Poor Spirit. She’s getting old, arthritic and forgetful. The “oldest” of the two Mars Exploration Rovers had another bout of what engineers from JPL are calling “amnesia.” About a week ago, she experienced some unexpected reboots of her computer. Then, she had three good days in a row, completing Earth-commanded activities without incident. But then on April 17 and 18, she became forgetful – she failed to record data into her flash memory (where information is preserved when Spirit is powered down) and rebooted herself again. The last reboot put Spirit into autonomous operation in which the rover keeps itself healthy, and engineers are running diagnostics to try to regain control of the rover.
“We are proceeding cautiously, but we are encouraged by knowing that Spirit is stable in terms of power and thermal conditions and has been responding to all communication sessions for more than a week now,” said JPL’s Sharon Laubach, chief of the rover sequencing team, which develops and checks each day’s set of commands.
Engineers operating Spirit are investigating the reboots, and trying to determine if the amnesia events are related to the reboots. Spirit has had three of these amnesia events in the past 10 days, plus one on Jan. 25. No causal link has been determined between the amnesia events and the reboots.
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Engineers have found ways to cope with various symptoms of aging on both rovers. The current diagnostic efforts with Spirit are aimed at either recovering undiminished use of the rover or, if some capabilities have been diminished, to determine the best way to keep using the rover.
Laubach said, “For example, if we do determine that we can no longer use the flash memory reliably, we could design operations around using the random-access memory.” Spirit has 128 megabytes of random-access memory, or RAM, which can store data as long as the rover is kept awake before its next downlink communications session.
During the past week of diagnostic activities, the rover has successfully moved its high-gain dish antenna and its camera mast, part of checking whether any mechanical issues with those components may be related to the reboots, the amnesia events, or the failure to wake up for three consecutive communication sessions two weeks ago.
Spirit and her twin, Opportunity, have been on Mars since 2004. Spirit’s right front wheel is stuck, and so she now drives backwards and drags the crippled wheel behind. The top image shows how the wheel is dragged through the Martian regolith.