March 17, 2006

Dwayne Brown/Erica Hupp
Headquarters, Washington
(202) 358-1726/1237

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
(818) 354-6278

RELEASE: 06-101


NASA’s long-lived Mars rovers demand lots of care, as they age and the
Martian winter approaches.

John Callas, newly named project manager for NASA’s Mars Exploration
Rover missions, is coordinating the work to meet these challenges. He
is a scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena,
Calif. He was named project manager after earlier roles as science
manager and deputy project manager for the Spirit and Opportunity

“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 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 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 its 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.

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 toward the hill. It has approximately 120
meters (about 390 feet) to go. Expected progress is approximately 12
meters (40 feet) per day.

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 called Victoria.

Callas has worked on the Mars rovers’ operation since 2000 and five
other Martian 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: