Mars Exploration Rover Update - November 1, 2007

http://marsrovers.jpl.nasa.gov/mission/status.html#opportunity
OPPORTUNITY UPDATE: Opportunity Studies "Bathtub Ring" In "Victoria
Crater" - sol 1301-1308, Nov 01, 2007:
Opportunity is healthy, with energy levels ranging from about 450 watt-hours to 475 watt-hours (100 watt-hours is the amount of electricity needed to light a 100-watt bulb for one hour).
Recently, Opportunity was temporarily unable to send scientific data to Earth because the Odyssey orbiter experienced a computer crash and went into "safing" mode. While in safing mode, the spacecraft shuts off unnecessary power loads, orients itself for maximum sunlight to the solar arrays, switches to communication modes most likely to receive commands from Earth, and basically stops all unnecessary activity while waiting for the folks back home to fix it and put it back in service.
While in safing mode, Odyssey did not send communications from either Mars rover. Opportunity continued to collect as much science as possible while waiting for Odyssey to be fixed.
After Odyssey was back in service, Opportunity began making up for lost time. Following a series of "toe dips," during which the rover drove a short way into "Victoria Crater" and backed out again, then drove a little farther and backed out again, Opportunity began examining the crater's interior.
Victoria Crater is interesting because it affords a chance to study rock layers down to a depth of about 70 meters (230 feet) below the surrounding surface. The modern surface isn't the original surface -- it has been altered by an incoming meteor. When a meteor strikes, it throws up a huge amount of debris that falls back around the crater and creates an "ejecta blanket." This blanket is thickest near the crater rim and thinnest farther away from the crater.
Below Victoria's raised rim is a light-colored band nicknamed the "bathtub ring." Scientists hypothesize that this band is the dividing line between the original surface and the ejecta blanket above it. Opportunity has now reached this area -- but not without difficulty.
To reach the ring, Opportunity drove across a slope of about 25 degrees, nearly the maximum allowable tilt for the rover. The rover approached the ring on sol 1302 (Sept. 22, 2007) and then partially drove and partially slipped into closer position. On sol 1305 (Sept. 25, 2007), the rover unstowed the robotic arm and began studying the rocks that make up the top, or "Alpha," layer of the ring. Below that are two more layers, known as "Beta" and "Gamma," respectively.
Halfway through the last short drive of about 20 centimeters (8 inches), Opportunity automatically stopped when the rover violated the tilt limit. As a result, the rover drove laterally about 10 centimeters (4 inches) and then slid downslope 10 centimeters (4 inches). Subsequent analysis suggested that one of the downslope wheels rolled off a slight curb, producing a jolt that caused the rover to slip. Images showed that the rover had stopped on a hard outcrop of rock rather than sand or soil and was unlikely to slip farther.
Given the steep slope, Opportunity was extremely careful about moving the robotic arm. Before placing it on Alpha Layer, Opportunity moved the arm out, to the left, and to the right, while also checking for any vehicle motion with both the inertial measurement unit and cameras. The first rock target was dubbed "Steno."
Opportunity continued to conduct untargeted remote sensing by, among other things, measuring Tau, or atmospheric opacity, several times each Martian day, or sol. Now that the dust storms are over, the dust is settling. How fast it settles is of both scientific and engineering interest because it affects solar energy levels. Opportunity also periodically checked deposition and movement of dust on the panoramic camera mast assembly and solar arrays. This provides data for estimating wind directions and speeds, dust particle sizes, and dust composition.
Opportunity performed two "Quick Fine Attitude" checks. These are calibration activities that compensate for drift, or changes in time, in the inertial measurement unit. The unit uses gyroscopes and accelerometers to estimate the rover's motion, from which its position can be calculated. However, the gyroscopes show a slight change in attitude while the rover is still. (Older, mechanical gyroscopes drifted because of friction; newer, electronic gyroscopes drift for more complex reasons.)
The attitude checks compute where the sun should be based on the current time and the rover's movement and then compares this to the actual location of the sun in images from the panoramic camera. The difference forms the basis of the attitude correction for the rover.
