Spirit Updates: 2008
sol 1763-1775, December 18 - December 30, 2008: Spirit Alters Course, Begins Driving Downhill
With only the summer to reach new terrain on Mars, Spirit has aborted efforts to take a shortcut by driving uphill. The rover has changed course and begun driving downhill instead.
Spirit's goal is to drive to outcrops known as "Goddard" and "von Braun," some 300 meters (1,000 feet) south of the rover's current location. The shortest way is directly across the volcanic plateau called "Home Plate." Spirit has been trying to drive back up onto Home Plate to take the more direct route. The effort, however, involves pushing rather than dragging the rover's stuck right front wheel while also fighting gravity. Initial drives seemed promising but later drives only resulted in sliding to the west along the north slope of Home Plate and slipping back downhill.
As Mars swings into spring (the spring equinox was on Dec. 25, 2008, Earth time), the Sun is moving farther and farther south. As a result, the northerly tilt that helped Spirit survive the winter is now costing energy. With a thick coating of dust on the rover's solar panels, energy is severely limited and will only keep falling unless Spirit can drive to a flatter site.
Spirit is also at some of the highest tilts of the mission and very nearly at the angle of repose. When the slope exceeds the angle of repose, dust, sand and other granular material slide downward. Spirit has been trying to take advantage of the steep tilt by spinning the middle wheels before driving to shake dust off the arrays. Engineers hope that as the wheel cleats bounce on the rocks, they will shake the solar arrays and cause dust to slide down and off. Once Spirit achieves a flatter tilt, this strategy will be less effective.
On sol 1763 (Dec. 18, 2008), Spirit's attempt to climb Home Plate ended after 0.23 meters (0.75 feet) of driving, when the rover slid to the right (west) and slipped down about 6 centimeters (2 inches). The rover autonomously ended the drive when the tilt increased to 29 degrees, the maximum allowed for safety reasons. On sol 1768 (Dec. 23, 2008), Spirit again attempted to climb Home Plate, again slid to the right, and slipped down about 5 centimeters (2 inches).
On Sol 1772 (Dec. 27, 2008), engineers decided to abandon the uphill drive and have Spirit drive downhill instead. Because the previous drive on sol 1768 ended before Spirit's front and back wheels were straight, the first step was to straighten the right front wheel. Only rarely does straightening a wheel cause vehicle motion but in this case it did. A resulting spike in the rover's tilt caused Spirit to again immediately halt the drive.
On Sol 1775 (Dec. 30, 2008), engineers were unable to transmit commands to Spirit to resume driving downhill as a result of Earth-based antenna problems.
Spirit is healthy and all subsystems are performing as expected as of information transmitted to Earth by the Mars Odyssey orbiter on sol 1775. Solar-array energy and tau (the amount of sunlight blocked by dust in the atmosphere) are at 160 watt-hours and 0.644, respectively. The dust factor has declined to 0.2413, meaning that only about 24 percent of sunlight reaching the solar panels penetrates the dust layer to generate electricity. Put another way, more than three-quarters of the light hitting the solar arrays is lost.
Tau, a measure of atmospheric clarity, has improved. Between sols 1763 and 1768, it averaged about 0.73. Following a noticeable drop on sol 1768, indicating a somewhat clearer atmosphere, tau averaged about 0.64.
The dust factor - the percentage of light penetrating dust on the solar arrays - has declined every sol except sol 1768, the same sol that saw tau drop. Overall, tau and the dust factor account for roughly half the change in solar-array energy; the tilt of the solar panels accounts for the rest.
Sol-by-sol summary
In addition to measuring dust-related changes in atmospheric opacity each Martian day, or sol, with the panoramic camera, Spirit completed the following activities:
Sol 1763 (Dec. 18, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and checked the health of the instrument using the external calibration target on the rover deck. After measuring atmospheric opacity (haze) caused by suspended dust, Spirit parked and stowed the panoramic-camera mast assembly to point it slightly to the west and downhill. (This parking and stowing maneuver shields the camera optics from dust settling out of the atmosphere and, in the event the camera elevation motor should fail, retains a partial view of nearby terrain for navigation purposes.) Spirit drove uphill and acquired images in support of the drive with the hazard-avoidance and navigation cameras. In the Martian evening, Spirit transmitted data to Earth via NASA's Odyssey orbiter.
