes,(the(Southern(equatorial(cap,( and(regions(in(the(North(along(the(ecliptic( receive(fewer(visits.(((There(is(similar(coverage(in( the(u,(g,(i,(z,(and(y(filters.((From(the(LSST(Science( Book((2009).(  \n<!-- image -->', '': "The# Euclid# and# WFIRST# missions# are# complementary# and# have# a# number# of# synergies# for# both# cosmological#measurements#and#for#extragalactic#science.##These#are#summarized#below:#  \n1)#A#large#uncertainty#for#both#Euclid#and#WFIRST#are#systematics#and#assumptions#in#the#Weak#Lensing# (WL)# and# Baryon# Acoustic# Oscillation# (BAO)# measurements# (e.g.# Refregier# et# al.# 2004# ApJ,# 127,# 310,# Hirata# &# Eisenstein# 2009,# astro2010,127).# Euclid# and# WFIRST# probe# different# optimizations# for# these# measurements,# mitigating# many# of# these# systematic# effects.# # In# particular,# the# weak# lensing# measurements#will#use#different#detector#technology#and#probe#different#wavelengths#providing#a#truly# independent#measurement#of#the#shear#signal.##In#addition#both#the#Lensing#and#BAO#surveys#will#probe# different# galaxy# populations# with# different# biases,# yielding# different# systematic# effects# in# the# measurements.#  \n2)# WFIRST#will# add# 1W2um# images# of# similar# depth# and# resolution# as# those# provided# by# Euclid# in# the# optical# (0.6W1um)# enabling# a# range# of# galaxy# evolution# science.# # Star# formation# is# known# to# drop# precipitously# at# z<2# (Hopkins# et# al.# 2006,# ApJ,# 651,# 142),# and# this# is# believed# to# be# a# largely# secular# (internal)# process# best# probed# with# large# statistics# (e.g.# Peng# et# al.# 2010,# ApJ,# 721,# 193,# Wuyts# et# al.# 2011,#ApJ,#742,#96).##Studying#what#is#causing#this#global#decline#in#star#formation#requires#resolved#highW resolution#rest#frame#UV#measurements#that#probe#the#instantaneous#star#formation#rate#and#resolved# rest#frame#optical#measurements#to#probe#the#accumulated#stellar#mass.##WFIRST#will#not#independently# probe#the#rest#frame#UltraWViolet#(UV)#at#z<~1.8#and#Euclid#has#poor#sensitivity#and#resolution#to#the# restWframe#optical#light#at#z>0.7,#so#both#instruments#will#be#required#to#conduct#these#studies.##  \nAt#z>4#the#global#star#formation#rate#density#is#rapidly#increasing,#peaking#at#z~2#(Hopkins#et#al.#2006,# ApJ,#651,#142).##However,#WFIRST#alone#will#only#be#able#to#select#and#study#these#first#galaxies#at#z>8# due#to#its#lack#of#an#optical#channel,#while#Euclid#will#not#have#the#nearWIR#sensitivity#to#probe#'typical'# systems#at#z>5.##So,#again#both#instruments#are#required#to#study#these#first#epochs#of#galaxy#formation.#  \n3)#If#WFIRST#includes#longer#wavelength#(1.5W2.5um)#coverage#the#spectra#will#complement#the#0.9W2um# spectra# from# Euclid.# # This# increased# wavelength# coverage# will# expand# the# redshift# range# over# which# standard#spectral#line#diagnostics#(e.g.#Kewley#&#Ellison#2008,#ApJ,#681,#1183)#can#be#used#from#1<z<2# with#Euclid#and#2<z<2.8#with#WFIRST#to#1<z<2.8#with#the#combined#instruments.##This#redshift#range#is# crucial#because#star#formation#is#known#to#peak#and#start#declining#in#the#1<z<3#redshift#range#and#the# combination# of# Euclid# and# WFIRST# will# enable# studies# of# ionization# parameters,# AGN# content,# and# metalicity#during#this#key#epoch.#", 'Appendix K Microlensing Path Forward': 'The basic input ingredients that are required for estimating  the  yield  of  a  microlensing  exoplanet  survey are (1) a model for the spatial, kinematic, and luminosity distribution of source stars, (2) a model for the spatial, mass,  and  kinematic  distributions  of  the  host lenses,  which  are  then  used  to  estimate  microlensing event rates and event parameter distributions, and (3) a model  for  the  probability  distribution  of  planets  as  a function of planet mass and semi-major axis, and host mass and distance.  \nUnfortunately,  for  the  regimes  of  interest  for WFIRST-AFTA,  the  properties  of  the  populations  of sources and host lenses are poorly constrained by empirical data, leading directly to relatively large uncertainties  in  the  final  yields.  (We  note,  however,  that  these uncertainties  are  shared  amongst  all  of  the  different WFIRST  designs.  We  therefore  expect  the  relative yields between the designs to be substantially more robust.) In particular, the magnitude distribution of source stars in the fields of interest has not been measured in the pass bands and to the faint magnitudes that will be probed  by  WFIRST-AFTA.  Similarly,  the  microlensing event rates for some of the fields of interest have not been measured, as these fields typically suffer high optical  extinction,  and  to  date  all  microlensing  surveys have been performed in the far optical.  \nAnother,  somewhat  subtler,  source  of  uncertainty in  the  planet  yields  that  may  significantly  impact  the choice of target fields is the relative frequency of planets in the Galactic bulge versus disk. The relative contribution of the bulge and disk lenses to the event rate varies  as  a  function  of  Galactic  latitude  b,  with  bulge lenses expected to dominate at low |b|. If the Galactic bulge happens to be devoid of planets, e.g., because of an  extreme  radiation  environment  during  a  starburstlike  bulge  formation  event  (Thompson  2013),  then  it would  likely  be  desirable  to  avoid  such  low  latitude fields.  \nThese uncertainties motivate the precursor observations proposed in Appendix G, specifically a groundbased,  near-IR  survey,  and  a  variety  of  optical  and near-IR HST observations of (a subset of) the WFIRSTAFTA target fields.  \nIn  addition,  there  are  several  additional  activities that  are  needed  to  properly  prepare  for  the  WFIRSTAFTA microlensing survey. These include refined predictions  of  the  science  yield  of  WFIRST-AFTA,  which may in turn affect the survey strategies and mission re-  \nquirements, and focused development of the US microlensing community, which will ensure that the maximum amount  of  science  is  extracted  from  the  microlensing survey.  \n- ∞ Detailed  properties  of  detected  systems. Detailed  and  quantitative  estimates  of  the  ability  to measure detailed properties of the detected planetary  systems  are  needed,  including  expectations for measurement uncertainties for the masses, distances, and orbital parameters of the planets from the  WFIRST-AFTA  data  alone,  and  by  combining WFIRST-AFTA data with contemporaneous or follow-up  observations  from  the  ground  and  other satellites.\n- ∞ Refined  yields. The  yields  for  planets  near  the edge  of  the  sensitivity  of  WFIRST-AFTA  suffer from additional  uncertainties  beyond  those  arising from  the  sources  discussed  above.  These  uncertainties arise from the fact that there is a relatively strong dependence of number of detections on the minimum  detection  threshold  in  these  regimes, which include planets with very small or very large separations, and very low mass planets. As a result  of  the  strong  scaling with detection threshold, small differences in the assumptions and approximations needed to make these predictions result in large  changes  in  the  estimates  of  the  number  of detected planets.\n- ∞ Yields  of  Habitable  Planets. Predictions  for  the yield of habitable planets suffer from all of the uncertainties  above,  but  are  also  sensitive  to  additional  assumptions,  such  as  the  mass-bolometric luminosity  relationship  for  stars  in  the  bulge  and disk,  the  age  and  metallicity  of  the  stars  in  the bulge and disk, and the precise definitions for the mass and semi-major axes boundaries of the habitable zone. Therefore, the yields of habitable planets presented in 2.4.2.7.2 are quite uncertain, and substantially  more  work  needs to be done to provide robust estimates of the habitable planet yield.