Spirit Updates

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M I S S I O N     M A N A G E R S
	Cindy Oda		Richard Morris		Al Herrera		Byron Jones

P R E V I O U S    M I S S I O N    M A N A G E R S
	Mark Adler		Leo Bister		Beth Dewell		Emily Eelkema		Jeff Favretto

	Saina Ghandchi		Andy Mishkin		Art Thompson		Rick Welch

sol 1532-1538, Apr 24-30, 2008:  "Catch-22":  Staying Awake vs. Going to Sleep

Spirit's Tau measurements of atmospheric dust have remained steady, but solar array input has dropped a bit to 235 watt-hours per sol. Spirit still has enough energy to squeeze in Mössbauer studies of iron-bearing minerals at a time of year when the rover's handlers expected Spirit to be concerned only with survival. At present, the rover's target of scientific interest is a soil exposure nicknamed after Arthur C. Harmon, a former Tuskegee airman. Spirit conducted 8 more hours of Mössbauer integration, for a total of 12 hours. Scientists hope the rover will be able to collect 36 more hours' worth of data from the same target. Meanwhile, Spirit continued to acquire panoramic-camera images, using all 13 color filters, of the "Bonestell panorama," informally named in honor of famed space artist Chesley Bonestell.

Concerned that cold winter temperatures on Mars might trigger the survival heaters on the rover electronics module, rover planners took the extra precaution of disabling those particular heaters on sol 1533 (April 25, 2008) to conserve power. With the heaters turned off, the rover's handlers must monitor temperatures carefully to make sure the module doesn't get too cold. Besides the survival heaters, the remaining means of keeping the module warm enough during the night is to generate more heat during the day by keeping the rover awake for about one additional hour. Of late, 39 minutes is the shortest possible awake time for conducting minimal activities. Another 20-plus minutes of awake time are needed on days when the rover transmits data to NASA's Odyssey orbiter during its overhead pass. On other sols, rover planners may arbitrarily increase the rover's awake time to 50 minutes or longer to generate enough heat to keep the electronics module alive, even if science activities do not require Spirit to be awake that long.

In summary, the challenge for Spirit's handlers during each planning cycle is to recharge the battery enough to do significant science, then recharge the battery again to transmit data to Odyssey for downlink to Earth. By keeping the rover awake for shorter periods, they conserve energy but generate less thermal inertia (heat) for keeping the rover electronics module alive. The more consecutive sols that go by without transmitting temperature and power updates to Odyssey and from there to Earth, the more Spirit's handlers must rely on margin ("wiggle room") from earlier predictions and keep the rover awake longer to protect the electronics module. As a result, Spirit is caught in a "catch-22" set of tradeoffs among power, heat, communications, and science. This delicate balance will become increasingly more precarious as the rover moves closer to the winter solstice, with its even colder temperatures and lower solar array input.

Sol-by-sol summary:

In addition to measuring atmospheric dust levels with the panoramic camera and receiving direct-from-Earth instructions via the rover's high-gain antenna, Spirit completed the following activities:

Sol 1532 (April 24, 2008): Spirit spent 8 hours acquiring data from Arthur C. Harmon with the Mössbauer spectrometer.

Sol 1533: In the morning, Spirit took spot images of the sky with the panoramic camera for calibration purposes and acquired panoramic-camera images of the dune field known as "El Dorado." The rover recharged the battery, disabled the survival heaters on the rover electronics module, and shortened the "Up_Too_Long" computer sequence to 30 minutes.

Sol 1534: Spirit recharged the battery and relayed data to NASA's Odyssey orbiter for transmission to Earth.

Sol 1535: Spirit recharged the battery.

Sol 1536: Spirit recharged the battery and relayed data to the Odyssey orbiter. The rover checked for drift (changes with time) in the miniature thermal emission spectrometer and surveyed the sky and ground with the instrument. The rover was awake for a total of 61 minutes.

Sol 1537: In the morning, Spirit acquired full-color images, using all 13 filters of the panoramic camera, of column 12, part 2 of the Bonestell panorama. The rover recharged the battery, checked for drift in the miniature thermal emission spectrometer, and surveyed the sky and ground with the miniature thermal emission spectrometer. Spirit was awake for a total of 39 minutes.

Sol 1538 (April 30, 2008): Spirit checked for drift in the miniature thermal emission spectrometer and surveyed the sky and ground with the instrument. After sending data to Odyssey, the rover used the alpha-particle X-ray spectrometer to measure argon gas in the Martian atmosphere. Plans for the next morning called for Spirit to complete work on column 12, part 3 of the Bonestell panorama.

Odometry:

As of sol 1538 (April 30, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).

sol 1525-1531, Apr 17-23, 2008:  Rover "Spirit" High Despite Low Power Levels

Given the substantial coating of dust on the solar array, Spirit continues to enjoy energy levels that are higher than expected for this time of year, at around 240 watt-hours per sol (enough energy to light two 100-watt bulbs and one 40-watt bulb for one hour).

Spirit continues to make progress on the full-color "Bonestell panorama" of the rover's winter surroundings. Of 27 columns of stacked images needed for a complete mosaic, Spirit has completed work on 11 columns, each comprising three parts. Each Martian day, or sol, Spirit has enough energy to complete one part. Science team members have nicknamed the panorama after Chesley Bonestell (1888-1986), considered the father of modern space art.

Analysis of iron-bearing minerals in a patch of undisturbed soil will require an estimated 24 hours of data collection during the coming week with the Mössbauer spectrometer. The soil target is known informally as "Arthur C. Harmon." Spirit can complete 4 to 8 hours of integration with the spectrometer before needing to recharge the batteries. To conserve power, Spirit is on a communications diet, in which the rover limits data transmissions to Earth to, at most, every other sol.

Spirit is healthy and all systems are operating as expected.

Sol-by-sol summary:

In addition to communication activities that include direct-from-Earth instructions via the rover's high-gain antenna and, power permitting, data relays to Earth via the Odyssey orbiter, Spirit continues to monitor atmospheric dust levels with the panoramic camera, check for drift (changes with time) in the miniature thermal emission spectrometer, and survey the sky and ground with the spectrometer. During the past week, Spirit also completed the following activities:

Sol 1525 (April 17, 2008): Spirit acquired column 10, part 1 of the Bonestell panorama, using all 13 filters of the panoramic camera.

Sol 1526: In the morning, Spirit surveyed the external calibration target with the miniature thermal emission spectrometer and parked the panoramic camera mast assembly with the panoramic camera pointed below the horizon to minimize dust accumulation.

Sol 1527: In the morning, Spirit completed work on column 10, part 2 of the Bonestell panorama, then parked the panoramic camera mast assembly with the panoramic camera pointed below the horizon to minimize dust accumulation. The rover exchanged tools to put the Mössbauer spectrometer in position to study Arthur C. Harmon.

Sol 1528: Spirit spent the morning working on column 10, part 3 of the Bonestell panorama. The rover relayed data to Odyssey for transmission to Earth.

Sol 1529: Spirit acquired column 11, part 1 of the Bonestell panorama and spent 4.5 hours acquiring data from Arthur C. Harmon with the Mössbauer spectrometer.

Sol 1530: In the morning, Spirit monitored dust on the panoramic camera mast assembly and acquired column 11, part 2 of the Bonestell panorama. The rover then completed work on column 11, part 3 of the panorama and relayed data to Odyssey.

Sol 1531: (April 23, 2008): Spirit recharged the battery. The following morning, Spirit was to acquire column 12, part 1 of the Bonestell panorama.

Odometry:

As of sol 1531 (April 23, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).

sol 1517-1524, Apr 09-16, 2008:  Spirit Still "Sitting Pretty" for This Time of Year

Despite a slight increase in atmospheric opacity caused by dust, Spirit is still enjoying higher-than-expected energy levels for this time of year. Solar array input has been approximately 240 watt-hours per Martian day, or sol (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour).

Clear skies have had the unfavorable effect, however, of causing a drop in temperatures at the surface of Mars, increasing the bitter cold experienced by Spirit's rover electronics module. Nighttime temperatures are creeping closer to the point where they will trigger the survival heaters, which draw a large amount of power. A much more desirable strategy is to keep Spirit awake long enough each day to keep the electronics module sufficiently warm with heat from normal operations, providing more time for science observations. "Awake time" vs. heating time is just one of the many trade-offs the team makes each day to keep Spirit going through the Martian winter.

Sol-by-sol summary:

In addition to daily communications that include direct-from-Earth instructions via the rover's high-gain antenna and, as power permits, data relays to Earth via the Odyssey orbiter, Spirit continues to monitor atmospheric dust levels each day with the panoramic camera. In addition, during the past week, Spirit completed the following activities:

Sol 1517 (April 9, 2008): Spirit completed a mini-survey of the sky and ground with the miniature thermal emission spectrometer; acquired column 8, part 3 of the full-color "Bonestell Panorama" using all 13 filters of the panoramic camera; and shot movie frames in search of clouds with the navigation camera.