Sol 1764: Spirit recharged the batteries, measured albedo (surface reflectivity) with the panoramic camera, and parked and stowed the panoramic-camera mast assembly to keep the camera pointed downhill and slightly to the west.
Sol 1765: After measuring tau, Spirit parked and stowed the panoramic camera mast assembly and recharged the batteries.
Sol 1766: After the usual assessment of dust-related darkness, Spirit parked and stowed the panoramic-camera mast assembly, recharged the batteries, checked for drift in the miniature thermal emission spectrometer, checked the health of the spectrometer, and transmitted data to Earth via Odyssey.
Sol 1767: After looking at atmospheric dust, Spirit parked, stowed, and monitored dust accumulation on the panoramic-camera mast assembly.
Sol 1768: After measuring atmospheric dust, Spirit parked and stowed the panoramic-camera mast assembly and drove uphill. Spirit then acquired post-drive images with the hazard-avoidance and navigation cameras, including navigation-camera images to help target the panoramic camera to take super-resolution images. The rover sent data to Odyssey to be transmitted to Earth.
Sol 1769: After the day's measurement of atmospheric dust, Spirit parked and stowed the panoramic camera mast assembly, checked for drift in the miniature thermal emission spectrometer, checked the health of the instrument, and recharged the batteries.
Sol 1770: Following the usual panoramic-camera measurement of atmospheric dust, Spirit recharged the batteries.
Sol 1771: Spirit checked for drift in the miniature thermal emission spectrometer, monitored the health of the instrument, and parked and stowed the panoramic-camera mast assembly after using it to measure atmospheric dust.
Sols 1772: Spirit acquired navigation-camera images pointed in the new, downhill drive direction. The rover took additional navigation-camera images as well as a quarter-frame, panoramic-camera image of the spacecraft deck to see if vibrations during recent drives had dislodged any dust. Spirit straightened the right front wheel and took post-drive images to document progress with the hazard-avoidance cameras. In the evening, Spirit transmitted data to Earth via the Odyssey orbiter.
Sol 1773: Spirit checked for drift in the miniature thermal emission spectrometer, checked the health of the instrument, parked and stowed the panoramic-camera mast assembly after measuring sunlight-blocking dust, and recharged the batteries.
Sol 1774: After the usual morning measurement of atmospheric dust, Spirit parked and stowed the panoramic-camera mast assembly and recharged the batteries.
Sol 1775: (Dec. 30, 2008): Spirit did not receive commands directing the rover to continue driving downhill because of transmission problems on Earth. Instead, Spirit used the backup runout sequences designed for such situations. After measuring tau, the rover parked and stowed the panoramic-camera mast assembly and relayed data to Odyssey to be transmitted to Earth.
Odometry
As of sol 1775 (Dec. 30, 2008), Spirit's total odometry was 7,529.87 meters (4.68 miles).
sol 1737-1762, November 21 - December 17, 2008: Conjunction's Over, Let's Start Driving!
Spirit survived solar conjunction, when the Sun temporarily blocked communication between Earth and Mars, with flying colors. Since the pre-conjunction dust storm, power has been slowly but steadily improving.
To survive the dust storm, Spirit turned off the heaters to the miniature thermal emission spectrometer. They have remained off since. A health check of the instrument prior to solar conjunction on Sol 1738 (Nov. 22, 2008) revealed no problems. Results of another health check after solar conjunction on Sol 1761 (Dec. 16, 2008) are pending.
The slope at the edge of "Home Plate" that helped the rover survive the winter is becoming a liability as the Sun continues to climb higher in the sky. Spirit will need to achieve a more even tilt to take full advantage of the solar arrays.
Near-term plans call for Spirit to drive toward science targets south of Home Plate. Spirit has been attempting to climb back on top of Home Plate to take a shortcut. So far this has been proving difficult. If Spirit is unable to get on top of Home Plate, the rover will have to drive down off the slope and around Home Plate's western edge.
