Peter Tsou, Jet Propulsion Laboratory scientist, shows off a sample of Aerogel, used on the Stardust spacecraft to capture comet particles from Comet Wild-2. NASA Jet Propulsion Laboratory
NASA's Stardust spacecraft is returning to Earth after a whirlwind 2.8 billion-mile tour of the inner solar system, and will pass over Nevada during its return to Earth. The Stardust spacecraft holds inside a precious cargo - a pinch of particles from the comet Wild-2.
It is the first time materials from deep space will return to Earth since the last Apollo moon landing in December 1972.
Dr. Don Brownlee, with the University of Washington in Seattle, is the chief scientist who came up with the concept. He said, "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. (We're) sampling the building blocks of the solar system."
The $212-million, 3-foot-diameter, 101-pound Stardust capsule will re-enter the Earth's atmosphere over the Pacific Northwest 1:57 a.m. Sunday. It will be traveling at 28,860 mph, the fastest any spacecraft has re-entered the Earth's atmosphere. That speed will result in the spacecraft glowing white hot as its heat shield starts to char and burn away.
Unlike the super-delicate thermal tiles on the space shuttle which absorb heat and are reusable, a heat shield gradually burns away to remove the heat while protecting the contents inside. The same high-tech materials in Stardust's heat shield are planned for use on NASA's future Crew Exploration Vehicle, so NASA is hoping to obtain data on how well the heat shield performs.
"As we come in over the Western United States, this thing will light up the night sky for a brief period of time," said Stardust Project Manager Tom Duxbury.
NASA's especially interested in what the re-entry will look like from a wide variety of locations. A specially instrumented DC-8 aircraft will track the re-entry, and NASA is encouraging amateur astronomers to videotape or take photos of the re-entry. A Web site with plenty of technical data has been set up with recommendations for how to take the best images and where to submit them.
The spacecraft will travel across Northern California and Nevada on its way to Utah. Northern Nevada will have the best viewing angles, but central Nevada is also well placed. From Carson City, Stardust will appear in the north at 1:57 a.m., about a quarter of the way up the sky.
Stardust will speed to the east, setting in the northeast before its parachute opens to slow its descent into the U.S. Air Force Utah Test and Training Range, southwest of Salt Lake City. The whirlwind 6.9-year journey ends when the capsule parachutes to a gentle landing at 2:12 a.m.
The re-entry will be bright - under the best circumstances - bright enough to cast a shadow on the ground.
In astronomical terms, it will reach negative-7 magnitude, 1,500 times as bright as the brightest stars.
Amateur astronomer Robert Stevens said, "The best choice is to find a dark area away from city lights with a clear view of the northern horizon. Pick your viewing site in advance, and check the weather forecast that night. If there's a light overcast, then the re-entry will be bright enough to light up the clouds. Stardust will look like a giant meteor as it enters the atmosphere - it's going to be impressive."
Astronaut Don Pettit was the first NASA astronaut to return to Earth inside a Russian Soyuz spacecraft, a similar type of re-entry.
"This is going to be a really cool sight - to see a spacecraft returning to Earth from deep space. If you have the opportunity to see this, I would certainly not miss the opportunity," he said.
Even if the weather doesn't cooperate, some space enthusiasts are still hoping to observe the re-entry through other means. If the night is quiet then it may be possible to hear a sonic boom, sounding like a distant thunder clap. Even more esoteric, some ham radio operators are going to try to bounce a signal off the super-hot, ionized trail.
Some hams will point their antennas toward the spacecraft and transmit signals while others will listen for those transmissions from distant states. Other hobbyists are going for the simple approach. Take an old television set and hook up an ordinary antenna, like a pair of rabbit ears. Tune the TV to an unused station in your area and watch. With any luck, you'll see images from distant stations for a short period as their signals bounce off of the re-entry tail.
Viewing the re-entry isn't the first time NASA has encouraged the public to participate in the Stardust project. The spacecraft has a pair of microchips with more than a million etched names.
One microchip is in the capsule which is returning to Earth, the other is in the spacecraft bus which will remain in space. NASA's considering reusing the spacecraft bus for additional science.
Ultimately, in a million years or so, it will either crash into one of the solar system's planets or be ejected out of the solar system.
"As an astrobiology person, I'm intrigued by the thought that those names on the spacecraft will far outlive the Earth," Brownlee said. "Those names will still be floating around the galaxy - somewhere."
On the Net
For recommendations on how to take the best images and where to
submit them, go to
http://re-entry.arc.nasa.gov/viewingforum.html.
To learn more about the Stardust spacecraft, go to
http://stardust.jpl.nasa.gov/photo/index.html.