It is expected that the core aperture correlation statistic will exceed the
halo aperture correlation statistic for a given TCE when the observed target
is the source of the transit signature; targets are generally well centered in
the photometric apertures. A set of 3402 “golden” KOIs was identified for
assessing the performance of the final version (SOC 9.3) of the Pipeline code
base (Twicken et al., 2016). The bulk of these well-established, high-quality
KOIs were classified by TCERT as PC (i.e., likely to represent transiting
planets on the associated target stars). The Q1–Q17 DR25 DV run produced ghost
diagnostic results for 3348 of the “golden” KOIs that were also classified (at
the time) as PC. The core aperture correlation statistic exceeded the halo
aperture correlation statistic for 3291 (98.1%) of these PC KOIs as would be
expected.

For TCEs due to broad optical ghosts (or other distributed contamination), it
is expected that the halo aperture correlation statistic will exceed the core
aperture correlation statistic because the mean flux per halo pixel is
subtracted from the mean flux per core pixel before the core statistic is
computed. It has also been observed that the halo aperture correlation
statistic may exceed the core aperture correlation statistic for astrophysical
false positive TCEs attributable to background objects (e.g., background
eclipsing binaries) that lie outside the quarterly photometric apertures
associated with the given target. We discussed other DV diagnostic tests
specifically designed to identify such cases earlier (difference imaging and
centroid offset analysis in Section 3.4 and centroid motion test in Section
3.6).

The DR25 core and halo aperture flux time series for KOI 3900.01 are folded
and displayed versus orbital phase in Fig. 26 after normalizing by the number
of pixels in the quarterly core and halo apertures, and correcting the core
values by subtracting the respective halo values cadence by cadence. The
transit model light curve is overlaid on the core and halo aperture time
series data. It is evident that the core time series is not highly correlated
with the transit model (core aperture correlation statistic = 1.33), whereas
the halo time series is highly correlated with the transit model (halo
aperture correlation statistic = 29.02). Once again, KOI 3900.01 has been
attributed to the antipodal ghost of a bright eclipsing binary.

Figure 26: Optical ghost diagnostic test result for KOI 3900. This false
positive KOI is due to the antipodal ghost reflection of a bright eclipsing
binary from the Schmidt corrector plate (Coughlin et al., 2014). Relative flux
is plotted in black versus orbital phase in hours. Binned and averaged flux
values are displayed in cyan. The transiting planet model that was fitted to
the photometric light curve is overlaid in red. The scaling is identical in
both panels. Top: optical ghost diagnostic core aperture time series. Bottom:
optical ghost diagnostic halo aperture time series.

Optical ghost diagnostic test results for some representative KOIs in the
Q1–Q17 DR25 transit search are displayed in Table 2. The core aperture
correlation statistic exceeded the halo aperture correlation statistic for the
three KOIs (157.03, 701.04, and 571.05) associated with well-known confirmed
planets (Kepler-11e, Kepler-62f, Kepler-186f). The halo aperture correlation
statistic exceeded the core correlation statistic for the KOI (3900.01)
attributable to antipodal reflection and the KOI (4718.01) attributable to
field flattener reflection of RR Lyrae (Coughlin et al., 2014). Furthermore,
the halo aperture correlation statistic exceeded the core correlation
statistic for the KOI (140.01) attributable to a background eclipsing binary
that fell at the boundary or beyond the photometric aperture of the target
star in most observing quarters.

