[meteorite-list] Dawn Is 'Go' For Asteroid Belt

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 25 Sep 2007 12:42:20 -0700 (PDT)
Message-ID: <200709251942.MAA02068_at_zagami.jpl.nasa.gov>

09.25.07

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov

George Diller
Kennedy Space Center, Fla.
321-867-2468
george.h.diller at nasa.gov

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

RELEASE: 48-07

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. The Dawn
spacecraft will venture into the heart of the asteroid belt, where it
will document in exceptional detail the mammoth rocky asteroid Vesta,
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. EDT. 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 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 gravity fields of the celestial bodies.

"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 in 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 is managed by JPL for NASA's Science Mission
Directorate in 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 the 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.

For more information about Dawn, visit:

http://www.nasa.gov/dawn

For more information about NASA and agency programs on the Internet,
visit:

http://www.nasa.gov

Note to Editors: A video file with animation, b-roll and sound bites
is airing on NASA TV today.

        
-end-
Received on Tue 25 Sep 2007 03:42:20 PM PDT