* Astronomy

SPIRIT UPDATE: Difficult progress with five-wheel drive - sol 790-797 , Mar 31, 2006:

NASA's Mars Odyssey orbiter resumed communication-relay support of the Mars Exploration Rovers on March 25, 2006. Spirit executed drives on sols 792 and 794 (March 26 and 27), but has been having trouble making progress given the current terrain and driving conditions. The team is developing new drive strategies for five-wheel driving in the test facility at the Jet Propulsion Laboratory. The new techniques for turning the rover to face waypoints are proving successful on Mars, but soft soil and inclines in Spirit's current location make uphill progress difficult to achieve. At the end of the week, the team decided to stop trying to advance along a route Spirit had been attempting in recent sols and, instead, to drive back downhill a few metres and then begin a different route toward a north-facing slope for surviving the Martian winter.

Right-front wheel status
Diagnostic tests run on the drive motor for Spirit's right-front wheel at various voltage levels resulted in no motion. These tests were consistent with results in the test facility, and they indicate an open connection in the motor. As a result, the team has precluded further use of this motor, so Spirit will continue driving with five wheels.

Sol-by-sol highlights:

Sol 790 (March 24): Spirit completed its usual morning science observations of assessing the clarity of the sky (a variable called "tau") with the panoramic camera, and checking the sky and ground with the miniature thermal emission spectrometer. Before shutting down for this light-activity sol, the rover used 13 different filters of the panoramic camera to examine soil that had been churned up in wheel tracks.

Sol 791: The Mars Odyssey orbiter, which had been unavailable for communication-relay support for three days because it went into a precautionary "safe" mode temporarily, resumed relay work. Spirit used the panoramic camera for assessing sky clarity and for surveying some rocks. It used the miniature thermal emission spectrometer for sky and ground observations and to examine the disturbed soil in the wheel tracks.

Sols 792 and 793: With a new downlink from Odyssey, the team came in on Saturday to plan a two-hour drive for sol 792. Spirit turned about 125 degrees to face a new drive target and began to drive toward it. The drive ended a few meters later when Spirit detected 71-percent slippage. On sol 793, Spirit completed a light schedule of remote-sensing observations.

Sols 794 and 795: Spirit drove 5.7 metres on sol 794, but most of the odometry change was a part of the heading change, rather than progress toward a destination. Again, high slip terminated the drive. As in the previous two-sol plans, there was light remote sensing on the second sol.

Sols 796 and 797: Spirit's sol 796 uplink time was during a Mars Reconnaissance Orbiter aerobraking manoeuvre and the two spacecraft cannot use the same radio band at the same time, so the rover team used forward commanding relayed via Odyssey to uplink Spirit's sequences of commands for sols 796 and 797. The plan for sol 796 was to turn 60 degrees clockwise toward a new waypoint and drive toward it using visual odometry to help check for slip. The rover drove 4 metres before the drive stopped due to excessive (61 percent) slippage. As on the previous drive attempt, most of the added odometry was in the turning, not forward progress. After the drive, Spirit acquired images to help the uplink team analyse possible alternative routes to north-tilted slopes.

As of sol 796 (March 30, 2006), Spirit's total odometry was 6,836.48 metres.

Sol 774



This false-colour image combines several separate images that Spirit took as it was leaving 'Home Plate' on its way to 'McCool Hill'

SPIRIT UPDATE: Spirit Studies Surface and Atmosphere on Way to 'McCool' - sol 771-777, Mar 11, 2006:

Since backing down from the top of "Home Plate" on Martian day, or sol, 764 (Feb. 25, 2006), Spirit has driven southeast 103 metres toward "McCool Hill." Along the way, the rover used its robotic arm to analyse a rock target dubbed "Fuzzy Smith" and conducted remote scientific studies of outcrops along the side of Home Plate and on "Mitcheltree Ridge." Scientists plan to acquire long-baseline stereo images of McCool Hill before driving too close to the hillside. The images will provide measurements of surface features necessary for planning the rover's path.

During the week, NASA's Odyssey spacecraft has been relaying commands from Earth to Spirit via the UHF link. Communications over X-band frequencies have been allocated for use by the Deep Space Network to track the Mars Reconnaissance Orbiter during its approach to the red planet. Next week, Spirit is expected to resume operations via X-band uplinks.

Sol-by-sol summaries:

Sol 771 (March 4, 2006): Spirit completed an analysis of targets dubbed "Rube Foster" and "Willie Wells" using the Mössbauer spectrometer and 13 filters on the panoramic camera. During the afternoon Odyssey pass, Spirit collected data with the miniature thermal emission spectrometer. Spirit then began a study of a rock target called Fuzzy Smith with the Mössbauer spectrometer.

Sol 772: Spirit stowed the robotic arm and took panoramic camera images of Fuzzy Smith, then drove 27 metres southeast across Home Plate. After the drive, Spirit conducted opacity observations of afternoon dust and measurements of the sky and ground using the miniature thermal emission spectrometer.

Sol 773: After waking, Spirit continued atmospheric studies by taking thumbnail images of the sky with the panoramic camera and images of both the sky and ground with the miniature thermal emission spectrometer. In the afternoon, Spirit acquired images with both the panoramic and navigation cameras to provide essential data for selecting targets and planning routes. The rover also completed a systematic ground survey and survey of rock clasts using the panoramic camera.

Sol 774: Spirit drove off of Home Plate and back into the "Dugout" - a gully near the southeast edge of Home Plate. The rover acquired mid-drive images and post-drive images of surrounding terrain, then completed opacity observations and measurements of the sky and ground with the miniature thermal emission spectrometer.

Sol 775: In the morning, Spirit took thumbnail images of the sky with the panoramic camera and miniature thermal emission spectrometer measurements of the sky and ground. With the robotic arm still stowed, Spirit spent 30 minutes collecting temperature data using the alpha particle X-ray spectrometer. In the afternoon, Spirit conducted reconnaissance with the miniature thermal emission spectrometer.

Sol 776: Plans for this sol call for Spirit to begin collecting a long-baseline stereo mosaic of images of the hill by taking panoramic camera images from one site, driving 8 metres, and then acquiring the part of the second half of the stereo mosaic.

Sol 777 (March 11, 2006): Plans for this sol include morning atmospheric studies, finishing the long-baseline stereo mosaic, and taking pictures of a target called "Bitty Cloud."

As of sol 775 (March 9, 2006), Spirit's total odometry was 6,756 metres.

Sol 771