Third Extrication Drive Ends With Wheel Stall Spirit experienced a wheel stall with the right-rear wheel during the second step of a two-step drive on Sol 2092 (Saturday, Nov. 21). This is not the same wheel that stalled on Sol 1899 (May 6), the left-middle wheel. On Sol 2092, the right-rear wheel did not experience a hard stall like what was seen on Sol 1899. Instead, it stalled because the wheel's progress fell behind the expected rotation rate. The rover had completed about 4 metres of commanded wheel spin before the stall terminated the drive. The center of the rover moved about 4 millimetres forward, 3 millimetres to the left and about 3 millimetres down. The rover suspension stayed within the tighter limits set for the drive, and there was only a fractional change in rover tilt.
Because the first extrication drive for Spirit, on Sol 2088 (Nov. 17), stopped as soon as it began due to an exceeded tilt limit, the plan for an extrication drive on Sol 2090 (Nov. 19) will essentially be a repeat of the first drive plan, but with improved rover attitude knowledge. The updated attitude knowledge comes from the rover's measurement of its tilt on Sol 2088.
Credit: NASA/JPL-Caltech/Cornell/USGS This mosaic of images from the Spirit rover, taken on Sol 1925 (June 2, 2009), helped engineers assess the rover's state and plan Spirit's extraction from the soft soil at the site called "Troy." The images were taken by Spirit's microscopic imager instrument, mounted on the end of the robotic arm. This is the first time the microscopic imager has been used to assist in planning a rover's escape from an embedding event. The imager isn't intended to take these types of images; it is designed to focus on targets only 6 centimetres in front of its optics. As a result, the images in this mosaic are well out of focus.
The preliminary results from the first extrication drive for Spirit on Sol 2088 (Nov. 17, 2009) indicate the rover stopped less than 1 second after it began, sensing more vehicle lateral tilt than permitted.
This full-circle view from the panoramic camera on NASA's Mars Exploration Rover Spirit shows the terrain surrounding the location called "Troy," where Spirit became trapped in soft soil during the spring of 2009. Hundreds of images were combined into this view were taken from Sol 1,906 (May 14, 2009) to Sol 1943 (June 20, 2009).
Expand (115kb, 800 x 797) Credit: NASA/JPL-Caltech
The Mars Rover Spirit took this image with its front hazard-avoidance camera on Sol 1899. This view looks northward, with Husband Hill on the horizon. The rover is dragging its right front wheel, which no longer rotates. For scale, the distance between the wheel tracks is about 1 metre.
The Spirit Mars rover may have met its match in a patch of sandy soil that has ensnared it on Mars, but Nasa scientists said Thursday they will make a last effort to free "the little rover that could".
Data show Spirit is straddling the edge of a 26-foot-wide crater that had been filled long ago with sulfate-bearing sands produced in a hot water or steam environment. The deposits in the crater formed distinct layers with different compositions and tints, and they are capped by a crusty soil. It is that soil that Spirit's wheels broke through. The buried crater lies mainly to Spirit's left. Engineers have plotted an escape route from Troy that heads up a mild slope away from the crater. Read more
The rover became stuck when the wheels broke thoough a crust which covered course sulfate rich sand, which inturn caused the underbelly of the rover to possibly become stuck on a rock. The science team "haven't found a clear solution" how to get the rover out, but on Monday, they will attempt to drive forward, retracing the tracks out of Ulysses, the volcanic area the rover is stuck in.
There is a annual review in February 2010, so they have untill them to try to get out or decide to leave the rover stationed at the location.
"This is going to be a lengthy process, and there's a high probability attempts to free Spirit will not be successful" - NASA's Doug McCuistion.
-- Edited by Blobrana on Thursday 12th of November 2009 07:54:19 PM