NASA Dawn Spacecraft Returns Close-Up Image of Asteroid Vesta

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Dwayne C. Brown 202-358-1726
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News release: 2011-213 July 18, 2011

NASA Dawn Spacecraft Returns Close-Up Image of Asteroid Vesta

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2011-213&cid=release_2011-213

PASADENA, Calif. -- NASA's Dawn spacecraft has returned the first close-up image after beginning
its orbit around the giant asteroid Vesta. On Friday, July 15, Dawn became the first probe to enter
orbit around an object in the main asteroid belt between Mars and Jupiter.

The image taken for navigation purposes shows Vesta in greater detail than ever before. When Vesta
captured Dawn into its orbit, there were approximately 9,900 miles (16,000 kilometers) between the
spacecraft and asteroid. Engineers estimate the orbit capture took place at 10 p.m. PDT Friday, July
15 (1 a.m. EDT Saturday, July 16).

Vesta is 330 miles (530 kilometers) in diameter and the second most massive object in the asteroid
belt. Ground- and space-based telescopes have obtained images of Vesta for about two centuries, but
they have not been able to see much detail on its surface.
"We are beginning the study of arguably the oldest extant primordial surface in the solar system,"
said Dawn principal investigator Christopher Russell from the University of California, Los Angeles.
"This region of space has been ignored for far too long. So far, the images received to date reveal a
complex surface that seems to have preserved some of the earliest events in Vesta's history, as well as
logging the onslaught that Vesta has suffered in the intervening eons."

Vesta is thought to be the source of a large number of meteorites that fall to Earth. Vesta and its new
NASA neighbor, Dawn, are currently approximately 117 million miles (188 million kilometers) away
from Earth. The Dawn team will begin gathering science data in August. Observations will provide
unprecedented data to help scientists understand the earliest chapter of our solar system. The data also
will help pave the way for future human space missions.

After traveling nearly four years and 1.7 billion miles (2.8 billion kilometers), Dawn also
accomplished the largest propulsive acceleration of any spacecraft, with a change in velocity of more
than 4.2 miles per second (6.7 kilometers per second), due to its ion engines. The engines expel ions
to create thrust and provide higher spacecraft speeds than any other technology currently available.
"Dawn slipped gently into orbit with the same grace it has displayed during its years of ion thrusting
through interplanetary space," said Marc Rayman, Dawn chief engineer and mission manager at
NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It is fantastically exciting that we will begin
providing humankind its first detailed views of one of the last unexplored worlds in the inner solar
system."

Although orbit capture is complete, the approach phase will continue for about three weeks. During
approach, the Dawn team will continue a search for possible moons around the asteroid; obtain more
images for navigation; observe Vesta's physical properties; and obtain calibration data.

In addition, navigators will measure the strength of Vesta's gravitational tug on the spacecraft to
compute the asteroid's mass with much greater accuracy than has been previously available. That will
allow them to refine the time of orbit insertion.

Dawn will spend one year orbiting Vesta, then travel to a second destination, the dwarf planet Ceres,
arriving in February 2015. The mission to Vesta and Ceres is managed by JPL for the agency'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 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.

To view the image and obtain more information about the Dawn mission, visit:
http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov/

To follow the mission on Twitter, visit: http://www.twitter.com/NASA_Dawn .

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