Sol 1518: Spirit completed a mini-survey of the sky and ground with the miniature thermal emission spectrometer; acquired a 2-by-1-by-1 stack of microscopic images of the rover's solar array; acquired column 9, part 1 of the Bonestell panorama; and took spot images of the sky for calibration purposes with the panoramic camera.

Sol 1519: Spirit surveyed the rover's external calibration target with the miniature thermal emission spectrometer and acquired column 9, part 2 of the Bonestell panorama. To conserve energy, the rover did not relay data to Odyssey.

Sol 1520: Spirit completed a mini-survey of the sky and ground with the miniature thermal emission spectrometer; measured atmospheric opacity caused by dust with the navigation camera (as well as the panoramic camera); and acquired movie frames in search of clouds with the navigation camera. The rover took spot images of the sky and surveyed the horizon with the panoramic camera. Spirit did not relay data to Odyssey.

Sol 1521: Spirit completed a mini-survey of the sky and ground with the miniature thermal emission spectrometer; calibrated the elevation of the miniature thermal emission spectrometer; and acquired column 9, part 3 of the Bonestell panorama.

Sol 1522: Spirit completed a mini-survey of the sky and ground with the miniature thermal emission spectrometer; took thumbnail images of the sky and surveyed the horizon with the panoramic camera; and acquired lossless-compression images of wind-blown deposits next to the rover with the hazard-avoidance cameras. Spirit did not relay data to Odyssesy.

Sol 1523: Spirit recharged the battery and did not relay data to Odyssey.

Sol 1524: (April 16, 2008): Spirit recharged the battery.

Odometry:

As of sol 1524 (April 16, 2008), Spirit's total odometry remained at 7,528.07 meters (4.68 miles).

sol 1511-1516, Apr 03-08, 2008:  Clear Skies at "Home Plate"

Spirit is currently experiencing the clearest skies seen by either of NASA's two Mars Exploration Rovers. On sol 1511 (April 3, 2008), Tau measurements of atmospheric dust hit an all-time low of 0.127. By sol 1516 (April 8, 2008), this measurement had increased slightly to 0.170. The low Tau values have held power levels at around 250 watt-hours (enough energy to light a 100-watt bulb for about 2.5 hours). If Tau were not so cooperative, Spirit would be getting only about 200 watt-hours of energy, compelling the rover's handlers to disable the heaters on the miniature thermal emission spectrometer and take other measures to conserve power.

The engineering team still expects to implement energy-conservation strategies, but not for several weeks. Meanwhile, Spirit continues to make progress on remote-sensing activities, scientific investigations, and the "Bonestell panorama" of the rover's view from the north rim of "Home Plate."

Sol-by-sol summary:

To conserve energy, mission planners have restricted the number of sols on which Spirit receives direct-from-Earth instructions via the rover's high-gain antenna and transmits data to Earth via the Odyssey orbiter. Spirit continues, on a daily basis, to monitor atmospheric dust levels with the panoramic camera and survey the sky and ground with the miniature thermal emission spectrometer. In addition, during the past week, Spirit completed the following activities:

Sol 1511 (April 3, 2008): Spirit took thumbnail images of the sky with the panoramic camera.

Sol 1512: Spirit gathered compositional data from the soil target known as "Arthur C. Harmon" using the alpha-particle X-ray spectrometer. The rover used the panoramic camera to acquire super-resolution images of a target informally named "Arthur C. Clarke."

Sol 1513: Spirit acquired column 7, part 3 of the full-color Bonestell panorama, using all 13 filters of the panoramic camera.

Sol 1514: Spirit pointed the alpha-particle X-ray spectrometer skyward to measure argon gas in the Martian atmosphere and acquired stability images of the rover's 30-degree tilt. The rover transmitted data to Odyssey and spent about 4.5 hours measuring atmospheric argon. Spirit also acquired column 8, part 1 of the Bonestell panorama and took spot images of the sky for calibration purposes with the panoramic camera.

Sol 1515: Spirit surveyed the sky with the panoramic camera and monitored dust on the panoramic camera mast assembly.

Sol 1516: (April 8, 2008): Spirit acquired column 8, part 2 of the Bonestell panorama and surveyed the horizon with the panoramic camera.

Odometry:

As of sol 1516 (April 8, 2008), Spirit's total odometry remained at 7,528.07 meters (almost 4.68 miles).

sol 1504-1510, Mar. 27 - Apr 02, 2008:  Spirit Advances Toward Midwinter

Seasons are about twice as long on Mars as on Earth and are offset relative to Earth because Mars takes about twice as long to complete one orbit around the Sun. At Spirit's location, the fall equinox -- the start of fall, when night and day are equal in length -- arrived Dec. 12, 2007. The winter solstice -- the time of year with the shortest day -- will arrive June 25, 2008.

Solar array energy has varied from 244 watt-hours to 256 watt-hours, averaging 250.4 watt-hours for this period (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Tau, the measure of atmospheric dust, has averaged 0.16, varying by only a hundredth. The dust factor has been nearly constant at 0.35, meaning 35 percent of the sunlight reaching the arrays penetrates the dust layer to make electricity. A low Tau is good because it means the skies are fairly clear; a low dust factor is bad because it means the solar arrays are coated with a fair amount of dust.

Astronomers use the symbol L(s) -- pronounced L-sub-s -- to denote how far Mars has progressed in its orbit around the Sun. If you imagine looking down at the solar system, with the Sun in the middle and Mars orbiting around it, L(s) gives the location of Mars. By definition, L(s) = 0 degrees when the Sun crosses the Martian equator. This is the first day of Martian spring, the vernal equinox, when night and day are equal in length, in the northern hemisphere. It's also the first day of fall, the autumnal equinox, in the southern hemisphere. At Spirit's location in Mars' southern hemisphere, the season is currently mid- to late fall, and L(s) is about 55 degrees, roughly equivalent to Nov. 17 in Earth's northern hemisphere and May 18 in Earth's southern hemisphere. L(s) will equal 90 degrees at the time of the winter solstice.

Spirit is healthy and all subsystems are performing as expected.

Sol-by-sol summary:

To conserve energy, mission planners have restricted the number of sols on which Spirit receives direct-from-Earth instructions via the rover's high-gain antenna and transmits data to Earth via the Odyssey orbiter. Spirit continues, on a daily basis, to monitor atmospheric dust levels with the panoramic camera, check for drift (changes with time) in the miniature thermal emission spectrometer, and survey the sky and ground with the instrument. In addition, during the past week, Spirit completed the following activities:

Sol 1504 (March 27, 2008): Spirit calibrated the miniature thermal emission spectrometer and acquired a microscopic image of the capture magnet.

Sol 1505: Upon awakening, Spirit took spot images of the sky for calibration purposes with the panoramic camera and acquired column 6, part 1 of the full-color "Bonestell panorama" using all 13 filters of the panoramic camera. The rover also recharged the battery.

Sol 1506: Spirit acquired column 6, part 2 of the Bonestell panorama and monitored dust on the panoramic-camera mast assembly. Spirit looked at the miniature thermal emission spectrometer for calibration purposes, acquired microscopic images of the solar panel, and acquired images of the external magnets, which capture magnetic dust particles, using the panoramic camera.

Sol 1507: Spirit acquired column 6, part 3 of the full-color Bonestell panorama and recharged the battery.

Sol 1508: Spirit acquired column 7, part 1 of the full-color Bonestell panorama and relayed data to Odyssey during the orbiter's afternoon pass overhead.

Sol 1509: Spirit surveyed the sky at high Sun with the panoramic camera and completed a "runout" of previously loaded activities after not being able to receive new instructions from Earth. The rover recharged the battery and relayed data to Odyssey.

Sol 1510: (April 2, 2008): Spirit acquired a 1-by-1-by-3 stack of microscopic images of a soil target known informally as "Arthur_C_Hammon" and placed the alpha-particle X-ray spectrometer on the soil target. Plans for the following morning called for Spirit to acquire column 7, part 2 of the full-color Bonestell panorama.

Odometry:

As of sol 1509 (April 1, 2008), Spirit's total odometry was 7,528 meters (almost 4.7 miles).

sol 1498-1503, Mar. 20-26, 2008:  Spirit Sees Clearest Skies Since Landing on Mars!

Like a calm after the recent Martian dust storms, atmospheric dust above Spirit's overwintering site has reached the lowest levels the rover has seen since arriving on Mars. To be sure, sunblocking dust that has settled on the rover's solar panels and low-angle winter sunlight have combined to reduce Spirit's energy levels. But clear skies mean more sunlight penetrates the atmosphere, making rover planners optimistic that Spirit will have a slim but adequate amount of energy to survive until Martian spring.

Earlier estimates predicted a near-starvation energy diet for Spirit during the darkest days of winter. The coming winter solstice, the peak of Martian winter, will be June 25, 2008. To conserve energy, Spirit may have to disable some heaters and curtail communications and other activities, but is expected to be able to conduct limited scientific investigations.

