Mars Exploration Rover Update - October 20, 2004

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SPIRIT UPDATE: Spirit investigating ancient rocks - sol 272-278,
October 20, 2004
Spirit had a productive week investigating the rock "Tetl." On sol 277,
Spirit attempted a drive to the next rock target, "Uchben," which means
"ancient" in the old Mayan language. Halfway into that drive, Spirit
experienced a repeat problem in the steering motor control system that
engineers first saw on sol 265. Engineers repeated diagnostic tests for
the problem on sol 278. Those tests showed that the electronics relay in
question is still functional, but appears to operate intermittently.
Spirit is otherwise healthy and is in a safe location.
On sol 272, Spirit took images with the microscopic imager to create a
mosaic of Tetl's layered rock face.
On sol 273, Spirit captured more microscopic images of Tetl's layered
face, then put the alpha particle X-ray spectrometer in place for an
early morning observation.
On sol 274, Spirit woke up at 4:00 a.m. to start the alpha particle
X-ray spectrometer observation. The alpha particle X-ray spectrometer
stayed on until the start of normal morning atmospheric science
observations. Spirit also used its miniature thermal emission
spectrometer to observe nearby rocks named "Zackuk" and "Palenque,"
which are possible future targets for in-depth observations. Later,
Spirit changed tools on its robotic arm, placing the Mossbauer
instrument on Tetl for an observation the next morning.
On sol 275, Spirit completed a 6-hour Mossbauer integration and
performed daily atmospheric observations. This was the final sol of
Spirit's weekend plan and was purposely simple to enable the sequencing
team to complete a 3-day plan on Friday.
On sol 276, Spirit restarted the Mossbauer instrument at 4:00 a.m. for
another 10 hours of integration time on the same spot. Spirit also took
a few final microscopic images of Tetl, then stowed the robotic arm in
preparation for the next sol's drive.
On sols 277 and 278, Spirit attempted a drive to Uchben, another layered
rock roughly 6 meters (20 feet) northeast of Tetl. About 2.5 meters (8
feet) into the drive, the mobility software attempted to move a steering
motor by first commanding open a relay (electronic switch) that releases
a dynamic brake. The feedback from that command indicated that the relay
was still closed, so the motor control software declared an error. Due
to the error, the rover ignored that steering command and all subsequent
driving commands. The root cause of the failed relay command is under
investigation. A diagnostic test last run on sol 270 was repeated on sol
278, which ended on Oct. 14. That test showed that the steering motor's
dynamic brake relay can still be opened and closed, but does
occasionally (5 out of 10 times) indicate that it is still closed after
being commanded open.
More diagnostics tests are needed before the source of the problem can
be positively identified. Until then, engineers will continue to drive,
but will steer the rover in a tank-like fashion, not using the steering
actuator in question.
Future plans are to clear the drive error and attempt another drive to
Uchben on sol 281. Engineers are also planning to run more diagnostic
tests starting on sol 282.
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