Rover Finds Way to Brush Rock Surfaces Despite
Opportunity is still parked in front of the rock layer known as "Smith" inside Victoria Crater. The rover has now lost two encoders that operate motors on the rock abrasion tool during the grinding and brushing of surfaces. Science team members and engineers have been working in test beds and computer sequencing rooms to devise creative ways of using the rock abrasion tool without the grind and revolve encoders.
On sol 1347 (Oct. 7, 2007), they achieved their goal when Opportunity successfully completed a new, seek-scan procedure. Using this technique, the rover locates a rock surface by simultaneously spinning its grind teeth and wire brush while also extending toward the rock surface. Normally, the rock abrasion tool software monitors the safe operation of the grind or brush using the two encoders, which detect stalls that can occur during grinding and encoding. In the event of a stall, the encoders measure the z-axis position (the point where the rock abrasion tool contacts the rock surface). Without the encoders, engineers must rely on current limits and contact switches to know when grind teeth come into contact with a rock surface.
Opportunity followed a command to run both the grind and revolve motors along with a parallel command to move in toward the rock surface. When the rock abrasion tool made contact with the surface, contact switches disengaged, ending the activity. The following day, sol 1348 (Oct. 8, 2007), the science team directed the rover to retract the rock abrasion tool 1 millimeter and brush the surface. The brushing proceeded as planned!
Grind testing will continue next week using a rock abrasion tool with new grind bits on a surrogate rover on Earth in preparation for grinding new targets on Smith.
Opportunity is also scheduled to test communications next week with NASA's Mars Reconnaissance Orbiter. This test, along with other tests conducted recently with the European Space Agency's Mars Express orbiter, are demonstrations of the capability to conduct UHF communications in preparation for next year's arrival of the Phoenix lander.
Opportunity's solar array energy has been approximately 670 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour) per sol with atmospheric dust opacity, known as tau, of 0.87.
In addition to morning uplinks directly from Earth via the rover's high-gain antenna, evening downlinks to Earth via the Odyssey orbiter at UHF frequencies, standard measurements of atmospheric dust with the panoramic and navigation cameras, and surveys of the horizon with the panoramic camera, Opportunity completed the following activities:
Sol 1343 (Nov. 3, 2007): Opportunity ran diagnostic tests of the rock abrasion tool and collected compositional data from Smith using the Mössbauer spectrometer. The rover relayed data overnight to Odyssey.
Sol 1344: Opportunity continued to acquire compositional data from Smith with the Mössbauer spectrometer and scanned the sky for clouds with the navigation camera. Opportunity took full-color images, using all 13 filters of the panoramic camera, of a rock target known as "Jin," and took panoramic camera images of Smith and the rock layer known as "Lyell."
Sol 1345: Opportunity continued the compositional analysis of Smith with the Mössbauer spectrometer and monitored dust on the camera mast. The rover acquired color images using all 13 filters of the panoramic camera of a rock target dubbed "Gressly," scanned the sky for clouds, and took thumbnail images of the sky with the panoramic camera.
Sol 1346: Opportunity ran more diagnostic tests of the rock abrasion tool, placed the Mössbauer spectrometer back on Smith, and collected 11 hours' worth of compositional data with the instrument. The rover acquired a mosaic of images of Lyell as well as spot images of the sky with the panoramic camera.
Sol 1347: Opportunity completed a seek-scan procedure with the rock abrasion tool (during which the rover locates a rock surface by simultaneously spinning its grind teeth and wire brush while extending toward the rock surface). In addition, Opportunity took panoramic camera images of Lyell, measured atmospheric argon with the alpha-particle X-ray spectrometer, relayed data to the Odyssey orbiter overnight, and scanned the sky for clouds with the navigation camera.
Sol 1348 (Nov. 8, 2007): Plans called for Opportunity to complete an encoder-less brush of the surface of Smith, acquire microscopic images of Smith, place the alpha-particle X-ray spectrometer on Smith, and study composition of Smith with the spectrometer. The rover was to take panoramic camera images of "Cabo Frio," a promontory at the rim of Victoria Crater. Opportunity was to acquire full-color images, using all 13 filters of the panoramic camera, of a layered rock target known as "Brongniart."
As of sol 1348 (Nov. 8, 2007), Opportunity's total odometry remained at 11,584.32 meters (7.2 miles).