Solar-array energy during the past week has varied between 244 watt-hours and 254 watt-hours, averaging 249.5 watt-hours for the period (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Tau, the measure of atmospheric dust, has averaged 0.2, varying by only a few hundredths. The dust factor has been nearly constant at 0.36 (meaning 36 percent of the sunlight reaching the arrays penetrates the dust layer to make electricity). A low Tau is good; a low dust factor is bad.

Because dust is constantly settling out from the Martian atmosphere onto the solar arrays, Tau and the change in the dust factor are related. When Tau is high, the dust factor rapidly decreases as dust from the atmosphere rains onto the arrays. When Tau is low (as it is now), the atmosphere carries less dust and the dust factor decreases more slowly. The clearer atmosphere doesn't affect dust already on the solar arrays, but it does affect the rate at which new dust is added.

The atmosphere above the Spirit site is remarkably clear at present and Tau has been as low as 0.170 -- the lowest seen by Spirit in the entire mission. Not surprisingly, the dust factor has been virtually unchanged.

Spirit also analyzed material on the external capture magnet. Spirit has several magnets of which two, the capture and filter magnets, are mounted at the front of the solar array. The capture magnet is relatively strong, the filter magnet only half as strong.

Viking data from the 1970s showed that Martian dust was slightly magnetic, comprising 1 to 7 percent magnetic material. Spirit's filter and capture magnets winnow the dust for this material. The capture magnet, being stronger, gathers all magnetic materials while the filter magnet retains only the most magnetic particles. Using the alpha-particle X-ray spectrometer, Spirit can determine the chemical composition of the captured particles. The observations will help scientists ascertain whether the magnetic material is uniform or has more than one constituent. The dust composition provides insight into whether the magnetic material is the product of weathering in the presence of water or weathering of dry bedrock.

Spirit continued to scale back the frequency of afternoon communications with the Odyssey orbiter to save energy. Overhead passes by Odyssey happen late in the day when little solar energy is available, requiring the use of significant battery power. By deleting some of the passes, Spirit can conserve energy acquired earlier in the day to provide power for subsequent science observations. The downside is that fewer passes slow the rate at which pictures and other data can be downlinked to Earth.

Spirit continued work on the Bonestell (Bon-ES-tell) panorama, a high-resolution, 360-degree mosaic of images divided into wedges (columns) spanning roughly 5 compass degrees and extending from near the rover to just above the horizon. Each column typically has three or four separate images or "parts." The panorama is named for Chesley Bonestell (1888-1986), considered the "father of modern space art."

Spirit is healthy and all subsystems are performing as expected.

Sol-by-sol summary:

To conserve energy, mission planners have restricted the number of sols on which Spirit receives direct-from-Earth instructions via the rover's high-gain antenna and transmits data to Earth via the Odyssey orbiter. Spirit continues, on a daily basis, to monitor atmospheric dust levels with the panoramic camera, check for drift (changes with time) in the miniature thermal emission spectrometer, and survey the sky and ground with the instrument. In addition, during the past week, Spirit completed the following activities:

Sol 1498 (March 20, 2008): Spirit placed the alpha-particle X-ray spectrometer on the capture magnet, took images with the hazard avoidance cameras, took images with the navigation camera for lossless-compression visual odometry, and relayed data to Odyssey.

Sol 1499: Spirit acquired column 4, part 2 of the full-color Bonestell panorama, using all 13 filters of the panoramic camera.

Sol 1500: Spirit acquired column 4, part 3 of the full-color Bonestell panorama, using all 13 filters of the panoramic camera.

Sol 1501: Spirit acquired column 5, part 1 of the full-color Bonestell panorama and relayed data to Odyssey during the orbiter's afternoon pass.

Sol 1502: Spirit took six movie frames in search of clouds with the navigation camera and acquired column 5, part 2 of the Bonestell panorama. Using the alpha-particle X-ray spectrometer, Spirit acquired data on the elemental composition of magnetic particles on the external capture magnet.

Sol 1503 (March 26, 2008): Spirit acquired column 5, part 3 of the Bonestell panorama and relayed data to Odyssey. Plans for the following morning called for Spirit to acquire super-resolution images of a rock target informally named "Roger_Zelazny" (after the science fiction author) with the panoramic camera.

Odometry:

As of sol 1501 (March 23, 2008), Spirit's total odometry was 7,528.07 meters (4.68 miles).

sol 1491-1497, Mar. 13-19, 2008: Spirit Phones Home to Set Clock

Spirit is feeling the strain of juggling activities on Mars in the face of declining power levels as the winter Sun sinks lower on the horizon. After acquiring compositional data from a rock target informally named "Wendell Pruitt," Spirit had to wait a few sols (Martian days) to have enough energy to conduct atmospheric studies and move the robotic arm out of the way for a panoramic-camera portrait of a rock target known as "Freeman." First, the rover had to make a "phone call" to Earth to correct for drift -- changes in time -- in the spacecraft clock.

When Spirit phones home using a direct-to-Earth, X-band communications link, the rover's transmitter has to be running, which requires a fair amount of energy. During more typical, direct-from-Earth communications, only the rover's receiver has to be on. To set the spacecraft clock, Spirit transmits a data product called a time packet. The time packet is used to synchronize the rover's clock back to Earth time (also known as Universal Time). A previous attempt to relay the time packet was unsuccessful, causing Spirit's clock to be off by as much as a minute and a half.

In addition to resetting the clock, Spirit completed a light schedule of activities on sols 1493-1494 (March 15-16, 2008). By sol 1496 (March 18, 2008), Spirit had generated enough solar power to proceed with measurements of argon gas in the Martian atmosphere and studies of the Freeman rock target. Interspersed with those activities, Spirit continued to work on the "Bonestell panorama" and take panoramic-camera images of a target dubbed "C.S. Lewis." The rover spent sols 1492, 1494, and 1497 (March 14, 16, and 19, 2008) recharging the battery, conducting only minimal science activities, and storing data for later transmission to Earth.

Spirit continued to have difficulty receiving spacecraft commands via the rover's high-gain, X-band, dish antenna as a result of the mast that holds the panoramic and navigation cameras getting in the way and partially obscuring the signal. To help address this challenge, rover planners had Spirit complete a self-assessment to see if the rover could independently recognize an occlusion of the high-gain signal and respond by swiveling the high-gain antenna to a different position. The self-assessment, on sol 1493 (March 15, 2008), was successful. Spirit used the technique prior to an actual uplink session on sol 1496 (March 18, 2008), when the rover's handlers were expecting a particularly severe occlusion. The activity was successful and the uplink did not appear to be impeded in any way. Currently, this activity involves having the rover use a temporary parameter that then goes away when the rover shuts down for a nap. Rover planners are considering making the temporary parameter permanent.

Looking forward, Spirit will go increasingly into "hibernate" mode as the Sun continues to dim. Rover planners predict Spirit will be able to conduct science activities until about late April.

Spirit is healthy and all subsystems are performing as expected. The latest available power readings from sol 1496 (March 18, 2008) showed power at 249 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Spirit has no plans to move before the next Martian spring and is hard at work accomplishing as much as possible before power levels drop to a point that temporarily precludes use of the scientific instruments on the rover's arm.

Sol-by-sol summary:

To conserve energy, mission planners have restricted the number of sols on which Spirit receives direct-from-Earth instructions via the rover's high-gain antenna and transmits data to Earth via the Odyssey orbiter. Spirit continues, on a daily basis, to monitor atmospheric dust levels with the panoramic camera, check for drift (changes with time) in the miniature thermal emission spectrometer, and survey the sky and ground with the instrument. In addition, during the past week, Spirit completed the following activities:

Sol 1491 (March 13, 2008): After communicating with Odyssey, Spirit studied the elemental composition of "Wendell Pruitt" with the alpha-particle X-ray spectrometer.

Sol 1492: In addition to monitoring atmospheric dust and conducting surveys with the miniature thermal emission spectrometer, Spirit recharged the battery.

Sol 1493: Spirit initiated a direct-to-Earth communications link using the X-band antenna and transmitted a data packet to correct the spacecraft clock.

Sol 1494: In addition to monitoring atmospheric dust and conducting surveys with the miniature thermal emission spectrometer, Spirit recharged the battery.

Sol 1495: In the morning, Spirit acquired column 3, part 1 of the full-color Bonestell panorama, using all 13 filters of the panoramic camera. Spirit positioned the alpha-particle X-ray spectrometer to measure argon gas in the Martian atmosphere. The rover took a single-frame image with the navigation camera. After communicating with Odyssey, Spirit measured argon with the alpha-particle X-ray spectrometer.

Sol 1496: Spirit monitored dust accumulation on the rover mast and acquired column 3, part 3 of the full-color Bonestell panorama. The rover acquired full-color images, using all 13 filters of the panoramic camera, of the Freeman rock target.

Sol 1497 (March 19, 2008): Spirit looked for changes in the "El Dorado" dune field with the panoramic camera and acquired column 4, part 1 of the Bonestell panorama. The rover recharged the battery. The following morning, Spirit was to acquire movie frames in search of clouds with the navigation camera, acquire super-resolution, panoramic-camera images of a target dubbed "C.S. Lewis half," and survey the horizon with the panoramic camera.

