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One of Mars Rover's Wheels Stops Working

Posted on: Friday, 17 March 2006, 21:00 CST

PASADENA, Calif. - One of the Mars rover Spirit's wheels has stopped working and the solar-powered robot must use its five other wheels to drag itself up a slope to catch enough sunshine to keep operating in the descending Martian winter, NASA said Friday.

The right front wheel previously had an episode of balkiness but this week the motor that turns the wheel stopped working, the space agency's Jet Propulsion Laboratory said in a statement.

"It is not drawing any current at all," Jacob Matijevic, rover engineering team chief, said in the statement.

Spirit and its twin, Opportunity, landed on opposite sides of the Red Planet in January 2004 and have long outlasted missions originally planned to span 90 Martian days, which are a different length than Earth days.

Spirit's new wheel problem occurred this week during the rover's 779th Martian day.

JPL said engineers were considering whether the electrical motor's brushes - contacts that deliver power to the rotating part of the motor - have lost contact.

The same wheel began drawing unusually high current five months after landing. Controllers dealt with it by driving the rover backwards to redistribute lubricant. The wheel then began operating normally.

Spirit is again dragging the wheel as it tries to reach a position where it can get as much sunlight as possible during winter, but although the point of minimum sunshine is more than 100 days away, there is already only enough to power about one hour of driving on flat ground per day, JPL said.

Spirit is currently rolling toward a spot on the north-facing side of a feature called McCool Hill, where it could spend the southern-hemisphere winter with its solar panels angled toward the sun, JPL said.

The rover was 390 feet from that location Friday, with progress slowed by frequent need to stop and check whether the right front wheel had caught on anything.

Electrical generation from the solar panels is down about 15 percent since February and less than half of their output during summer. JPL said Spirit would make about 40 feet a day under the current conditions.

Opportunity, meanwhile, is closer to Mars' equator and won't have to winter over on a slope. The rover has finished a four-month study of a crater named Erebus and is making a 1.2-mile drive to giant Victoria crater.

The space agency also announced that JPL scientist John Callas has been named project manager for the Mars Exploration Rover mission. Callas was previously science manager and deputy project manager for the rovers.

"Even though the rovers are well past their original design life, they still have plenty of capability to conduct outstanding science on Mars," he said.

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On the Net:

Rovers: http://www.nasa.gov/rovers

Source: Associated Press/AP Online

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