Mars Exploration Rover Update - March 31, 2006

http://marsrovers.jpl.nasa.gov/mission/status.html
SPIRIT UPDATE: Difficult progress with five-wheel drive - sol 790-797,
Mar 31, 2006:
NASA's Mars Odyssey orbiter resumed communication-relay support of the Mars Exploration Rovers on March 25, 2006. Spirit executed drives on sols 792 and 794 (March 26 and 27), but has been having trouble making progress given the current terrain and driving conditions. The team is developing new drive strategies for five-wheel driving in the test facility at the Jet Propulsion Laboratory. The new techniques for turning the rover to face waypoints are proving successful on Mars, but soft soil and inclines in Spirit's current location make uphill progress difficult to achieve. At the end of the week, the team decided to stop trying to advance along a route Spirit had been attempting in recent sols and, instead, to drive back downhill a few meters and then begin a different route toward a north-facing slope for surviving the Martian winter.
Right-front wheel status
Diagnostic tests run on the drive motor for Spirit's right-front wheel at various voltage levels resulted in no motion. These tests were consistent with results in the test facility, and they indicate an open connection in the motor. As a result, the team has precluded further use of this motor, so Spirit will continue driving with five wheels.
Sol-by-sol highlights:
Sol 790 (March 24): Spirit completed its usual morning science observations of assessing the clarity of the sky (a variable called "tau") with the panoramic camera, and checking the sky and ground with the miniature thermal emission spectrometer. Before shutting down for this light-activity sol, the rover used 13 different filters of the panoramic camera to examine soil that had been churned up in wheel tracks.
Sol 791: The Mars Odyssey orbiter, which had been unavailable for communication-relay support for three days because it went into a precautionary "safe" mode temporarily, resumed relay work. Spirit used the panoramic camera for assessing sky clarity and for surveying some rocks. It used the miniature thermal emission spectrometer for sky and ground observations and to examine the disturbed soil in the wheel tracks.
Sols 792 and 793: With a new downlink from Odyssey, the team came in on Saturday to plan a two-hour drive for sol 792. Spirit turned about 125 degrees to face a new drive target and began to drive toward it. The drive ended a few meters later when Spirit detected 71-percent slippage. On sol 793, Spirit completed a light schedule of remote-sensing observations.
Sols 794 and 795: Spirit drove 5.7 meters (19 feet) on sol 794, but most of the odometry change was a part of the heading change, rather than progress toward a destination. Again, high slip terminated the drive. As in the previous two-sol plans, there was light remote sensing on the second sol.
Sols 796 and 797: Spirit's sol 796 uplink time was during a Mars Reconnaissance Orbiter aerobraking maneuver and the two spacecraft cannot use the same radio band at the same time, so the rover team used forward commanding relayed via Odyssey to uplink Spirit's sequences of commands for sols 796 and 797. The plan for sol 796 was to turn 60 degrees clockwise toward a new waypoint and drive toward it using visual odometry to help check for slip. The rover drove 4 meters (13 feet) before the drive stopped due to excessive (61 percent) slippage. As on the previous drive attempt, most of the added odometry was in the turning, not forward progress. After the drive, Spirit acquired images to help the uplink team analyze possible alternative routes to north-tilted slopes.
As of sol 796 (March 30, 2006), Spirit's total odometry was 6,836.48 meters (4.25 miles).
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