\n- ∞ Development of Exoplanet Microlensing Expertise. The US microlensing community is quite small with  only  2  PhD  granting  institutions  active  in  microlensing  research,  and  only  4  US  researchers beyond the postdoctoral level. NASA would be better  prepared  for  the  WFIRST-AFTA exoplanet microlensing  survey  if  it  would  support  some  of  the  \ncurrent  and  near  future  exoplanet  microlensing programs  at  a  higher  level.  These  programs  include  ground-based  exoplanet  microlensing  surveys and follow-up observations, space-based microlensing  parallax  observations  with  Spitzer  and Kepler,  and  high  angular  resolution  follow-up  observations  with  the  Hubble  Space  Telescope  and Adaptive Optics systems to develop the WFIRSTAFTA method for measuring planet and host star masses.  Research  to  develop  tools  that  reduce barriers  for  other  scientists  to  enter  the  microlensing field would be especially welcome.', 'Appendix L Acronym List': "2MASS  \n2 Micron All Sky Survey  \n4MOST  \n4 Metre Multi-Object Spectroscopic Telescope  \nΛ CDM  \nLambda Cold Dark Matter  \nA&A  \nAstronomy and Astrophysics  \nACS  \nAdvanced Camera for Surveys  \nACS  \nAttitude Control System  \nAFTA  \nAstrophysics Focused Telescope Assets  \nAGB  \nAsymptotic Giant Branch  \nAGN  \nActive Galactic Nuclei  \nAIT  \nAssembly, Integration and Test  \nAJ  \nAstronomical Journal  \naka  \nAlso Known As  \nALMA  \nAtacama Large Millimeter/submillimeter Array  \nALTAIR  \nALTitude conjugate Adaptive optics for the InfraRed (Gemini instrument)  \nAMS  \nAft Metering Structure  \nAO  \nAdaptive Optics  \nAO  \nAnnouncement of Opportunity  \nAOX  \nAOA Xinetics  \nAPh  \nAstroparticle Physics  \nApJ  \nAstrophysical Journal  \nApJS  \nAstrophysical Journal Supplement Series  \nAPLC  \nApodized Pupil Lyot Coronagraph  \nAU  \nAstronomical Unit  \nBAO  \nBaryon Acoustic Oscillations  \nBDBS  \nBlanco DECam Bulge Survey  \nBH  \nBlack Hole  \nBOSS  \nBaryon Oscillation Spectroscopic Survey  \nC&DH  \nCommand and Data Handling  \nCADC  \nCanadian Astronomy Data Centre  \nCANDELS  \nCosmic Assembly Near-infrared Deep Extragalactic Legacy Survey  \nCASTOR  \nCosmological Advanced Survey Telescopes for Optical and uv Research  \nCCD  \nCharged Coupled Device  \nCCE  \nCryocooler Electronics  \nCDM  \nCold Dark Matter  \nCDR  \nCritical Design Review  \nCDS  \nCorrelated Double Sample  \nCEI-OU  \nCentre for Electronic Imaging at the Open University  \nCfAI  \nCenter for Advanced Instrumentation  \nCFHT  \nCanada-France-Hawaii Telescope  \nCFP  \nCall for Proposal  \nCFTHLS  \nCFHT Legacy Survey  \nCGI  \nCoronagraph Instrument  \nCIB  \nCosmic Infrared Background  \nCIC  \nClock Induced Charge  \nCIEMAT  \nCentro de Investigaciones Energéticas, Medioambientales y Tecnológicas  \nCITA  \nCanadian Institute for Theoretical Astrophysics  \nCLASH  \nCluster Lensing And Supernova survey with Hubble  \nCMB  \nCosmic Microwave Background  \nCMD  \nColor-Magnitude Diagram  \nCNES  \nCentre National d'Études Spatiales  \nCoC  \nCenter of Curvature  \nCo-I  \nCo-Investigator  \nCOL  \nCollimator  \nCOR  \nCoronagraph  \nCOSMOS  \nCosmic Evolution Survey  \nCPT  \nComprehensive Performance Test  \nCSA  \nCanadian Space Agency  \nCSB  \nCollimator Sub-Bench  \nCTE  \nCoefficient of Thermal Expansion  \nDC  \nDirect Current  \nDES  \nDark Energy Survey  \nDESI  \nDark Energy Spectroscopic Instrument  \nDETF  \nDark Energy Task Force  \nDDX  \nDebris Disk Explorer  \nDECam  \nDark Energy Camera  \nDLR  \nDeutsches Zentrum für Luft-und Raumfahrt  \nDM  \nDeformable Mirror  \nDOE  \nDepartment of Energy  \nDOF  \nDegree of Freedom  \nDRM  \nDesign Reference Mission  \nDRM1  \nDesign Reference Mission #1  \nDRM2  \nDesign Reference Mission #2  \nDSN  \nDeep Space Network  \nDTAC  \nDetector Technology Assessment Committee  \neBOSS  \nExtended Baryon Oscillation Spectroscopic Survey  \nEDU  \nEngineering Development Unit  \nEE  \nEncircled Energy  \nELG  \nEmission Line Galaxy  \nELT  \nExtremely Large Telescope  \nEM  \nElectron Multiplying  \nEMCCD  \nElectron Multiplying Charge Coupled Device  \nEMI/EMC  \nElectromagnetic Interference/Electromagnetic Compatibility  \nENSCI  \nEuclid NASA Science Center at IPAC  \nEPO  \nEducation and Public Outreach  \neROSITA  \nextended ROentgen Survey with an Imaging Telescope Array  \nEROS  \nExpérience pour la Recherche d'Objets Sombres  \nESA  \nEuropean Space Agency  \nESO  \nEuropean Southern Observatory  \nETC  \nExposure Time Calculator  \nETE  \nEnd to End  \nEW  \nElement Wheel  \nEXCEDE  \nThe EXoplanetary Circumstellar Environments and Disk Explorer  \nExoPAG  \nExoplanet Exploration Program Analysis Group  \nF2  \nFold Flat #2  \nFEM  \nFinite Element Model  \nFDF  \nFlight Dynamics Facility  \nFGS  \nFine Guidance Sensor  \nFLAMES  \nFibre Large Array Multi Element Spectrograph  \nFLI  \nFirst Light Imaging  \nFMA  \nFold Mirror Assembly  \nFMOS  \nFiber Multi Object Spectrograph  \nFOA  \nForward Optics Assembly  \nFoM  \nFigure of Merit  \nFoV  \nField-of-View  \nFP  \nFocal Plane  \nFPA  \nFocal Plane Assembly  \nFPE  \nFocal Plane Electronics  \nFPGA  \nField-Programmable Gate Array  \nFSA  \nForward Structure Assembly  \nFSM  \nFast Steering Mirror  \nFSW  \nFlight Software  \nFT  \nFunctional Test  \nFUSE  \nFar Ultraviolet Spectroscopic Explorer  \nFWHM  \nFull-Width Half-Maximum  \nFY  \nFiscal Year  \nGALEX  \nGalaxy Evolution Explorer  \nGbps  \nGigabits per Second  \nGC  \nGalaxy Clustering  \nGEO  \nGeosynchronous Orbit  \nGGL  \nGalaxy-Galaxy Lensing  \nGI  \nGuest Investigator  \nGMT  \nGiant Magellan Telescope  \nGO  \nGuest Observer  \nGOODS  \nGreat Observatories Origins Deep Survey  \nGOODS-S  \nGreat Observatories Origins Deep Survey-South  \nGPI  \nGemini Planet Imager (Gemini instrument)  \nGPM  \nGlobal Precipitation Measurement  \nGR  \nGeneral Relativity  \nGRS  \nGalaxy Redshift Survey (includes BAO & RSD)  \nGSE  \nGround Support Equipment  \nGSFC  \nGoddard Space Flight Center  \nGSMT  \nGiant Segmented Mirror Telescope  \nGW  \nGravitational Wave  \nGW  \nGuide Window  \nHGA  \nHigh Gain Antenna  \nHCIT  \nHigh Contrast Imaging Testbed  \nHgCdTe  \nMercury Cadmium Telluride  \nHK  \nHousekeeping  \nHLC  \nHybrid Lyot Coronagraph  \nHLS  \nHigh-Latitude Survey  \nHOSTS  \nHunt for Observable Signatures of Terrestrial planetary Systems  \nHQ  \nHeadquarters  \nHSC  \nHyper Suprime-Cam  \nHST  \nHubble Space Telescope  \nH/V  \nHorizontal and Vertical  \nHV  \nHigh Voltage  \nHZ  \nHabitable Zone  \nI&T  \nIntegration and Test  \nIA  \nIntrinsic Alignment  \nIAP  \nInstitut Astrophysique de Paris  \nIAU  \nInternational Astronomical Union  \nIC  \nInstrument Carrier  \nICDH  \nInstrument Command and Data Handling  \nICE  \nInstitut de Ciències de l'Espai  \nICG  \nInstitute for Cosmology and Gravitation  \nICL  \nIntracluster Light  \nIDL  \nInteractive Data Language  \nIDRM  \nInterim Design Reference Mission  \nIFAE  \nInstitut de Física d'Altes Energies  \nIFS  \nIntegral Field Spectrograph  \nIFT  \nInstituto de Física Teórica  \nIFU  \nIntegral Field Unit  \nIGM  \nIntergalactic Medium  \nIM  \nIntegrated Modeling  \nIMF  \nInitial Mass Function  \nIMO  \nInverted Mode Operation  \nIndIGO  \nIndian Initiative in Gravitational-wave Observations  \nIOA  \nInstitute of Astronomy  \nIOC  \nInstrument Operations Center  \niPTF  \nIntermediate Palomar Transient Factory  \nIR  \nInfrared  \nIRAC  \nInfrared Array Camera  \nIRIS  \nInfrared Imaging Spectrograph (TMT instrument)  \nIRMS  \nInfrared Multi-object Spectrometer (TMT instrument)  \nIRSA  \nInfrared Science Archive  \nISAS  \nInstitute of Space and Astronautical Science  \nIUBMB  \nInternational Union of Biochemistry and Molecular Biology  \nIWA  \nInner Working Angle  \nJASMINE  \nJapan Astrometry Satellite Mission for Infrared Exploration  \nJAXA  \nJapanese Aerospace Exploration Agency  \nJDEM  \nJoint Dark Energy Mission  \nJM  \nJitter Mirror  \nJMAPS  \nJoint Milli-Arcsecond Pathfinder Survey  \nJPL  \nJet Propulsion Laboratory  \nJRASC  \nJournal