* Astronomy

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 tantalising, new terrain to the south, but maximises 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-colour 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-colour 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-colour 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-colour, 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 metres.

Panorama of the Homeplate feature in Gusev crater, taken by the Spirit rover on October 30, 2007 (Sol 1359)


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Credit NASA

SPIRIT UPDATE: Spirit Considers Options for Surviving Another Winter on Mars - sol 1348-1354, October 30, 2007:

Spirit's handlers are currently confronted with the decision of where to send the rover for the winter. Dust deposition on the rover's solar panels, a product of the recent dust storms, has made power predictions for the upcoming winter even worse than those experienced during Spirit's last Martian winter. Members of the science team hope to find a place where Spirit can achieve a tilt of 20 degrees or more toward the north, facing the sun.
During the week, Spirit drove approximately 50 meters in a southerly and southeasterly direction toward a potential off-ramp from the top of the elevated plateau known as "Home Plate."
Proposed locations for a winter haven include driving south down the off-ramp and making a break for "von Braun," a hill approximately 120 metres away; heading north across Home Plate and driving down the north-facing edge; or driving west of Home Plate to a hill tentatively identified as "West Knob."
On sols 1349 and 1351 (Oct. 19 and Oct. 21, 2007), Spirit acquired long-baseline stereo images of von Braun, to the south of Home Plate.
Spirit has been generating approximately 345 watt-hours of solar array energy (enough to run a 100-watt bulb for almost 3 1/2 hours) per Martian day (or sol). Measurements of atmospheric dust opacity, known as Tau, have been approximately 0.7 (higher Tau measurements correspond to more dust).

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 1348 (Oct. 18, 2007): Spirit drove approximately 14 metres to get into position for the first "eye," or vantage point, of the long-baseline stereo panorama. The rover took a 7-by-1, post-drive image mosaic, measured the thermal characteristics of the external calibration target with the miniature thermal emission spectrometer, and acquired thumbnail images of the sky with the panoramic camera.

Sol 1349: Spirit created a list of files on board and then proceeded to acquire the left-eye portion of the long-baseline stereo panorama. The rover relayed data to Earth during the overnight pass of the Odyssey orbiter, completed a systematic ground survey using all 13 filters of the panoramic camera, and took spot images of the sky with the panoramic camera.

Sol 1350: Spirit drove approximately 8 metres to the second vantage point for the long-baseline stereo view and then acquired a post-drive image mosaic (a 6-by-1 panel) with the navigation camera. The rover acquired images of the external magnets through all filters of the panoramic camera.

Sol 1351: Spirit acquired the right-eye portion of the long-baseline stereo panorama and spent 6 1/2 hours collecting measurements of atmospheric argon with the alpha-particle X-ray spectrometer. The rover surveyed the horizon with the panoramic camera and watched for dust devils.

Sol 1352: Spirit acquired pre-drive images with the panoramic camera to fill in portions of the right-eye view of the stereo image mosaic. The rover drove approximately 6 metres south-southeast toward the potential south off-ramp of Home Plate and acquired a 5-by-1 mosaic of images with the navigation camera as well as a 4-by-1 mosaic of images with the panoramic camera. Spirit took spot images of the sky, conducted a survey of rock clasts with the panoramic camera, and searched for dust devils with the navigation camera.

Sol 1353: Spirit drove approximately 10 meters south-southeast toward the potential south off-ramp and acquired a 5-by-1, post-drive image mosaic with the navigation camera and a 4-by-1, post-drive image mosaic with the panoramic camera. The rover surveyed the horizon and completed a survey of rock clasts with the panoramic camera. Spirit watched for dust devils.

Sol 1354 (Oct. 24, 2007): Spirit acquired a 4-by-1, pre-drive panel of images of "West Knob" with the panoramic camera and drove approximately 12 meters south-southeast toward the potential off-ramp. The rover acquired a 5-by-1, post-drive image mosaic with the navigation camera and a 4-by-1 image mosaic with the panoramic camera. Spirit tested communications with the Mars Express orbiter, a European Space Agency mission, in preparation for next year's arrival of NASA's Phoenix lander. The rover completed a systematic ground survey and horizon survey with the panoramic camera.

Odometry:
As of sol 1354 (Oct. 24, 2007), Spirit's total odometry was 7,338.78 metres.

Image taken by the Spirit rover on Sol 1337


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Credit NASA