Odometry:

As of sol 1496 (March 18, 2008), Spirit's total odometry was 7,528 meters (almost 4.7 miles).

sol 1484-1490, Mar. 6-12, 2008: Spirit Begins Preparing for "Hibernation" Mode

Spirit has reached its final position for the coming Martian winter and has no plans to move before the next Martian spring. During the next few months, the rover will increasingly go into a "hibernate" mode as the sun continues to dim.

Spirit is currently wrapping up a campaign of scientific studies of the rock target known as "Wendell Pruitt," interspersed with remote science observations of targets nicknamed "Lucius Theus" and "Theopolis Johnson." These targets were all named in honor of distinguished members of the "Tuskegee Airmen," the popular name for the 332nd Fighter Group, an all African-American unit of the U.S. Army Air Corps that served in the European Theater during World War II.

Spirit's previous attempt to use the wire brush on the rock abrasion tool on sol (Martian day) 1479 (March 1, 2008) failed to sufficiently brush the surface of Wendell Pruitt. The rover repeated the effort on sol 1484 (March 6, 2008) with greater success. On sol 1486 (March 8, 2008), Spirit acquired a 2-by-2-by-5 stack of stereo microscopic images of Wendell Pruitt. The rover placed the alpha-particle X-ray spectrometer on the target on sol 1489 (March 11, 2008) but postponed data collection with the instrument to conserve power for an operational readiness test in support of the Phoenix mission scheduled for the late morning of sol 1491 (March 13, 2008). At that time, the rover was to send a tone at UHF frequencies directly to the Green Bank radio telescope in West Virginia. The tone was to serve as a beacon; the rover would not be transmitting data.

Spirit continued to take panoramic-camera images for the 360-degree "Bonestell panorama." The rover recharged its battery on sols 1485, 1487, 1488, and 1490 (March 7, 9, 10, and 12, 2008). On recharge days, the rover typically conducts minimal science activity and does not relay Eartbound data to the Odyssey orbiter as it passes overhead.

A complication in Spirit's current circumstances is that the mast holding the panoramic and navigation cameras is partially obscuring the X-band, high-gain antenna that Spirit's handlers use to command the spacecraft from Earth. Engineers have been experimenting with "parking" these instruments in positions that minimize this obscuration.

Spirit is healthy and all subsystems are performing as expected. The latest available power readings from sol 1489 (March 11, 2008) showed power at 254 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour).

Sol-by-sol summary:

To conserve energy, mission planners have restricted the number of sols on which Spirit receives direct-from-Earth instructions via the rover's high-gain antenna and transmits data to Earth via the Odyssey orbiter. Spirit continues, on a daily basis, to monitor atmospheric dust levels with the panoramic camera, check for drift (changes with time) in the miniature thermal emission spectrometer, and survey the sky and ground with the instrument. In addition, during the past week, Spirit completed the following activities:

Sol 1484 (March 6, 2008): Spirit brushed the surface of Wendell Pruitt, acquired a single-frame, lossless-compression (high-resolution) image of the area in front of the rover with the navigation camera, and took stereo images with the front hazard avoidance cameras.

Sol 1485: Spirit acquired super-resolution images of half of Lucius Theus and recharged the battery.

Sol 1486: Spirit surveyed the horizon and took spot images of the sky for calibration purposes with the panoramic camera. Spirit monitored dust on the rover mast and acquired a 2-by-2-by-5 stack of stereo microscopic images of Wendell Pruitt. The rover acquired a single-frame, lossless-compression image of the area in front of the rover with the navigation camera as well as stereo images with the front hazard avoidance cameras.

Sol 1487: In the morning, Spirit acquired column 2, part 3 and column 3, part 1 of the full-color Bonestell panorama, using all 13 filters of the panoramic camera, then spent much of the Martian day recharging the battery.

Sol 1488: In the morning, Spirit used the navigation camera to take images of the sky (called "sky flats") for calibration purposes and used the panoramic camera to take super-resolution images of Theopolis Johnson. The rover turned the panoramic camera mast assembly to prepoint the camera, then recharged the batteries.

Sol 1489: Spirit placed the alpha-particle X-ray spectrometer on Wendell Pruitt and, after relaying data to Odyssey, acquired data with the instrument.

Sol 1490 (March 12, 2008): Spirit acquired column 3, part 2 of the Bonestell panorama and recharged the batteries. Plans for the next morning called for Spirit to acquire thumbnail panoramic-camera images of the sky looking starboard (to the rover's right) for calibration purposes.

Odometry:

As of sol 1489 (March 11, 2008), Spirit's total odometry remained at 7,528.07 meters (4.68 miles).

sol 1478-1483, Feb. 29- Mar. 05, 2008: Work Continues on 360-Degree View of Spirit's Winter Perch

Spirit continued work on the "Bonestell panorama," a full-color, 360-degree view of the rover's surroundings from its overwintering perch on the north-facing edge of "Home Plate." Spirit acquired images for the panoramic mosaic on sols 1478, 1479, 1480 and 1483 (Feb. 29, March 1-2, and March 5, 2008). By the time the final product is ready, the rover will have completed an estimated 60 separate pointings of the panoramic camera in all different directions. Rover planners have nicknamed the panorama in honor of Chesley Bonestell (1888-1986), considered the father of modern space art.

Spirit has also been engaged in efforts to brush away dust from a rock target known as "Wendell Pruitt." The rover used the rock abrasion tool to brush the surface on sol 1479 (March 1, 2008), but the brushing cleared only about half the expected area. On the basis of the results, the rover's handlers adjusted the command sequence to have Spirit perform a "grind scan" to locate the surface of Wendell Pruitt on sol 1482 (March 4, 2008). The goal of this maneuver was to get the rock abrasion tool in place for another attempted brushing, scheduled for sol 1484 (March 6, 2008).

Spirit is healthy and all subsystems are performing as expected.

Sol-by-sol summary:

To conserve energy, mission planners have restricted the number of sols on which Spirit receives direct-from-Earth instructions via the rover's high-gain antenna and transmits data to Earth via the Odyssey orbiter. Spirit continues, on a daily basis, to monitor atmospheric dust levels with the panoramic camera, check for drift (changes over time) in the miniature thermal emission spectrometer, and survey the sky and ground with the instrument. In addition, during the past week, Spirit completed the following activities:

Sol 1478 (Feb. 29, 2008): Spirit acquired column 1, part 2 of the full-color, panoramic camera images, using all 13 filters of the camera, that will make up the Bonestell panorama. Spirit also recharged the batteries.

Sol 1479: Using the wire brush on the rock abrasion tool, Spirit brushed the surface of Wendell Pruitt. The rover acquired a single-frame, lossless-compression (highly detailed) image of the area in front of the rover using the navigation camera. Spirit relayed data at UHF frequencies to NASA's Odyssey orbiter for transmission to Earth.

Sol 1480: Spirit acquired column 1, part 3 of the Bonestell panorama and measured argon gas in the Martian atmosphere with the alpha-particle X-ray spectrometer.

Sol 1481: Spirit acquired column 2, part 1 of the Bonestell panorama, and recharged the batteries.

Sol 1482: Spirit acquired an image with the panoramic camera pointing south, then completed "Grind Scan2" of the surface of "Wendell Pruitt." The rover acquired a single-frame, lossless-compresson image of the area in front of the spacecraft with the navigation camera. Spirit relayed data at UHF frequencies to NASA's Odyssey orbiter for transmission to Earth.

Sol 1483 (March 5, 2008): Early in the day, Spirit acquired a super-resolution image of the target nicknamed "FredericBrown half" with the panoramic camera. The rover recharged the batteries. The following morning, Spirit was to acquire full-color, panoramic camera images of column 2, part 2 of the Bonestell panorama.

Odometry:

As of sol 1482 (March 4, 2008), Spirit's total odometry remained at 7,528.07 meters (4.68 miles).

sol 1471-1477, Feb. 22-28, 2008: Sturdy Rover Gets No Penalty for Tilting

Scarcely a pinball wizard on Earth could tilt the machine nearly 30 degrees without ending play, yet engineers tilted NASA's Spirit rover 29.9 degrees and completed the robotic equivalent of a one-armed toe-touch to test its stability. The rover remained in play, racking up scientific data points after remaining perfectly balanced even while pressing the ground with the Möessbauer spectrometer at the end of its robotic arm.

During the past week, Spirit began work on a 360-degree, full-color panorama of the rover's winter surroundings as viewed from the north edge of the elevated, volcanic plateau known as "Home Plate." The resulting mosaic of high-resolution images, to be acquired during approximately 60 individual pointings of the panoramic camera, will be nicknamed the "Bonestell panorama" in honor of Chesley Bonestell (pronounced BON-es-tell), a science fiction illustrator and designer. (Last year's spectacular image mosaic of Spirit's winter haven was called the "McMurdo panorama.")