of the Royal Astronomical Society of Canada  \nJWST  \nJames Webb Space Telescope  \nKAGRA  \nKamioka Gravitational Wave  \nKBO  \nKuiper Belt Object  \nKDP  \nKey Decision Point  \nKMOS  \nK-band Multi Object Spectrograph  \nKSC  \nKennedy Space Center  \nL2  \nSun-Earth 2 nd Lagrangian Point  \nLAM  \nLaboratoire d'Astrophysique de Marseille  \nLAT  \nLarge Area Telescope  \nLBT-I  \nLarge Binocular Telescope Interferometer  \nLCDM  \nLambda Cold Dark Matter  \nLDCM  \nLandsat Data Continuity Mission  \nLESIA  \nLaboratoire d'Études Spatiales et d'Instrumentation en Astrophysique  \nLF  \nLuminosity Function  \nLIGO  \nLaser Interferometer Gravitational-Wave Observatory  \nLMC  \nLarge Magellanic Cloud  \nNIRCam  \nNear Infrared Camera  \nNIRISS  \nNear-Infrared Imager and Slitless Spectrograph (JWST instrument)  \nNISP  \nNear Infrared Spectrometer and Photometer (Euclid Instrument)  \nNRA  \nNASA Research Announcement  \nNRC  \nNational Research Council  \nNRO  \nNational Reconnaissance Office  \nNS  \nNeutron Star  \nNSF  \nNational Science Foundation  \nNWNH  \nNew Worlds, New Horizons in Astronomy and Astrophysics  \nOA  \nOptical Alignment  \nOAP  \nOff-Axis Parabola  \nOB  \nOptical Bench  \nOBA  \nOuter Barrel Assembly  \nOBE  \nOuter Barrel Extension  \nOMC  \nOcculting Mask Coronagraph  \nONERA  \nOffice National d'Études et de Recherches Aérospatiales  \nOPD  \nOptical Path Difference  \nOTA  \nOptical Telescope Assembly  \nOVU  \nOptical Verification Unit  \nOWA  \nOuter Working Angle  \nPAF  \nPayload Attach Fitting  \nPanSTARRS  \nPanoramic Survey Telescope & Rapid Response System  \nPASP  \nPublication of the Astronomical Society of the Pacific  \nPAU  \nPhysics of the Accelerating Universe  \nPBS  \nPolarizing Beam Splitter  \nPDR  \nPreliminary Design Review  \nPFS  \nPrime Focus Spectrograph  \nPHAT  \nPanchromatic Hubble Andromeda Treasury  \nPhoto-z  \nPhotometric Redshift  \nPI  \nPrincipal Investigator  \nPIAA-CMC  \nPhase-Induced Amplitude Apodization Complex Mask Coronagraph  \nPID  \nProportional-Integral-Derivative  \nPISN  \nPair Instability SuperNovae  \nPLATO  \nPLanetary Transits and Oscillations of stars  \nPM  \nPrimary Mirror  \nPMA  \nPrimary Mirror Assembly  \nPMN  \nLead Magnesium Niobate  \nPNAS  \nProceedings of the National Academy of Sciences of the United States of America  \nPSD  \nPower Spectral Density  \nPSDU  \nPower Switching & Distribution Unit  \nPSF  \nPoint Spread Function  \nPSI  \nPlanetary System Imager  \nPSR  \nPre-Ship Review  \nPZCS  \nPhoto-Z Calibration Survey  \nPZT  \nLead Zirconate Titanate  \nQE  \nQuantum Efficiency  \nQLF  \nQuasar Luminosity Function  \nQSO  \nQuasi-Stellar Object (Quasar)  \nQUEST  \nQuasar Equatorial Survey Team  \nR1  \nRelay #1  \nR2  \nRelay #2  \nR3  \nRelay #3  \nSRR  \nSystem Requirements Review  \nSTE  \nSpecial Test Equipment  \nSTM  \nSafe to Mate  \nSTOP  \nStructural/Thermal/Optical  \nSTScI  \nSpace Telescope Science Institute  \nSuMIRe  \nSubaru Measurement of Images and Redshifts  \nSWEEPS  \nSagittarius Window Eclipsing Extrasolar Planet Search  \nSWG  \nScience Working Group  \nSZ  \nSunyaev-Zel'dovich  \nTBD  \nTo Be Determined  \nTAC  \nTechnology Assessment Committee  \nTAC  \nTime Allocation Committee  \nTBR  \nTo Be Resolved  \nTDEM  \nTechnology Development for Exoplanet Missions  \nTDP  \nTechnology Development Plan  \nTESS  \nTransiting Exoplanet Survey Satellite  \nTMM  \nThermal Math Model  \nTMT  \nThirty Meter Telescope  \nTNO  \nTrans-Neptunian Objects  \nTRL  \nTechnology Readiness Level  \nTVAC  \nThermal Vacuum  \nUDF  \nUltra Deep Field  \nUK  \nUnited Kingdom  \nUKATC  \nUnited Kingdom Astronomy Technology Centre  \nUKIDSS  \nUKIRT Infrared Deep Sky Survey  \nUKSA  \nUnited Kingdom Space Agency  \nULE  \nUltra Low Expansion Fused Silica  \nUS  \nUnited States  \nUV  \nUltraviolet  \nVdc  \nVolts Direct Current  \nVIS  \nVisible Instrument (Euclid instrument)  \nVISTA  \nVisible and Infrared Survey Telescope for Astronomy  \nVLASS  \nVery Large Area Sky Survey  \nVLT  \nVery Large Telescope  \nVNC  \nVisible Nulling Coronagraph  \nVST  \nVLT Survey Telescope  \nVVC  \nVector Vortex Coronagraph  \nVVV  \nVista Variables in the Via Lactea  \nWACO  \nWFIRST-AFTA Coronagraph  \nWF  \nWide-Field  \nWFC3  \nWide Field Camera 3  \nWFC3/IR  \nWide Field Camera 3/Infrared channel  \nWFCS  \nWavefront Control System  \nWFE  \nWavefront Error  \nWFI  \nWide-Field Instrument  \nWFIRST  \nWide-Field Infrared Survey Telescope  \nWIM  \nWide-field Imaging Mode  \nWIMPS  \nWeakly Interacting Massive Particles  \nWISE  \nWide-field Infrared Survey Explorer  \nWL  \nWeak Lensing  \nWSM  \nWide-field Spectroscopy Mode  \nXMM  \nX-ray Multi-Mirror Mission Redshift  \nZ  \nZTF  \nZwicky Transient Facility  \nZWFS  \nZernike Wavefront Sensor", 'Appendix M References': '- Abdalla, F.B., Amara, A., Capak, P., Cypriano, E.S., Lahav, O., Rhodes, J., \'Photometric redshifts for weak lensing tomography from space: the role of optical and near infrared photometry\', MNRAS, 387 , 969 (2008)\n- Aime, C., Soummer, R., Ferrari, A., \'Interferometric apodization of rectangular apertures\', A&A 379 , 697-707 (2001) Albrecht, A., Bernstein, G., Cahn, R., et al., "Report of the Dark Energy Task Force", arXiv:astro-ph/0609591 (2006)\n- Albrow, M.D., Beaulieu, J.-P., Caldwell, J.A.R., et al. \'Limb Darkening of a K Giant in the Galactic Bulge: PLANET Photometry of MACHO 97-BLG-28\', ApJ, 522 , 1011 (1999)\n- Alcock, C., Allsman, R., Alves, D., et al., \'EROS and MACHO Combined Limits on Planetary-Mass Dark Matter in the Galactic Halo\', ApJ, 499 , L9 (1998)\n- Alcock,  C.,  Allsman,  R.A.,  Alves,  D.,  et  al.  \'Binary  Microlensing  Events  from  the  MACHO  Project\'  ApJ, 541 ,  270 (2000)\n- Anderson, L., Aubourg, E., Bailey, S., et al., \'The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: baryon acoustic oscillations in the Data Releases 10 and 11 Galaxy samples\', MNRAS, 441 ,  24 (2014)\n- Angel, J. R. P., \'Ground-based imaging of extrasolar planets using adaptive optics\', Nature, 368 , 203-207 (1994) Antichi, J., Dohlen, K., Gratton, R. G., et al . ,  \'BIGRE: A Low Cross-Talk Integral Field Unit Tailored for Extrasolar\n- Planets Imaging Spectroscopy\', ApJ, 695 , 1042 (2009)\n- Aubourg  et  al.,  Bailey,  S.,  Bautista,  J.  E.,  et  al.,  \'Cosmological  implications  of  baryon  acoustic  oscillation  (BAO) measurements\', arXiv:1411.1074 (2014)\n- Balasubramanian, K., Wilson, D., White, V., Muller, R., Dickie, M., Yee, K.; Ruiz, R; Shaklan, S.; Cady, E.; Kern, B.; Belikov, R, Guyon, O., Kasdin, N.J., \'High contrast internal and external coronagraph masks produced by various techniques,\' Proc. SPIE 8864, 88641R (2013)\n- Baltz, E., & Gondolo, P., \'Binary Events and Extragalactic Planets in Pixel Microlensing,\' ApJ, 559 , 41 (2001)\n- Baudoz, P., Boccaletti, A., Riaud, P., et al., \'Feasibility of the Four-Quadrant Phase Mask in the Mid-Infrared on the James Webb Space Telescope \', PASP, 118 , 765 (2006)\n- Baudoz, P., Boccaletti, A., Baudrand, J., Rouan, D., \'The Self-Coherent Camera: a new tool for planet detection\', Proc. IAU, 200 , 553-558 (2006)\n- Baudoz, P., Galicher, R., Baudrand, J. & Boccaletti, A., \'Theory and laboratory tests of the multi-stage phase mask coronagraph\', Proc. SPIE, 7015 , 70156C (2008)\n- Baudoz, P., Mas, M., Galicher, R., Rousset, G., \'Focal plane wavefront sensor sensitivity for ELT planet finder\', Proc. SPIE , 7736 , 77365S (2010)\n- Baudoz, P., Mazoyer, J., Mas, M., Galicher, R., Rousset, G., \'Dark hole and planet detection: laboratory results using the self-coherent camera\', Proc. SPIE proc., 8446 , 84468C (2012)\n- Baudoz, P., Mazoyer, J., Galicher, R., \'Laboratory tests of planet signal extraction in high contrast images\', Proc. 3 rd AO4ELT conf. , Simone Esposito and Luca Fini, eds., Firenze, Italy (2013)\n- Beaulieu, J.