sols 2159-2165, January 29 - February 4, 2010: Improving Northerly Tilt

Spirit is still embedded in the area called "Troy" on the west side of Home Plate.

Energy levels for Spirit have been decreasing rapidly as winter approaches. To increase energy production and to prepare for winter, the rover mobility system is being driven to improve northerly tilt.

On Sol 2161 (Jan. 31, 2010), Spirit drove her wheels backwards, employing several autonomous recovery techniques to prevent early termination of the drive from mobility faults. These autonomous recovery techniques have been effective in permitting the driving to continue much further than otherwise. Several centimeters of backward progress were made by the rover without further sinkage. Northerly tilt improved by about a degree. Every degree in improvement in northerly tilt enhances daily energy production by about 5 watt-hours.

On Sol 2165 (Feb. 4, 2010), another drive was sequenced. This drive achieved less progress and had only a modest improvement in tilt. The next drive plan is to cause the rover suspension to lift one side of the rover, improving northerly tilt. This is likely to be the last rover motion before winter, as energy levels are dropping below levels able to sustain driving. The project is configuring the rover's communication settings and fault parameters in preparation for the winter.

As of Sol 2165 (Feb. 1, 2010), the rover solar array energy production was to 188 watt-hours with an atmospheric opacity (tau) of 0.359 and a dust factor of 0.523. Total odometry is 7,730.48 meters (4.80) miles.

sols 2151-2158, January 20-28, 2010: Spirit Prepares for Winter

Spirit is still embedded in the area called "Troy" on the west side of Home Plate. Energy levels for Spirit have been decreasing rapidly as winter approaches. To prepare for winter, the project is taking actions to improve northerly tilt of the rover to maximize solar illumination.

The best approach has been to drive Spirit backwards. The drives employ a wheel steering action "frog kick" with each drive step. To mitigate against wheel stalls associated with driving in this embedded terrain, an autonomous wheel diagnostics has been added. If a wheel stall occurs, the diagnostic test is run on the stalled wheel. If the wheel passes the diagnostic, then driving resumes. This has been effective in permitting the driving to continue much further than otherwise.

Spirit continues to make several centimeters of backward progress with each drive without further sinkage. In some cases, the rover has gained in elevation. However, northerly tilt has not improved due mainly to the counterclockwise yaw of the rover. Backward driving will continue with the aim to position the rover for the winter with the most favorable orientation achievable.

As of Sol 2158 (Jan. 28, 2010), the rover solar array energy production was down to 182 watt-hours with an atmospheric opacity (tau) of 0.379 and a dust factor of 0.522. Total odometry is 7,730.46 meters (4.80 miles).

sols 2144-2150, January 13-19, 2010: Little Progress in Backward Driving

Spirit is still embedded in the area called "Troy" on the west side of Home Plate.

The project has begun backward driving with Spirit as the next technique to try for extrication. On Sol 2145 (Jan. 14, 2010), the first backward drive was performed. Up until this point, all extrication attempts had been with forward driving. Backward driving includes the additional technique of steering the wheels side-to-side before performing each drive step. The hypothesis on the wheel steering is two-fold. It clears out material in front of the wheel and allows material to slough off the face of the wheel trench providing traction under the wheel, and the flat surface of the wheel side (hub) "kicks" against the loose material like a swimmer's frog kick or breast stroke to provide motive force.

This backward driving technique has shown promise on sols 2145 (Jan. 14, 2010), 2147 (Jan. 16, 2010) and 2050 (Jan. 19, 2010) with the rover moving 3 to 4 centimeters (1.2 to 1.6 inches) per drive and the rover climbing in elevation, even with only four functioning drive wheels.

During the last drive, the left-middle wheel experienced a motor stall. The nature of the stall is not known: whether it is an external obstruction (e.g., a rock) or an internal actuator problem. A set of diagnostics have been sequenced on the rover before the next drive is attempted. As of Sol 2150 (Jan. 19, 2010), the rover solar array energy production was to 211 watt-hours with an atmospheric opacity (tau) of 0.400 and a dust factor of 0.542. Total odometry is 7,730.24 meters (4.80 miles).

sols 2137-2143, January 6-12, 2010: Little Forward Progress

Spirit remains embedded at the location called "Troy" on the West side of Home Plate. Extrication drives were tried on sols 2138, 2140 and 2142 (Jan. 7, 9 and 11, 2010). Each of these drives employed a new technique of steering the wheels back and forth before driving. This has shown some efficacy at sweeping material out of the wheel tracks and allowing fresh material to slough off the leading trench face providing traction under the wheel. Slower wheel speeds were also tried on two of the drives. However, even with these new techniques, little forward progress has been achieved. And excessive sinkage continues to occur with each attempt.

Both the right-front and right-rear wheel continue to be non-functional.

Next, Spirit will switch directions and attempt to drive backward to see if that provides better progress.

As of Sol 2143 (Jan. 12, 2010), Spirit's solar-array energy production is 225 watt-hours, with an atmospheric opacity (tau) of 0.490 and a dust factor of 0.539. Total odometry is 7,730.12 meters (4.80 miles).

sols 2131-2136, December 31, 2009 - January 5, 2010: Toe-In Maneuver Before Drive

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).