Table 2: Q1–Q17 DR25 Optical Ghost Diagnostic Results for Representative KOIs KOI | Description | Core | Halo | Core $>$ Halo?
---|---|---|---|---
Number |  | Statistic | Statistic |
157.03 | Confirmed planet (Kepler-11e) | 61.79 | 14.21 | Y
701.04 | Confirmed planet (Kepler-62f) | 8.87 | 2.11 | Y
571.05 | Confirmed planet (Kepler-186f) | 4.54 | 1.96 | Y
3900.01 | Antipodal reflection ghost | 1.33 | 29.02 | N
4718.01 | Field flattener ghost (RR Lyrae) | 3.86 | 7.05 | N
140.01 | Background eclipsing binary | –16.40 | 117.40 | N

##  4 KOI Matching

All TCEs identified in the Kepler Pipeline transit search and fitted in DV are
(optionally) matched against the ephemerides of KOIs known at the time that DV
is executed. The KOI ephemerides are downloaded by a Pipeline operator from
the cumulative KOI table at the Exoplanet Archive at NExScI, and imported into
the Pipeline database prior to firing DV. Ephemeris matches at the target
(e.g., KOI 157) and planet (e.g., KOI 157.01) levels are reported in the DV
archive products for the benefit of the Kepler Project and science community.
KOIs that are not matched are also reported. KOI matching was enabled in DV
for the Q1–Q17 DR24 and DR25 runs. The algorithm implemented in DV for
matching ephemerides of known KOIs and Pipeline TCEs is discussed in this
section. A different matching algorithm has been employed by TCERT for
federating Pipeline TCEs with existing KOIs (Mullally et al., 2015; Coughlin
et al., 2016; Thompson et al., 2018).

We wish to emphasize that prior knowledge of KOI ephemerides is not employed
in TPS or DV to guide the transit search or data validation. DV results are
matched against KOI ephemerides strictly as a benefit to consumers of DV
products. KOI matching permits users to quickly differentiate the known from
the unknown, and to focus their efforts accordingly.

KOI matching at the target level is performed by simple comparison of integer
KIC IDs. Planet level matching of KOI and TCE ephemerides is performed by
computing correlation coefficients for rectangular transit time series
generated from the ephemerides (orbital period, epoch of first transit, and
transit duration) of each of the known KOIs associated with a given target
against similar time series generated from DV fit ephemerides for all TCEs
associated with the same target. The time series consist of transit indicators
such that each temporal in-transit sample is assigned value $=1$, while each
out-of-transit sample is assigned value $=0$. The time series are oversampled
at $\sim$5 min intervals whereas the LC data in the pipeline are sampled at
$\sim$30 min. Scaling is such that the correlation coefficient $\sim 1$ when
the in-transit samples of the KOI and TCE match exactly, and the correlation
coefficient $\sim 0$ when there is no overlap between the in-transit samples
associated with the KOI and TCE over the duration of the time series.

If $t_{1}$ and $t_{2}$ denote two rectangular transit time series, the
ephemeris matching correlation coefficient $\rho$ is computed by

$\rho=\cfrac{t_{1}\boldsymbol{\cdot}t_{2}}{\big{\|}t_{1}\big{\|}\big{\|}t_{2}\big{\|}}.$
(19)

The coefficients computed for correlations between KOIs and Pipeline TCEs are
compared against a configurable matching threshold (typically 0.75). A KOI and
TCE are determined to match if the correlation between them is greater than or
equal to the matching threshold. There are two caveats, however. First, an
ephemeris match is not reported if the correlation coefficients between one
KOI on a given target and more than one TCE on the same target exceed the
matching threshold. Second, an ephemeris match is not reported if the
correlation coefficients between one TCE on a given target and more than one
KOI on the same target exceed the matching threshold. This occurs for
duplicate KOIs, e.g. KOIs 1101.01/1101.02 and KOIs 2768.01/2768.03.