-P., Bennett, D. P., Fouque, P., et al., \'Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing\', Nature, 439 , 437-440 (2006)\n- Becker, R., Fan, X., White, R., et al., \'Evidence for Reionization at z~6: Detection of a Gunn-Peterson Trough in a z= 6.28 Quasar\', AJ, 122 , 2850 (2001)\n- Beichman, C. A., Bryden, G., Stapelfeldt, K. R., et al., \'New Debris Disks around Nearby Main-Sequence Stars: Impact on the Direct Detection of Planets\', ApJ, 652 , 1674 (2006)\n- Bennett, D. P., & Rhie, S. H., \'Simulation of a Space-based Microlensing Survey for Terrestrial Extrasolar Planets\', ApJ, 574 , 985 (2002)\n- Bennett, D. P., Anderson, J. Gaudi, B. S., \'Characterization of Gravitational Microlensing Planetary Host Stars\', ApJ, 660 , 781 (2007)\n- Bennett, D. P., Bond, I. A., Udalski, A., et al., \'A Low-Mass Planet with a Possible Sub-Stellar-Mass Host in Microlensing Event MOA-2007-BLG-192\', ApJ, 684 , 663 (2008)\n- Bennett, D. P., Rhie, S. H., Nikolaev, S., et al., \'Masses and Orbital Constraints for the OGLE-2006-BLG-109Lb,c Jupiter/Saturn Analog Planetary System,\' ApJ, 713 , 837 (2010)  \n- Biller, B., Liu, M. C., Wahhaj, Z., et al., \'THE GEMINI/NICI PLANET-FINDING CAMPAIGN: THE FREQUENCY OF PLANETS AROUND YOUNG MOVING GROUP STARS\', ApJ, 777 , 160 (2013)\n- Boccaletti, A., Riaud, P., Baudoz, P., et al., \'The Four-Quadrant Phase Mask Coronagraph. IV. First Light at the Very Large Telescope\', PASP, 116 , 1061-1071 (2004)\n- Boccaletti, A., Baudoz, P., Baudrand, J., Reess, J. M. & Rouan, D., \'Imaging exoplanets with the coronagraph of JWST/MIRI\', Advances in Space Research, 36 , 1099-1106 (2005)\n- Boccaletti, A., Abe, L., Baudrand, J., et al., \'Prototyping coronagraphs for exoplanet characterization with SPHERE\', Proc. SPIE, 7015 , 70151B (2008)\n- Boccaletti, A., Augereau, J.-C., Baudoz, P., Pantin, E., Lagrange, A.-M., \'VLT/NACO coronagraphic observations of fine structures in the disk of beta Pictoris\', A&A, 495 , 523-535 (2009)\n- Boccaletti, A., Schneider, J., Traub, W., et al . , \'SPICES: spectro-polarimetric imaging and characterization of exoplanetary systems\', Experimental Astronomy, 34 , 355-384 (2012)\n- Boccaletti, A., Augereau, J.-C., Lagrange, A.-M., et al., \'Morphology of the very inclined debris disk around HD 32297\', A&A, 544 , A85 (2012)\n- Boccaletti, A., Pantin, E., Lagrange, A.-M., et al., \'Multiple spiral patterns in the transitional disk of HD 100546\', A&A, 560 , A20 (2013)\n- Boccaletti, A., Lagrange, A.-M., Bonnefoy, M., Galicher, R. & Chauvin, G., \'Independent confirmation of β Pictoris b imaging with NICI\', A&A, 551 , L14 (2013)\n- Boccaletti, A., et al., to appear in PASP (2014)\n- Bond, J. C., O\'Brien, D. P., Lauretta, D. S., \'THE COMPOSITIONAL DIVERSITY OF EXTRASOLAR TERRESTRIAL PLANETS. I. IN SITU SIMULATIONS\', ApJ, 715 , 1050 (2010)\n- Bonnefoy, M., Lagrange, A.-M., Boccaletti, A., et al . , \'High angular resolution detection of β Pictoris b at 2.18 ∝ m\', A&A, 528 , L15 (2011)\n- Bonnefoy, M., Boccaletti, A., Lagrange, A.-M., et al . , \'The near-infrared spectral energy distribution of β Pictoris b\', A&A, 555 , 107 (2013)\n- Bordoloi,  R.,  Lilly,  S.J.,  Amara,  A.,  etc.,  \'Photo-z  performance  for  precision  cosmology  -  II.  Empirical  verification\', MNRAS, 421 , 1671 (2012)\n- Borgani, S., Murante, G., Springel, V., et al., \'X-ray properties of galaxy clusters and groups from a cosmological hydrodynamical simulation\', MNRAS, 348 , 1078-1096 (2004)\n- Bouwens, R. J., Illingworth, G. D., Labbe, I., et al., \'A candidate redshift z ≈ 10 galaxy and rapid changes in that population at an age of 500 Myr\', Nature, 469 , 504 (2011)\n- Bower, R., Benson, A. J., Malbon, R., et al., \'Breaking the hierarchy of galaxy formation\', MNRAS, 370 , 645 (2006) Bradley, L. D., Bouwens, R. J., Ford, H. C. et al., \'Discovery of a Very Bright Strongly Lensed Galaxy Candidate at z ≈ 7.6\', ApJ, 678 , 647 (2008)\n- Bradley, L. D., Trenti, M., Oesch, P. A., et al., \'The Brightest of Reionizing Galaxies Survey: Constraints on the Bright End of the z~8 Luminosity Function\', ApJ, 760 , 108 (2012)\n- Brown, R., \'Single-Visit Photometric and Obscurational Completeness\', ApJ, 624 , 1010 (2005)\n- Brown, R.A., \'True Masses of Radial-Velocity Exoplanets\', arXiv:1501.02673 (2015)\n- Brown, T., Sahu, K., Zoccali, M., et al. \'The WFC3 Galactic Bulge Treasury Program: A First Look at Resolved Stellar Population Tools\', AJ, 137 , 3172 (2009)\n- Burke, C.J., Bryson, S.T., Mullally, F., et al., \'Planetary Candidates Observed by Kepler , IV: Planet Sample from Q1Q8 (22 Months)\', ApJS, 210 , 19 (2014)\n- Burrows,  A.,  \'Scientific  Return  of  Coronagraphic  Exoplanet  Imaging  and  Spectroscopy  Using  WFIRST\', arXiv:1412.6097 (2014)\n- Burrows, A., Saumon, D., Guillot, T., Hubbard, W. B., & Lunine, J. I., \'Prospects for detection of extra-solar giant planets by next-generation telescopes\', Nature, 375 , 299-301 (1995)\n- Caceres, C., Kabath, P., Hoyer, S., et al., \'Ground-based transit observations of the super-Earth GJ 1214 b\', A&A 565 , A7 (2014)\n- Carlotti, A., Kasdin, N. J., Vanderbei, R. J., Delorme, J.-R., \'Optimized shaped pupil masks for pupil with obscuration\', Proc. SPIE 8442, article id. 844254 (2012)  \n- Carlotti, A., Kasdin, N. J., Vanderbei, R. J., \'Shaped pupil coronagraphy with WFIRST-AFTA\', Proc. SPIE 8864, article id. 886410 (2013)\n- Cassan, A., Kubas, D., Beaulieu, J.-P., et al., \'One or more bound planets per Milky Way star from microlensing observations\', Nature, 481 , 167 (2012)\n- Chatterjee, S., Ford, E. B., Matsumura, S., Rasio, F. A., \'Dynamical Outcomes of Planet-Planet Scattering\', ApJ, 686 , 580 (2008)\n- Chauvin, G., Lagrange, A.-M., Beust, H., et al., \'Orbital characterization of the β Pictoris b giant planet\', A&A, 542 , 41 (2012)\n- Chotard, N., Gangler, E., Aldering, G., et. al., \'The reddening law of type Ia supernovae: separating intrinsic variability from dust using equivalent widths\', A&A, 529 , L4 (2011)\n- Clowe, D., Bradac, M., Gonzalez, A., et al., \'A Direct Empirical Proof of the Existence of Dark Matter\', ApJ, 648 , L109 (2006)\n- Clowe, D., Markevitch, M., Bradac, M., et al., \'On Dark Peaks and Missing Mass: A Weak-Lensing Mass Reconstruction of the Merging Cluster System A520\', ApJ, 758 , 128 (2012)\n- Coe, D., Zitrin, A., Carrasco, M., et al., \'CLASH: Three Strongly Lensed Images of a Candidate z ≈ 11 Galaxy\', ApJ, 762 , 32 (2013)\n- Colbert, J.W., Teplitz, H., Atek, H., \'Predicting Future Near-IR Grism Surveys Using the WFC3 Infrared Spectroscopic Parallels Survey\', ApJ, 779 , 34 (2013)\n- Cooray, A., Smidt, J., De Bernardis, F., et al., \'Near-infrared background anisotrophies from diffuse intrahalo light of galaxies\', Nature, 490 , 514-516 (2012)\n- Currie, T., Daemgen, S., Debes, J., et al., \'Direct Imaging and Spectroscopy of a Candidate Companion Below/Near the Deuterium-burning Limit in the Young Binary Star System, ROXs 42B\', ApJ, 780 , L30 (2014)\n- Davies, D. W., \'Direct imaging of planetary systems around nearby stars\', Icarus 42 , 145-148 (1980)\n- Dawson, W. A., Wittman, D., Jee, M. J., et al., \'Discovery of a Dissociative Galaxy Cluster Merger with Large Physical Separation\', ApJ, 747 , L42 (2012)\n- Delorme, J. R., Galicher, R., Baudoz, P., et al., \'High-contrast imaging in wide spectral band with a self-coherent camera and achromatic coronagraphs\', Proc. SPIE , 9151 , 91515Q (2014)\n- Djorgovski, S. G., Castro, S., Stern, D., Mahabal, A. A., \'On the Threshold of the Reionization Epoch\', ApJ, 560 , L5 (2001)\n- Dohlen, K., Madec, F., N\'Diaye, M., et al., \'Lab demonstration of the Zernike phase mask near-coronagraph quasi static aberrations sensor, ZELDA\', Proc. 3 rd AO4ELT conf. , Simone Esposito and Luca Fini, eds., Firenze, Italy (2013)\n- Dominik, M., & Sahu, K., \'Astrometric Microlensing of Stars\', ApJ, 534 , 213 (2000)\n- Dressing, C.D. & Charbonneau, D., \'The Occurrence of Potentially Habitable Planets Orbiting M Dwarfs Estimated\n- from the Full Kepler Dataset and an Empirical Measurement of the Detection Sensitivity\', arXiv:1501.01623 (2015) Dressler, A., Spergel, D. Mountain, M., et al., "Exploring the NRO Opportunity for a Hubble-sized Wide-field Near-IR\n- Space Telescope -- NEW WFIRST", arXiv:1210.7809 (2012)\n- Fan, X., Strauss, M. A., Schneider, D. P., et al., \'A Survey of z > 5.7 Quasars in the Sloan Digital Sky Survey. II. Discovery of Three Additional Quasars at z > 6\', AJ, 125 , 1649 (2003)\n- Ferrarese, L & Merritt, D., \'A Fundamental Relation between Supermassive Black Holes and Their Host Galaxies\', ApJ, 539 , L9 (2000)\n- Fluri, D.M., & Berdyugina, S. V., \'Orbital Parameters of extrasolar planets derived from polarimetry\', A&A, 512 , A59 (2010)\n- Fressin, F., Torres, G., Charbonneau, D., et al., \'The False Positive Rate of Kepler and the Occurrence of Planets\', ApJ 766 , 81 (2013)\n- Fryer, C., Belczynski, K., Wiktorowicz, G., et al., \'Compact Remnant Mass Function: Dependence on the Explosion Mechanism and Metallicity,\' ApJ, 749 , 91 (2012)\n- Galicher, R. & Baudoz, P., \'Expected performance of a self-coherent camera\', Comptes Rendus Physique, 8 , 333339 (2007)\n- Galicher, R., Baudoz, P., Rousset, G., \'Self-Coherent Camera: active correction and post-processing for Earth-like planet detection\', Proc. SPIE, 7015 , 70156P (2008)  \nAppendix M: References  \n- Galicher, R., Baudoz, P., Rousset, G., Totems, J. & Mas, M., \'Self-coherent camera as a focal plane wavefront sensor: simulations\', A&A, 509 , A31 (2010)\n- Galicher, R., Baudoz, P. & Baudrand, J., \'Multi-stage four-quadrant phase mask: achromatic coronagraph for spacebased and ground-based telescopes\', A&A, 530 , A43 (2011)\n- Galicher, R., Marois, C., Zuckerman, B. & Macintosh, B., \'Fomalhaut b: Independent Analysis of the Hubble Space Telescope Public Archive Data\', ApJ, 769 , 42 (2013)\n- Galicher, R., Rameau, J., Bonnefoy, M., et al.,  \'Near-infrared  detection  and  characterization  of  the  exoplanet  HD 95086 b with the Gemini Planet Imager\', A&A, 565 , L4 (2014)\n- Gaudi, B. S., \'Microlensing Surveys for Exoplanets\', ARAA, 50 , 411 (2012)\n- Gaudi, B.S., Bennett, D. P., Udalski, A., et al., \'Discovery of a Jupiter/Saturn Analog with Gravitational Microlensing\', Science, 319 , 927 (2008)\n- Gautier, T. N., III,  Charbonneau, D., Rowe, J. F., et al., \'Kepler-20: A Sun-like  Star  with  Three  Sub-Neptune Exoplanets and Two Earth-size Candidates\', ApJ, 749 , 15 (2012)\n- Geach, J.E., Sobral, D., Hickox, R. C., et al., "The clustering of H α emitters at z=2.23 from HiZELS", MNRAS, 426 , 679 (2012)\n- Gebhardt, K., Bender, R., Bower, G., et al., \'A Relationship between Nuclear Black Hole Mass and Galaxy Velocity Dispersion\', ApJ, 539 , L13 (2000)\n- Give\'on, A., Kern, B., Shaklan, S., Moody, D., Pueyo, L., \'Broadband wavefront correction algorithm for high-contrast imaging systems,\' Proc. SPIE 6691, 66910A (2007)\n- Golimowski, D. A., Clampin, M., Durrance, S. T., Barkhouser, R. H., \'High-resolution ground-based coronagraphy using image-motion compensation\', Appl. Opt. 31 , 4405 -4416 (1992)\n- Gonzalez, O. A., Rejkuba, M., Zoccali, M., et al., \'Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS. II. The complete high resolution extinction map and implications for Galactic bulge studies,\' A&A, 543 , A13 (2012)\n- Goto, T., Utsumi, Y., Hattori, T., Miyazaki, S., Yamauchi, C., \'A Gunn-Peterson test with a QSO at z = 6.4\', MNRAS, 415, L1 (2011)\n- Gouda, N., Yano, T. Yamada, Y., et al., \'Japan Astrometry Satellite Mission for Infrared Exploration (JASMINE)\', Proceedings of the Gaia Symposium "The Three-Dimensional Universe with Gaia", eds: C. Turon, K.S. O\'Flaherty, M.A.C. Perryman (2005)\n- Gould, A., \'Extending the MACHO search to about 10 exp 6 solar masses\', ApJ, 392 , 442 (1992)\n- Gould, A., \'Proper motions of MACHOs\', ApJ, 421 , L71 (1994)\n- Gould, A., \'Geosynchronous Microlens Parallaxes\', ApJ, 763 , L35 (2013)\n- Gould, A., \'Microlens Masses from 1-D Parallaxes and Heliocentric Proper Motions\', JKAS, 47 , 215 (2014a)\n- Gould, A., \'WFIRST Ultra-Precise Astrometry I: Kuiper Belt Objects\', JKAS, 47 , 279 (2014b)\n- Gould, A., & Yee, J.C., \'Microlens Masses from Astrometry and Parallax in Space-based Surveys: From Planets to Black Holes\', ApJ, 784 , 64 (2014)\n- Gould, A., Gaudi, B.S., & Han, C., \'Resolving the Microlens Mass Degeneracy for Earth-Mass Planets\', ApJ, 591 , L53 (2003)\n- Gould, A., Huber, D., Penny, M., Stello, D., \'WFIRST Ultra-Precise Astrometry II: Asteroseismology\', JKAS, in press, arXiv:1410.7395 (2015)\n- Green,  J.,  Schechter,  P.,  Baltay,  C.,  et  al.,  \'Wide-Field  InfraRed  Survey  Telescope  (WFIRST)  Final  Report\', arXiv:1208.4012 (2012)\n- Griest, K., Alcock, C., Axelrod, T.S., et al., \'Gravitational microlensing as a method of detecting disk dark matter and faint disk stars\', ApJ, 372 , L79 (1991)\n- Griest, K., Cieplak, A. M., Lehner, M. J., \'Experimental Limits on Primordial Black Hole Dark Matter from the First 2 Yr of Kepler Data\', ApJ, 786 , 158 (2014)\n- Groff, T., Kasdin, N. J., Limbach, M. A., et al., \'Construction and status of the CHARIS high contrast imaging spectrograph\', Proc. SPIE 9147, id. 91471W (2014)\n- Gunn, J.E. & Peterson, B.A., "On the Density of Neutral Hydrogen in Intergalactic Space", ApJ, 142 , 1633 (1965)\n- Guo, Y., Ferguson, H.C., Giavalisco, M., et al., \'CANDELS Multi-wavelength Catalogs: Source Detection and Photometry in the GOODS-South Field\', ApJS, 207 , 24 (2013)  \n- Appendix M: References M-5 Guyon, O., Pluzhnik, E.A., Galicher, R., Martinache, F., Ridgway, S.T., and Woodruff, R.A., \'Exoplanet Imaging with a Phase-induced Amplitude Apodization Coronagraph. I. Principle,\' ApJ, 622 , 744 (2005) Han, C., Gaudi, B. S., An, J. H., Gould, A., \'Microlensing Detection and Characterization of Wide-Separation Planets\', ApJ, 618 , 962 (2005) Heavens, A., Panter, B., Jimenez, R. & Dunlop, J., \'The star-formation history of the Universe from the stellar populations of nearby galaxies\', Nature, 428 , 625 (2004) Helling, C., Woitke, P., Rimmer, P.B., Kamp, I., Thi, W.-F., Meijerink, R., \'Disk evolution, element abundances and cloud properties of young gas giant planets\', IUBMB Life, 4 , 142 (2014) Henderson, C., \'Prospects for Characterizing Host Stars of the Planetary System Detections Predicted for the Korean Microlensing Telescope Network\', ApJ, 800 , 58 (2015) Hinkley, S., Oppenheimer, B. R., Soummer, R., et al., \'Temporal Evolution of Coronagraphic Dynamic Range and Constraints on Companions to Vega\', ApJ, 654 , 633 (2007) Hinkley, S., Oppenheimer, B. R., Zimmerman, N., et al., \'A New High Contrast Imaging Program at Palomar Observatory\', PASP 123 , 74-86 (2011) Howard,  A.W.  &  Fulton,  B.J.,  \'Limits  on  Planetary  Companions  from  Doppler  Surveys  of  Nearby  Stars\', https://exep.jpl.nasa.gov/reportsAndDocuments/completenessStudy (2014) Howard, A.W., Marcy, G.W., Bryson, S.T., et al., \'Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler \', ApJS, 201 , 15 (2012) Hsu, L.-T., Salvato, M., Nandra, K., et al., \'CANDELS/GOODS-S, CDFS, ECDFS: Photometric Redshifts for Normal and X-Ray Detected Galaxies\', ApJ, 796 , 60 (2014) Hu, R, \'Ammonia, Water Clouds and Methane Abundances of Giant Exoplanets and Opportunities for Super-Earth Exoplanets\', arXiv:1412.7582 (2014) Hu, R., Seager, S., Bains, W., \'Photochemistry in Terrestrial Exoplanet Atmospheres. I. Photochemistry Model and Benchmark Cases\', ApJ, 761 , 166 (2012) Hugot, E., Ferrari, M., El Hadi, K., et al., \'Active optics methods for exoplanet direct imaging - Stress polishing of supersmooth aspherics for VLT-SPHERE planet finder\', A&A, 538 , A139 (2012) Ida, S. & Lin, D. N. C., \'Toward a Deterministic Model of Planetary Formation. I. A Desert in the Mass and Semimajor Axis Distributions of Extrasolar Planets,\' ApJ, 604 , 388 (2004) Ilbert, O, McCracken, H.J., Le Fevre, O., et al. \'Mass assembly in quiescent and star-forming galaxies since z ≃ 4 from UltraVISTA\', A&A, 556 , A55 (2013) Iye, M., Ota, K., Kashikawa, N., et al., \'A galaxy at a redshift z = 6.96\', Nature, 443 , 186 (2006) Johnston, K.V., Spergel, D.N. & Haydn, C., \'How Lumpy is the Milky Way\'s Dark Matter Halo?