Mars Rovers Get New Manager During Challenging Period 20 March 2006

about one hour per day of driving on flat ground. And the supply is dropping fast.

Spirit's right-front wheel became a concern once before, when it began drawing unusually high current five months after the January 2004 landing on Mars. Driving Spirit backwards redistributed lubricant and returned the wheel to normal operation. This week, during the 779th Martian day of what was originally planned as a 90-Martian-day Spirit's view of intricately layered exposures of rock at mission, the motor that rotates that wheel stopped the feature known as "Home Plate." The image was working. taken in Feb. 2006. Image credit: NASA/JPL- Caltech/USGS/Cornell "It is not drawing any current at all," said JPL's Jacob Matijevic, rover engineering team chief. One possibility engineers are considering is that the motor's brushes, contacts that deliver power to the NASA's long-lived Mars rovers demand lots of care rotating part of the motor, have lost contact. The as they age and the Martian winter approaches. motors that rotate Spirit's wheels have revolved Dr. John Callas, newly named project manager for more than 13 million times, far more than called for NASA's Mars Exploration Rover mission, is in the rovers' design. coordinating the work to meet these challenges. He is a scientist at NASA's Jet Propulsion Spirit's solar panels have been generating about Laboratory in Pasadena, Calif. He was named 350 watt-hours of electricity daily for the past week. project manager after earlier roles as science That is down about 15 percent since February and manager and deputy project manager for the Spirit less than one-half of their output during the Martian and Opportunity rovers. summer.

"It continues to be an exciting adventure with each The best spot for Spirit is the north-facing side of day like a whole new mission," Callas said. "Even "McCool Hill," where it could spend the southern- though the rovers are well past their original design hemisphere winter tilted toward the sun. Spirit life, they still have plenty of capability to conduct finished studying a bright feature called "Home outstanding science on Mars. The JPL operations Plate" last week and is driving from there toward team and the remote science team working on the the hill. It has approximately 120 meters (about 390 project are the best in the solar system at what feet) to go. Driving backwards with the right-front they do. It is a pleasure and a privilege to lead wheel dragging, the rover needs to stop and check such an outstanding team and great mission." frequently that the problem wheel has not snagged on anything and caused other wheels to slip One of Spirit's six wheels has stopped working. excessively. Expected progress is around 12 Dragging that wheel, the solar-powered rover must meters (40 feet) per day under current conditions. reach a slope where it can catch enough sunshine to continue operating during the Martian winter. Opportunity is closer to the equator, so does not The period of minimum sunshine is more than 100 need to winter on a slope like Spirit. Opportunity days away, but Spirit gets only enough power for spent most of the past four months at "Erebus

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Crater." It examined layered outcrops, while the rover team determined and tested a strategy for dealing with degraded performance by a motor in the shoulder of its robotic arm. Opportunity left Erebus this week and is on a 2 kilometer (1.2 mile) journey to a giant crater called "Victoria."

Callas has worked on the Mars rovers' mission since 2000 and five other Mars missions since joining JPL in 1987. He succeeds Jim Erickson, who switched to a leadership role with NASA's Mars Reconnaissance Orbiter. Callas grew up near Boston and graduated from Tufts University, Medford, Mass. He earned his doctorate in physics from Brown University, Providence, R.I.

Source: NASA

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