KOI and TCE ephemeris matching results for the Q1–Q17 DR25 transit search were
presented by Twicken et al. (2016). That publication focused on the matching
results for a set of 3402 “golden” KOIs on 2621 unique target stars. DV
reported an ephemeris match at the KOI matching threshold or better for 3354
of the “golden” KOIs; furthermore, 92.0% of the matches were reported with
correlation coefficient $>0.9$. The authors also stated that 40 of the 48
remaining “golden” KOIs were recovered in the transit search without producing
ephemeris matches at the specified threshold. The reasons for failure to meet
the matching threshold were varied, but are illuminating. Some ephemeris
matching failures resulted from differences between the KOI and TCE periods by
an integer factor; there were instances where the DV period appeared to be
incorrect, instances where the KOI period appeared to be incorrect, and one
instance where the true period was ambiguous due to data gaps. A number of
ephemeris matching failures occurred in systems with TTVs where there is no
true linear ephemeris. There were failures to match ephemerides of eclipsing
binaries and one heartbeat star (Kirk et al., 2016) that does not feature
conventional transits or eclipses. There were also failures to match
ephemerides of the duplicate KOIs described earlier because DV does not report
matches against duplicates by design.

The matching threshold (0.75) was selected to ensure that matches are only
reported when an actual KOI-TCE ephemeris match is highly likely. The
correlation coefficients for matches against well-established, high-quality
KOIs are typically well above 0.75 as evidenced earlier, so the chosen
threshold leaves some margin for low-level discrepancies between respective
KOI and TCE ephemerides. The matching threshold does not generally permit
matches to be declared when KOI and TCE orbital periods differ by integer
factors. This can occur in the Pipeline, for example, when secondary events
associated with circular eclipsing binaries are folded onto primary events (as
discussed in Section 3.3); the KOI may have been assigned the correct
eclipsing binary orbital period which would be twice the period reported by
DV. The correlation coefficient in cases where the orbital periods differ by
an integer factor N is generally on the order of $1/\sqrt{N}$; this is less
than the matching threshold employed in the Pipeline for all $N>1$.
Differences in the respective KOI and TCE epochs of “first” transit by an
integer number of orbital periods have no effect on the computation of the
correlation coefficient.

It should be noted that Kepler Names are also reported at the target and
planet levels (e.g., KOI 157 = Kepler-11 and KOI 157.01 = Kepler-11c) in the
DV archive products for matches against KOIs associated with confirmed
planets. A Kepler Names file for associating confirmed planets with known KOIs
is downloaded from the Kepler Names table at the Exoplanet Archive and
imported into the Pipeline database prior to firing DV. The Kepler Names
reported in the DV archive products of course apply only to planets confirmed
at the time that DV is executed.

##  5 Archive Products

Archive products are generated for export to the community at large that
summarize the information that is provided to DV and the results of the
transiting planet model fits and diagnostic tests within DV. We reiterate that
the design specification of DV was not to determine the likelihood that a
particular TCE represents a legitimate transiting planet; rather the design
goals of DV were to characterize each TCE and perform a uniform set of
diagnostic tests to enable consumers of DV products to vet the TCEs and assess
the candidate planets. The DV products can only be briefly summarized here.
Space does not permit a complete description of all aspects of these products.
It should be noted that the DV products evolved with each release of the
Kepler Pipeline code base. The descriptions provided apply to SOC 9.3 which
was employed for the final Q1–Q17 transit search (DR25).

Four types of DV archive products are generated. Comprehensive DV Reports are
produced in PDF format for each target with at least one TCE; the DV Report is
summarized in Section 5.1. One-page DV Report Summaries are produced in PDF
format for each TCE; the Report Summary is summarized in Section 5.2. DV Time
Series files are produced in FITS format for each target with at least one
TCE; this product is summarized in Section 5.3. Reports, Report Summaries, and
Time Series files are exported to the NASA Exoplanet Archive (see Section 2)
where they are available to the science community and general public. Finally,
a single XML file is produced which contains the tabulated results for all
targets in a given DV run. The XML file is used to populate tables at the
Exoplanet Archive. Although it is a text file, it is not considered to be
human readable and will not be discussed further in this publication.

###  5.1 DV Report

A comprehensive DV Report is produced in PDF format for each target with a
least one TCE in a given Pipeline run. The Reports are automatically generated
with LaTeX and delivered to the NASA Exoplanet Archive at NExScI where they
are accessible by the science community and general public. The DV Report is
organized into logical sections; these will be summarized below. The PDF files
include tabs for sections and sub-sections to allow users to quickly locate
specific DV results for a given target. The DV Report evolved significantly
over the course of the Kepler Mission.

