Engineers have found a way to halt Spirit's computer from resetting itself by putting the spacecraft into a mode that avoids use of flash memory. Flash memory is a type common in many electronic products, such as digital cameras, for storing information even when the power is off.
The Mars Exploration Rovers have random-access memory. But the robots cannot hold onto information during overnight sleep sessions.
Surgery or heavy hammer?
One of the next steps planned for Spirit is to erase from flash memory the files stored there from the spacecraft's cruise to Mars from Earth. That is intended to lessen the task of managing the flash memory files.
This requires care in abstracting the correct files, said JPL's Jennifer Trosper, Mission Manager for the Mars Exploration Rover (MER) project.
"If we are not able to successfully complete our surgical techniquewe have larger hammers that we can use in order to solve this problem," Trosper said yesterday at a morning press briefing here at JPL.
Trosper said that the intent of the last few days has been to maintain the state of the flash memory. "We actually think that the flash is not corrupted. We would like to keep the data thats in the flash memory," she said.
But if that proves unsuccessful, the next step is to actually delete the data thats in the flash memory. This heavy hammer approach would wipe out science data collected by Spirit before it ran into trouble on the 18th day of Mars operations.
Risk trade, time trade
Trosper said that, in talks with science teams, almost all of the onboard science data is replaceable.
Of the scientific information that would be lost, however, a coordinated, data-gathering session with Europes Mars Express is the most unique, she said. This activity involved Spirits instruments looking up while Mars Express science equipment peered down at Gusev Crater.
Trosper said that Spirit did relay thumbnail images from that coordinated look-up/look-down session with Mars Express. "So most of the science that was desired to be done can be done from the thumbnail images," she said.
The science team has agreed that smaller, thumbnail images should prove adequate to glean data that was the focus of the coordinated experiment.
"Clearly they would like to get the rest of it down. But in order to get all of the data down it will take many sols [martian days] We have to make a risk trade and time trade. The science team, I believe, would prefer to have more sols to do new things," Trosper told SPACE.com .
Scene of the crime
Teams of troubleshooting software and hardware experts remain perplexed in trying to find "the scene of the crime" that led to Spirits predicament.
If surgical removal of files in flash memory doesnt solve the problem, reformatting that memory is the next phase, in order to move forward and get back to the science of the mission.
"We can muck around with this thing for a while, clearly. Theres something that we dont understanding about the problem," Trosper said. Its also entirely possible that the "heavy hammer" approach of reformatting wont do exactly what is expected.
By going down the pathway of reformatting the flash memory, all evidence of what happened onboard Spirit would be destroyed.
On the other hand, all that evidence may have already been destroyed after the initial reset, Trosper said. "We just need to weigh the risks against the time it would take to do some of these things and get back on track."
Dont go there mode
Trosper said that there is a suspicion as to where Spirits self-thinking problems occur. "We believe that the flash memory is fine. But it might be that the only way we can get beyond this is just to wipe that flash memory clean," she said.
The good news, Trosper said, is that Spirits mission can be done in the state the robot is in right now.
The rover could be hardwired in a "dont go there" mode of thinking. The outcome of this approach would be that Spirit carries out a more restrictive start-stop type of mission, but still yield a wealth of science during long-distance roving.
"Were still very mindful of the fact that Spirit is out there and many of us on the team want to get back into that investigation and try and solve the puzzles of Gusev," said Jim Bell, Payload Element Lead for the Panoramic Camera from Cornell University.
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