A flash memory reformat left NASA's Mars rover Opportunity with a brief episode of what the agency calls “amnesia” – thankfully, without any loss of scientific data.
NASA adds that Opportunity was also able to continue its normal activities, such as using its robotic arm to examine a rock target called Athens.
It's one of a string of problems with the rover's flash memory. The 256 MB flash acts as staging for data gathered by the radiation-hardened 20 MHz RAD6000 RISC processor before it's uploaded to Earth.
While the flash can't be trusted, NASA has instructed the rover to use volatile memory to fire off its daily data load to Earth before being shut down for the night to preserve its power.
As NASA explained in August 2014 when it first decided to reformat the flash to try and cure frequent and persistent system resets.
At the time, Jet Propulsion Lab's John Callas explained that worn out cells in the memory were the “leading suspect”, and the agency hoped the reset would let the system mark the bad cells so they weren't used.
As well as reformatting the flash, the Opportunity team roped off one of the seven banks of flash memory as not-to-be-used after tracing earlier problems to Bank 7.
While that fixed the problem of multiple daily resets, the team has been disappointed that the “amnesia” persists.
“Although we are a little disappointed at the occurrence of an amnesia event only five days after reformatting, we are not surprised,” Callas said of the latest event. “There is still no clear understanding of what is causing the problems. Only time will tell if we have been successful in mitigating the most serious flash problems”.
It's hardly surprising that issues might arise with the little-rover-that-could: Opportunity has been operating since 2003, far beyond its original 90-day design life, and last week it ticked over 42.195 km to become the first man-made object to complete a marathon on another planet. ®
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