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Fwd = Mars rover recovering from memory problems

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  • Frits Westra
    Mars rover recovering from memory problems 13:35 28 January 04 http://www.newscientist.com/news/news.jsp?id=ns99994610 NewScientist.com news service A full
    Message 1 of 1 , Jan 29 8:17 AM
      Mars rover recovering from memory problems

      13:35 28 January 04

      http://www.newscientist.com/news/news.jsp?id=ns99994610

      NewScientist.com news service

      A full revival of the Mars rover Spirit from its electronic ailments now
      seems highly likely. Engineers now think there is no real hardware or
      software problems, but something much easier to fix - a simple overload of
      files in its onboard memory.

      If further testing confirms this diagnosis, that will be very good news
      for Spirit's twin, Opportunity. Any software bug or hardware weakness
      would probably be present in both rovers and might require weeks of
      analysis and repair.

      But if, as it appears, the problem is a previously unrecognised limit on
      the number of files that can be stored in the craft's flash memory, then
      Opportunity's data collection and file management can be planned to
      prevent the problem.

      This would avoid the bleak situation faced by engineers when Spirit fell
      silent for more than a day and failed to respond to commands. Having
      initially described the Spirit's troubles as "critical", mission manager
      Jennifer Trosper says "the patient is now in rehab".

      However, Opportunity has developed a problem of its own, according to
      another mission manager Jim Erickson. The rover is losing power,
      apparently due to a heating unit that is switching itself on when it
      should not. What this will mean for the rover's mission and whether it can
      be fixed are not yet known.


      Coaxed communication

      Spirit's controllers have been coaxing the rover back into communication
      since it ended its silence on Thursday with a single bleep. The
      engineering data returned has allowed them to piece what had happened.

      The rover first failed halfway through a test of a moving mirror that
      directs light to the mini-TES instrument. The high-gain antenna was also
      being used at the time, and the spacecraft entered a "safe mode"
      associated with antenna problems.

      Later data returns showed the craft had entered a repeating cycle of
      resetting its computer system, preventing it from carrying out anything
      but the simplest commands. At last count, it had rebooted itself more than
      120 times. This constant resetting prevented it from entering its night
      sleep cycle, needed to conserve its batteries.

      But detailed analysis of the start of each reset cycle eventually led to
      the apparent answer to the mystery. The problem was clearly associated
      with the handling of files being written to one of its three types of
      internal memory: a non-volatile 256 megabyte flash memory.

      Testing on Monday and Tuesday suggests that it is not the flash memory
      itself that is at fault, but the software's file-handling system.
      Unbeknownst to the engineers, there seems to be a limit on the number of
      files that can be simultaneously stored in the flash memory, even though
      the overall memory capacity is not full.

      The solution is likely to be simply deleting unneeded files, many of which
      were accumulated during the eight-month journey to Mars. It will require
      some skillful programming to get the computer to do this without falling
      back into its resetting cycle, but Trosper says a full recovery is now
      expected.

      David L Chandler


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