Spirit is healthy and all subsystems are performing as expected as of the latest report on Sol 1761. Energy is currently around 192 watt-hours, Tau (a measure of atmospheric dust) is at 0.664, and the dust factor (an estimate of dust-penetrating sunlight on the solar arrays) is 0.2770.
Sol-by-sol summary
In addition to measuring dust-related changes in atmospheric opacity with the panoramic camera, Spirit completed the following activities:
Sol 1737 (Nov. 21, 2008): Spirit measured dust-related changes in atmospheric opacity with the panoramic camera.
Sol 1738: Spirit measured dust-related changes in atmospheric opacity with the panoramic camera, checked the health of the miniature thermal emission spectrometer, and acquired a quarter-frame image of the spacecraft deck with the panoramic camera.
Sol 1739: Spirit measured dust-related changes in atmospheric opacity with the panoramic camera.
Sol 1740: Spirit measured dust-related changes in atmospheric opacity with the panoramic camera.
Sol 1741: Spirit measured dust-related changes in atmospheric opacity with the panoramic camera.
Sol 1742: Spirit measured dust-related changes in atmospheric opacity with the panoramic camera.
Sol 1743: Spirit measured dust-related changes in atmospheric opacity with the panoramic camera.
Sol 1744: Spirit measured dust-related changes in atmospheric opacity with the panoramic camera.
Sol 1745 (Nov. 29, 2008): Spirit measured dust-related changes in atmospheric opacity with the panoramic camera.
Sols 1746-1760 (Nov. 30, 2008-Dec. 15, 2008): Spirit could not communicate with Earth because of solar conjunction.
Sol 1761 (Dec. 16, 2008): Spirit measured dust-related changes in atmospheric opacity with the panoramic camera, acquired a quarter-frame image of the spacecraft deck, and checked the health of the miniature thermal emission spectrometer.
Sol 1762: (Dec. 17, 2008): Spirit measured dust-related changes in atmospheric opacity with the panoramic camera, adjusted position slightly, and acquired a single-frame image with the navigation camera.
Odometry
As of sol 1762 (Dec. 17, 2008), Spirit's total odometry remained at 7,529.02 meters (4.68 miles).
sol 1730-1736, November 14 - November 20, 2008: Serious but Stable
Spirit's condition has improved during the past week, though skies remain fairly dusty after the recent Martian dust storm. Since sol 1730 (Nov. 14, 2008), solar-array energy has averaged 169 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for 1 hour). The latest measurement of atmospheric darkness caused by dust, known as Tau, is 0.858. The dust factor, representing the portion of sunlight penetrating the coating of dust on the solar panels, is 0.2912.
Spirit performed a cursory check of the health of the miniature thermal emission spectrometer. After three nights with the spectrometer's heaters disabled, the instrument appeared to be undamaged as of sol 1730. Power is not yet sufficient to re-enable those heaters, though Spirit will continue to monitor the spectrometer while waiting for power to improve. For the most part, Spirit is limiting activities to those necessary for maintaining engineering health and safety.
Spirit endured another challenge when new commands from Earth for sol 1734 (Nov. 18, 2008) did not arrive. At that point, Spirit began to execute a backup set of activities known as a runout plan. On Earth, engineers created a new sequence of commands for sol 1736 (Nov. 20, 2008) to manage communications and preserve power. Meanwhile, they are investigating why Spirit did not receive their previous commands.
According to the latest Martian weather report for Nov. 15 (sol 1731), skies are expected to continue to clear during the next couple of weeks. No other storms have been identified within a couple of thousand kilometers of Spirit's location.
Spirit is preparing for solar conjunction, where the Sun is between Earth and Mars, preventing communications. This period begins Nov. 29th. Before and during solar conjunction, Spirit's activities will remain conservative as the rover waits for the skies to clear and for the power situation to improve.
Sol-by-sol summary
In addition to measuring dust-related changes in atmospheric opacity with the panoramic camera, Spirit completed the following activities:
Sol 1730 (Nov. 14, 2008): Spirit observed the sky briefly with the miniature thermal emission spectrometer.
Sol 1731: Spirit rested and soaked up the Sun's rays to recharge the batteries.
Sol 1732: Spirit rested and soaked up the Sun's rays to recharge the batteries.
