Spirit Healthy but Computer Reboots Raise Concerns

MEDIA RELATIONS OFFICE
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Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif. April 13, 2009
Guy.Webster@jpl.nasa.gov

Mars Exploration Rover Mission Status Report

Spirit Healthy but Computer Reboots Raise Concerns

The team operating NASA's Mars Exploration Rover Spirit is examining data received
from Spirit in recent days to diagnose why the rover apparently rebooted its computer at
least twice over the April 11-12 weekend.

"While we don't have an explanation yet, we do know that Spirit's batteries are charged,
the solar arrays are producing energy and temperatures are well within allowable ranges.
We have time to respond carefully and investigate this thoroughly," said John Callas of
NASA's Jet Propulsion Laboratory, Pasadena, Calif., project manager for Spirit and twin-
rover Opportunity. "The rover is in a stable operations state called automode and taking
care of itself. It could stay in this stable mode for some time if necessary while we
diagnose the problem."

Spirit communicated with controllers Friday, Saturday and Sunday, but some of the
communication sessions were irregular. One of the computer resets apparently coincided in
timing with operation of the rover's high-gain dish antenna.

The rover team has the advantage of multiple communication options. Spirit can
communicate directly with Earth via either the pointable high-gain antenna or, at a slower
data rate, through a low-gain antenna that does not move. Additionally, communications
can be relayed by Mars orbiters, using the UHF (ultra-high frequency) transceiver, a
separate radio system on the rover.

"To avoid potential problems using the pointable antenna, we might consider for the time
being just communicating by UHF relay or using the low-gain antenna," Callas said.

Spirit finished its three-month prime mission on Mars five years ago and has kept operating
through multiple mission extensions.

The rover's onboard software has been updated several times to add new capabilities for
the mission, most recently last month. The team is investigating whether the unexpected
behavior in recent days could be related to the new software, but the same software is
operating on Opportunity without incident.

"We are aware of the reality that we have an aging rover, and there may be age-related
effects here," Callas said.

In the past five weeks, Spirit has made 119 meters (390 feet) of progress going
counterclockwise around a low plateau called "Home Plate" to get from the place where it
spent the past Martian winter on the northern edge of Home Plate toward destinations of
scientific interest south of the plateau. On March 10, after several attempts to get past
obstacles at the northeastern corner of Home Plate, the rover team decided to switch from
a clockwise route to the counterclockwise one. Subsequent events have included Spirit's
longest one-day drive since the rover lost use of one of its wheels three years ago, plus
detailed inspection of light-toned soil exposed by the dragging of the inoperable wheel.

Halfway around Mars, meanwhile, Opportunity has continued progress on a long-term trek
toward Endeavour Crater, a bowl 22 kilometers (14 miles) in diameter and still about 12
kilometers (12 miles) away. Last week, a beneficial wind removed some dust from
Opportunity's solar array, resulting in an increase by about 40 percent in the amount of
electrical output from the rover's solar panels.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars
Exploration Rover project for NASA's Science Mission Directorate, Washington.

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