Flash memory
What has been pinned down, JPLs Theisinger said, is a problem involving the robots flash memory and the software used to communicate with that memory. Spirits flash memory is mostly used for the storage and retrieval of engineering and scientific data, Theisinger reported.
"Our working hypothesis is one that we can work around to significant measureif it turns out that our working hypothesis is correct," Theisinger told reporters.
Spirit can operate without using the flash memory, an avenue called the "cripple mode." That mode tells the flight software upon booting up that it should operate with its file directory out of the robot's random access memory, rather than the flash memory.
"That would avoid any issues that we might have with either the flash memory itself or the flight software that was used to write to it," Theisinger added.
On the road again
A couple of weeks will be needed to decide what had happened and to rebuild confidence in using Spirit in a more "routine" manner. "I think were probably three weeks away from drivingbut Im guessing," Theisinger said.
While engineers here at JPL try to sort out what ails the Spirit Mars rover, the robot patient has begun to at least lend a helping hand in the diagnosis.
Shortly before noon yesterday, Spirit did on its own what it had been told not to do. Ground controllers here were surprised to receive a spurt of data from Spirit via the Mars Odyssey orbiter -- a NASA spacecraft circling the red planet.
Spirit sent 73 megabits at a rate of 128 kilobits per second. That unexpected transmission included power subsystem engineering data -- extremely helpful to software and hardware teams trying to grapple with Spirits onboard woes.
Last picture show
Still locked within Spirits memory is science data, including its "last picture show" -- images taken by the robot from its position near a science target -- the football-sized rock that scientists have nicknamed "Adirondack".
Spirit had completed runs of two German-built spectrometers that analyzed Adirondack. The results of those studies are buried within Spirit. Scientists are eager to acquire those precious measurements.
Preparations were also underway to utilize the robots Rock Abrasion Tool, or RAT, to probe the internal composition of the object.
Reboot, reboot, reboot
Despite repeated "go to bed" orders from controllers here at JPL, the Spirit rover had refused to listen to parental command. It did not go to sleep even after ground controllers sent commands twice for it to do so.
Theisinger said today that this situation has now been correctedand it appears Sprit was successfully commanded to sleep.
At a press briefing yesterday, Theisinger said Spirit's flight software had rebooted more than 60 times in the past three days.
Too many chiefs?
There is a growing feeling here that the robot may have been taxed too much. Perhaps too many "do this, do that" instructions were sent. That multi-tasking could have sparked the problem, according to sources here.
Prior to its troubles on Mars, Spirit was being put through its paces -- doing things that were not tested with as much vigor here at JPL before being launched.
Spirit does not have a huge track record of testing, a source said, for fear of damaging the robot and not meeting an unforgiving launch window.
Following todays JPL press briefing, Theisinger told SPACE.com that Spirit may have been overloaded with too many job tasks to handle at one time. "Thats possiblecertainly that cannot be discounted," he said.
Spirit-Opportunity problem link?
Theisinger said that the prospects for quick restoration of Spirit is not in the cards, a situation that could be the case for many days, into weeks -- even in the best of circumstances.
"We believe, based on everything we know now, we can sustain the current state of the spacecraft from a health standpoint for an indefinite amount of time," Theisinger said. That will give troubleshooting teams time to work on the problem.
One issue still to be sorted out: Are the problems "Spirit-specific" or could they also be lurking within the soon-to-land Opportunity?
"I feel as uncertain as I did yesterday," Theisinger said. If it is in within the software domain, he said, that implies either a software bug or a set of rules that dont understand how to operate the vehicle correctly. If thats the case, a repeat performance of Spirits tribulations could manifest themselves in Opportunity.
"If it is in fact not within the software-only domain, but has been triggered by some kind of hardware/software interaction, then it is likely to be a single event in Spirit. We just dont know yet enough to be sure," he said.
Window of Opportunity
While experts attempt to mend Spirit, sister ship Opportunity arrives at Mars tonight, landing at 12:05 a.m. EST. That robot is headed for a landing spot on the opposite side of the planet from Spirit -- Meridiani Planum.
Meridiani Planum promises to offer a landscape unlike that seen by any previous lander. This smooth, flat region of Mars is within an Oklahoma-sized outcropping of gray hematite.
That mineral can form in the presence of water. Opportunitys scientific gear is expected to resolve whether the gray hematite layer comes from sediments of a long-gone ocean, from volcanic deposits altered by hot water, or from other ancient environmental conditions.
Scientists also think that this region could offer clues as to the habitability of Mars by microbial life at some point in the planets past.
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