\', ApJ, 570 , 656 (2002) Juric, M. & Tremaine, S., \'Dynamical Origin of Extrasolar Planet Eccentricity Distribution\', ApJ, 686 , 603 (2008) Kalas, P., Graham, J.R., Chiang, E., et al., \'Optical Images of an Exosolar Planet 25 Light-Years from Earth\', Science, 322 , 1345-1348 (2008) Kalirai, J.S., \'The age of the Milky Way inner halo\', Nature, 486 , 90 (2012) Kalirai, J., Richer, H.B., Anderson, J., et al., \'A Deep, Wide-Field, and Panchromatic View of 47 Tuc and the SMC with HST : Observations and Data Analysis Methods\', AJ, 143 , 11 (2012) Karachentsev, I., Karachentseva, V.E., Huchtmeier, W.K., Makarov, D.I., \'A Catalog of Neighboring Galaxies\', AJ, 127 , 2031 (2004) Kasdin, N. J., Vanderbei, R. J., Spergel, D. N., Littman, M. G., \'Extrasolar Planet Finding via Optimal Apodized-Pupil Coronagraphs\', ApJ, 582 , 1147 (2003) Kashlinsky, A., Arendt, R.G., Mather, J., Moseley, S.H., \'On the Nature of the Sources of the Cosmic Infrared Background\', ApJ, 654 , L1 (2007) Kashlinsky, A., Arendt, R.G., Ashby, M.L.N, Fazio, G.G., Mather, J., Moseley, S.H., \'New Measurements of the Cosmic Infrared Background Fluctuations in Deep Spitzer /IRAC Survey Data and Their Cosmological Implications\', ApJ, 753 , 63 (2012) Kenknight, C. E., \'Methods of detecting extrasolar planets. I - Imaging\', Icarus 30 , 422-433 (1977) Kiraga, M. & Paczynski, B., \'Gravitational microlensing of the Galactic bulge stars\', ApJ, 430 , L101 (1994) Kirkpatrick, J.D., Gelino, C.R., Cushing, M.C., et al., \'Further Defining Spectral Type \'Y\' and Exploring the Low-Mass End of the Field Brown Dwarf Mass Function\', ApJ, 753 , 156 (2012)  \n- Kopparapu, R.K., Ramirez, R., Kasting, J.F., et al., \'Habitable Zones Around Main-Sequence Stars: New Estimates\', ApJ, 765 , 131 (2013)\n- Kouveliotou,  C.,  Agol,  E.,  Batalha,  N.,  et  al.  \'Enduring  Quests  -  Daring  Visions  (NASA  Astrophysics  in  the  Next Three Decades\', http://science.nasa.gov/science-committee/subcommittees/nac-astrophysicssubcommittee/astrophysics-roadmap or arXiv:1401.3741 (2014)\n- Kraus, A.L., Ireland, M.J., Cieza, L.A., et al., \'Three Wide Planetary-mass Companions to FW Tau, ROXs 12, and ROXs 42B\', ApJ, 781 , 20 (2014)\n- Kreidberg, L., Bean, J.L., Desert, J.-M., et al., \'A Precise Water Abundance Measurement for the Hot Jupiter WASP43b\', ApJ, 793 , L27 (2014)\n- Krist, J., \'PROPER: an optical modeling program for IDL,\' Proc. SPIE 6675, 66750P (2007)\n- Krist, J., \'End-to-end numerical modeling of AFTA coronagraphs,\' Proc. SPIE 9143, 91430V (2014)\n- Krist, J. E., Hartig, G. F., Clampin, M., et al., \'The Advanced Camera for Surveys coronagraph on the Hubble Space Telescope\', Proc. SPIE 4860, 20 (2003)\n- Krist, J., Belikov, R., Pueyo, L., et al., \'Assessing the performance limits of internal coronagraphs through end-to-end modeling: a NASA TDEM study,\' Proc. SPIE 8151, 81510E (2011)\n- Krist, J., Belikov, R., Mawet, D., et al., \'Assessing the performance limits of internal coronagraphs though end-to-end modeling Technology Milestone #1 Results Reports\', JPL Document D-74425 (available at exep.jpl.nasa.gov/technology) (2012a)\n- Krist, J., Belikov, R., Mawet, D., et al., \'Assessing the performance limits of internal coronagraphs though end-to-end modeling Technology Milestone #2 Results Reports\', JPL Document D-74426 (available at exep.jpl.nasa.gov/technology) (2012b)\n- Kuchner, M. & Traub, W., \'A Coronagraph with a Band-limited Mask for Finding Terrestrial Planets\', ApJ 570 ,  900 (2002)\n- Kuzuhara, M., Tamura, M., Kudo, T., et al., \'Direct Imaging of a Cold Jovian Exoplanet in Orbit Around the Sun-Like Star GJ 504\', 774 , 11 (2013)\n- Lagrange, A.-M., Gratadour, D., Chauvin, G., et al., \'A probable giant planet in the β Pictoris disk - VLT/NaCo deep L \'-band imaging\', A&A, 493 , L21-L25 (2009)\n- Lagrange, A.-M., Bonnefoy, M., Chauvin, G., et al., \'A Giant Planet Imaged in the Disk of the Young Star β Pictoris\', Science, 329 , 57-59 (2010)\n- Lagrange, A.-M., Boccaletti, A., Milli, J., et al., \'The position of β Pictoris b relative to the debris disk\', A&A, 542 , A40 (2012)\n- Langlois, M., Vigan, A., Dohlen, K., et al., \'Infrared differential imager and spectrograph for SPHERE: performance assessment for on-sky operation\', Proc. SPIE 9147, id. 91479P (2014)\n- Laslandes, M., Hourtoule, C., Hugot, E., et al . , \'Space active optics: performance of a deformable mirror for in-situ wave-front correction in space telescopes\', Proc. SPIE, 8442 , 844220 (2012)\n- Laslandes, M., Hugot, E., Ferrari, M., et al., \'Mirror actively deformed and regulated for applications in space: design and performance\', Optical Engineering, 52 , 091803 (2013)\n- Latham, D.W., Mazeh, T., Stefanik, R.P, Mayor, M. Burki, G., \'The unseen companion of HD114762 - A probable brown dwarf,\' Nature, 339 , 38 (1989)\n- Laureijs, R., Amiaux, J., Arduini, S., et al., "Euclid Definition Study Report", arXiv:1110.3193 (2011)\n- Lawson, P. R., Belikov, R., Cash, W., Clampin, M., T. Glassman, T., Guyon, O, Kasdin, N. J., Kern, B. D., Lyon, R.,\n- Mawet, D., Moody, D., Samuele, R., Serabyn, E., Sirbu, D., and Trauger, J., \'Survey of experimental results in\n- high-contrast imaging for future exoplanet missions,\' Proc. SPIE Vol. 8864, 88641F (2013)\n- Lin, D.N.C., Bodenheimer, P., Richardson, D.C., \'Orbital migration of the planetary companion of 51 Pegasi to its present location\', Nature, 380 , 606-607 (1996)\n- Lissauer,  J.J.,  \'Timescales  for  planetary  accretion  and  the  structure  of  the  protoplanetary  disk\',  Icarus, 69 ,  249 (1987)\n- Lissauer, J.J., \'Planets Formed in Habitable Zones of M Dwarf Stars Probably Are Deficient in Volatiles\', ApJ, 660 , L149 (2007)  \n- Lissauer, J.J., Fabrycky, D.C., Ford, E.B., et al., \'A closely packed system of low-mass, low-density planets transiting Kepler-11\', Nature, 470 , 53-58 (2011)\n- Lyot, B., \'The study of the solar corona and prominences without eclipses\', MNRAS, 99 , 580 (1939)\n- Macintosh, B., Graham, J. R., Ingraham, P., et al., \'First light of the Gemini Planet Imager\', PNAS 111 , 12661-12666 (2014)\n- Madhusudhan, N. & Burrows, A., \'Analytic Models for Albedos, Phase Curves, and Polarization of Reflected Light from Exoplanets\', ApJ, 747 , 25 (2012)\n- Maire, A.-L., Galicher, R., Boccaletti, A., et al., \'Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope\', A&A, 541 , A83 (2012)\n- Mandel, K., Foley, R., Kirshner, R., \'Type  Ia  Supernova  Colors  and  Ejecta  Velocities:  Hierarchical  Bayesian  with Non-Gaussian Distributions\', ApJ, 797 75 (2014)\n- Mandelbaum, R., Seljak, U., Kauffmann, G., Hirata, C.M., Brinkmann, J., \'Galaxy halo masses and satellite fractions from galaxy-galaxy lensing in the Sloan Digital Sky Survey: stellar mass, luminosity, morphology and environment dependencies\', MNRAS, 368 , 715 (2006)\n- Mantz, A.B., Allen, S.W., Morris, R.G., et al., \'Cosmology and astrophysics from relaxed galaxy clusters - II. Cosmological constraints\', MNRAS, 440 , 2077 (2014)\n- Marcy, G.W. & Butler, R.P., \'A Planetary Companion to 70 Virginis,\' ApJ, 464 , 147 (1996)\n- Marcy,  G.W.,  Weiss,  L.M.,  Petigura,  E.A.,  Isaacson,  H.,  Howard,  A.W.,  Buchhave,  L.A.,  \'Occurrence  and  coreenvelope structure of 1-4x Earth-size planets around Sun-like stars\', PNAS, 111 , 12655-12660 (2014)\n- Marley, M.S., Saumon, D., Cushing, M., Ackerman, A.S, Fortney, J.J., Freedman, R., \'Masses, Radii, and Cloud Properties of the HR 8799 Planets\', ApJ, 754 , 135 (2012)\n- Marley, M., Lupu, R., Lewis, N., Line, M., Morley, C., Fortney, J., \'A Quick Study of the Characterization of Radial Velocity Giant Planets in Reflected Light by Forward and Inverse Modeling\', arXiv:1412.8440 (2014)\n- Marois, C., Doyon, R., Racine R., et al., \'Direct Exoplanet Imaging around Sun-like Stars: Beating the Speckle Noise with Innovative Imaging Techniques\', JRASC, 99 , 130 (2005)\n- Marois, C., Lafreniere, D., Doyon, R., Macinstosh, B., Nadeau, D., \'Angular Differential Imaging: A Powerful HighContrast Imaging Technique\', ApJ 641 , 556 (2006)\n- Marois, C., Macintosh, B., Barman, T., et al., \'Direct Imaging of Multiple Planets Orbiting the Star HR 8799\', Science, 322 , 1348-1352 (2008)\n- Martinache, F., \'The Asymmetric Pupil Fourier Wavefront Sensor\', PASP, 125 , 422-430 (2013)\n- Martinache, F., \'Super resolution imaging with an ELT: Kernal-phase interferometry\', Proc. 3 rd AO4ELT conf. , Simone Esposito and Luca Fini, eds., Firenze, Italy (2013)\n- Martinache, F., Guyon, O., Jovanovic, N., et al., \'On-Sky Speckle Nulling Demonstration at Small Angular Separation with SCExAO\', PASP, 126 , 565-572 (2014)\n- Martinache, F., Guyon, O., Clergeon, C. & Blain, C., \'Speckle Control with a remapped-pupil PIAA-coronagraph\', arXiv:1206.2996 (2012)\n- Martinez, P., Loose, C., Aller-Carpentier, E. & Kasper, M., \'Speckle temporal stability in XAO coronagraphic images\', A&A, 541 , A136 (2012)\n- Martinez, P., Aller-Carpentier, E., Kasper, M., et al., \'Laboratory comparison of coronagraphic concepts under dynamical seeing and high-order adaptive optics correction\', MNRAS, 414 , 2112-2124 (2011)\n- Martinez, P., Dorrer, C., Kasper, M., Boccaletti, A. & Dohlen, K., \'Design, analysis, and testing of a microdot apodizer for the apodized pupil Lyot coronagraph - III. Application to extremely large telescopes\', A&A, 520 , A110 (2010) Martinez, P., Dorrer, C., Aller-Carpentier, E., et al., \'Design, analysis, and testing of a microdot apodizer for the\n- Apodized Pupil Lyot Coronagraph\', A&A, 495 , 363-370 (2009)\n- Martinez, P., Boccaletti, A., Kasper, M., et al., \'Comparison of coronagraphs for high-contrast imaging in the context of extremely large telescopes\', A&A, 492 , 289-300 (2008)\n- Martinez, P., Boccaletti, A., Kasper, M., Baudoz, P. & Cavarroc, C., \'Optimization of apodized pupil Lyot coronagraph for ELTs\', A&A, 474 , 671-678 (2007)\n- Massey, R., Rhodes, J., Ellis, R., et al., \'Dark matter maps reveal cosmic scaffolding\', Nature, 445 , 286-290 (2007)\n- Mayor, M., & Queloz, D., \'A Jupiter-Mass Companion to a Solar-Type Star\', Nature, 378 , 355 (1995)  \n- Mazoyer, J., Baudoz, P., Galicher, R., Mas, M., Rousset, G., \'Estimation and correction of wavefront aberrations using the self-coherent camera: laboratory results\', A&A, 557 , A9 (2013)\n- Mazoyer, J., Boccaletti, A., Augereau, J.-C., et al., \'Is the HD 15115 inner disk really asymmetrical\', A&A, 569 , A29 (2014)\n- Mazoyer,  J.,  Baudoz,  P.,  Galicher,  R.  &  Rousset,  G.,  \'High-contrast  imaging  in  polychromatic  light  with  the  selfcoherent camera\', A&A, 564 , L1 (2014)\n- McDonald, I., Kerins, E., Penny, M., et al., \'ExELS: an exoplanet legacy science proposal for the ESA Euclid mission - II. Hot exoplanets and sub-stellar systems\', MNRAS, 445 , 4137 (2014)\n- Merten, J., Coe, D., Dupke, R., et al., \'Creation of cosmic structure in the complex galaxy cluster merger Abell 2744\', MNRAS, 417 , 333 (2011)\n- Minniti, D., Lucas, P.W., Emerson, J.P., et al., \'VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way\', New Astronomy, 15 , 433 (2010)\n- Miralda-Escude, J., \'Reionization of the Intergalactic Medium and the Damping Wing of the Gunn-Peterson Trough\', ApJ, 501 , 15 (1998)\n- Mordasini, C., Alibert, Y., Benz, W., Naef, D., \'Extrasolar planet population synthesis. II. Statistical comparison with observations," A&A, 501 , 1161 (2009)\n- Morley, C., Fortney, J.J., Kempton, E.M.-R., et al., \'Quantitatively Assessing the Role of Clouds in the Transmission Spectrum of GJ 1214b\', ApJ 775 , 33 (2013)\n- Muraki, Y., Han, C., Bennett, D.P., et al., \'Discovery and Mass Measurements of a Cold, 10 Earth Mass Planet and Its Host Star\', ApJ, 741 , 22 (2011)\n- Nakajima, T., \'Planet detectability by an adaptive optics stellar coronagraph\', ApJ 425 , 348 (1994)\n- Nataf, D.M, Udalski, A., Gould, A., Pinsonneault, M.H., \'OGLE-III Detection of the Anomalous Galactic Bulge Red Giant Branch Bump: Evidence of Enhanced Helium Enrichment\', ApJ, 730 , 118 (2011)\n- N\'Diaye, M., Dohlen, K., Cuevas, S., Soummer, R., Sanchez, C., \'Experimental advances in phase mask coronagraphy\', Proc. SPIE, 7739 , 77391Z (2010)\n- N\'Diaye, M., Dohlen, K., Fusco, T., et al., \'Lab results of the circular phase mask concepts for high-contrast imaging of exoplanets\', Proc. SPIE, 8450 , 84500N (2012)\n- Neistein, E., Van Den Bosch, F.C., & Deksel, A., \'Natural downsizing in hierarchical galaxy formation\', MNRAS, 372 , 933 (2006)\n- Newman, J., \'Calibrating Redshift Distributions beyond Spectroscopic Limits with Cross-Correlations\', ApJ, 684 , 88 (2008)\n- Newman, J.A., Abata, A., Abdalla, F.B., et al., \'Spectroscopic needs for imaging dark energy experiments\', APh, 63 , 81 (2015)\n- Oguri,  M.  &  Takada,  M.,  \'Combining  cluster  observables  and  stacked  weak  lensing  to  probe  dark  energy:  Selfcalibration of systematic uncertainties\', Phys. Rev. D, 83 023008 (2011)\n- Oppenheimer, R. and Hinkley, S., \'High-Contrast Observations in Optical and Infrared Astronomy\', ARAA, 47 ,  253 (2009)\n- Orsi, A., Baugh, C.M., Lacey, C.G., Cimatti, A., Wang, Y., Zamorani, G., "Probing dark energy with future redshift surveys: a comparison of emission line and broad-band selection in the near-infrared", MNRAS, 405 , 1006 (2010) Paczynski, B., Stanek, K.Z., Udalski, A.,  et  al.,  \'Are  the  OGLE  microlenses  in  the  galactic  bar?\',  ApJ, 435 ,  L113 (1994)\n- Padgett, D., Stapelfeldt, K., Leisawitz, D., Fajardo-Acosta, S., \'Herschel Observations of Debris Disks from WISE\', Proceedings of the symposium "From Atoms to Pebbles: Herschel\'s view of Star and Planet Formation\', Ed. J.-C. Augereau, Grenoble, France (2012)\n- Padmanabhan, N., Schlegel, D.J., Finkbeiner, D.P., et al., "An Improved Photometric Calibration of the Sloan Digital Sky Survey Imaging Data", ApJ, 674 , 1217 (2008)\n- Paul, B., Mugnier, L. M., Sauvage, J.-F., Ferrari, M. & Dohlen, K., \'High-order myopic coronagraphic phase diversity (COFFEE) for wave-front control in high-contrast imaging systems\', Optics Express, 21 , 31751 (2013)\n- Paul, B., Sauvage, J.-F., Mugnier, L. M., et al., \'Compensation of high-order quasi-static aberrations on SPHERE with the coronagraphic phase diversity (COFFEE)\', A&A, 572 , A32 (2014)  \n- Penny, M., \'Speeding Up Low-Mass Planetary Microlensing Simulations and Modeling: The Caustic Region of Influence\', ApJ, 790 , 142 (2014)\n- Penny, M., Kerins, E., Rattenbury, N., et al., \'ExELS: an exoplanet legacy science proposal for the ESA Euclid mission I. Cold exoplanets\', MNRAS, 434 , 2 (2013)\n- Penny, M., et al.,  \'Predictions  for  the  WFIRST  Microlensing  Survey  I:  Bound  Planet  Detection  Rates  and  Design Trades\', in prep (2015a)\n- Penny, M., et al., \'Predictions for the WFIRST Microlensing Survey II: Free Floating Planets\', in prep (2015b)\n- Penny, M., et al., \'Predictions for the WFIRST Microlensing Survey III: Planets In and Near the Habitable Zone\', in prep (2015c)\n- Perrin, M. D., Schneider, G., Duchene, G., et al., \'The Case of AB Aurigae\'s Disk in Polarized Light: Is There Truly a Gap\', ApJ, 707 , L132 (2009)\n- Petigura, E.A., Howard, A.W., Marcy, G.W., \'Prevalence of Earth-size planets orbiting Sun-like stars\', PNAS, 110 , 19273 (2013)\n- Postman, M., Coe, D., Benitez, N., et al., \'The Cluster Lensing and Supernova Survey with Hubble: An Overview\', ApJS, 199 , 25 (2012)\n- Racine, R., Walker, G.A.H., Nadeau, D., Doyon, R., Marois, C., \'Speckle Noise and the Detection of Faint Companions\', PASP, 111 , 587-594 (1999)\n- Rameau, J., Chauvin, G., Lagrange, A.