Mars Exploration Rovers Update: Spirit Works on Exit Strategy – sols 1907-1912, May 15-20, 2009

Rover team members continue their recovery strategy to extricate Spirit from the loose, soft terrain on the west side of “Home Plate.” The rover continues to conduct extensive remote sensing observations of the local terrain.

With the extra energy Spirit has gained from recent solar array dust cleaning events, morning UHF relay passes have been added. A low- voltage continuity test of the motor on the left middle wheel was performed on Sol 1908 (May 16, 2009). The results showed normal resistance for a healthy motor. Even though very small voltages were used in that test, a tiny amount of motion (less than a degree) was observed. This is not unexpected, as the motion was opposite of the apparent jam from Sol 1899 (May 6, 2009) and is likely due to the unwinding (relaxation) of the strain in the 1500:1 gearbox. The small motion means it is now less likely there is a jam in the gearbox. A small 4-degree backward wheel motion test is planned for Sol 1913 (May 21, 2009) to investigate the wheel further.

On the ground, work continues on the preparation of the sandbox at JPL to recreate the terrain and conditions of the rover on Mars. A “shoebox” test of a soil simulant, called Bag House dust (a ground basaltic cinder), will be performed under one wheel of the surface system testbed (SSTB) rover to see if the simulant exhibits the characteristics of the soil on Mars. However, testing with the SSTB rover at JPL is held up due to a computer server disk crash. That server loss is being remedied, but will take some time.

As of Sol 1912 (May 20, 2009), solar-array energy production was 716 watt-hours, with atmospheric opacity (tau) around 0.628 and the dust factor improved to 0.680. Spirit has been responsive and communicative, with no reoccurrence of the anomalies from 30 sols ago.

As of Sol 1912 (May 20, 2009), Spirit’s total odometry remains 7,729.93 meters (4.8 miles).