[ExI] NASA Spacecraft is a 'Go' for Asteroid Belt

[Amara Graps]

Here is the final news release. I will be out of Internet range
Thursday through Sunday (no, not in Florida), so if you are
interested in this launch, I suggest to pay attention to the
following. You can catch it on NASA TV (over the Internet too).

Presently the launch dates/times are:

Launch Date: Sept. 27
Launch Window:
7:20 a.m. - 7:49 a.m. EDT

Go here for the Dawn coverage at Kennedy / Cape Canaveral:
http://www.nasa.gov/mission_pages/dawn/main/index.html

NASA TV channel specification
http://www.nasa.gov/multimedia/nasatv/digital.html

latest preparation pictures:
http://mediaarchive.ksc.nasa.gov/search.cfm?cat=173

Some background science here:
http://www.scientificblogging.com/amaragraps/dawns_early_light_ceres_and_vesta

==================================================================

DC Agle/Jane Platt 818-393-9011/818-354-0880
Jet Propulsion Laboratory, Pasadena, Calif.
David.c.agle at jpl.nasa.gov/jane.platt at jpl.nasa.gov


Tabatha Thompson/Dwayne Brown 202-358-3895/1726
NASA Headquarters, Washington
Tabatha.Thompson-1 at nasa.gov/dwayne.c.brown at nasa.gov


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



NEWS RELEASE: 2007-108                               September 25, 2007


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,
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 at
<http://www.kintera.org/TR.asp?a=evKSK7PRJnIYLkK&s=ouK2JfNRIfKYI8OWF&m=
hkLQIbPRIbI2G>http://www.nasa.gov/dawn
or <http://www.kintera.org/TR.asp?a=arJKLVOBJjKSLaI&s=ouK2JfNRIfKYI8OWF&
m=hkLQIbPRIbI2G>http://dawn.jpl.nasa.gov .  For more information about
NASA and agency programs on the Internet,
visit <http://www.kintera.org/TR.asp?a=arKKJVOBIkLVIcI&s=
ouK2JfNRIfKYI8OWF&m=hkLQIbPRIbI2G>http://www.nasa.gov .



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-- 

Amara Graps, PhD      www.amara.com
Associate Research Scientist, Planetary Science Institute (PSI), Tucson
INAF Istituto di Fisica dello Spazio Interplanetario (IFSI), Roma, Italia