Daily Updates - January 24, 2005
Spirit Status at end of sol 367-373
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.
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