Bouts of "amnesia" due to flash memory storage failures are experienced in NASA's Mars Opportunity rover. NASA project manager John Callas said that the Opportunity rover uses two different types of memory: "volatile" and "non-volatile", the Verge reported.
The volatile memory is akin to a computer's RAM, so any data stored there is wiped every time the rover shuts down, while non-volatile memory is where the important data like telemetry - the measurements the rover is collecting - is stored so that it can be accessed whenever Opportunity is powered on.
AdvertisementThe problem with the non-volatile memory, as with most physical storage, is that there are limits to how many times you can read from and write to it before it starts to degrade.
The researchers said that the degradation has begun to occur more frequently, and at times has left the rover unable to access the non-volatile memory and when this happens, Opportunity defaults to trying to write the telemetry data to the volatile memory, which inevitably gets wiped when the rover goes to sleep - something that occurs often to keep the batteries charged.
The memory issue can be mitigated as long as the rover has a chance to relay telemetry data to the orbiting Mars Odyssey spacecraft, but there are times when that isn't possible in between shutdowns. There's also a bigger problem at hand - repeated, unsuccessful attempts to save to the non-volatile flash memory are causing Opportunity to completely reboot. That means command sequences, which are sometimes sent in bunches, can also be forgotten, drastically slowing the team's progress.
However, NASA engineers believe that the corruption is occurring primarily in one of the Rover's seven memory banks, and if that's the case then they believe it could only be a matter of weeks before they can program Opportunity to only use the six that aren't corrupted.