NASA's Stardust spacecraft successfully completed a close flyby Saturday of an asteroid named Annefrank, taking dozens of pictures expected to be released to the public this week.
The event was used as a dress rehearsal of procedures the spacecraft will use during its Jan. 2, 2004, encounter with it primary science target, comet Wild 2.
Although still being assessed, Stardust appears to have flown by at about 1,900 miles (3,000 kilometers) away from the asteroid, which had previously been estimated to be about 4 kilometers (2.5 miles) in diameter. Though no pictures have been released to the public yet, the flyby revealed surprising detail on the asteroid, SPACE.com has learned, and the rock may be larger than expected.
Stardust engineers at Lockheed Martin Astronautics near Denver, Colorado are pleased with the performance of their company-built spacecraft.
"It was extremely successful. We're very happy here," said Lockheed Martin's Allan Cheuvront, Stardust spacecraft engineer.
Radio signals confirming the basic health of the spacecraft after the flyby were received about 30 minutes later via an antenna at the Canberra, Australia, complex of NASA's Deep Space Network, said Thomas Duxbury, project manager for Stardust at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
JPL manages the mission for NASA.
Stardust visually tracked the asteroid for 30 minutes as it flew by at a relative speed of about 4 miles per second (7 kilometers per second).
"We always thought it would be too dim or just outside the field of view. That was kind of the expectation going in. It was to be difficult at best. An initial set exposure time of Stardust's camera was lengthened in the event the object proved too dim to be seen.
"It all went like clock work," Cheuvront said. Stardust was on its own for some 35 minutes and then, right on time, the spacecraft came back on and started communicating, he added.
Overall, 106 images were taken of the asteroid, with 72 images archived and being relayed back to Earth. "It looks like Annefrank is in 71 of those images," Cheuvront said.
While some images have already been received, the entire set of pictures taken by Stardust will have arrived on Earth on Friday. The images have not yet been released to the public.
A surprise to scientists and engineers was the size of the odd shaped body, found to be larger than anticipated.
"We were expecting to see, basically, just a blob. But we got shape definitions. It's kind of like a triangle-shaped object. There are definite peaks and valleys there," Cheuvront told SPACE.com.
Although no dust was anticipated near the asteroid, the spacecraft's dust counter and other instruments were in use as they will be at Wild 2.
Images and information from the flyby period are being transmitted from the spacecraft today and through this week. Stardust's scientists and engineers are analyzing the data to maximize the probability of success during the 2004 encounter with comet Wild 2, NASA officials said in a statement.
Stardust will bring samples of comet dust back to Earth in 2006 to help answer fundamental questions about the origins of the solar system.
SPACE.com Senior Science Writer Robert Roy Britt contributed to this report.
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