Status Report

NASA Mars Rover Status 30 August 2004

By SpaceRef Editor
August 31, 2004
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NASA Mars Rover Status 30 August 2004

OPPORTUNITY UPDATE: Trying Traverses – sol 204-208, August 30, 2004

Sol 204 was planned as a rather circuitous 6-meter (about 20-foot)
traverse to the vicinity of a target called “Shag” on one side of a rock
called “Ellesmere.” The route was necessary to avoid a significant rock
hazard close to the rover’s position. Unfortunately, due to the steep
slopes and lack of traction when driving in this terrain, the rover
experienced up to 50 percent slip during parts of its traverse. It ended
up more than 50 centimeters (about 20 inches) downslope from the planned
final position. This left the rover close to the edge of its safe
terrain zone.

For sol 205, the team shifted its objective from Shag to another target,
“Auk,” on the other side of Ellesmere. Auk, though farther from the
rover’s current position, was of higher scientific priority, in safer
terrain, and more accessible to the rover arm. To avoid the significant
slip observed during turns in place, the traverse was planned as a
tight-radius turn covering 1.6 meters (5.2 feet). Mindful of the
uncertainties inherent in navigating in this terrain, planners designed
the traverse to cover only a portion of the total distance to Auk. This
proved to be prudent, since the rover again ended up slipping more than
50 percent during most of its drive, with little progress away from
dangerous terrain. On the bright side, analysis of the drive indicated
that the rover was getting better traction during its last moves.

On sol 206 the rover was commanded to perform a drive to turn away from
its cross-slope orientation and move upslope toward Auk. The drive
succeeded. After the slips of the sol 205 traverse, this traverse
managed nearly all of the desired yaw response to get the rover pointed
uphill and then found good traction to deliver the rover more than a
meter (3.3 feet) farther upslope. Serendipitously, the rock directly in
front of the rover at the end of the drive proved to be so interesting
to the science team that efforts were redirected to study it. The rock
was dubbed “Escher.”

On sol 207 the team entered restricted planning. This happens when the
timing of the rover’s sol on Mars and our day in the California time
zone get out of sync due to the nearly 40-minute difference in length of
Earth days and Mars sols. The afternoon downlink arrives at JPL too late
in the day to plan the next sol unless the team works through the night.
Instead of staying up all night, the team plans with restrictions that
forbid rover movement or arm activity on a sol immediately following a
sol on which the rover has moved. This gives additional time for the
data to become available so that planners can use up-to-date knowledge
about the rover’s position and orientation.

So, rather than any driving on sol 207, Opportunity conducted
remote-sensing work, including atmospheric observations and panoramic
camera imaging of several features.

For sol 208, which ended on Aug. 25, Opportunity drove again. It bumped
forward to put Escher well within the arm’s work volume. The sol also
included panoramic camera imaging of Escher and of a trench created by
Opportunity’s prior wheel movements in the vicinity. Opportunity slept
deeply on the night of sol 208 for the second night in a row. The
purpose of successive deep sleeps was to align the deep-sleep nights
with poorer overnight Mars Odyssey passes, leaving the rover ready to
take advantage of higher-volume passes on alternate nights.

SpaceRef staff editor.