Sol-by-sol summary:
In addition to daily observations that included frequent measurements of atmospheric dust with the panoramic and navigation cameras, surveys of the sky and ground with the miniature thermal emission spectrometer, and checks for drift (changes with time) in the miniature thermal emission spectromeer, Opportunity completed the following activities:
Sol 1301 (Sept. 21, 2007): Opportunity acquired panoramic camera images of the foreground, checked for drift in the miniature thermal emission spectrometer, checked the operation of the spectrometer, and surveyed the rover's external calibration target with the spectrometer. Before going into a deep sleep, the rover surveyed the horizon at low sun with the panoramic camera. The next morning, Opportunity monitored dust on the rover mast.
Sol 1302: Opportunity stowed the robotic arm, drove toward Alpha Layer, acquired images with the hazard avoidance cameras just prior to and after completing the drive, and completed a "quick fine attitude" update to confirm the rover's exact location. The rover unstowed the robotic arm, acquired post-drive images with the navigation camera, and acquired panoramic camera images of the work volume (the area reachable by instruments on the robotic arm). After that, Opportunity went into a deep sleep.
Sol 1303: Opportunity assessed the external calibration target with the miniature thermal emission spectrometer, recalibrated the panoramic camera, and spent six hours measuring atmospheric argon with the alpha-particle X-ray spectrometer. The rover went into a mini-deep sleep.
Sol 1304: Opportunity surveyed the external calibration target with the miniature thermal emission spectrometer, recalibrated the panoramic camera, and went into a deep sleep. The next morning, the rover took spot images of the sky with the panoramic camera.
Sol 1305: Opportunity stowed the robotic arm, bumped (drove a short distance) to Alpha Layer, and acquired penultimate and ultimate images with the hazard avoidance cameras. The rover completed a "quick fine attitude" check, acquired panoramic camera images of the work volume, unstowed the robotic arm, and acquired post-drive navigation camera images. Opportunity recalibrated the panoramic camera and went into a deep sleep.
Sol 1306: Opportunity acquired data from the external calibration target with the miniature thermal emission spectrometer and recalibrated the panoramic camera.
Sol 1307: Opportunity completed a "quick fine attitude" check, conducted a safety test with the robotic arm, acquired left-eye images of the alpha-particle X-ray spectrometer with the panoramic camera, and acquired stereo images of Steno with the microscopic imager. The rover placed the alpha-particle X-ray spectrometer on Steno and, after relaying data to Odyssey and recalibrating the panoramic camera, collected data from Steno with the spectrometer for 12 1/2 hours.
Sol 1308 (Sept. 28, 2007): After the usual dust monitoring and imaging activities as well as data relays to Odyssey, Opportunity went into a deep sleep.
Odometry:
As of sol 1308 (Sept. 28, 2007), Opportunity's total odometry was 11,572.94 meters (7.19 miles).
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http://marsrovers.jpl.nasa.gov/mission/status.html
SPIRIT UPDATE: Spirit to Head North for the Winter - sol 1355-1362, November 02, 2007:
With Martian winter approaching, the science and engineering teams have been hard pressed to select a site where Spirit can spend the winter. After previously narrowing the list of candidates to two sites, Spirit's handlers decided to send the rover to the northern edge of the elevated plateau known as "Home Plate," which Spirit has been exploring for many months now.
Previously considered sites included "von Braun," "South Promontory," "Batter's Box" ("West Knoll"), and "North Home Plate." The decision means the rover will move farther away from tantalizing, new terrain to the south, but maximizes the rover's chances of surviving another winter given the excessive coating of dust on the solar arrays.
As Project Manager John Callas announced in an e-mail, "the principal discriminator was the achievable slope at each site. The north side of 'Home Plate' offers slopes of 25 degrees of northerly tilt, while 'South Promontory' offers 20 degrees of northerly tilt. That difference is about 10 watt-hours per sol, which can mean the difference between surviving and not surviving the cold, dark winter."
Meanwhile, Spirit remains healthy and all subsystems are nominal. Energy has been averaging 355 watt-hours (100 watt-hours is the amount of electricity needed to light one 100-watt bulb for one hour) and atmospheric dust measurements (Tau) have been steady at about 0.63.
Plans called for Spirit to head in a northerly direction, toward an area known as "Site 5" on top of Home Plate, starting on sol 1362 (Nov. 2, 2007). Once there, Spirit may investigate some targets with instruments on the robotic arm before continuing to the north end of Home Plate.
Meanwhile, engineers working on the rover's miniature thermal emission spectrometer have determined that degradation in performance of the spectrometer on both Spirit and its twin, Opportunity, is the result of dust deposition on the scan mirror or in the panoramic camera mast assembly. They have decided not to use the instrument on Opportunity and to use it only for high-priority targets and weekly atmospheric measurements on Spirit while they try to develop strategies for removing the dust.
In addition, tests run on sols 1355, 1358, and 1360 (Oct. 25, Oct. 29, and Oct. 31) determined that the grind motor on Spirit's rock abrasion tool failed on sol 1341 (Oct. 11, 2007) , as it did previously on Opportunity on sol 1045 (Jan. 1, 2007). However, because the rover's handlers have devised an alternate technique for grinding and brushing that takes two Martian days, they are still able to use the brushes on both rock abrasion tools.
Sol-by-sol summary
In addition to receiving morning instructions directly from Earth via the high-gain antenna, sending evening data to Earth at UHF frequencies via the Odyssey orbiter, measuring atmospheric dust levels with the panoramic camera, and surveying the sky and ground with the miniature thermal emission spectrometer, Spirit completed the following activities:
Sol 1355 (Oct. 25, 2007): Spirit unstowed the robotic arm, conducted imaging diagnostics of the rock abrasion tool, and took microscopic images of the capture magnet. The rover placed the alpha-particle X-ray spectrometer on the capture magnet, took panoramic camera images of the rover deck, and transmitted data overnight via the Odyssey orbiter. Spirit monitored dust on the panoramic camera mast assembly, surveyed the horizon with the panoramic camera, acquired a mosaic of images with the navigation camera, and acquired movie frames in search of dust devils with the navigation camera.
Sol 1356: Spirit acquired panoramic camera images of the rover deck and of rock targets nicknamed "Grays Peak," "Elk," and "San Juan." The rover acquired 6 hours worth of data with the alpha-particle X-ray spectrometer and took thumbnail images of the sky with the panoramic camera.
Sol 1357: Spirit used the navigation camera to survey the surface darkened by the rover's shadow. The rover acquired full-color images of its tracks using all 13 filters of the panoramic camera. Spirit acquired another 6 hours of data with the alpha-particle X-ray spectrometer and took spot images of the sky with the panoramic camera.
Sol 1358: Spirit took images of the filter magnet with the microscopic imager, performed diagnostic tests on the rock abrasion tool, and used the panoramic camera to take images of the rover deck and survey the horizon.
Sol 1359: Spirit turned in place for communications relays and performed a "get quick fine attitude" to check for changes in the inertial measurement unit to determine the rover's precise location. Spirit acquired post-drive images with both the navigation and panoramic cameras. In the morning, the rover completed a systematic ground survey with the panoramic camera.
Sol 1360: Spirit unstowed the robotic arm, performed diagnostic tests of the rock abrasion tool, and acquired a mosaic of microscopic images of a soil target known as "Pumpkin Pie" before placing the alpha-particle X-ray spectrometer on the target. Spirit acquired full-color images, using all 13 filters of the panoramic camera, of another soil target known as "Candy Corn." The rover collected data from Pumpkin Pie with the alpha-particle X-ray spectrometer and in the morning, scanned the sky for clouds with the navigation camera. Spirit also surveyed the horizon with the panoramic camera and acquired movie frames in search of dust devils with the navigation camera.
Sol 1361: Spirit stowed the robotic arm in preparation for the next day's drive and took full-color images, using all 13 filters of the panoramic camera, of Elk and San Juan. The rover acquired a mosaic of images with the navigation camera as part of a 360-degree panorama for drive planning. Spirit surveyed the sky at both low sun and high sun with the panoramic camera.
Sol 1362 (Nov. 2, 2007): Plans called for Spirit to drive toward Site 5, acquire full-color, mid-drive images of Pumpkin Pie with all 13 filters of the panoramic camera, and acquire post-drive images with both the navigation and panoramic cameras. The following morning, Spirit was to complete a survey of rock clasts with the panoramic camera and scan the sky for clouds with the navigation camera.
Odometry:
As of sol 1359 (Oct. 30, 2007), Spirit's total odometry was 7,339.70 meters (4.56 miles).
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