Mars Rover Team Diagnosing Unexpected Behavior

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif. January 28, 2009
Guy.Webster@jpl.nasa.gov

MARS EXPLORATION ROVER MISSION STATUS REPORT

Mars Rover Team Diagnosing Unexpected Behavior

CORRECTION: In paragraph 3--Early Tuesday, Spirit reported that it had followed
the commands, and in fact had located the sun, but not in its expected location.

PASADENA, Calif. - The team operating NASA's Mars Exploration Rover Spirit plans
diagnostic tests this week after Spirit did not report some of its weekend activities, including
a request to determine its orientation after an incomplete drive.

On Sunday, during the 1,800th Martian day, or sol, of what was initially planned as a 90-sol
mission on Mars, information radioed from Spirit indicated the rover had received its driving
commands for the day but had not moved. That can happen for many reasons, including the
rover properly sensing that it is not ready to drive. However, other behavior on Sol 1800 was
even more unusual: Spirit apparently did not record the day's main activities into the non-
volatile memory, the part of its memory that persists even when power is off.

On Monday, Spirit's controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif.,
chose to command the rover on Tuesday, Sol 1802, to find the sun with its camera in order to
precisely determine its orientation. Not knowing its orientation could have been one possible
explanation for Spirit not doing its weekend drive. Early Tuesday, Spirit reported that it had
followed the commands, and in fact had located the sun, but not in its expected location.

"We don't have a good explanation yet for the way Spirit has been acting for the past few
days," said JPL's Sharon Laubach, chief of the team that writes and checks commands for the
rovers. "Our next steps will be diagnostic activities."

Among other possible causes, the team is considering a hypothesis of transitory effects from
cosmic rays hitting electronics. On Tuesday, Spirit apparently used its non-volatile memory
properly.

Despite the rover's unexplained behavior, Mars Exploration Rovers' Project Manager John
Callas of JPL said Wednesday, "Right now, Spirit is under normal sequence control, reporting
good health and responsive to commands from the ground."

JPL, a division of the California Institute of Technology, Pasadena, manages the Mars
Exploration Rover project for the NASA Science Mission Directorate, Washington. Spirit and
its twin, Opportunity, landed on Mars in January 2004 and have operated 20 times longer than
their original prime missions.

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