space.com animation: Deep Space 1 Asteroid Flyby (394k)

CAPE CANAVERAL, Fla. - Despite a last minute case of jitters that nearly canceled the show, NASA's Deep Space 1 probe pulled off an unparalled maneuver 117 million miles from Earth early Thursday, flying itself about 10 miles away from an asteroid for a close-up photo shoot.

"This has been by far the most challenging, dramatic and stressful day of the project," said Deep Space 1 chief engineer Marc Rayman, with the Jet Propulsion Laboratory in Pasadena, Calif.
In an interview, Rayman said the maneuver would be risky - not necessarily to the spacecraft, but because it was questionable whether the robot would be able to properly align its cameras to snap pictures as it soared past the asteroid at 35,000 mph - about 50 times faster than a commercial jet aircraft. And that was before the probe threw the team a curve ball and put itself into a standby mode after an unsuccessful computer reboot.

As a result, the Deep Space 1 team spent the final hours before the rendezvous coaxing the spacecraft back into operation, rather than fine-tuning plans for the maneuver, said JPL spokesman John Watson.

Nevertheless, Deep Space 1, which has been touring the inner solar system since its launch on Oct. 24, 1998, seems to have recovered in time to complete the flyby. Since the spacecraft had to turn its antenna away from Earth to aim its camera at the asteroid, flight managers will not know until late Thursday or Friday the final results of the flyby.

The close encounter occurred at 12:46 a.m. EDT Thursday. The spacecraft is about 25 percent farther away from Earth than the sun, which means its radio signals, traveling at the speed of light, are taking about 10 minutes to reach ground control teams.

Anxiously peering at computer monitors, the team broke into applause when Deep Space 1's signal appeared, indicating the spacecraft had turned to face its camera toward the asteroid, said JPL spokesman John Watson.

The turn was indicated by a Doppler shift - a slight change in the signal's wavelength due to its turn. Like a siren that changes pitch as it passes by, a Doppler shift indicates movement past an object.

The close approach to the asteroid caps a successful primary mission for Deep Space 1, which is scheduled to end on Sept. 18. However, the team has requested a mission extension to allow the spacecraft to transition from an engineering testbed to science probe. The spacecraft was designed to test 12 new technologies for future spacecraft, including autonomous navigation software and an ion engine.

If Deep Space 1 is granted a second life, plans call for it to encounter two comets in 2001.