The terrain that Opportunity is crossing has been steadily getting more wavy. After a long drive southward from "Voyager" crater, Opportunity's right-front steering motor stalled out on sol 433 during an end-of-drive turn. While performing tests to help the team diagnose the condition of that motor, the rover also continued to make remote-sensing observations. Testing in sol 435 did show motion in the steering motor, but analysis is still underway. The rover resumed normal science and driving operations on sol 436, but with restrictions on use of the right-front steering motor. It drove 30 meters on sol 437. Opportunity and Spirit are capable of driving with one or more steering motors disabled, though turns would be less precise. The latest revision in flight software on both rovers, uploaded in February, gives them improved capabilities for dealing with exactly this type of condition. It gives them upgraded ability to repeatedly evaluate how well they are following the intended course during a drive, and to adjust the steering autonomously if appropriate.
Sol-by-sol summaries:
Sols 430-432 (April 9-11, 2005): The weekend plan scheduled Opportunity to do some remote-sensing science on sol 430, a drive on sol 431 and more remote sensing on sol 432. However, the drive did not happen, due to a sequencing error that left the rover suspension limit active when it should not have been.
Sol 433: Opportunity drove 151 meters (495 feet) on its continued trek southward. During a turn at the end of the drive, the steering motor (not the drive motor) faulted out.
Sol 434: The rover completed some remote-sensing observations. Then it backed up
85 centimeters (33 inches) to see if the right-front wheel had bumped up against anything to cause the steering-motor stall. No rock or other obstacle was there. During the first attempt to straighten the wheels after backing up, the right-front steering motor stalled again. The wheel remained pointed about 8 degrees left of straight ahead.Sol 435: The sol's plan included more remote sensing, plus diagnostic tests using attempts to change the steering direction of the right-front wheel very slightly at different times of day and at different voltage levels. The testing did show motion in the steering motor. While analysis continues, the rover is resuming normal science and driving activities with restrictions on the use of the right-front steering motor.
Sol 436: Opportunity used the panoramic camera for some ground and sky observations, and continued testing of the miniature thermal emission spectrometer.
Sol 437: The team planned a southward drive of about 45 meters, but Opportunity curved left, sensed it was off course, and ended the drive after 30 meters. The same driving commands produced the same results in a software testbed at JPL, indicating that the curving resulted from how software parameters were set, rather than a hardware problem. Observations with the panoramic camera were completed as planned.
Odometry total as of sol 437 (April 16, 2005): 5,225 meters (3.25 miles).