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.
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).
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.
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.”
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.
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.
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.”
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.
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.
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.
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.