Spirit took microscopic images of dust that has settled out of the Martian sky onto the solar panels. The rover also made two attempts to complete the first of a two-part process for brushing the surface of a rock target dubbed "Wendell Pruitt" with the rock abrasion tool, another of the instruments on the rover's robotic arm. Because the results were inconclusive after the first try, Spirit's handlers decided to have the rover repeat the procedure, known as a "grind scan," during which the rover locates the surface by touching it with the brush and the grinding bit, two days later. The second attempt was successful, clearing the way for actual brushing of Wendell Pruitt.

Spirit is healthy and all subsystems are performing as expected.

Sol-by-sol summary:

In addition to measurements of atmospheric dust levels with the panoramic camera and daily communications activities, which include morning direct-from-Earth uplinks over the rover's high-gain antenna and evening relays to Earth via the UHF antenna on the Mars Odyssey orbiter, Spirit completed the following activities:

Sol 1471 (Feb. 22, 2008): Spirit completed a mini-survey of the sky and ground with the miniature thermal emission spectrometer, touched the ground and exerted 10 newtons of force with the Möessbauer spectrometer to test the rover's stability at the new tilt of 29.9 degrees, and acquired super-resolution images of a target dubbed "Gekko." Spirit took spot images of the sky for calibration purposes using the panoramic camera.

Sol 1472: Spirit checked for drift (changes over time) in the miniature thermal emission spectrometer, surveyed the external calibration target and completed a mini-survey of the sky and ground with the miniature thermal emission spectrometer, and acquired super-resolution images of a rock target known as "Monolith" with the panoramic camera.

Sol 1473: Spirit acquired full-color images, using all 13 filters of the panoramic camera, of a rock target dubbed "William A. Johnston," a deceased member of the Tuskegee Airmen. Spirit checked for drift in the miniature thermal emission spectrometer, completed a mini-survey of the sky and ground with the instrument, and acquired a 2-by-2-by-1 stack of microscopic images of a target on the rover's solar panels as well as microscopic images of the external capture magnet and filter magnet. The rover acquired single-frame, lossless-compression (high-definition) images of the area directly in front of the rover with the navigation camera.

Sol 1474: Spirit monitored dust on the rover mast, surveyed the sky at varying elevations and the ground with the miniature thermal emission spectrometer, completed another mini-survey of the sky and ground, and checked for drift in the spectrometer.

Sol 1475: Spirit took full-color images, using all 13 filters of the panoramic camera, of a rock target nicknamed "Bennett Hardy" (also a Tuskegee Airman). The rover checked for drift in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. Spirit made the first attempt to use a grind-scan procedure to contact the surface of Wendell Pruitt. The rover took single-frame, lossless-compression (high-definition) images with the navigation camera.

Sol 1476: Spirit acquired super-resolution images of a rock target dubbed "Reuben C. Franklin" (a Tuskegee Airman) with the panoramic camera, checked for drift in the miniature thermal emission spectrometer, and completed a mini-survey of the sky and ground with the instrument. The rover took diagnostic images of the rock abrasion tool and recharged the batteries.

Sol 1477 (Feb. 28, 2008): Spirit acquired column 1 of part 1 of the full-color Bonestell panorama, using all 13 filters of the panoramic camera. The rover checked for drift in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. Spirit completed the second, successful attempt to locate the surface of Wendell Pruitt using the grind-scan procedure with the rock abrasion tool. The rover acquired single-frame, lossless-compression images with the navigation camera. Plans for the following morning called for Spirit to point the panoramic camera starboard and take thumbnail images of the sky.

Odometry:

As of sol 1476 (Feb. 27, 2008), Spirit's total odometry remained at 7,528.07 meters (4.68 miles).

sol 1464-1470, Feb. 14-21, 2008: Tenacious Rover Just Might Make It

Spirit has achieved a northerly tilt of 29.9 degrees! As a result, based on power projections, Spirit has a fighting chance of surviving another winter on Mars, if the weather and environment cooperate.

Plans for sol 1471 (Feb. 22, 2008) called for a test of the stability of Spirit's new perch prior to using the rock abrasion tool by having the rover touch the Martian surface with the Mössbauer spectrometer and apply 10 newtons of pressure (called a pre-load).

Sol-by-sol summary:

In addition to measurements of atmospheric dust levels with the panoramic camera and daily communications activities, which include morning direct-from-Earth uplinks over the rover's high-gain antenna and evening relays to Earth via the UHF antenna on the Mars Odyssey orbiter, Spirit completed the following activities:

Sol 1464 (Feb. 14, 2008): Spirit edged downslope another 4 centimeters (about 1.5 inches). The rover took thumbnail images of the sky for calibration purposes with the panoramic camera.

Sol 1465: Spirit took mid-field images and spot images of the sky for calibration purposes with the panoramic camera.

Sol 1466: Spirit acquired images for updating the rover's precise attitude relative to the Sun, surveyed the horizon and took spot images of the sky with the panoramic camera, and surveyed the external calibration target with the miniature thermal emission spectrometer.

Sol 1467: Spirit acquired images of the "El Dorado" dune field with the panoramic camera and snapped movie frames in search of dust devils with the navigation camera. The rover took thumbnail images of the sky with the panoramic camera.

Sol 1468: Spirit surveyed the sky at high Sun using the panoramic camera.

Sol 1469: Spirit surveyed the sky and ground with the miniature thermal emission spectrometer and took before-and-after stereo images with the navigation camera to enable the on-board visual odometry software to determine the rover's position. Spirit acquired a 5-by-1 mosaic of forward-looking images and a 5-by-1 mosaic of rearward-looking images with the navigation camera. Also with the navigation camera, the rover assessed atmospheric opacity caused by dust and scanned the sky for clouds.

Sol 1470 (Feb. 21, 2008): Spirit unstowed the robotic arm and moved it to test the rover's stability. Spirit measured atmospheric opacity caused by dust using both the panoramic and navigation cameras. The rover took spot images of the sky with the panoramic camera and surveyed the sky and ground with the miniature thermal emission spectrometer.

Odometry:

As of sol 1470 (Feb. 21, 2008), Spirit's total odometry was 7,528.07 meters (4.68 miles).

sol 1457-1463, Feb. 7-13, 2008: Spirit Inches Downward

Spirit is tiptoeing ever so carefully down the north edge of the elevated volcanic plateau known as "Home Plate." Having completed a 4-centimeter (1.6-inch) drive on sol 1463 (Feb. 13, 2008), the rover's current northerly tilt is 27.1 degrees. Spirit's handlers plan to have the rover drive another 4 centimeters on sol 1464 (Feb. 14, 2008).

They expect Spirit to be at the rover's final winter perch by the end of next week, following a few more 4-centimeter drives. Given recent progress, Spirit may achieve a northerly, Sun-facing tilt of 30 degrees, higher than originally anticipated. Spirit remains healthy.

Sol-by-sol summary:

In addition to measurements of atmospheric dust levels with the panoramic camera and daily communications activities, which include morning direct-from-Earth uplinks over the rover's high-gain antenna and evening relays to Earth via the UHF antenna on the Mars Odyssey orbiter, Spirit completed the following activities:

Sol 1457 (Feb. 7, 2008): Spirit surveyed the Martian sky and ground using the miniature thermal emission spectrometer, stowed the rover's robotic arm, and drove downslope.

Sol 1458: Spirit acquired images of the dune field known as "El Dorado," surveyed the Martian horizon, and took spot images of the sky for calibration purposes using the rover's panoramic camera. Spirit acquired movie frames in search of dust devils using the navigation camera.

Sol 1459: Spirit drove 12 centimeters (4.7 inches) further down the north edge of Home Plate. The rover surveyed the sky and ground with the miniature thermal emission spectrometer.

Sol 1460: Spirit surveyed the sky and ground using the miniature thermal emission spectrometer and took thumbnail images of the sky with the panoramic camera.

Sol 1461: Spirit acquired mid-field and far-field images using the panoramic camera.

Sol 1462: Spirit acquired a second set of mid-field images as well as thumbnail images of the sky using the panoramic camera.

Sol 1463 (Feb. 13, 2008): Spirit drove another 4 centimeters (1.6 inches) downslope. Using the panoramic camera, Spirit surveyed the horizon, monitored changes in the El Dorado dune field, and took spot images of the sky.

Odometry:

As of sol 1463 (Feb. 13, 2008), Spirit's total odometry was 7,528.01 meters (4.68 miles).

sol 1450-1456, Jan. 31 - Feb 6, 2008: Dust on Spirit's Solar Panels Increases as Dust in the Atmosphere Decreases

Spirit is healthy and all subsystems are operating as expected. Energy has been steady at about 260 watt-hours per Martian day, or sol (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). On Sol 1450 (Jan. 31, 2008), measurements of atmospheric opacity caused by dust -- known as Tau -- increased by 0.02 to 0.4, then fell back to 0.38, then drifted lower still to 0.333. Small changes such as these are typical of sol-by-sol variations during Martian fall and winter. As the atmosphere cleared, however, a different measurement known as the dust factor -- an estimate of the ability of sunlight to penetrate the layer of dust on the solar arrays -- also dipped slightly and continued to slowly decline, causing overall energy levels to remain about constant.

