23 Dec 2004
(Source: Jet Propulsion Laboratory)
SPIRIT UPDATE: Spirit Eats a Potato-Sized Rock - sol 333-345, December 23, 2004
Spirit finished work at a rock called "Wishstone," then continued to make slow progress up "Husband Hill." Wishstone is different than any rock Spirit previously studied either on the plains or in the hills. Scientists and engineers used the miniature thermal emission spectrometer to find similar rocks for further study.
A potato-sized rock got caught in Spirits's right rear wheel on sol 339, causing the wheel to stall and ending the drive for that sol. Small moves of the wheel on subsequent sols dislodged the rock, but the rock remains close to the wheel, so the team is planning small, careful steps to move the wheel away from the rock so it will not become jammed again. Spirit remains in excellent health.
Atmospheric observations using the miniature thermal emission spectrometer, navigation camera, and panoramic camera continue on a daily basis.
On sol 333, Spirit used the brush of the rock abrasion tool brush to scrub a small section of Wishstone and took microscopic images of the spot. Spirit then placed the alpha particle X-ray spectrometer on the spot for collecting data overnight.
On sol 334, Spirit removed the alpha particle X-ray spectrometer and then used the rock abrasion tool to drill into Wishstone. After taking more microscopic images, Spirit placed the alpha particle X-ray spectrometer on the hole for an overnight observation.
On sol 335, Spirit removed the alpha particle X-ray spectrometer from the hole and replaced it with the Mossbauer spectrometer. Spirit also started a long series of Mossbauer observations that would last until the early morning of sol 337.
On sol 337, Spirit stowed its robotic arm, then bumped backwards to take final images of Wishstone and the rock abrasion tool hole. Spirit was commanded to drive 15 meters (49 feet), but drove only about 6 meters (20 feet) due to experiencing slippage of up to 80 percent on uphill portions of the drive.
On sol 338, Spirit drove 8 meters (26 feet) with 25 meters (82 feet) of commanded motion. Spirit saw up to 95-percent slip on some of the drive segments due to sandy terrain and the rover's tilt of 15 to 20 degrees.
On sol 339, the rover team attempted another 25-meter (82-foot) drive. This was cut short at the start when the right rear wheel ingested a potato-sized rock. The rock apparently jammed between the inner part of the wheel and the drive mechanism, causing the drive current to exceed a pre-set limit, resulting in a safe motor stall.
Sol 340 - Spirit made observations with the miniature thermal emission spectrometer to seek other rock targets similar to Wishstone. Turning the right rear wheel about 60 degrees successfully un-jammed the rock, but it remained inside the wheel.
Sols 341, 342 and 343 were planned as a combined three-sol plan that included observations with the miniature thermal emission spectrometer each sol. On sol 341, Spirit used its microscopic imager and its Mossbauer spectrometer to examine disturbed soil in front of the rover. It switched to the alpha particle X-ray spectrometer overnight to gather more compositional information about the same target. On sol 342, Spirit performed a mid-day tool change back to the Mossbauer spectrometer. On sol 343, the rover stowed the robotic arm and took images with the panoramic camera of targets that had been observed with the miniature thermal emission spectrometer. Spirit then performed a small maneuver but did not significantly change the position of the rock in the wheel.
Sol 344 - Spirit performed more remote sensing and did a maneuver that lifted the right rear wheel slightly out of a hole, but the rock remains partially in the wheel. The wheel is about one-third buried in the soft soil, making it difficult for the rock to escape until the wheel gets out of the hole.
Sol 345 - Spirit successfully executed another small maneuver to get the right rear wheel out of hole and get the rock out of the wheel, but more steps will be required. The rover also used the panoramic camera and miniature thermal emission spectrometer to acquire information about nearby targets. Sol 345 ended on Dec. 22.