Dawn Glides Into New Year

DC Agle 818-393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle@jpl.nasa.gov

Dawn Glides Into New Year Nov. 20, 2008

JPL's Dawn spacecraft shut down its ion propulsion system today as scheduled.
The spacecraft is now gliding toward a Mars flyby in February of next year.

"Dawn has completed the thrusting it needs to use Mars for a gravity assist to
help get us to Vesta," said Marc Rayman, Dawn's chief engineer, of NASA's Jet
Propulsion Laboratory, Pasadena, Calif. "Dawn will now coast in its orbit around
the sun for the next half a year before we again fire up the ion propulsion system
to continue our journey to the asteroid belt."

Dawn's ion engines may get a short workout next January to provide any final
orbital adjustments prior to its encounter with the Red Planet. Ions are also
scheduled to fly out of the propulsion system during some systems testing in
spring. But mostly, Dawn's three ion engines will remain silent until June, when
they will again speed Dawn toward its first appointment, with asteroid Vesta.

Dawn's ion engines are vital to the success of the misson's 8-year, 4.9-billion-
kilometer (3-billion-mile) journey to asteroid Vesta and dwarf planet Ceres. One
of these extremely frugal powerhouses can generate more than 24 hours of
thrusting while consuming about .26 kilograms (about 9 ounces) of the
spacecraft's xenon fuel supply -- less than the contents of a can of soda. Over
their lifetime, Dawn's three ion propulsion engines will fire cumulatively for about
50,000 hours (over five years) -- a record for spacecraft.

Dawn will begin its exploration of asteroid Vesta in 2011 and the dwarf planet
Ceres in 2015. These two icons of the asteroid belt have been witness to so
much of our solar system's history. 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 shape, surface
topography, tectonic history, elemental and mineral composition, and will seek
out water-bearing minerals. In addition, the Dawn spacecraft itself and how it
orbits both Vesta and Ceres will be used to measure the celestial bodies' masses
and gravity fields.

The Dawn mission to asteroid Vesta and dwarf planet Ceres is managed and
operated by JPL for NASA's Science Mission Directorate, Washington, D.C. The
University of California, Los Angeles, is responsible for overall Dawn mission
science. Other scientific partners include: Max Planck Institute for Solar System
Research, Katlenburg, Germany; DLR Institute for Planetary Research, Berlin,
Germany; Italian National Institute for Astrophysics, Rome; and the Italian Space
Agency. Orbital Sciences Corporation of Dulles, Virginia, designed and built the
Dawn spacecraft.

Additional information about Dawn is online at http://www.nasa.gov/dawn and
http://dawn.jpl.nasa.gov.

-end-

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