The dust factor is now 0.374, meaning that only about three-eighths of the sunlight reaching the arrays penetrates the dust layer to generate electricity. The dust factor continues to set new lows nearly every sol. The good news is that the decline has been slower than predicted, resulting in absolute values that are higher than predicted. The difference isn't great -- about 10 to 15 watt-hours, or enough energy to light a 15-watt sewing machine bulb for one hour -- but every bit is welcome.

Sol-by-sol summary:

In addition to receiving morning instructions directly from Earth via the high-gain antenna, measuring atmospheric dust levels with the panoramic camera, checking for drift (changes in time) in the miniature thermal emission spectrometer, and surveying the sky and ground with the miniature thermal emission spectrometer, Spirit completed the following activities:

Sol 1450 (Jan. 31, 2008): Spirit brushed the surface of the rock target known as "Freeman" (commemorating the Freeman Field Mutiny, a series of attempts in 1945 by African-Americans in the U.S. Air Force to integrate an all-white officers' club) using the wire brush on the rock abrasion tool. Spirit took high-resolution images with the navigation camera to verify on-board software measurements of rover slippage based on comparison of before-and-after stereo images of the terrain (the software is known as the visual odometry system). After communicating with the Odyssey orbiter, the rover acquired panoramic-camera images of the sunset.

Sol 1451: Spirit acquired data from a rock known as "Fuzzy Smith" using the miniature thermal emission spectrometer.

Sol 1452: Spirit took measurements of the external calibration target with the miniature thermal emission spectrometer and acquired a 2-by-2-by-5 mosaic of stereo microscopic images of the brushed surface of Freeman. The rover then placed the alpha-particle X-ray spectrometer on Freeman.

Sol 1453: Spirit took measurements of the external calibration target, a rock target known as "Winston_Gaskins3," and the background of Fuzzy Smith (the specific target was nicknamed "Fuzzy Smith bg2") using the miniature thermal emission spectrometer. After sending data to the Odyssey orbiter, Spirit spent about 6.3 hours integrating data from the brushed surface of Freeman with the alpha-particle X-ray spectrometer.

Sol 1454: Spirit took measurements of the external calibration target with the miniature thermal emission spectrometer.

Sol 1455: Spirit surveyed the external calibration target with the miniature thermal emission spectrometer and, after communicating with Odyssey, spent about 6.3 hours collecting additional data from Freeman with the alpha-particle X-ray spectrometer.

Sol 1456 (Feb. 6, 2008): Spirit took measurements of the external calibration target with the miniature thermal emission spectrometer. The following morning, the rover was to acquire full-color images, using all 13 filters of the panoramic camera, of a rock target known as "Samuel_Hughes."

Odometry:

As of sol 1455 (Feb. 5, 2008), Spirit's total odometry remained at 7,527.83 meters (4.68 miles).

sol 1445-1449, Jan. 26-30, 2008: Spirit Takes Steps to Conserve Energy During Martian Winter

Spirit is responding to declining winter power levels by dipping into the batteries on one sol (Martian day), then recharging them on the next. In addition, one of the first things the rover did to conserve energy was eliminate afternoon data transfers to the Odyssey orbiter on days when the batteries were being recharged. Though this approach meant the rover wouldn't be able to send data on those sols, it saved enough energy to be worth the sacrifice. As Martian winter deepens, it's possible that, as the Opportunity rover did during the depth of the dust storm a few months ago, Spirit will use only every third Odyssey pass or adopt even more stringent power-conserving measures.

Meanwhile, Spirit remains healthy. For the most part, all subsystems are performing as expected. Energy has been holding steady in the range of 260 watt-hours. Tau (atmospheric opacity) continues to decline slightly, but the dust factor (the ability of sunlight to penetrate dust on the solar panels) also continues to decline slightly.

The winter Sun continues to dip lower in the sky. As of sol 1450 (Jan. 31, 2008), the noontime Sun was 64.6 degrees above the northern horizon, indicating that the optimal northern tilt of the rover deck would be 25.4 degrees from vertical (90 - 64.6 = 25.4). Spirit's current northward tilt is 22 degrees, relatively close to optimal. By mid-February, the optimal tilt will increase to about 28 degrees, the maximum Spirit is anticipated to be able to achieve. That's about the time when rover drivers plan to have the rover complete one more short drive to get into position for the winter.

The orbiting Odyssey spacecraft continues to provide a relay from the rovers to Earth. Each rover sends data to Odyssey via a UHF link. (UHF is "Ultra High Frequency" and represents the same band of frequencies used by the UHF channels on a TV set, channels 14-83, which transmit signals at roughly 400-500 megahertz.) Odyssey stores the data until it can transmit it to Earth using the X-band link. X-band is a microwave frequency that operates at roughly 7-8 gigahertz (megahertz and gigahertz refer, respectively, to millions of cycles per second and billions of cycles per second).

Originally, the Mars rover mission was intended to be an X-band mission, with the rovers using their X-band transmitters to return data directly to Earth. The UHF radio was intended to serve as a backup. But because relay operations via Odyssey proved wildly successful, Odyssey became the preferred avenue for returning data. For one thing, the UHF link can accommodate data at either 128 kilobits per second or 256 kilobits per second (in these cases, "kilo" actually means 1,024 rather than the usual 1,000). The highest X-band data rate for the rovers is only 28.4 kilobits per second, and most of the time, even that rate is unachievable. Odysssey, however, can return data at up to 124.4 kilobits per second using the X-band link. In fact, the lowest rate of data transmission from Odyssey is the same as the highest rate for the rovers.

During the past week, Spirit twice conducted a "grind scan" procedure with the rock abrasion tool. After the tool's encoder failed some time ago, engineers redesigned how the tool is used. Part of that redesign includes doing a "scan" before the rover grinds or brushes any surface (except, of course, that Spirit is no longer grinding into rock surfaces -- after performing more than 10 times longer than expected and contributing a great deal of science data to the mission, the grind bit wore out.)

During the "scan" procedure, the rover pushes the brush and bit into a targeted surface until it measures an increase in electrical current, which implies contact with the rock surface. Detecting the exact location of a possibly irregular surface is important for safely operating the rock abrasion tool.

The only reason Spirit is using the rock abrasion tool at this time is that the rover has moved to a new location as of sol 1440 (Jan. 21, 2008). As Spirit inches down the north-facing slope of "Home Plate," the rover will sample each new location for insight into how the rocks change and how Home Plate was formed.

As Spirit is stationed on a fairly steep slope, engineers have been concerned that moving the robotic arm might cause the rover to slip. The arm is very light and represents only a percent or two of Spirit's weight, but on a slope, it's always possible that even a slight shift could cause a slide. On top of that, the "grind scan" function requires the rover to press down on ("preload") the target. The pressure isn't much, only 15 newtons (not quite 3.5 pounds), but that, too, could conceivably cause a slip. The rover's handlers have created a plan that includes some safety checks.

The first time around, based on receipt of erroneous data, they had to double-check that the slope beneath the rover didn't exceed 20 degrees, the maximum slope previously allowed. Because Spirit was already tilted 22.4 degrees, the safety check tripped immediately and the rover did not conduct any of the planned activities with the rock abrasion tool. Rover handlers re-planned the activities and successfully completed the "scan" procedure on sol 1448 (Jan. 29, 2008).

The next step will be to actually brush the surface. But that's a story for another week.

Sol-by-sol summary:

In addition to receiving morning instructions directly from Earth via the high-gain antenna, measuring atmospheric dust levels with the panoramic camera, and checking for drift (changes in time) in the miniature thermal emission spectrometer, Spirit completed the following activities:

Sol 1445 (Jan. 26, 2008): Spirit conducted a grind scan procedure at a target called "Freeman." Spirit took high-resolution images with the navigation camera to verify on-board software measurements of rover slippage based on comparison of before-and-after stereo images of the terrain (the software is known as the visual odometry system).

Sol 1446: Spirit re-took part 12 of a mosaic of images of the rover deck and took thumbnail images of the sky with the panoramic camera. The rover acquired data from rock targets known as "Fuzzy_Smith_2" and "Winston_Gaskins_2" using the miniature thermal emission spectrometer.

Sol 1447: Spirit monitored dust accumulation on the rover mast, completed a survey of rock clasts with the panoramic camera, and surveyed the external calibration target, the sky, and the ground with the miniature thermal emission spectrometer.

Sol 1448: Spirit took spot images of the sky and surveyed the horizon with the panoramic camera and scanned the sky for clouds with the navigation camera. The rover monitored changes in the distant dune field known as "El Dorado" with the panoramic camera. Spirit conducted a grind scan at Freeman with the rock abrasion tool. Spirit took high-resolution images with the navigation camera to verify on-board software measurements of rover slippage based on comparison of before-and-after stereo images of the terrain.

Sol 1449: (Jan. 30, 2008): Spirit surveyed the sky and ground with the miniature thermal emission spectrometer and acquired movies in search of dust devils using the navigation camera. The following day, plans called for the rover to survey the external calibration target using the miniature thermal emission spectrometer.

