Mars Exploration Rovers Update - January 24, 2005
SPIRIT UPDATE: Spirit at 'Peace' - sol 367-373, January 24, 2005
Spirit is healthy, but reduced sunlight has been reaching the rover
through the atmosphere due to a possible dust storm identified from orbital data. Despite limited energy during the period from sol 367 through sol 373, Spirit made good progress by driving about 20 meters (66 feet) closer to top of "Cumberland Ridge." Spirit is investigating a rock called "Peace."
Sol-by-sol summaries:
During a two-sol plan on sols 367 and 368, Spirit traversed about 14 meters (46 feet) up the steep hillside toward the ridge and a target named "Larry's Lookout." The average slippage during the drive is estimated at 14 percent, indicating much firmer footing than previous drives. Sol 368 was a remote sensing sol. Spirit made observations with its panoramic camera and its miniature thermal emission spectrometer and performed a successful test of the right eye of the panoramic camera to find the Sun. The rover team usually uses the left panoramic camera to locate the Sun.
"Sun finding" is sometimes called "get fine attitude" or "attitude update," and is something engineers do every couple of weeks to correct error in the rover's knowledge of attitude -- mostly which way is north. This takes the same kind of images of the Sun that the atmospheric science team does, but the engineers use the data to determine attitude. Between the updates, the rover uses the onboard computer to keep track of attitude changes, but error builds up in this measurement over time. In general, most of the panoramic camera images of the Sun are acquired for atmospheric science. Many images are used to determine how much dust is in the atmosphere (atmospheric opacity or Tau). Usually engineers take these images three or four times during the day. With the current dust storms, the team is taking even more images of the Sun.
Sols 369, 370, and 371 were part of a three-sol plan. On sols 369 and 370, Spirit looked for more science targets en route to Larry's Lookout. On sol 371, Spirit completed a 6-meter (20-foot) drive to arrive at the rock target "Peace." Due to the slope and small rocks in area, Spirit sat at an overall tilt of 19 degrees to the north-northeast, which was very good for maximizing solar energy.
On sol 372, Spirit deployed the rover arm and acquired a set of images of Peace taken by the microscopic imager. A sequencing error prevented the alpha particle X-ray spectrometer from being placed on the rock, delaying the planned integration. The opacity of the sky, or Tau, which is the amount of light that cannot penetrate through the atmosphere, rose sharply from 0.8 to 1.1.
On sol 373, Spirit acquired more images with the microscopic imager and brushed Peace with the rock abrasion tool. The rover then placed the alpha particle X-ray spectrometer on Peace successfully for a nighttime integration. Tau continued upwards to 1.3, further reducing solar energy for Spirit.
Solar energy continues to be a precious resource because of the high Tau on sol 373. Although dust storms are more likely at this time of martian year, the start of the true dust storm season is still months away. Sol 373 ended on Jan. 20, 2005.
OPPORTUNITY UPDATE: Opportunity Checks Out the First Meteorite Found on Another Planet! - sol 347-352, January 24, 2005
Opportunity completed its work on "Heat Shield Rock" during sols 347 through 352, then got into position for more observations of the heat shield. This rock is now known to be an iron-rich meteorite, thanks to findings of the alpha particle X-ray spectrometer, Mossbauer spectrometer and the miniature thermal emission spectrometer. The rover remains in good health.
The team continues to closely monitor orbital images for signs of dust storms. Tau, a measure of the sky opacity, has hovered in the 0.8 to 0.9 range for the past week; tau was roughly 0.5 before recent dust disturbances in the region.
Since sol 331, a mottled pattern has been seen on sky portions of images from the rear hazard avoidance camera. The pattern was originally thought to be a sky pattern caused by the dust storm occurring at that time. After a closer look at the mottled pattern in subsequent images, it appears that there is actually a deposit of some sort on the rear hazard avoidance camera lenses. The deposit may be storm dust that blew in their direction. It might also be fine dust from the heat shield debris that blew onto them or was kicked up by Opportunity's wheels as it drove around the debris site. The team decided to go ahead with a final close-up imaging campaign of the heat shield despite the risk of further deposition on the camera lenses because of the rare opportunity to examine a spent heat shield on Mars. Rover drivers are taking extra precautions to drive around debris and to find safe orientations for the rover as it works. The team has decided to forgo observations at the heat shield divot due to the possibility of further contamination at that site.
Sol-by-sol summaries:
On sol 347, Opportunity unstowed its instrument deployment device (robotic arm) to take microscopic images of Heat Shield Rock, and then placed the Mossbauer spectrometer instrument on the rock for a 19-hour observation. Mossbauer integration times are longer now because the Mossbauer source has weakened as expected since landing.
On sol 348, the rover placed the alpha particle X-ray spectrometer instrument on Heat Shield Rock during the afternoon for an overnight observation. That instrument provides best results when it is cold.
On sol 349, the rover brushed an area on Heat Shield Rock using the rock abrasion tool, took microscopic images of the brushed spot, then placed the alpha particle X-ray spectrometer on the spot for another overnight observation.
350 - Opportunity changed tools on the arm to the Mossbauer instrument for another long observation on the brushed area.
351 - The rover changed tools on the arm back to the alpha particle X-ray spectrometer instrument again, putting it in place for another overnight observation of Heat Shield Rock.
352 - Opportunity took some final microscopic images of the rock then backed away for observations with the panoramic camera and miniature thermal emission spectrometer. The rover then drove to within about 1 meter (about 3.3 feet) of the largest piece of the heat shield in preparation for more observations of spent heat shield material with the microscopic imager.
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