Mars Rover Goes Silent

NASA's Spirit rover stopped transmitting data from the surface of Mars for more than 24 hours, mission members said Thursday.

NASA last heard from Spirit early Wednesday. Since then, it has returned just random, meaningless data — and only then sporadically, scientists said. Initially, the scientists said they believed weather problems on Earth caused the glitch. They now said they believe the rover was experiencing hardware or software problems.

"There's been some sort of a glitch on the spacecraft, they're not sure exactly what," says CBS News Space Consultant Bill Harwood.

"This is a serious problem. This is an extremely serious anomaly," project manager Pete Theisinger said.

Spirit is one half of a $820 million mission. Its twin, Opportunity, is scheduled to land on Mars on Saturday.

"It's not clear that there's one cause that when we trace it through would explain the observables that we've seen, and that's what's perplexing us at the moment," said Richard Cook, deputy project manager for the Mars exploration rover mission.

Theisinger said engineers would regroup later Thursday to continue troubleshooting and to determine a plan of action.

The loss of contact came at one of the worst possible times for engineers at JPL. An identical rover, named Opportunity, is on target to enter the martian atmosphere around midnight Saturday. But Theisinger said Spirit's troubleshooting would not interfere with Opportunity's descent. The second lander is on target and in good health. Managers are still debating whether to simply stand down on Spirit operations until after Opportunity makes it to the surface.

In the meantime, tension mounted.

"If this problem on Spirit is somehow a software corruption issue, or memory corruption issue that's reflecting itself in software, and there's not a serious power fault, for example, then I think Spirit can go for quite a long time and we can pick up the pieces again," Theisinger said. "But if on the other hand it's had some kind of major power fault ... it may be more difficult to recover from that."

A rainstorm in Australia yesterday interfered with commands being uplinked to Spirit. At that time, the spacecraft sent a short signal indicating it had received the instructions but engineers said the strength of the uplink was much lower than desired and that not all of the commands got through.

The rover's electronic brain is programmed to ignore incomplete commands and engineers thought Spirit would simply stand by, executing previous instructions before calling Earth with daily downlinks of science and engineering data and awaiting further instructions.

Had the rover been operating properly, that would have happened during afternoon and evening overflights by NASA's Mars Global Surveyor and Mars Odyssey orbiters, which are being used as communications satellites for the Mars rover mission.

No data was received during the first overflight. A short signal was received late Wednesday during a Global Surveyor relay pass, but it contained no data. Nothing was heard from Spirit during subsequent passes, either through satellite relay or through programmed direct-to-Earth transmissions using the rover's high-gain antenna.

"There were beeps we heard yesterday afternoon on Mars and then we got the Mars Global Surveyor signal that indicated it heard from the (rover's) UHF link. It was not what we expected. We saw a signal, meaning the rover's radio was on, but there wasn't data present. ... The computer wasn't sending information over to it. But we did at least see a signal."

Thursday morning, flight controllers sent a low-data-rate signal to Spirit on the assumption the computer believed it had run into a problem and had loaded fault-protection routines. What may have been a brief response was received. If that data turn out to be valid, it would indicate Spirit is still alive, giving engineers hope they might be able to recover from whatever has gone wrong.

"That would tell us the spacecraft thinks it's on the fault side of the tree somehow, for some reason, that would mean we have positive power, some element of the software is working. ... But, you know, we need to confirm that. So don't take that further than it deserves to go right now."