Odometry:

As of sol 1448 (Jan. 29, 2008), Spirit's total odometry remained at 7,527.83 meters (4.68 miles).

sol 1437-1444, Jan. 18-25, 2008: Atmospheric Dust Levels Decline Slightly for Spirit

Spirit received some welcome news, as atmospheric dust levels decreased slightly, enabling power levels to remain fairly steady at 260 watt-hours to 270 watt- hours, even as the Martian sun continued to sink toward the northern horizon. (One hundred watt-hours is the amount of energy needed to light a 100-watt bulb for one hour.) Tau measurements of atmospheric opacity decreased from 0.44 to 0.36. The dust factor -- representing the fraction of predicted solar power actually generated after blocking of sunlight by dust on the solar panels -- was nearly steady, declining only 0.05 from 0.39 to 0.385.

Spirit remained perched on the north edge of "Home Plate," a slightly bowl-shaped surface feature with a raised rim that, along its northern edge, is roughly 2 meters (6 feet) above the surrounding area. Directly below Spirit, the slope is about 28 degrees. As Martian winter approaches and the Sun gets lower and lower in the sky, engineers will direct Spirit farther and farther down the slope, increasing the rover's tilt to follow the sun.

As of Sol 1444 (Jan. 25, 2008), Spirit's 22.4-degree northerly tilt was almost perfectly matched to the position of the Sun, which is about 22 degrees below the zenith (the point in the Martian sky directly above the rover). In roughly two to three weeks, Spirit will be adjusted to a final winter position with an expected tilt of about 28 degrees to the north. This will be the best Spirit can do, given the absence of steeper slopes in the vicinity. Even if there were steeper slopes nearby, safety concerns would probably preclude their use.

With more dust on the solar arrays than ever before in the mission, Spirit's third winter will be especially challenging. Estimates indicate that at the winter solstice, the point where the noontime sun will be lowest in the sky, Spirit's energy production will be near the edge of survival. But with Tau and dust accumulation both slightly better than expected and with careful management, the rover's handlers are hopeful that Spirit will ride out the winter and begin roving again in the spring.

While parked for the winter, Spirit will not be idle. Except for the period of very lowest power, the rover will be studying the atmosphere, watching for clouds, monitoring the dust accumulation, checking for frost, and surveying the immediate surroundings, along with completing other tasks.

One of the ways the rover maximizes efficiency is by replacing a large amount of redundant data with a smaller amount of data. This is known as image compression. A simple, everyday analogy is multiplication, in which the mathematical operation, (5 * 4), takes fewer characters than (4 + 4 + 4 + 4 + 4). The rover uses a process called lossless compression, or LOCO for short. There are two classes of compression, lossless and lossy. Lossy compression is sort of like standard television, producing images that are usually sufficient. Lossless compression is analogous to high-definition television and is used for a few images that need to be mathematically processed to include all the detail the cameras can capture. For Spirit, lossless compression is particularly important for collecting detailed images of the area in front of the rover directly after moving to a new location. It is used to generate maps of surfaces reachable with the robotic arm and each of the instruments, called "reachability maps," as well as mathematical models of the area around the rover that are used to simulate the rover's motion during planning, called "terrain meshes." Lossless compression is also used to create slope maps that show steepness and orientation toward the Sun.

Sol-by-sol summary:

In addition to receiving morning instructions directly from Earth via the high-gain antenna and measuring atmospheric dust levels with the panoramic camera, Spirit completed the following activities:

Sol 1437 (Jan. 18, 2008): Spirit communicated with the Odyssey orbiter while surveying the background of the rock known as "Fuzzy Smith" with the miniature thermal emission spectrometer.

Sol 1438: Spirit surveyed the sky and ground with the miniature thermal emission spectrometer, surveyed the horizon with the panoramic camera, and checked for drift -- changes with time -- in the miniature thermal emission spectrometer.

Sol 1439: Spirit acquired full-color images of the external dust capture magnets using all 13 filters of the panoramic camera, took spot images of the sky with the panoramic camera, and checked for drift in the miniature thermal emission spectrometer. The rover studied Fuzzy Smith and a rock known as "Winston Gaskins" with the miniature thermal emission spectrometer.

Sol 1440: Spirit acquired several panoramic camera images of the rover deck, scanned the sky for clouds with the navigation camera, and took spot images of the sky with the panoramic camera. The rover checked for drift in the miniature thermal emission spectrometer and adjusted position to achieve a greater northerly tilt. After adjusting position, Spirit took images with the hazard avoidance cameras and a single-frame LOCO image with the navigation camera.

Sol 1441: Spirit surveyed the horizon with the panoramic camera, surveyed the external calibration target with the miniature thermal emission spectrometer, and watched for dust devils. The rover also checked for drift in the miniature thermal emission spectrometer.

Sol 1442: Spirit acquired a 1-by-1 panoramic camera mosaic of the work volume reachable with the robotic arm and took thumbnail images of the sky with the panoramic camera. Spirit checked for drift in the miniature thermal emission spectrometer, unstowed the robotic arm, acquired diagnostic images of the rock abrasion tool with the hazard avoidance and panoramic cameras, and exchanged tools to the alpha-particle X-ray spectrometer. The rover sent data to Odyssey during the overhead pass of the orbiter.

Sol 1443: Spirit acquired a 5-by-1 standard tier of images as well as a 5-by-1, rearward-looking mosaic of images with the navigation camera. The rover conducted a horizon survey and acquired more images of the rover deck with the panoramic camera. Spirit checked for drift in the miniature thermal emission spectrometer, communicated with the Odyssey orbiter, and spent 6.75 hours acquiring data with the alpha-particle X-ray spectrometer.

Sol 1444 (Jan. 25, 2008): Spirit surveyed the sky at high Sun with the panoramic camera and checked for drift in the miniature thermal emission spectrometer. The following morning, the rover was to scan the sky for clouds with the navigation camera and take spot images of the sky with the panoramic camera.

Odometry:

As of sol 1444 (Jan. 25, 2008), Spirit's total odometry was 7,527.83 meters (4.68 miles).

sol 1430-1436, Jan. 11-17, 2008: Spirit Continues to Increase Northerly Tilt

Spirit is currently engaged in a campaign of short bumps -- adjustments in position -- that will incrementally increase the rover's northerly tilt to 22 degrees and eventually to 29 degrees by month's end. Spirit is healthy and all subsystems are operating as expected. The latest power levels measured on sol 1436 (Jan. 17, 2008) were 261 watt-hours (by definition, 100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour).

After successfully adjusting position on sol 1429 (Jan. 9, 2008) to achieve a northerly tilt of about 16 degrees, Spirit completed scientific studies of the rock target known as "Chanute." From sols 1431-1433 (Jan. 12-14, 2008), Spirit acquired a microscopic image mosaic of the brushed surface, placed the alpha-particle X-ray spectrometer on the target, and collected compositional data for about six hours. Sol 1433 was a recharge sol with no UHF-band communication. After reviewing the data, scientists agreed there was too much dust and debris in the alpha-particle X-ray spectrometer measurements. They thus decided to move the instrument to a "cleaner" location in the activity plan for sols 1434-1435 (Jan. 15-16, 2008) and collect another six hours worth of data. They documented the new site with a single-frame microscopic image.

Following sol 1435, also a recharge sol with no UHF communication, the rover's handlers planned another bump on sol 1436 (Jan. 17, 2008). Because of power limitations, they delayed a plan to inspect some strange-appearing brush patterns that may indicate normal brush wear or possible damage. They planned to use the miniature thermal emission spectrometer on sol 1437 (Jan. 18, 2008) at the start of a three-part imaging campaign on a rock known as "Fuzzy Smith."

Spirit's bump on sol 1436 was successful and put the rover at a new northerly tilt of approximately 18 degrees. The impact on power will not be known until receipt of data on sol 1437. The science team's goal is to achieve a northerly tilt of 22 degrees as soon as possible, at which point they will likely pause to perform scientific studies of a new target.

Sol-by-sol summary:

In addition to receiving morning instructions directly from Earth via the high-gain antenna, Spirit completed the following activities:

Sol 1430 (Jan. 11, 2008): Spirit monitored atmospheric dust with the panoramic camera.

Sol 1431: Spirit took full-color images of Chanute using all 13 filters of the panoramic camera. The rover monitored atmospheric dust, unstowed the robotic arm, and acquired navigation camera images. Spirit acquired a 2-by-2-by-5 mosaic of stereo microscopic images of the brushed surface of Chanute and placed the alpha-particle X-ray spectrometer on the target. The rover took images following instrument placement with the navigation camera.

Sol 1432: Spirit measured atmospheric opacity caused by dust with the panoramic and navigation cameras and scanned the sky for morning clouds with the navigation camera. The rover acquired compositional data from the brushed surface of Chanute with the alpha-particle X-ray spectrometer.

Sol 1433: Spirit monitored atmospheric dust levels using the panoramic and navigation cameras and scanned the sky for clouds with the navigation camera.