####  5.1.1 Summary

Following a cover page and table of contents, the DV Report begins with a
summary. This may be considered an executive summary; if a user only wants the
basic DV results for a given target it may not be necessary to delve any
further than this.

The summary includes tables with target properties, data characteristics, and
planet candidate properties. The target properties represent the stellar
parameters (and associated uncertainties) that are provided to DV: magnitude,
celestial coordinates, radius, effective temperature, surface gravity, and
metallicity. A provenance string is included for each stellar parameter to
inform users about the source of the information. Keys to the provenance
strings are published separately.

The data characteristics table includes one entry for each quarter in which
the given target was observed. For each quarter, the table specifies the
quarter, the CCD module output, the crowding metric and flux fraction in
aperture employed to correct the light curve in PDC (Twicken et al., 2010b;
Stumpe et al., 2012), and the limb darkening coefficients determined from the
stellar parameters. DV was designed to accommodate quarter (and hence module
output) specific limb darkening coefficients, but this functionality was never
deemed sufficiently necessary to implement in the Pipeline. Hence, the target-
specific limb darkening coefficients do not change on a quarterly basis.

The planet candidate characteristics table includes one entry for each TCE
associated with the given target. The table specifies period, epoch, semimajor
axis, planet radius, and equilibrium temperature for each DV candidate, along
with a flag to indicate whether or not DV suspected the candidate to be an
eclipsing binary (based on transit depth alone, typically 250,000 ppm) and
therefore omitted the transit model fits which do not implement an eclipsing
binary model.

DV was updated in SOC 9.2 to include KOI numbers and Kepler Names (for
confirmed planets) where applicable in the target and planet properties
tables. Matches at the target level are determined by KIC ID; matches at the
planet level are determined by correlating KOI and DV model fit ephemerides as
described in Section 4. We emphasize that the KOI and Kepler Name information
displayed in the DV archive products pertain to known KOIs at the time that DV
was executed; new KOIs identified from the TPS/DV results of a given run will
not be marked as such in the archive products produced for that particular
run. We also note that the Pipeline and the matching process at the planet
level are not perfect. The summary includes a list of planet-level KOIs that
could not be matched successfully against the DV results for the given target.

####  5.1.2 UKIRT Images

The celestial context in the vicinity of the target star can be invaluable for
digesting and interpreting the DV diagnostics that attempt to establish the
location of the transit source with respect to the target. To that end, we
have downloaded images from the UKIRT Wide Field Camera (WFCAM) J-band survey
(Casali et al., 2007) for nearly every target that has appeared on a Kepler
target list. For each target, the image displayed in the DV Report covers a
region approximately one arcmin square. Difference image centroid offsets and
centroid motion test source offsets are also displayed on UKIRT images for the
associated target stars. Right ascension and declination grid lines are
overlaid on the UKIRT images. We were unable to obtain images for all Kepler
targets due to lack of coverage in the survey data.

####  5.1.3 Flux Time Series

The quarter-stitched PDC (i.e., systematic error corrected) light curve is
displayed with markers to indicate the transit times of the various candidates
associated with the given target. This is the light curve that is first
subjected to the transiting planet search. The light curve is segmented by
quarter, and each quarter is displayed separately with a vertical offset for
clarity. As part of the quarter-stitching process, the quarterly segments are
normalized and strong harmonic content is removed. Gaps are filled in the
quarter-stitching process, but gap filled data are not displayed in this
section. Gaps for monthly data downlinks and spacecraft safe modes are clearly
visible in these figures. The figures are particularly valuable diagnostic
tools for TCEs based on relatively few transits. The detection is suspect if
the transit markers in such cases overlay uncorrected or partially corrected
SPSDs or spacecraft attitude adjustments, fall on the boundaries of data gaps,
or occur during particularly noisy data segments.

The quarterly PA (i.e., SAP) light curves are also shown in this section. This
is a valuable diagnostic tool because the data are displayed prior to
systematic error correction in PDC and quarter-stitching in TPS/DV. Gross
discrepancies between the PA and quarter-stitched PDC light curves may imply
that post-PA processing has been off-nominal for the given target. For
example, short period transit signatures may be inadvertently degraded in some
or all quarters in the harmonics identification and removal function of the
quarter-stitching algorithm (Christiansen et al., 2013, 2015). It is a red
flag if transits are clearly visible in the PA SAP light curve, but are not
present in the quarter-stitched PDC light curve. The error corrected and
quarter-stitched light curve in question has been distorted in a well-
intentioned attempt to improve sensitivity to the most valued planets in the
Kepler Mission, i.e., small planets orbiting in the HZ of Sun-like stars.
Christiansen et al. (2015) measured the degradation in Pipeline sensitivity to
short-period transit signatures as a function of orbital period. The reduction
in completeness at short periods due to harmonics identification and removal
must be accounted for in determination of occurrence rates.

####  5.1.4 Dashboards

There is one dashboard figure for each planet candidate associated with the
given target. The dashboards summarize the model fit and selected DV
diagnostic test results. Each region on the dashboard figure is color coded;
the caption on the dashboard fully explains the coding. In general, nominal
results are displayed in green, borderline results in yellow, and results that
may call the planetary nature of any TCE into question are displayed in red.
The regions are colored blue when results are unavailable.

The dashboard provides a means to view DV results at a glance and focus
quickly on issues pertaining to any given candidate. It must be emphasized,
however, that if a region is colored red the candidate may still be planetary
in nature. We discussed in Section 3.3 that short period planets with
detectable occultations may trigger the eclipsing binary discrimination test
for equal periods. We also discussed in Section 3.6 that there may be
significant centroid motion during transit for targets with transiting planets
in crowded fields. In neither of these cases does red coloring invalidate the
planetary nature of the candidate.

####  5.1.5 Centroid Cloud Plot

The change in flux is displayed versus change in right ascension (blue) and
declination (red) centroid coordinates. The flux and respective centroid time
series are unwhitened and median detrended. In-transit centroid motion
manifests itself as a deviation from the vertical below the out-of-transit
jitter cloud. The centroid cloud plot is a course representation of the motion
detection statistic and peak in-transit centroid shift discussed in Section
3.6 in regard to the centroid motion diagnostic test. If correlated centroid
motion is present in the centroid cloud plot then its presence is
incontrovertible. Significant centroid motion may still be present, however,
if correlated centroid motion is not visible in the centroid cloud plot.

####  5.1.6 Image Artifacts

The rolling band contamination diagnostic (see Section 3.2) results are
displayed in a table for each DV planet candidate. The table indicates the
number of transits (and fraction of total) that are coincident with rolling
band image artifacts at each of the defined severity levels (see Table 1). As
discussed earlier, the severity levels range from 0 (low) to 4 (high). The
reliability of a TCE is questionable if a significant fraction of the total
number of transits are coincident with severity levels $>0$, particularly for
long-period TCEs with relatively few transits. Individual transits with non-
zero severity levels are highlighted in a panel on the one-page DV Report
Summary, and the fraction of good transits with severity level $=0$ is
indicated.

####  5.1.7 Pixel Level Diagnostics

Pixel level diagnostic test results are displayed separately for each planet
candidate associated with the given target. The difference image summary
quality metrics (see Section 3.4.1) are presented in a table; the table
includes the correlation threshold that defines the cutoff between good and
bad quality difference images. The difference image centroid offsets discussed
in Section 3.4.2 are displayed in both graphical and tabular form. Offsets are
displayed with respect to the out-of-transit centroid and with respect to the
KIC position of the target. Robust mean results are also displayed for all
TCEs. The value of the error term that is added in quadrature to the robust
mean offsets is included in the figure captions. The offsets are also overlaid
on the UKIRT image associated with the given target if such an image is
available.

