NASA Spacecraft Is a 'Go' for Asteroid Belt
CAPE CANAVERAL, Fla. -- Launch and flight teams are in final preparations for the 
planned Sept. 27 liftoff from Pad 17-B at Cape Canaveral Air Force Station, Fla., of 
NASA's Dawn mission.
CAPE CANAVERAL, Fla. -- Launch and flight teams are in final preparations for the 
planned Sept. 27 liftoff from Pad 17-B at Cape Canaveral Air Force Station, Fla., of 
NASA's Dawn mission. The Dawn spacecraft will venture into the heart of the asteroid 
belt, where it will document in exceptional detail the mammoth rocky asteroid Vesta, and 
then, the even bigger icy dwarf planet Ceres."If you live in the Bahamas this is one time you can tell your neighbor, with a straight 
face, that Dawn will rise in the west," said Dawn Project Manager Keyur Patel of NASA's 
Jet Propulsion Laboratory in Pasadena, Calif. "Weather permitting, we are go for launch 
Thursday morning -- a little after dawn."Dawn's Sept. 27 launch window is 7:20 to 7:49 a.m. Eastern Daylight Time (4:20 to 4:49 
a.m. Pacific Daylight Time).  At the moment of liftoff, the Delta II's first-stage main 
engine along with six of its nine solid-fuel boosters will ignite. The remaining three solids 
are ignited in flight following the burnout of the first six. The first-stage main engine will 
burn for 4.4 minutes. The second stage will deposit Dawn in a 185-kilometer-high (100-
nautical-mile) circular parking orbit in just under nine minutes. At about 56 minutes after 
launch, the rocket's third and final stage will ignite for approximately 87 seconds. When 
the third stage burns out, actuators and push-off springs on the launch vehicle will 
separate the spacecraft from the third stage."After separation, the spacecraft will go through an automatic activating sequence, 
including stabilizing the spacecraft, activating flight systems and deploying Dawn's two 
massive solar arrays," said Patel. "Then and only then will the spacecraft energize its 
transmitter and contact Earth. We expect acquisition of signal to occur anywhere from 
one-and-a-half hours to three-and-a-half hours after launch."The Dawn mission will explore Vesta, and later Ceres, because these two asteroid belt 
behemoths have been witness to so much of our solar system's history."Visiting both Vesta and Ceres enables a study in extraterrestrial contrasts," said Dawn 
Principal Investigator Christopher Russell of the University of California, Los Angeles. 
"One is rocky and is representative of the building blocks that constructed the planets of 
the inner solar system. The other may very well be icy and represents the outer planets. 
Yet, these two very diverse bodies reside in essentially the same neighborhood. It is one of 
the mysteries Dawn hopes to solve."Using the same spacecraft to reconnoiter two different celestial targets makes more than 
fiscal sense. It makes scientific sense. By utilizing the same set of instruments at two 
separate destinations, scientists can more accurately formulate comparisons and contrasts. 
Dawn's science instrument suite will measure mass, shape, surface topography and 
tectonic history, elemental and mineral composition, as well as seek out water-bearing 
minerals. In addition, the Dawn spacecraft itself and the way it orbits both Vesta and 
Ceres will be used to measure the celestial bodies' gravity fields."Understanding conditions that lead to the formation of planets is a goal of NASA's 
mission of exploration," said David Lindstrom, Dawn program scientist at NASA 
Headquarters, Washington. "The science returned from Vesta and Ceres could unlock 
many of the mysteries of the formation of the rocky planets including Earth."Before all this celestial mystery unlocking can occur, Dawn has to reach the asteroid belt 
and its first target - Vesta. This is a four-year process that begins with launch and 
continues with the firing of three of the most efficient engines in NASA's space motor 
inventory - ion propulsion engines. Employing a complex commingling of solar-derived 
electric power and xenon gas, these frugal powerhouses must fire for months at a time to 
propel as well as steer Dawn.  Over their eight-year, almost 4-billion-mile lifetime, these 
three ion propulsion engines will fire cumulatively for about 50,000 hours (over five 
years) - a record for spacecraft.The Dawn mission to asteroid Vesta and dwarf planet Ceres is managed by JPL, for 
NASA's Science Mission Directorate, Washington, D.C. JPL is a division of the 
California Institute of Technology in Pasadena.  The University of California, Los 
Angeles, is responsible for overall Dawn mission science. Other scientific partners 
include: Los Alamos National Laboratory, New Mexico; Max Planck Institute for Solar 
System Research, Katlenburg, Germany; and Italian National Institute of Astrophysics, 
Rome. Orbital Sciences Corporation of Dulles, Va., designed and built the Dawn 
spacecraft.Additional information about Dawn is online athttp://www.nasa.gov/dawnorhttp://dawn.jpl.nasa.gov.  For more information about NASA and agency programs on the 
Internet, visithttp://www.nasa.gov.Note to Editors:  A video file with animation, b-roll and sound bites is airing on 
NASA TV today.