T-minus 48 hours and counting to a historic rendezvous,
NASA's Stardust spacecraft has officially entered a comet's
coma, the cloud of dust and gas surrounding the nucleus.
Stardust is scheduled to hurtle past comet Wild 2 on January
2, 2004, at approximately 2:40 p.m. EST.
"Just like in Star Trek we have our shields up," said Tom
Duxbury, Stardust program manager at NASA's Jet Propulsion
Laboratory (JPL), Pasadena, Calif. "The spacecraft has
entered Wild 2's coma, which means at any time we could run
into a cometary particle. At 6.1 kilometers per second
(approximately 3.8 miles per second), this is no small
event."
To protect Stardust against the blast of expected particles
and rocks as it travels approximately 300 kilometers (186
miles) from the Wild 2 nucleus, the spacecraft rotated, so it
is flying in the shadow of its "Whipple Shields". The shields
are named for American astronomer Dr. Fred L. Whipple. In the
1950s, he came up with the idea of shielding spacecraft from
high-speed collisions with bits and pieces ejected from
comets.
The system includes two bumpers at the front of the
spacecraft, which protect Stardust's solar panels, and
another shield protecting the main spacecraft body. Each of
the shields is built around composite panels designed to
disperse particles as they impact. Blankets of Nextel ceramic
cloth that dissipates and spreads debris augment them.
Stardust has traveled approximately 3.7 billion kilometers
(approximately 2.3 billion miles) since its February 7, 1999
launch. It is closing the gap with Wild 2 at 22, kph
(approximately 13,640 mph).
On Jan. 2, Stardust will fly through the halo of dust and gas
that surrounds the nucleus of comet Wild 2. While large
portions of the spacecraft will be hidden behind Whipple
shields, others are designed to endure the celestial
sandblasting as they collect, analyze and store samples. The
Stardust spacecraft will return to Earth in January 2006, and
its sample return capsule will make a soft landing at the
U.S. Air Force Utah Test and Training Range. The collected
microscopic particle samples of comet and interstellar dust
will be taken to the planetary material curatorial facility
at NASA's Johnson Space Center, Houston, for analysis
Stardust's cometary and interstellar dust samples may help
provide answers to fundamental questions about the origins of
the solar system. More information about the Stardust mission
is available on the Internet, at:
http://stardust.jpl.nasa.gov
Stardust is part of NASA's Discovery Program of low-cost,
highly focused science missions. It was built by Lockheed
Martin Space Systems, Denver, and is managed by JPL for
NASA's Office of Space Science, Washington. JPL is a division
of the California Institute of Technology in Pasadena, Calif.
The principal investigator is astronomy professor Donald E.
Brownlee of the University of Washington in Seattle.
For information about NASA and other agency missions on the
Internet, visit:
http://www.nasa.gov
