After more than three years and two trips around the Sun, the Deep Space 1 spacecraft's mission will end Tuesday, Dec. 18, when NASA cuts off communication with the craft.
Shortly after 3 p.m. EST Tuesday, engineers will send a final command turning off the probe's engine, NASA officials said Monday.
Deep Space 1 launched in October 1998. It has had successes and failures, been battered by solar storms, suffered long stretches of silence and disorientation. Yet in the end it emerged as one of NASA's most surprising success stories in years.
The craft was designed primarily to test a dozen futuristic technologies, including a high-tech ion engine and an auto-navigation setup. But it also provided some useful and relatively inexpensive science, highlighted by a Sept. 22 flyby of comet Borrelly that yielded images scientists call the best ever.
"It's hard not to feel wistful at the end of the mission," said Marc Rayman, Deep Space 1's mission manager at NASA's Jet Propulsion Laboratory. "But we squeezed far, far more out of DS1 than I ever expected, with successful primary, extended, and hyperextended missions, and I'm very happy that we can end the mission on our terms, when we are ready."
NASA had said weeks ago that the mission, which had been extended multiple times in order to reap relatively inexpensive additional science and technology benefits, would end sometime this month.
The future
Rayman said that rather than being sad, he's happy that the craft accomplished so much.
"I think the rich harvest of science data from Borrelly is tremendously exciting, and it is particularly rewarding given that it was a bonus after the primary mission," he said.
But it's the future that excites Rayman the most.
"I have always believed that the greatest science return from Deep Space 1 will be in the future missions that are now feasible because of the technology testing," he said. "Many exciting and ambitious missions that otherwise would have been unaffordable or truly impossible now are within our reach."
One mission that benefits directly is Deep Impact, which will attempt to slam a camera-packing probe into a comet on July 4, 2005. The images from Deep Space 1 will play a crucial role in refining predictions of the targeting environment for Deep Impact, says Michael A'Hearn, a University of Maryland astronomer who will manage Deep Impact.
Other missions that require inexpensive propulsion to cross vast distances will also draw from the experiences of Deep Space 1, several mission planners have said. DS1 flew on an original budget of just $152 million. The ion engine, powered by xenon, requires much less fuel than a conventional rocket engine. While it is slower, it also makes for a lighter and therefore cheaper spacecraft.
Final hours
Deep Space 1 was not expected by Rayman to survive the comet encounter. He worried that dust in the coma, a shroud of debris that surrounds the comet's nucleus, would destroy the craft. But during the flyby researchers spotting something puzzling: A significant portion of the dust around the comet was concentrated in a single jet that shot out into space, leaving much of the rest of the coma relatively dust-free.
"While we know DS1 was hit, it did not experience enough blows to suffer damage," he said.
Since the comet encounter, mission managers have put the 1,071-pound (486-kilogram) probe through some paces to further test the limits of its ion engine.
Once engineers sever ties between the spacecraft and Earth's Deep Space Network of tracking antennas, Deep Space 1 will drift through space deaf, mute and out of control. It will slowly rotate until its solar panels no longer point properly toward the Sun, and then its battery will drain.
For some unknown time, it will continue to orbit the Sun, cold, quiet and alone.
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