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Mission Control Center Status Update

http://spaceflightnow.com/stardust/status.html

THURSDAY, JANUARY 12, 2006

With its precious cargo of comet bits nestled inside, NASA's Stardust spacecraft is soaring inbound for Sunday's fiery descent and landing in Utah that will cap a 2.88-billion mile voyage spanning 7 years of looping around the solar system.

The armored space probe raced past Comet Wild 2 in January 2004, catching particles with its racquet-shaped collector. Comets are considered ancient relics serving as frozen time capsules that hold the chemical records from a time billions of years ago when the planets were forming.

The samples were stowed in a protective capsule that will separate from the spacecraft and return to Earth to the delight of anxious scientists.

"Comets are some of the most informative occupants of the solar system," said Dr. Mary Cleave, associate administrator for NASA's Science Mission Directorate.

"Locked within the cometary particles is unique chemical and physical information that could be the record of the formation of the planets and the materials from which they were made," added Dr. Don Brownlee, Stardust principal investigator at the University of Washington, Seattle.

Stardust is scheduled to conduct its final course-correcting maneuver at 11:53 p.m. EST Friday to tweak the flight path for Earth. The craft must be aimed precisely when it deploys the powerless descent capsule at 12:57 a.m. EST Sunday. The capsule has no means of propulsion and relies solely on the mothership firing it in the proper direction to enter the atmosphere a few hours later.

The separation happens 68,805 miles from Earth. Two cable cutters sever the umbilicals connecting the capsule and mothership, then three bolts break apart. A mechanism gives the capsule a push away while imparting a 14 to 16 revolution per minute spin. That spin is designed to help keep the capsule's orientation stablized during its free flight.

The mothership performs a divert maneuver about 15 minutes after the separation event to continue flying in orbit around the Sun. Scientists are looking at ways of reusing the instrument-laden craft for future missions.

The sample return capsule enters Earth's atmosphere with a velocity of 28,860 miles per hour, making it the fastest of any human-made object. It will surpass the record set in May 1969 during the return of the Apollo 10 command module of 24,861 mph.

The point of atmospheric entry occurs around 4:57 a.m. EST at about 78 miles (400,000 feet) over northwestern California -- 12 miles inland from the Pacific Ocean and 14 miles south of the Oregon-California border -- about 551 miles uprange from the landing zone.

The region of maximum heating on the capsule's thermal shield happens 52 seconds into the re-entry at an altitude of 38 miles. The heat shield will feel an amazingly intense temperature of 4,900 degrees F.

About 62 seconds into the atmospheric descent, peak deceleration occurs at 38 times the force of gravity.

The deceleration will decrease to 3 G's at entry plus one minute and 56 seconds, triggering an onboard timer. The capsule's avionics then issue the command for firing the mortar to deploy the drogue parachute at entry plus two minutes and 12 seconds. The capsule will be traveling at mach 1.4 and 20 miles overhead the landing area when the drogue chute is unfurled.

Just three minutes after slamming into the atmosphere, the falling capsule will be 15 miles above the ground and making a vertical descent.

The capsule moves within controlled airspace a minute later when it is 11 miles up.

The main parachute is deployed nearly two miles over the landing zone at 5:05 a.m. EST. This is done by cutting one of the lines holding the drogue chute, which pulls out the main chute.

The main chute's bridle holds a UHF locator beacon that is activated at deploy to assist ground teams in locating the capsule.

The 10 mile per hour touchdown at the U.S. Air Force Utah Test and Training Range, southwest of Salt Lake City, is expected at 5:12 a.m. EST. The landing area is 27 by 47 miles.

"There's a lot at stake. You just hope everything works, and I am confident it will work," said Brownlee.

"But the really big part of the research is just getting ready to start, when the material goes to the laboratory. The train is headed for the station and we're all waiting for it."

Recovery crews will move the 95-pound capsule via helicopter to the U.S. Army Dugway Proving Ground, Utah, for initial processing. The comet samples then head to NASA's Johnson Space Center in Houston for curation.

Scientists say tens of thousands of comet grains have been snared by the spacecraft's collector. Stardust flew by Comet Wild 2 on January 2, 2004, passing only 149 miles at closest approach.

The backside of the collector was used earlier in the Stardust mission, which launched atop a Boeing Delta 2 rocket from Cape Canaveral in February 1999, to pick up about 100 bits of interstellar dust grains streaming from other stars in the galaxy.

The collector used an exotic material, called aerogel, to trap the cometary particles -- impacting at speeds over five times that of a rifle bullet -- without damaging the cargo for scientists to analyze on Earth. Aerogel is 99.9 percent air and 0.1 percent silica dioxide. One thousand times less dense than glass, aerogel is like "solid smoke."

The Comet Wild 2 (pronounced Vilt 2) was discovered in 1978. Its solar orbit extended from Jupiter to beyond Uranus before 1974. But then, Jupiter's gravity altered Wild 2's course, bringing it just beyond the orbit of Mars. It now orbits the Sun once every 6.39 years.

Since Wild 2 only recently began orbiting close to the Sun, scientists believe our star's heat hasn't had enough time to damage the frozen evidence preserved inside the comet for billions of years while lurking in deep space.

"Virtually all the atoms in our bodies were in little grains like the ones we're bringing back from the comet, before the earth and sun were formed," Brownlee said. "Those grains carry elements like carbon, nitrogen and silicon from one place to another within our galaxy, and they helped form the sun, the planets and their moons."

Watch this page for live updates on Sunday morning.