Rover team members prepare an experiment for assessing how a test rover moves when embedded in loose soil and commanded to drive backward with wheels turned.
Mars Exploration Rover team members at NASA's Jet Propulsion Laboratory, Pasadena, Calif., prepare an experiment on July 13, 2009, for assessing how a test rover moves when embedded in loose soil and commanded to drive backward with wheels turned.
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Engineers checking possible rover movements to get Spirit out of the "Troy" sand trap on Mars are evaluating how a comparable rover at JPL fares in a crablike backward drive, with all four corner wheels turned 60 degrees toward the right.

This is the fifth of 11 maneuvers on the current testing list. Others ahead are crabbing backward with wheels turned 20 degrees to the right, a tight forward right arc, a clockwise turn in place, a counterclockwise turn in place, crabbing forward with wheels turned to the left, and driving while steering. Some of the maneuvers might be repeated.

The team is learning how the test rover reacts to various motions in a test sandbox built to simulate Spirit's situation at Troy. The steps eventually sent as driving commands to Spirit may be a combination of some of the 11 maneuvers being tested.

› Visit the Free Spirit website

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