Rover Wheel Jammed, Defunct One Revived

One of the biggest problems the rover Spirit had to deal with since two years after it arrived on Mars was the fact that it could no longer use its front-right wheel. The equipment had sustained damage, and this forced the robot to drive backwards for the last three years. In late May, it got stuck in Troy, the patch of loose sand that turned out to be the rim of a crater. As engineers were trying to remove the rover, the central-right wheel also jammed a few weeks ago. However, it would now appear that the long-defunct front-right wheel is operating again. Somewhat.

“Diagnostic tests were run on Spirit's right-rear wheel and right-front wheel on Sol 2013 (December 12). The right-rear wheel, which stalled during a drive two weeks earlier, continued to show no motion in the latest tests and exhibited very high resistance in the motor winding. The right-front wheel, which stopped operating on Sol 779 (March 13, 2006), surprised engineers by indicating normal resistance and turning slightly during a resistance test for that wheel,” engineers at the NASA Jet Propulsion Laboratory (JPL), who manage the mission, say in an official statement.

One of the reasons why the movement was so unexpected is the fact that the wheel's actuator was thought to be damaged beyond use. During electrical resistance tests, it is expected from the wheels to move slightly, but only if they have working actuators. The last time the front jammed wheel was checked was immediately after the 2006 failure, and it was established that it had an open circuit. Still, the damage was considered permanent, so engineers left it alone, and stopped sending commands to it for the last three years.

“Although no clear theory for failure had been established, the failure was generally regarded as permanent. It is important to remember that the Sol 2013 test of the right-front wheel was only a rotor resistance test, and no conclusions can be drawn at this point without further testing,” the team says. Later today, the JPL group is expected to release an assessment of the drive that was performed yesterday, December 15, with the purpose of gaining more information on the two wheels.