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PASSPORT TO KNOWLEDGE - To MARS with MER
Daily Updates - May 20, 2004
Spirit Status at end of sol 131 - 133
Spirit continued its trek to the "Columbia Hills" over the past four sols, but took an unplanned break on Sols 131 and 132 due to a software fault on sol 131. That fault left rover planners with some uncertainty about Spirit's final position and attitude, so Sol 132 was spent re-establishing that knowledge with panoramic, navigation and hazard avoidance camera imaging of the rover's surroundings. The unplanned break did have a silver lining though; it resulted in fully charged batteries, paving the way for a long drive on Sol 133. Spirit roved 113 meters (370.7 feet) on Sol 133, with a record 78-meter (256 feet) autonomous navigation segment. The previous record for an autonomous navigation drive was 62 meters (203.4 feet) on sol 125. Spirit's odometer now reads 2473 meters (1.53 miles) and it is roughly 780 meters (.5 miles) from the Columbia Hills and in excellent health.
So what went wrong on sol 131? The flight software team is uncovering the details, but it appears that the error occurred within a 3-microsecond window of vulnerability when a "write" command was attempted to a "write-protected" area of RAM. The flight software team believes this is an extremely low probability event, and has not adjusted the planning process to avoid the miniscule period of vulnerability. Opportunity has the same vulnerability to the fault.