NASA Mars Spirit Rover: Toe-In Maneuver Before Drive

Spirit Status for sol 2131-2136: Spirit remains embedded at the location called “Troy” on the west side of Home Plate. Attempts to extricate Spirit have been complicated by the lack of functionality in both the right-rear and right-front wheels.

Spirit Status for sol 2131-2136: Spirit remains embedded at the location called “Troy” on the west side of Home Plate. Attempts to extricate Spirit have been complicated by the lack of functionality in both the right-rear and right-front wheels.

On Sol 2132 (Jan. 1, 2010), the left-front, left-rear, and right-rear wheels were steered 60 degrees toe-in to try and cause material in front of the wheels to collapse into the trenches in which the wheels are embedded. The wheels were then steered back to straight forward in an attempt to use the flat outer surface of the wheel to push the previously collapsed material to the side of the wheel. The intent of this is to provide a free space in front of each wheel into which it may move. Four 2.5-meter (8.2-foot) forward drive steps were then commanded. The right-front wheel was then steered inward 60 degrees to allow driving with the wheel threads more aligned with the direction of motion.

The Sol 2132 drive was terminated during the initial steering of the wheels due to the flight software believing the left-rear steering motor had stalled. The left-rear wheel was continuing to steer but resistance from the surrounding soil had slowed it to a rate that the flight software did not detect as motion.

For Sol 2136 (Jan. 5, 2010), the team sequenced a drive to continue where the Sol 2132 drive terminated. The left-front, left-rear, and right-rear wheels were commanded back to straight. Four 2.5-meter (8.2-foot) drive steps were then commanded. The right-front wheel was then commanded to steer inward 60 degrees. An additional four 2.5-meter (8.2-foot) drive steps were commanded. The drive was terminated due to the onboard sinkage measurement in excess of 1 centimeter (0.4 inch). This drive achieved only 2.28 centimeters (0.9 inch) of forward progress.

As of Sol 2136 (Jan. 5, 2010), Spirit’s solar-array energy production is 243 watt-hours, with an atmospheric opacity (tau) of 0.482 and a dust factor of 0.545. Total odometry is 7,730.08 meters (4.80 miles).