The group working to unravel the glitch with Spirit and return the rover to action has narrowed the possible cause of its trouble to three potentials, officials said Sunday afternoon.

"Spirit is still serious but we are moving toward guarded condition now," rover project manager Pete Theisinger said. "I think we got a patient well on the way to recovery."

The rover experienced a problem last Wednesday, disrupting communications with Earth and halting all science activities. The breakdown happened while Spirit was performing a calibration of motors on the Mini-TES instrument.

"The leading theory is that the file management software module in the software has gone to some condition that it could not cope with -- that it was not robust enough for the operations we were engaged in when we had the flaw on Wednesday," Theisinger said.

On Saturday, engineers began focusing on the rover's flash memory and the way the software communicates with the computer memory. To get the rover operating, it was told to avoid using the flash memory for now.

On Sunday, the team was able to reset Spirit's computer to the non-flash utilization mode, Theisinger said. Also Sunday, the ongoing diagnostics determined the flash memory hardware aboard the rover to be healthy.

"There are two other theories that are not as well in competition but cannot be discounted, and they are being worked by anomaly subteams," Theisinger added.

"One is there was some kind of error or hardware issue on the motor control board. That's the circuit board with the electronics that control the motors. That's being examined.

"Also...there was a solar event Wednesday and the timing of that is being looked at with respect to correlation to the onset of our problems. The flash memories are sensitive to high-energy ions and neutrons when they are being read from and written to, and we were certainly engaged in a lot of that activity that day."

Theisinger remains hopeful that Spirit will resume its exploration adventure of Gusev Crater by mid-February.

"I think we've got a patient well on the way to recovery, and I think we have a very good chance now we will have a very good rover when we are done getting this thing back up. Although, once again, it will take some time to make sure that we have completely characterized the problem and that we are able to check out all of the functionality on the vehicle.

"You can't take anything for granted here. So I don't expect to be driving for a couple of weeks, maybe three."

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