Sol 1733: Spirit rested and soaked up the Sun's rays to recharge the batteries.
Sol 1734: Spirit completed basic activities in the runout plan.
Sol 1735: Spirit completed basic activities in the runout plan.
Sol 1736 (Nov. 20, 2008): Spirit completed basic activities in the runout plan.
Odometry:
As of sol 1736 (Nov. 20, 2008), Spirit.s total odometry was 7,529.02 meters (4.68 miles).
sol 1723-1729, November 07 - November 13, 2008: On a Dusty Planet, Spirit Perseveres
Last Saturday, Nov. 8th, 2008, the Mars rover team received an alert that a large, regional dust storm was headed toward Spirit's location. In an effort to reduce the power load on the vehicle, engineers assembled a team to report to work and delete planned communications for sol 1726 (Nov. 10, 2008).
On Sunday, they received a report from Spirit for sol 1725 (Nov. 9, 2008) and learned that atmospheric opacity (tau) had spiked to 2.3 (as observed by the rover). They also learned that energy from the solar arrays had plummeted to 89 watt-hours -- a record low for either rover, including Spirit's twin, Opportunity. Spirit faced a very real possibility of tripping a low-power fault, which would protect the vehicle from draining the batteries by shedding electronic loads until the batteries could be re-charged through the solar arrays.
On Monday, the team prepared two plans -- a nominal and a contingency plan. The nominal plan was extremely conservative with regard to power, permitting Spirit only to be awake briefly to collect data essential to monitoring the health and safety of the vehicle. This plan disabled the heaters to the miniature thermal emission spectrometer, saving about 27 watt-hours each sol even though it meant risking damage to the instrument from cold temperatures. This plan included only a single, short, UHF communication session on the afternoon of sol 1729 -- Thursday, Nov. 13, 2008. The communication would only happen if the vehicle did not trip a low-power fault. The contingency plan, on the other hand, allowed engineers to listen for a signal at specific time intervals, known as communications windows, in the event of a low-power fault.
Because the team would not hear from the vehicle until Thursday in the nominal case, engineers continued to listen for Spirit during the established time set aside for fault communications. On Tuesday through early Thursday, they did not hear from Spirit. This meant that Spirit was either under normal, low-power sequence control or had experienced a low-power fault and did not have sufficient energy to support communications.
Shortly after 11 a.m. Thursday, Spirit sent a normal transmission via the vehicle's UHF antenna to the Odyssey orbiter, and Odyssey relayed the signal to Earth. No fault had occurred on the vehicle. Solar-array energy had increased to 161 watt-hours; atmospheric opacity had fallen to about 1.0 from a peak of 2.3 during the storm; and the dust factor was around 0.30, a performance reduction from 0.33 before the storm. This meant that 30 percent of sunlight reaching the solar panels was penetrating the coating of dust to generate electricity.
At this time, weather reports indicate that the storm should continue to clear, though Spirit may continue to see seasonal storms of this nature in coming weeks. Engineers will continue to monitor power and weather conditions closely. They will monitor the miniature thermal emission spectrometer and turn the heaters back on as soon as it is safe to do so. They will continue preparations for solar conjunction, when the Sun will block communications between Mars and Earth.
Prior to the dust storm, Spirit had been attempting to back up the slope toward the top of Home Plate to achieve a more favorable tilt of the solar panels. This effort will continue only if it is deemed safe to do so. Though Spirit remains in a serious power situation, all subsystems are performing as expected as of the latest downlink of information on Sol 1729 (Nov. 13, 2008).
After a very intense week on Mars, rover planners are elated that Spirit is healthy. They still have a lot of work ahead, but continue to be amazed by the incredible resiliency of this vehicle. Spirit's perseverance is a true testament to the talent and dedication of the team that designed, built, and continues to operate this magnificent rover.
Sol-by-sol summary
In addition to measuring dust-related changes in atmospheric opacity with the panoramic camera, Spirit completed the following activities:
Sol 1723 (Nov. 7, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. Spirit budged forward slightly and acquired a single-frame image with the navigation camera as well as images with the hazard-avoidance cameras to document the move.
Sol 1724: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. Spirit again budged forward and acquired images with the navigation and hazard-avoidane cameras.
