* Astronomy

After three days of completing Earth-commanded activities without incident last week, NASA's Mars Exploration Rover Spirit had a bout of temporary amnesia Friday, April 17, and rebooted its computer Saturday, April 18, behaviour similar to events about a week earlier.
Engineers operating Spirit are investigating the reboots and the possibly unrelated amnesia events, in which Spirit unexpectedly fails to record data into the type of memory, called flash, where information is preserved even when power is off. Spirit has had three of these amnesia events in the past 10 days, plus one on Jan. 25. No causal link has been determined between the amnesia events and the reboots.

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The team operating NASA's Mars Exploration Rover Spirit is examining data received from Spirit in recent days to diagnose why the rover apparently rebooted its computer at least twice over the April 11-12 weekend.

"While we don't have an explanation yet, we do know that Spirit's batteries are charged, the solar arrays are producing energy and temperatures are well within allowable ranges. We have time to respond carefully and investigate this thoroughly. The rover is in a stable operations state called automode and taking care of itself. It could stay in this stable mode for some time if necessary while we diagnose the problem" - John Callas of NASA's Jet Propulsion Laboratory, Pasadena, California, project manager for Spirit and twin-rover Opportunity. 

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The Mars rover Spirit is ambling along just fine, after a recently reported glitch that turned out to be a minor "benign event," according to Steven Squyres, the Goldwin Smith Professor of Planetary Science and science team leader for the Mars rover mission.
That means that both rovers, designed to explore Mars for a mere 90 days, are still up and running some five years after landing.

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SPIRIT UPDATE:  On the Move - sol 1791-1797, January 15 - January 22, 2009:

Communication problems during the Martin Luther King, Jr. holiday led to the postponement of a drive planned for sol 1791 (Jan. 15, 2009) to sol 1793 (Jan. 17, 2009). Once the drive began, however, Spirit was able to go ahead with characterisation of a rock target known as "Stapledon." Studies began with a stack of microscopic images taken at different focal lengths, then moved to compositional analysis using the alpha-particle X-ray spectrometer. On sol 1797 (Jan. 22, 2009), Spirit was to drive toward a prospective "on-ramp" to Home Plate, but a portion of the commands was corrupted during transmission and rejected by the rover. That particular drive is now planned for sol 1798 (Jan. 23, 2009). Also on sol 1797 Spirit was slated to take a deep sleep for the first time, as part of overall attempts to minimise power usage when not driving.
Future plans call for Spirit to drive south across Home Plate toward Goddard/Von Braun with all haste in order to reach the next "Winter Haven" before the end of the summer season.
Spirit is healthy and all subsystems are performing as expected as of the downlink of information from Mars for sol 1797 (Jan. 22, 2009). Solar-array energy is around 199 watt-hours (almost enough energy to light a 100-watt bulb for two hours). Tau (a measure of the amount of sunlight blocked by dust in the atmosphere) dropped to 0.536, slightly lower than last week. The dust factor, a measure of the amount of sunlight penetrating dust on the solar panels, is 0.2461, meaning that only about one-fourth of the sunlight reaching Spirit's solar arrays penetrates the layer of dust to generate electricity.

Sol-by-sol summary:
In addition to making daily measurements of atmospheric darkness caused by dust, Spirit completed the following activities:

Sol 1791 (Jan. 15, 2009): Spirit completed a timed drive. At the end of the drive, Spirit took images with the hazard-avoidance and navigation cameras.

Sol 1792: Spirit took lossless-compression, full-colour images, using all 13 filters of the panoramic camera, of a patch of material exposed in the wheel tracks called "Thunderbolt."

Sol 1793: Spirit completed another timed drive, acquired hazard-avoidance camera images, and took a post-drive, 5-x-1 tier of navigation-camera images.

Sol 1794: Spirit acquired full-colour, lossless-compression images, using all 13 filters of the panoramic camera, of Thunderbolt.

Sol 1795: Spirit acquired a 3-by-1 tier of panoramic-camera images looking in the drive direction.

Sol 1796: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer, used the instrument to study the target called Robert Heinlein, unstowed the robotic arm, and acquired a 1-by-1-by-5 stack of stereo (3D) microscopic images of Stapledon. The rover placed the alpha-particle X-ray spectrometer on the target and, after relaying data to Odyssey, measured the elemental composition of Stapledon with the instrument.

Sol 1797: Spirit was slated to check for drift (changes with time) in the miniature thermal emission spectrometer, use the instrument to study the target called Robert Heinlein, stow the robotic arm, and drive, stopping mid-drive to take panoramic-camera images of Stapledon. At the end of the drive, the rover was to take images with the hazard-avoidance and navigation cameras. These events were rescheduled when a corrupted command sequence prevented them from taking place.

Sol 1798: Plans called for Spirit to take panoramic-camera images of a rock feature called "Mustang" along with spot images of the sky for calibration purposes.

Odometry:
As of sol 1797 (Jan. 22, 2009), Spirit's total odometry was 7,531.60 metres.