Old Opportunity Knocks Around On Mars, Suffers Brief Spell Of Amnesia
Mars rover Opportunity is in the news again, this time for suffering a spell of "brief amnesia" related to its 256MB flash memory just five (5) days after a full reformatting of its memory banks. No scientific data was lost as a result of the blip in the device's nonvolatile memory, though, and the rover continued its current schedule of activities, including the examining of a rock named "Athens" by its robotic arm.
Opportunity, which landed on Mars in January 2004 just three weeks after its sister rover Spirit, has thus far functioned a remarkable 4000+ days beyond its original 90 sol (92.5 day) mission, moving about* and performing various mostly geology-based experiments. The rover makes a daily broadcast to Earth of the data collected by its radiation-hardened 20 MHz RAD6000 RISC processor, up until recently using its 256MB of flash memory as a staging platform for that data.
Problems have plagued Opportunity for some time, as might be expected considering the rover's age and the conditions in which it serves, and last August the decision was made to reformat its flash memory in the hope that this would cure frequently occurring system resets. Individual cells in each section of its flash memory had been overwritten so many times by this point that Opportunity was resetting itself dozens of times a month. And with the rover's flash memory no longer felt to be reliable, NASA in December took steps to instead have the rover use volatile memory to fire off its daily data load to Earth before shutting down for the night to preserve its power.
The reformatting of Opportunity's seven banks of flash memory — a process that included revising the rover's onboard software to avoid using Bank 7, where some of the earlier problems had directly traced — appears to have rectified the issue of persistent system resets, with none occurring in the days since the remedy action. And the flash memory is once again serving its role as the staging area for data transmittal. Still, the amnesia event coming so quickly on the heels of Opportunity's full flash memory reformat is disappointing.
“We changed how the rover uses flash memory in an attempt to correct problems the rover had been experiencing,” said NASA Jet Propulsion Laboratory Opportunity project manager John Callas. “Although we are a little disappointed at the occurrence of an amnesia event only five days after reformatting, we are not surprised. 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.”
* NASA reported last week that Opportunity had clocked over 42.195 kilometers, thus extending its rover traversal record to the distance of a marathon (and needing just 11 years to accomplish the feat).
Problems have plagued Opportunity for some time, as might be expected considering the rover's age and the conditions in which it serves, and last August the decision was made to reformat its flash memory in the hope that this would cure frequently occurring system resets. Individual cells in each section of its flash memory had been overwritten so many times by this point that Opportunity was resetting itself dozens of times a month. And with the rover's flash memory no longer felt to be reliable, NASA in December took steps to instead have the rover use volatile memory to fire off its daily data load to Earth before shutting down for the night to preserve its power.
“We changed how the rover uses flash memory in an attempt to correct problems the rover had been experiencing,” said NASA Jet Propulsion Laboratory Opportunity project manager John Callas. “Although we are a little disappointed at the occurrence of an amnesia event only five days after reformatting, we are not surprised. 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.”
* NASA reported last week that Opportunity had clocked over 42.195 kilometers, thus extending its rover traversal record to the distance of a marathon (and needing just 11 years to accomplish the feat).
