Computer crash threatens Martian photo-op

[Alpine]

NASA has been forced to switch off the scientific instruments on board its Mars Global Surveyor (MGS) spacecraft, just a week before the photo opportunity of a lifetime.

Mission managers are hoping to get the craft up and running again in time for a fly by of the suspected crash site of the Mars Polar Lander, a US mission to the red planet that was lost in 1999. They will not have the opportunity to fly over the site again for two years, the BBC reports.

But the lander, thought to have crashed reasonably near the pole, is not in sunlight for very long. After 10 September, the region will be plunged into darkness, making it impossible to photograph from orbit.
Pictures of the site are important because elements of the 1999 mission have been recycled for Phoenix, a new Mars mission scheduled to launch in 2007. Images of the crash could help engineers decide whether or not to modify any of the systems for the 2007 flight.

The MGS had to be put into safe-mode after it started to switch between its main onboard computer and its backup for no apparent reason.

Safe mode switches off the scientific instruments, and turns the craft so that its solar panels directly face the sun, for maximum battery recharging. It also limits its communication with Earth to that possible with its low gain antenna.

NASA says that the MGS unexpectedly switched to its back-up computer on 30 July. The main computer was rebooted, but left in safe mode and the back-up machine was left in charge. In late August, it switched back to the main computer, again without warning. This plunged the whole craft into safe mode, and engineers have been working to restore normal function since then.

Both computers have now been rebooted, and the back-up machine is running in contingency mode. The engineers hope to have the main computer into contingency mode soon too, which will switch communications back to the main antenna.

"It's getting to be a fairly old spacecraft and it's been having a number of issues; none of them are considered life-threatening," Professor Phil Christensen, principal investigator on MGS's thermal emission spectrometer instrument told the BBC. "The spacecraft's operating fine; they can command and communicate with it. The poor engineers will work hard over the weekend and we'll be back on track early next week."

The MGS mission was originally designed to run until January 2001.

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