-M., et al . , \'Discovery of a Probable 4-5 Jupiter-Mass Exoplanet to HD 95086 by Direct Imaging\', ApJ, 772 , L15 (2013)\n- Randall, S. W., Markevitch, M., Clowe, D., Gonzalez, A.H., Bradac, M., \'Constraints on the Self-Interaction Cross Section of Dark Matter from Numerical Simulations of the Merging Galaxy Cluster 1E 0657-56\', ApJ, 679 ,  1173 (2008)\n- Rasio, F.A. & Ford, E.B., \'Dynamical Instabilities and the Formation of Extrasolar Planetary Systems\', Science, 274 , 954 (1996)\n- Raymond, S.N., Quinn, T., Lunine, J.I., \'Making Other Earths: Dynamical Simulations of Terrestrial Planet Formation and Water Delivery\', Icarus, 168 , 1 (2004)\n- Raymond, S.N., Armitage, P.J., Gorelick, N., \'Planet-Planet Scattering in Planetesimal Disks. II. Predictions for Outer Extrasolar Planetary Systems\', ApJ, 711 , 772 (2010)\n- Raymond, S.N., Armitage, P.J., Moro-Martin, A., et  al.,  \'Debris  disks  as  signposts  of  terrestrial  planet  formation\', A&A, 530, A62 (2011)\n- Riggs, A.J.E., Zimmerman, N., Carlotti, A., Kasdin, N.J., Vanderbei, R., \'Shaped pupil design for future space telescopes\', Proc. SPIE 9143, article id. 914325 (2014)\n- Rogers, L., \'Most 1.6 Earth-Radius Planets are not Rocky\', arXiv:1407.4457 (2014)\n- Rouan, D., Riaud, P., Boccaletti, A., Clénet, Y. & Labeyrie, A., \'The Four-Quadrant Phase-Mask Coronagraph. I. Principle\', PASP, 112 , 1479-1486 (2000)\n- Rozo, E., Wechsler, R.H., Rykoff, E.S., et al., \'Cosmological Constraints from the Sloan Digital Sky Survey maxBCG Cluster Catalog\', ApJ, 708 , 645 (2010)\n- Sahu, K.C., Casertano, S., Bond, H.E., et al., \'Transiting extrasolar planetary candidates in the Galactic bulge,\' Nature, 443 , 534 (2006)\n- Saito, R. K., Hempel, M., Minniti, D., Lucas, P.W., et al., \'VVV DR1: The first data release of the Milky Way bulge and southern  plane  from  the  near-infrared  ESO  public  survey  VISTA  variables  in  the  Via  Lactea\',  A&A, 537 ,  A107 (2012)\n- Saunders, C., Aldering, G., Antilogus, P., et al., \'Type Ia Supernova Distance Modulus Bias and Dispersion from Kcorrection Errors: A Direct Measurement Using Lightcurve Fits to Observed Spectral Time Series\', ApJ, (in press), arXiv:1412.5533 (2014)\n- Savransky, D., Kasdin, N.J., and Cady, E., \'Analyzing the designs of planet finding missions\', PASP 122 , 401 (2010) Schneider, G., \'A Quick Study of Science Return from Direct Imaging Exoplanet Missions: Detection and Characteri-\n- zation of Circumstellar Material with an AFTA or EXO-C/S CGI\', arXiv:1412.8421 (2014)\n- Schneider, G., Grady, C.A., Hines, D.C., et al., \'Probing for Exoplanets Hiding in Dusty Debris Disks: Disk Imaging, Characterization, and Exploration with HST /STIS Multi-Roll Coronagraph\', AJ, 148 , 59 (2014)\n- Seager, S. (editor), \'Exoplanets\', University of Arizona Press, ISBN: 978-0816529452 (2010)  \nAppendix M: References  \n- Sidick,  E.,  Shaklan,  S.,  Krist,  J.,  Cady,  E.,  Kern,  B.,  Balasubramanian,  K.,  \'HCIT  contrast  performance  sensitivity studies: simulation versus experiment,\' Proc. SPIE 8864, 88640Q (2013)\n- Sivaramakrishnan, A., Koresko, C.D, Makidon, R.B., Berkefeld, T., Kuchner, M.J., \'Ground-based Coronagraphy with High-order Adaptive Optics\', ApJ, 552 , 397 (2001)\n- Sobral, D., Smail, I., Best, P.N., et al., "A large H α survey at z=2.23, 1.47, 0.84 and 0.40: the 11 Gyr evolution of star-forming galaxies from HiZELS", MNRAS, 428 , 1128 (2013)\n- Soummer, R., Aime, C., Falloon, P.E., \'Stellar coronagraphy with prolate apodized circular apertures\',  A&A, 397 , 1161-1172 (2003)\n- Soummer, R., Dohlen, K. & Aime, C., \'Achromatic dual-zone phase mask stellar coronagraph\', A&A, 403 , 369-381 (2003)\n- Sparks, W. B. & Ford, H. C., \'Imaging Spectroscopy for Extrasolar Planet Detection\', ApJ, 578 , 543 (2002)\n- Spergel, D. N., \'A New Pupil for Detecting Extrasolar Planets\', arXiv:astro-ph/0101142 (2001)\n- Spergel, D., Gehrels, N., Breckinridge, J., et al., \'Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA Final Report\', arXiv:1305.5422 (2013)\n- Spitzer, L., \'The Beginnings and Future of Space Astronomy\', American Scientist, 50 , 473-483 (1962).\n- Springel, V., White, S.D.M., Jenkins, A., et al., \'Simulations of the formation, evolution and clustering of galaxies and quasars\', Nature, 435 , 629 (2005)\n- Springel, V. & Farrar, G.R., \'The speed of the \'bullet\' in the merging galaxy cluster 1E0657-56\', MNRAS, 380 , 911 (2007)\n- Stam, D.M., Hovenier, J.W., & Waters, L.B.F.M., \'Using polarimetry to detect and characterize Jupiter-like extrasolar planets\', A&A, 428 , 663 (2004)\n- Stark, C.C., Roberge, A., Mandell, A., Robinson, T.D., \'Maximizing the ExoEarth Candidate Yield from a Future Direct Imaging Mission\', ApJ accepted, arXiv:1409.5128 (2014)\n- Sullivan, M., Guy, J., Conley, A., et al., \'SNLS3: Constraints on Dark Energy Combining The Supernova Legacy Survey Three-Year Data With Other Probes\', ApJ, 737 , 102 (2011)\n- Sumi, T., Kamiya, K., Bennett, D.P., et al., \'Unbound or distant planetary mass population detected by gravitational microlensing\', Nature, 473 , 349 (2011)\n- Sumi,  T.,  Bennett,  D.P.,  Bond,  I.A.,  et  al.,  \'The  Microlensing  Event  Rate  and  Optical  Depth  Toward  the  Galactic Bulge from MOA-II", ApJ, 778 , 150 (2013)\n- Thomas, D., Maraston, C., Bender, R., & Medes de Oliveira, C., \'The Epochs of Early-Type Galaxy Formation as a Function of Environment\', ApJ, 621 , 673 (2005)\n- Thompson, T., \'Gas giants in hot water: inhibiting giant planet formation and planet habitability in dense star clusters through cosmic time\', MNRAS, 431 , 63 (2013)\n- Traub,  W.A.,  Belikov,  R.,  Guyon,  O.,  et  al.,  \'Science  yield  estimation  for  AFTA  coronagraphs\', Proc.  SPIE, 9143 , 91430N (2014)\n- Trauger, J., Moody, D., Gordon, B., Krist, J., Mawet, D., \'A hybrid Lyot coronagraph for the direct imaging and spectroscopy of exoplanet systems: recent results and prospects, Proc. SPIE 8151, 81510G (2011)\n- Trauger, J., Moody, D., Gordon, B., \'Complex apodized Lyot coronagraph for exoplanet imaging with partially obscured telescope apertures\', Proc. SPIE 8864, article id. 886412 (2013)\n- Vanderbei, R. J.; Spergel, D. N.; Kasdin, N. J., \'Spiderweb Masks for High-Contrast Imaging\', ApJ, 590 , 593 (2003)\n- Vigan,  A.,  Dohlen,  K.,  Mazzanti,  S.,  \'On-sky  multiwavelength  phasing  of  segmented  telescopes  with  the  Zernike phase contrast sensor\', Applied Optics, 50 , 2708 (2011)\n- Vigan, A., Langlois, M., Moutou, C., et al., \'Final performance of SPHERE/IRDIS in laboratory\', European Planetary Science Congress 2013, London, UK, 8 , 1052 (2013)\n- Walker, A., \'Microlensed Image Motions\', ApJ, 453 , 37 (1995)\n- Wang, Y., "Robust constraints on dark energy and gravity from galaxy clustering data", MNRAS, 423 , 3631 (2012)\n- Wang, Y., Percival, W., Cimatti, A., et al., \'Designing a space-based galaxy redshift survey to probe dark energy\',\n- MNRAS, 409 , 737 (2010)\n- Wang, Y., Chuang C.-H, Hirata, C.M., \'Towards more realistic forecasting of dark energy constraints from galaxy redshift surveys\', MNRAS, 430 , 2446 (2013)  \n- Weinberg, D.H., Mortonson, M.J.,  Eisenstein,  D.J.,  Hirata,  C.M.,  Riess,  A.R.,  Rozo,  E.,  "Observational  Probes  of Cosmic Acceleration", Physics Reports, 530 , 87(2013)\n- Wirth, A., Cavaco, J., Bruno, T., Ezzo, K., \'Deformable Mirror Technologies at AOA Xinetics,\' Proc. SPIE , Vol. 8780, 87800M (2013)\n- Wyatt, M. C., \'Evolution of Debris Disks\', ARAA, 46 , 339-383 (2008)\n- Yee, J., \' WFIRST Planet Masses from Microlens Parallax\', ApJ, 770 , L31 (2013)\n- Yee, J., Albrow, M., Barry, R.K., et al., \'NASA ExoPAG Study Analysis Group 11: Preparing for the WFIRST Microlensing Survey\', arXiv:1409.2759 (2014)\n- Yoo, J. and Seljak, U., \'Joint analysis of gravitational lensing, clustering, and abundance: Toward the unification of large-scale structure analysis\', Phys. Rev. D, 86 , 083504 (2012)\n- Zhao, H., Spergel, D.N., & Rich, R.M., \'Microlensing by the galactic bar\', ApJ, 440 , L13 (1995)\n- Zheng, W., Postman, M., Zitrin A., et al., \'A magnified young galaxy from about 500 million years after the Big Bang\', Nature, 489 , 406 (2012)'}