NASA Dawn Spacecraft Prepares for Trek Toward Dwarf Planet

Aug. 30, 2012

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

Jia-Rui C. Cook
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0850
jia-rui.c.cook@jpl.nasa.gov

RELEASE: 12-303

NASA DAWN SPACECRAFT PREPARES FOR TREK TOWARD DWARF PLANET

WASHINGTON -- NASA's Dawn spacecraft is on track to become the first
probe to orbit and study two distant destinations to help scientists
answer questions about the formation of our solar system. The
spacecraft is scheduled to leave the giant asteroid Vesta on Sept. 5
EDT (Sept. 4 PDT) to start its 2 1/2-year journey to the dwarf planet
Ceres.

Dawn began its 3-billion-mile odyssey to explore the two most massive
objects in the main asteroid belt in 2007. Dawn arrived at Vesta in
July 2011 and will reach Ceres in early 2015. These two members of
the asteroid belt have been witness to much of our solar system's
history.

The valuable evidence Dawn gathered from examining the first of these
cosmic fossils up close improved our understanding of asteroids and
provided context for a future human mission to visit an asteroid.

The spacecraft will spiral away from Vesta as gently as it arrived,
using a special, hyper-efficient system called ion propulsion. The
ion propulsion system uses electricity to ionize xenon to generate
thrust. The 12-inch-wide ion thrusters provide less power than
conventional engines but can maintain thrust for months at a time.

"Thrust is engaged and we now are climbing away from Vesta atop a
blue-green pillar of xenon ions," said Marc Rayman, Dawn's chief
engineer and mission director, at NASA's Jet Propulsion Laboratory
(JPL) in Pasadena, Calif. "We are feeling somewhat wistful about
concluding a fantastically productive and exciting exploration of
Vesta, but now we have our sights set on dwarf planet Ceres."

Dawn provided close-up views of Vesta and unprecedented detail about
the giant asteroid. Findings revealed that the asteroid had
completely melted in the past, forming a layered body with an iron
core. The spacecraft also revealed the collisions Vesta suffered in
its southern hemisphere. The asteroid survived two colossal impacts
in the last 2 billion years. Without Dawn, scientists would not have
known about the dramatic troughs sculpted around Vesta, which are
ripples from the two south polar impacts.

"We went to Vesta to fill in the blanks of our knowledge about the
early history of our solar system," said Christopher Russell, Dawn's
principal investigator, based at the University of California, Los
Angeles (UCLA). "Dawn has filled in those pages and more, revealing
to us how special Vesta is as a survivor from the earliest days of
the solar system. We now can say with certainty that Vesta resembles
a small planet more closely than a typical asteroid."

JPL manages the mission to Vesta and Ceres for NASA's Science Mission
Directorate in Washington. Dawn is a project of the directorate's
Discovery Program, which is managed by NASA's Marshall Space Flight
Center in Huntsville, Ala.

UCLA is responsible for the overall Dawn mission science. Orbital
Sciences Corp. of Dulles, Va., designed and built the spacecraft. The
German Aerospace Center, the Max Planck Institute for Solar System
Research, the Italian Space Agency and the Italian National
Astrophysical Institute are part of the mission's team.

For information about the Dawn mission, visit:

http://www.nasa.gov/dawn

and

http://dawn.jpl.nasa.gov


-end-



To subscribe to the list, send a message to:
hqnews-subscribe@mediaservices.nasa.gov
To remove your address from the list, send a message to:
hqnews-unsubscribe@mediaservices.nasa.gov