NASA's Mars
Exploration Rover Spirit mysteriously rebooted its computer twice over the
weekend; mission controllers are examining data sent back by Spirit to see if
they can diagnose the problem behind the glitch.
"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 Spirit
project manager John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "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.
Fortunately,
the high-gain antenna isn't the only communication option with Spirit; the
rover can also communicate 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, and
its rover
twin Opportunity, finished their three-month prime mission on Mars five
years ago and have 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 390 feet (119 meters) 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.
Meanwhile,
on the other side of Mars, Opportunity has continued progress on a long-term
trek toward
Endeavour Crater, a bowl 14 miles (22 kilometers) in diameter and still
about 7 miles (12 kilometers) 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.
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