NASA Declares End to Deep Impact Comet Mission

Communication cutoff leads to loss of comet hunter, say space officials.

NASA scientists ended the Deep Impact comet hunter mission on September 20.

NASA officials declared the Deep Impact mission lost on Friday, after a computer glitch doomed the comet-smashing spacecraft.

Launched in 2005, the spacecraft memorably smashed a copper-jacketed probe into the comet Tempel 1 at 22,800 miles an hour (36,700 kilometers an hour) on July 4 of that year. It then flew through the debris cloud to capture the resultant fireworks, the first close inspection of a comet's interior. (See "'Deep Impact' Comet Revealed by NASA Flyby.")

The $267 million spacecraft later flew by the comet Hartley 2 in 2010, and this year it captured images of comet ISON, which is headed toward a close encounter with the sun in November.

But now the Deep Impact spacecraft appears to be lost.

"The mission revolutionized the way we think about comets and raised all sorts of questions we still have to answer," said chief mission scientist Mike A'Hearn of the University of Maryland.

Mission controllers last radioed the spacecraft on August 8, after which communications were lost, according to a statement from the Jet Propulsion Laboratory in Pasadena, California. After a month of attempts to restore communications through the NASA Deep Space Network, the controllers have declared the mission "lost," concluding that a computer glitch likely doomed the spacecraft.

"Basically, it was a Y2K problem, where some software didn't roll over the calendar date correctly," said A'Hearn. The spacecraft's fault-protection software (ironically enough) would have misread any date after August 11, 2013, he said, triggering an endless series of computer reboots aboard Deep Impact.

Despite repeated attempts to send corrective commands, the spacecraft likely lost its bearings and failed to point its solar cell wings toward the sun, A'Hearn said, causing a catastrophic loss of power.

Comets Now Better Understood

Deep Impact had been enjoying a surprisingly long second act after its 2005 rendezvous with Tempel 1 and the two years of data analysis that followed the smash-up. "I considered everything afterwards as gravy," A'Hearn said.

Before Deep Impact, comet scientists had a relatively simple picture of comets as crusty, dirty snowballs from beyond Pluto. After the 2005 encounter, A'Hearn said, scientists understood that space weather reshaped comet surfaces, that comet tails contain dry ice and water, and that comets originated close to the sun at the dawn of the solar system.

The findings played into scientific discussions of how water delivered by comet impacts may have filled the oceans of the early Earth more than four billion years ago.

"I'm a little biased, but I think the taxpayers saw very good value from this mission," A'Hearn says.