[meteorite-list] Dawn Nears Position for Year-Long Stay at Vesta

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 23 Jun 2011 12:06:52 -0700 (PDT)
Message-ID: <201106231906.p5NJ6qRx002841_at_zagami.jpl.nasa.gov>

June 23, 2011

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

Priscilla Vega/Jia-Rui Cook
Jet Propulsion Laboratory, Pasadena, Calif.
626-298-3290/818-354-0850
priscilla.r.vega at jpl.nasa.gov / jccook at jpl.nasa.gov
RELEASE: 11-197

NASA PROBE NEARS POSITION FOR YEAR-LONG STAY AT GIANT ASTEROID

WASHINGTON -- NASA's Dawn spacecraft is on track to begin the first
extended visit to a large asteroid. The mission expects to go into
orbit around Vesta on July 16 and begin gathering science data in
early August. Vesta resides in the main asteroid belt and is thought
to be the source of a large number of meteorites that fall to Earth.

"The spacecraft is right on target," said Robert Mase, Dawn project
manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
"We look forward to exploring this unknown world during Dawn's one
year stay in Vesta's orbit."

After traveling nearly four years and 1.7 billion miles (2.7 billion
kilometers), Dawn is approximately 96,000 miles (155,000 kilometers)
away from Vesta. When Vesta captures Dawn into its orbit, there will
be approximately 9,900 miles (16,000 kilometers) between them. They
will be approximately 117 million miles (188 million kilometers) away
from Earth.

After Dawn enters Vesta's orbit, engineers will need a few days to
determine the exact time of capture. Unlike other missions where a
dramatic, nail-biting propulsive burn results in orbit insertion
around a planet, Dawn has been using its placid ion propulsion system
to subtly shape its path for years to match Vesta's orbit around the
sun.

Images from Dawn's framing camera, taken for navigation purposes, show
the slow progress toward Vesta. They also show Vesta rotating about
65 degrees in the field of view. The images are about twice as sharp
as the best images of Vesta from NASA's Hubble Space Telescope, but
the surface details Dawn will obtain are still a mystery.

"Navigation images from Dawn's framing camera have given us intriguing
hints of Vesta, but we're looking forward to the heart of Vesta
operations, when we begin officially collecting science data," said
Christopher Russell, Dawn principal investigator, at the University
of California, Los Angeles (UCLA). "We can't wait for Dawn to peel
back the layers of time and reveal the early history of our solar
system."

Dawn's three instruments are all functioning and appear to be properly
calibrated. The visible and infrared mapping spectrometer, for
example, has started to obtain images of Vesta that are larger than a
few pixels in size. During the initial reconnaissance orbit, at
approximately 1,700 miles (2,700 kilometers), the spacecraft will get
a broad overview of Vesta with color pictures and data in different
wavelengths of reflected light. The spacecraft will move into a high
altitude mapping orbit, about 420 miles (680 kilometers) above the
surface to systematically map the parts of Vesta's surface
illuminated by the sun; collect stereo images to see topographic
highs and lows; acquire higher resolution data to map rock types at
the surface; and learn more about Vesta's thermal properties.

Dawn then will move even closer, to a low-altitude mapping orbit
approximately 120 miles (200 kilometers) above the surface. The
primary science goals of this orbit are to detect the byproducts of
cosmic rays hitting the surface and help scientists determine the
many kinds of atoms there, and probe the protoplanet's internal
structure. As Dawn spirals away from Vesta, it will pause again at
the high-altitude mapping orbit altitude. Because the sun's angle on
the surface will have progressed, scientists will be able to see
previously hidden terrain while obtaining different views of surface
features.

"We've packed our year at Vesta chock-full of science observations to
help us unravel the mysteries of Vesta," said Carol Raymond, Dawn's
deputy principal investigator at JPL. Vesta is considered a
protoplanet, or body that never quite became a full-fledged planet.

Dawn launched in September 2007. Following a year at Vesta, the
spacecraft will depart for its second destination, the dwarf planet
Ceres, in July 2012. Dawn's mission to Vesta and Ceres is managed by
JPL for NASA's Science Mission Directorate in Washington. Dawn is a
project of the directorate's Discovery Program, managed by NASA's
Marshall Space Flight Center in Huntsville, Ala.

UCLA is responsible for 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 team.

For more information about Dawn, visit:

http://www.nasa.gov/dawn
        
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Received on Thu 23 Jun 2011 03:06:52 PM PDT