The difference images discussed in Section 3.4.1 are displayed quarter by
quarter. The caption for each difference image includes the value of the
quality metric for the given quarter. The caption also indicates the number of
transits and valid cadences that were used to compute the difference image for
the given quarter, and the number of in- and out-of-transit cadence gaps.
Quarterly PRF centroid results and centroid offsets are tabulated for the
focal plane (in units of pixels) and the sky (in units of arcsec). Nearby
catalog objects are marked on the respective difference images, as are the
image centroids and target KIC position.

####  5.1.8 Phased Light Curves

Full phase-folded light curves are displayed in both unwhitened and whitened
domains for each of the planet candidates associated with the given target.
Colored event triangles below each figure mark the phase of the transits
associated with all of the TCEs for the target. The phased light curves are
particularly useful in multiple TCE systems to study the phase relationships
between the candidates. This applies to multiple planet systems which may have
resonant relationships between candidates and to binary systems where primary
and secondary eclipses have a common period but different phase. The phased
light curves can also highlight false detections in multiple planet systems
due to image artifacts where “transits” of multiple candidates are observed on
the same module output(s). The long orbital periods are not identical, but
similar; in these cases the event triangles for the false detections share a
common region of phase space and appear in clusters.

Beginning with SOC 9.2, median detrending is applied to the unwhitened data
prior to phase folding. In earlier code releases, the unwhitened data were not
detrended prior to phase folding. In the SOC 9.3 release, phase-folded light
curves by quarter, by observing season151515Kepler observing seasons are
denoted by S0, S1, S2, S3. Each season corresponds to a specific photometer
roll orientation. As discussed earlier, the photometer was rolled by
90$\arcdeg$ between quarters in order to maintain illumination of the solar
panels., and by year are also displayed for each planet candidate. These
phase-folded light curves are derived from median detrended, unwhitened data.

####  5.1.9 Planet Candidate Results

The bulk of the transit model fit and diagnostic test results are presented in
a section of the DV Report dedicated to each planet candidate. Each section
begins with tables containing the TCE parameters for the given candidate and
the results of the model fit to all transits. Fit results include parameter
values and associated uncertainties. The quarter-stitched PDC light curve for
the given candidate is displayed in quarterly segments with markers
highlighting the transit events. This differs from the quarter-stitched PDC
light curve described in Section 5.1.3 in that transits for all DV candidates
prior to the given one have been removed. Essentially, the light curve
displayed here is the one in which the transiting planet detection was made
for the given candidate in TPS.

Diagnostic figures illustrating the phase-folded flux time series data in the
unwhitened and whitened domains are presented. The whitened transit model is
overlaid on the phase folded data in the whitened domain. Colored markers
differentiate between the data points that were included and emphasized in the
robust model fit and those that were deemphasized or otherwise ignored.
Reduced parameter fit results are displayed graphically and in tabular form as
a function of impact parameter. The quality of the fit results are often only
weakly dependent on impact parameter; the reduced parameter fits may therefore
represent a family of equally valid results for the given planet candidate.
This information is useful to the community because it clarifies that in many
cases the planet characteristics are not uniquely determined by transit model
fitting in the Pipeline. Robust transiting planet model fitting and reduced
parameter model fitting were summarized in Section 2.

Weak secondary test results are displayed both graphically and in tabular
form. The weak secondary test was described in Section 3.1. The centroid
motion test results (see Section 3.6), eclipsing binary discrimination test
results (see Section 3.3), statistical bootstrap test results (see Section
3.5), and optical ghost diagnostic test results (see Section 3.7) are
displayed in separate tables. Centroid motion test results are derived from
flux-weighted centroids that are computed in PA for all targets and cadences.
Finally, a series of diagnostic figures are displayed illustrating flux-
weighted centroid motion for the given candidate. Detrended phase-folded flux
and centroid time series are shown first, followed by figures that mark the
transit times on the respective quarterly flux and centroid time series.

