Over And Out

Mission controllers ordered NASA's Deep Space 1 probe to turn off its engine and cut its radio link to Earth on Tuesday, ending the spacecraft's three-year mission.

Deep Space 1 tested a dozen cutting-edge spacecraft technologies and then photographed an asteroid and a comet before the mission was brought to a close by a command sent from NASA's Jet Propulsion Laboratory in Pasadena, 86.5 million miles away.

"It makes one feel wistful, but it went very smoothly," said project manager Marc Rayman, who has worked on the mission since its inception.

Deep Space 1's core systems were left on to allow it to point its solar arrays at the sun to keep its batteries charged, control its temperature, monitor its own systems and to take corrective actions if necessary.

The radio transmitter was shut off, but its receiver was left on in the unlikely event NASA wants to contact it again before its batteries die, Rayman said.

"You never know when tomorrow somebody's going to say, 'Oh wait, I just thought of one more good thing,"' he said.

In three to 12 months, the probe will run out of the hydrazine fuel its thrusters use to keep the solar arrays pointed toward the sun. At that point, it will keep circling the sun, held in orbit by the sun's gravitational pull, Rayman said.

The mission will have cost just over $159 million when funding for the project runs out at the end of next year.

Among its technical achievements were tests of an autonomous navigation system, which allowed the spacecraft to plot its own course and make adjustments on its own once ground controllers told it where they wanted it to go. Previously, those adjustments had to be made on the ground.

Rayman said he considered the demonstration of ion propulsion, once the stuff of science fiction, to be the mission's greatest success. It allows a slow but steady acceleration that is more efficient than the sudden bursts of power created by quickly burning huge amounts of conventional rocket fuel.

"It will allow us to go places and do things that have, prior to Deep Space 1, been completely beyond our reach," Rayman said.

Deep Space 1's primary mission ended with a flyby of the asteroid Braille. The mission was extended, and in September 2001 it passed the comet Borrelly at a distance of 1,349 miles and sent to Earth the highest-resolution pictures ever taken of a comet.

By JOHN ANTCZAK
©MMI The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed