More Troubles for Spirit Rover
Written by Nancy Atkinson
NASA's Mars Exploration Rover Spirit drove 6.98 meters (22.9 feet) southeastward on the 1,871st Martian day, or sol, of the rover's mission on Mars (April 8, 2009). As usual since losing the use of its right-front wheel in 2006, Spirit drove backward, dragging the immobile wheel. Image credit: NASA/JPL-Caltech. Full image and caption
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.
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.
Spirit driving off into the sunset, a special effects image. credit: NASA/JPL-Caltech/Cornell
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.
Source: JPL
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April 20th, 2009 at 11:11 pm
This is more a question than a comment – is this all down to physical aging of the components (chemical and mechanical) or does the software somehow accumulate bad data over time which then leads to some of the observed problems ?
April 21st, 2009 at 2:07 am
Bjørn wonders:
"….does the software somehow accumulate bad data over time which then leads to some of the observed problems ?"
and I wonder: wouldn't those bad data be cleared during a reboot? Isn't such "cleaning up" the purpose of a reboot? That's why I occasionally re-launch applications or reboot my 'puter – to get rid of accumulated "rubbish".
So: is there something causing data become corrupted? Physical aging, after all?
Spirit has been going more than 30 times longer than her expected lifetime!!!!! If I was to do only half as well… gosh, the things I'd live to see…. and the mistakes I'd live to make…
April 21st, 2009 at 6:11 pm
Feenixx, Bjorn – I believe the circuits have had some notable cosmic ray strikes which have caused deterioration in performance.
Now is it just me or is anyone else moved to strong emotions over these heroic Rovers? In fact, the whole Mars shebang is a great source of wonder and I feel increasingly certain we will mount a manned expedition in the next thirty years. I hope there's room in the capsule for a can of WD-40 for Spirit and Opportunity.
April 22nd, 2009 at 9:25 am
I think Spirt is becoming sentient. All the cosmic radiation have allowed the rover to begin to think and its shedding its earth bound controllers. JK