####  5.1.10 Appendices

Appendices to the DV Report contain valuable diagnostic information despite
the fact that they are not displayed in the main body of the document. The
robust weights for the transit model fit to all transits for each candidate
associated with the given target are displayed as a time series and also with
folded phase. Issues with the robust transit model fit may be highlighted by
irregularities in the figures. Histograms of fit residuals for constraint
points and all valid data points are also displayed with Gaussian overlays.

Results of the model fits to the sequences of odd and even transits are
displayed for each candidate in tabular form. These support the eclipsing
binary discrimination tests discussed in Section 3.3. Of particular interest
are the transit depths and associated uncertainties for the odd and even
transit fits. The difference in the fitted depths for the odd and even
transits divided by the uncertainty in the difference essentially determines
the significance of the odd/even depth comparison test.

Diagnostic figures illustrating the phase folded flux time series data in both
unwhitened and whitened domains are presented for the odd and even transit
model fits for each candidate. As before, the whitened transit model is
overlaid on the phase folded data in the whitened domain. Colored markers
differentiate between the data points that were emphasized in the respective
robust model fits and those that were deemphasized or otherwise ignored.

####  5.1.11 Alerts

Alerts are generated at run time in DV (and other Pipeline components) to flag
off-nominal conditions. Pipeline alerts are categorized as either Warnings or
Errors. The alerts issued by DV largely flag Warning conditions only. An alert
consists of a time stamp, severity (i.e., “warning” or “error”) state, and
message string. DV alert message strings include the KIC ID of the target, the
index of the planet candidate where applicable, and the name of the DV sub-
component in which the alert was raised. The alerts were originally
implemented to support the operation and maintenance of the Pipeline, but it
was decided to include the alerts in the DV Report as a service to the user
community. The quantity or character of the alerts associated with a given TCE
should not, however, impact directly on the assessment of its planetary
nature.

###  5.2 DV Report Summary

A one-page Report Summary is produced in PDF format for each TCE identified in
the transit search. The Report Summary includes useful diagnostic figures and
tabulated model fit and diagnostic test results. The one-page summary was
first introduced in the SOC 8.2 code base; it has proven to be extremely
beneficial for assessing the character of DV planet candidates. The TCERT
vetting process was summarized in Section 1.3. Following its introduction, the
Report Summary served as the basis for the TCERT triage process to identify
Pipeline TCEs worthy of promotion to KOI status. The Report Summary was also
employed by TCERT along with other vetting products for KOI classification (as
PC or FP). Use of the one-page summary in manual TCERT vetting activities and
Kepler catalog generation was described by Burke et al. (2014); Rowe et al.
(2015), and Mullally et al. (2015).

The detrended, quarter-stitched light curve in which the TCE was identified by
TPS is displayed in one panel; quarter boundaries and transit events are
marked. The same light curve is displayed after phase folding in a second
panel; the transit model is overlaid on the full phase folded light curve. Two
additional panels display the phase folded light curve with reduced abscissa
ranges centered on the primary transit and strongest secondary eclipse
respectively. The phase folded light curve, transit model, and fit residuals
are displayed in one panel in the whitened domain where the limb-darkened
transiting planet model fit is performed. The detrended, phase folded odd and
even transit signals are displayed side by side for comparison in one panel;
the derived transit depth and associated uncertainties are marked in each
case. A final panel displays the quarterly centroid offsets with respect to
the out-of-transit centroid, and the robust mean offsets over all quarters.

DV model fit results are tabulated in a text box. These include both fitted
and derived transiting planet model parameters, and the secondary event model
parameters described in Section 3.1. Uncertainties are displayed for all
parameters. Selected DV diagnostic test results are also tabulated in the text
box; the significance is displayed for test results where applicable.
Diagnostic test results are highlighted in red if they are statistically
inconsistent with a planetary classification for the given TCE.

