|Mars Rovers Get New Manager During Challenging Period||03.17.06|
|NASA's long-lived Mars rovers demand lots of care as they age and
the Martian winter approaches.
Dr. John Callas, newly named project manager for NASA's Mars
Exploration Rover mission, is coordinating the work to meet these
challenges. He is a scientist at NASA's Jet Propulsion Laboratory in
Pasadena, Calif. He was named project manager after earlier roles as
science manager and deputy project manager for the Spirit and Opportunity rovers.
Image right: Spirit's view of intricately layered exposures of rock at the feature known as "Home Plate." The image was taken in Feb. 2006. Image credit: NASA/JPL-Caltech/USGS/Cornell
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"It continues to be an exciting adventure with each day like a whole new mission,"
Callas said. "Even though the rovers are well past their original design life, they
still have plenty of capability to conduct outstanding science on Mars. The JPL
operations team and the remote science team working on the project are the best
in the solar system at what they do. It is a pleasure and a privilege to lead
such an outstanding team and great mission."
One of Spirit's six wheels has stopped working. Dragging that wheel, the solar-powered
rover must reach a slope where it can catch enough sunshine to continue operating
during the Martian winter. The period of minimum sunshine is more than 100 days away,
but Spirit gets only enough power for 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 mission, the motor
that rotates that wheel stopped working.
"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 rotating part of the motor, have lost contact. The motors
that rotate Spirit's wheels have revolved more than 13 million times, far more than called
for in the rovers' design.
Spirit's solar panels have been generating about 350 watt-hours of electricity daily for
the past week. That is down about 15 percent since February and less than one-half of
their output during the Martian summer.
Image left: Dr. John Callas. Image credit: NASA/JPL
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The best spot for Spirit is the north-facing side of "McCool Hill," where it could
spend the southern-hemisphere winter tilted toward the sun. Spirit finished studying
a bright feature called "Home Plate" last week and is driving from there toward the
hill. It has approximately 120 meters (about 390 feet) to go. Driving backwards with
the right-front wheel dragging, the rover needs to stop and check frequently that the
problem wheel has not snagged on anything and caused other wheels to slip excessively.
Expected progress is around 12 meters (40 feet) per day under current conditions.
Opportunity is closer to the equator, so does not need to winter on a slope like Spirit.
Opportunity spent most of the past four months at "Erebus 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
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.
JPL, a division of the California Institute of Technology, Pasadena, manages the
Mars Exploration Rover and Mars Reconnaissance Orbiter projects for NASA's
Science Mission Directorate.
For images and information about the rovers on the Web, visit:
For information about NASA and agency programs on the Web, visit:
Guy Webster (818) 354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne Brown/Erica Hupp
NASA Headquarters, Washington