Sol 1434: Spirit measured atmospheric dust with the panoramic and navigation cameras and scanned the sky for clouds with the navigation camera. The rover acquired a 1-by-1-by-1 mosaic and a 1-by-1-by-3 mosaic of microscopic images of the brushed surface of Chanute and placed the alpha-particle X-ray spectrometer on the target. Spirit acquired navigation camera images after placing the spectrometer on the target. The rover communicated with the Odyssey orbiter and acquired data from the brushed target with the alpha-particle X-ray spectrometer.

Sol 1435: Spirit measured atmospheric dust opacity with the panoramic camera and acquired a 5-by-1 mosaic of navigation camera images of the rover deck, a 2-by-1 mosaic of panoramic camera images, and two views of the rover deck with the panoramic camera.

Sol 1436 (Jan. 17, 2008): Spirit took thumbnail images of the sky with the panoramic camera, meaasured atmospheric dust with the panoramic camera, took images of the brush on the rock abrasion tool, and bumped into a new position to increase northerly tilt. The rover took images with the hazard avoidance and navigation cameras after the bump. Spirit also acquired navigation camera images of Fuzzy Smith after the bump. The rover took a 1-by-1 image mosaic of the work volume with the panoramic camera. The following day's plans called for Spirit to measure atmospheric dust with the panoramic camera, monitor dust accumulation on the rover mast, and acquire additional images of the rover deck as well as spot images of the sky with the panoramic camera.

Odometry:

As of sol 1436 (Jan. 17, 2008), Spirit's total odometry was 7,527.71 meters (4.68 miles).

sol 1423-1429, Jan. 3-9, 2008: Spirit Tilts Toward the Sinking Sun

After directing the rover to brush the surface of the rock target known as "Chanute," engineers placed continued studies on hold while they adjusted Spirit's position to achieve a greater northerly tilt, in the direction of the sinking winter Sun. The latest available power levels measured on sol 1429 (Jan. 9, 2008) were 268 watt-hours, a sobering reminder of the onset of winter. Spirit was in the middle of a campaign of scientific studies with the brush on the rock abrasion tool, alpha-particle X-ray spectrometer, and microscopic imager. The move was successful and gave the rover a new northerly tilt of about 16 degrees.

Spirit is healthy and all subsystems are nominal.

After Spirit had completed acquisition of the "Tuskegee panorama" on sol 1423 (Jan. 3, 2008), planned science activities included brushing the surface of Chanute prior to continued investigation with the alpha-particle X-ray and Mössbauer spectrometers. To locate the surface, the rover performed a "seek scan" with the rock abrasion tool on sol 1424 (Jan. 4, 2008). This activity is a work-around procedure that compensates for a broken encoder and allows the rover to stall the motor of the rock abrasion tool when it makes contact with the surface.

The next two Martian days were recharge sols. Spirit brushed the surface of Chanute on sol 1427 (Jan. 7, 2008). This was also followed by another recharge sol. The rover's handlers then made two significant changes to the strategic plan to address the deteriorating power situation. First, because recharge sols were becoming less and less effective, they decided to begin deleting the UHF passes on these sols, starting on sol 1428 (Jan. 8, 2008). Second, they decided to proceed sooner than anticipated with plans to achieve a steeper northerly tilt of 20 degrees. Activities on sol 1429 (Jan. 9, 2008) involved a bump of 10 centimeters (4 inches) downslope. Sol 1430 (Jan. 11, 2008) was to be a recharge sol with no UHF.

The impact of the new, 16-degree northerly tilt on power will not be known until receipt of further data on sol 1431 (Jan. 12, 2008). The science team's goal is to reach 20 degrees as soon as possible, meaning they will likely execute additional short bumps similar to those of sol 1429 in the very near future. In the meantime, Spirit will complete work on Chanute.

Sol-by-sol summary:

In addition to receiving morning instructions directly from Earth via the high-gain antenna, sending data to Earth at UHF frequencies via the Odyssey orbiter, and measuring atmospheric dust levels, Spirit completed the following activities:

Sol 1423 (Jan. 3, 2008): Spirit acquired a 2-by-1 mosaic of the Tuskegee panorama.

Sol 1424: Spirit acquired a 4-by-1 mosaic of the Tuskegee panorama, performed a seek-scan maneuver to locate the surface of Chanute with the rock abrasion tool, and took navigation camera images following the procedure.

Sol 1425: Spirit acquired a 4-by-1 mosaic of the Tuskegee panorama.

Sol 1426: Spirit acquired morning thumbnail images of the sky with the panoramic camera.

Sol 1427: Spirit acquired spot images of the sky with the panoramic camera, monitored dust on the panoramic camera mast assembly, and scanned the sky for clouds with the navigation camera. The rover brushed the surface of Chanute, stowed the robotic arm, and acquired navigation camera images of the brushed surface.

Sol 1428: Spirit acquired a 4-by-1 mosaic of images of the Tuskegee panorama.

Sol 1429 (Jan. 9, 2008): Spirit surveyed the sky at low Sun with the panoramic camera, bumped downslope, took images with the hazard avoidance cameras, and acquired a navigation camera image after the change in position. The following day's plans called for the rover to survey the horizon with the panoramic camera and acquire movie frames in search of dust devils spaced at 8-minute intervals using the navigation camera.

Odometry:

As of sol 1429 (Jan. 9, 2008), Spirit's total odometry remained at 7,527.52 meters (4.68 miles).

sol 1416-1422, Dec. 27, 2007 - Jan. 2, 2008: After Four Years on Mars, Spirit Faces Toughest Test Yet

Four years ago on Jan. 4 (Pacific time), Spirit landed on the surface of Mars, in search of habitable environments. Now the rover is facing perhaps its greatest challenge so far -- surviving the third winter on Mars with substantial amounts of dust from last year's global storms on the solar arrays. As of sol 1406 (Dec. 17, 2007), the solar arrays were about 60 percent obscured by dust (a dust factor of 0.4), the most obscuration ever. By the time of the winter solstice on sol 1593 (June 26, 2008), the solar arrays are expected to be about 70 percent obscured (a dust factor of 0.3).

To increase Spirit's chances of survival, engineers have positioned the rover on a steep, north-facing slope to maximize exposure to sunlight. Still, even with an expected north-facing tilt of greater than 25 degrees, Spirit will likely need more energy than available each sol without additional changes, according to Project Manager John Callas. These changes may include disabling the survival heater on the miniature thermal emission spectrometer, putting the instrument at risk, and disabling the survival heater of the rover's electronic module. The module was successfully tested down to minus 55 degrees C. using brand-new electronics; disabling the heater would likely result in temperatures dipping below minus 40 degrees C., a significant dip given that the rover has now completed more than 1,400 thermal cycles.

Other survival strategies include tightly managing Spirit's energy budget each sol and minimizing operating time and communication sessions. During the darkest days of winter, Spirit may spend months facing the risk of low-power faults, when the rover takes the batteries off-line and goes to sleep due to inadequate power levels.

Meanwhile, Spirit remains healthy and all subsystems are operating as expected. The rover continues to study a rock feature dubbed "Chanute," so far gathering more than 60 hours of data about iron-bearing minerals using the Mössbauer spectrometer. Energy is around 255 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). As of sol 1421 (Jan. 1, 2008), atmospheric dust levels, known as Tau, were at 0.487 and the dust factor was at 0.49.

Sol-by-sol summary:

In addition to receiving morning instructions directly from Earth via the high-gain antenna, sending data to Earth at UHF frequencies via the Odyssey orbiter, and measuring atmospheric dust levels, Spirit completed the following activities:

Sol 1416 (Dec. 27, 2007): Spirit re-started the Mössbauer spectrometer and spent 23 hours integrating data from Chanute with the instrument. The rover acquired panoramic camera images of the dune field known as "El Dorado."

Sol 1417: Spirit acquired a 4-by-1 mosaic of the so-called "Tuskegee panorama," monitored dust accumulation on the panoramic mast assembly, and re-started the Mössbauer spectrometer for 5 hours of data integration from Chanute.

Sol 1418: Spirit acquired another 4-by-1 mosaic of the Tuskegee panorama, followed by a 2-by-1 mosaic.

Sol 1419: Spirit acquired a 4-by-1 mosaic of the Tuskegee panorama and re-started the Mössbauer spectrometer for 5 hours of data collection from Chanute. The rover watched for dust devils and acquired another 4-by-1 mosaic of the Tuskegee panorama.

Sol 1420: Spirit re-started the Mössbauer spectrometer and acquired 4 hours worth of data from Chanute with the instrument. After communicating with the Odyssey spacecraft, Spirit acquired new measurements of atmospheric dust levels.

Sol 1421: Spirit acquired a 4-by-1 and a 2-by-1 mosaic of the Tuskegee panorama.

Sol 1422 (Jan. 2, 2008): Spirit acquired a 4-by-1 mosaic of the Tuskegee panorama, re-started the Mössbauer spectrometer, and spent 4 hours studying Chanute with the instrument. The rover acquired a 2-by-1 and a 4-by-1 mosaic of the Tuskegee panorama.

Odometry:

As of the rover's last drive on sol 1406 (Dec. 17, 2007), Spirit's total odometry was 7,527.52 meters (4.68 miles).