Stellar parameters for the target star and KOI matching results for target and
TCE (where applicable) are also displayed on the one-page summary. Stellar
parameters are highlighted in red if Solar values were assumed in DV because
KIC values or overrides were unavailable. Finally, the date/time on which the
one-page summary was generated and the name of the SOC code branch employed to
run DV are displayed at the bottom.

A useful guide to the version of the Report Summary generated for the Q1–Q17
DR25 TCEs was produced by the Kepler Project, and is hosted at the Exoplanet
Archive.161616http://exoplanetarchive.ipac.caltech.edu/docs/DVOnePageSummaryPageCompanion-
dr25-V7.html This guide provides detailed explanations of all DV Report
Summary content; the case study is the DR25 Report Summary for Kepler-186f.

###  5.3 DV Time Series

A DV Time Series file in FITS format is generated for each LC target with at
least one TCE by the AR component of the Kepler Pipeline. The file includes
time series data relevant to the processing of each given target in TPS/DV and
all associated TCEs. The DV Time Series file was enhanced extensively in SOC
9.3. The Time Series file content applicable to the Q1–Q17 DR25 transit search
was documented by Thompson (2016b); this Kepler Mission document is hosted at
the Exoplanet
Archive.171717http://exoplanetarchive.ipac.caltech.edu/docs/DVTimeSeries-
Description.pdf

##  6 Conclusion

Data Validation (DV) is the final component of the Kepler Science Data
Processing Pipeline. All target stars for which a Threshold Crossing Event
(TCE) is generated in the Transiting Planet Search (TPS) component of the
Pipeline are processed in DV. The primary tasks of DV are to characterize
transiting planet candidates identified in the Pipeline transit search, to
search for additional planets after transit signatures are modeled and removed
from target light curves, and to perform a comprehensive suite of diagnostic
tests to aid in human and automated vetting of transiting planet candidates
identified in the Pipeline. We have described the architecture of the DV
component of the Pipeline, the suite of DV diagnostic tests, and the data
products produced by DV for vetting Pipeline transiting planet candidates. We
have focused the discussion on the final revision of the DV code base (SOC
9.3); the source files associated with the final code base have been released
through GitHub for the benefit of the community. We have also discussed how DV
is run on the Pleiades computing cluster of the NASA Advanced Supercomputing
(NAS) Division. Characterization of Pipeline planet candidates in DV and the
search for multiple transiting planet signatures on individual target stars
are described in a companion paper (Li et al., 2018). The final DV code base
was employed for the DR25 processing of the four-year primary Kepler Mission
data set (Q1–Q17). DV archive products for 17,230 long-cadence target stars
and 34,032 individual TCEs were generated for the DR25 transit search and
delivered to the Exoplanet Archive at the NASA Exoplanet Science Institute
(NExScI). The transit search results were documented by Twicken et al. (2016);
the DR25 planet catalog has been published by Thompson et al. (2018).

Kepler was competitively selected as the 10th NASA Discovery mission. Funding
for this mission is provided by the NASA Science Mission Directorate. The
authors gratefully acknowledge the contributions of the greater Kepler team in
building and operating the instrument, collecting and distributing the science
data, producing the light curves and validation products discussed in this
publication, and archiving the results. The light curves and validation
products were generated by the Kepler Science Data Processing Pipeline through
the efforts of the Kepler Science Operations Center and Science Office. The
Kepler Mission is led by the project office at NASA Ames Research Center. Ball
Aerospace built the Kepler photometer and spacecraft, which is operated by the
Mission Operations Center at LASP. The light curves are archived at the
Mikulski Archive for Space Telescopes; the Data Validation products are
archived at the NASA Exoplanet Archive. The authors also gratefully
acknowledge the support of the NASA Advanced Supercomputing (NAS) Division
within the Science Mission Directorate; the Kepler Science Data Processing
Pipeline is run on NAS Pleiades hardware. The authors finally wish to
acknowledge the years of effort of William J. Borucki and the late David G.
Koch. The Kepler Mission would not have been possible without them.
Facilities: Kepler

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