Sol 1725: Spirit surveyed the horizon with the panoramic camera and monitored dust accumulation on the panoramic-camera mast assembly.
Sol 1726: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument.
Sol 1727: Spirit measured atmospheric opacity caused by dust with the panoramic camera.
Sol 1728: Spirit measured atmospheric opacity caused by dust with the panoramic camera.
Sol 1729 (Nov. 13, 2008): Spirit measured atmospheric opacity caused by dust with the panoramic camera and sent a much-awaited signal to Earth.
Odometry:
As of sol 1729 (Nov. 13, 2008), Spirit's total odometry was 7,529.02 meters (4.68 miles).
sol 1716-1722, October 30 - November 06, 2008: Still Trying to Drive Uphill
Spirit has been trying to drive back up the slope toward the top of "Home Plate" to achieve a more favorable tilt of the solar panels toward the Sun as it moves higher in the sky. Spirit at first made promising progress on sols 1709 (Oct. 23, 2008) and 1713 (Oct. 27, 2008). Subsequent drives have not been as successful. Spirit began veering to the rover's right, which resulted in the right front wheel getting close to slipping off the top of Home Plate and onto the slope. The right front wheel is the one that no longer drives, so if it moves onto the slope it could be difficult to get it back on top of Home Plate.
Fortunately, rover planners have a seemingly bottomless bag of tricks and they continue to try different strategies to make progress up the slope. If necessary, they can direct the rover to drive downslope and take an alternate route back up Home Plate. They can save time if Spirit can make it up the slope from the rover's present location.
Spirit is also preparing for solar conjunction. This is a period of approximately two weeks, beginning November 29, when the Sun will be between Earth and Mars, preventing communication. Preparations include making sure that Spirit's battery is charged and that Spirit has sufficient computer memory available to store data collected during conjunction until it can be sent to Earth.
Spirit is healthy, with all subsystems performing as expected as of the latest transmission from NASA's Odyssey orbiter on sol 1722 (Nov. 6, 2008). Energy from Spirit's solar arrays has been averaging 230 watt-hours (equivalent to the amount of energy needed to light a 100-watt bulb for about 2 hours and 20 minutes).
Sol-by-sol summary
In addition to measuring dust-related changes in atmospheric clarity each day with the panoramic camera, Spirit completed the following activities:
Sol 1716 (Oct. 30, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. Spirit resumed inching uphill. After the drive, Spirit took a single-frame image with the navigation camera as well as images with the hazard-avoidance cameras.
Sol 1717: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. The rover recharged the batteries.
Sol 1718: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. Spirit continued inching uphill and, after the drive, acquired images with the navigation and hazard-avoidance cameras.
Sol 1719: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. The rover made observations of the spectrometer's calibration target and recharged the batteries.
Sol 1720: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. The rover acquired four, time-lapse movie frames in search of clouds with the navigation camera and took spot images of the sky for calibration purposes with the panoramic cameras. Spirit completed a "quick fine attitude" adjustment to determine the rover's precise position relative to the Sun. Spirit acquired images with the rear and front hazard-avoidance cameras and used visual odometry to track the rover's actual position based on the surface imprints made by its wheels.
Sol 1721: Spirit continued trying to inch upslope. After stopping, Spirit acquired a single-frame image with the navigation camera as well as images with the hazard-avoidance cameras.
Sol 1722 (Nov. 6, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer, completed a mini-survey of the sky and ground with the instrument, and recharged the batteries.
Odometry:
As of sol 1721 (Nov. 4, 2008), Spirit's total odometry was 7,528.56 meters (4.68 miles).
sol 1709-1715, October 23-29, 2008: Spirit Begins Driving Uphill
With the Sun moving higher in the sky, Spirit's solar panels must move in the same direction to maximize their exposure to sunlight. To achieve optimal solar input, the panels still must tilt to the north, but not as steeply as before. To change the tilt, rover drivers have begun moving Spirit back upslope toward the top of "Home Plate." Their goal is to reduce the rover's northerly tilt from 30 degrees to 20 degrees.
The change in tilt is vital, as Spirit is seeing the lowest energy levels of the mission. On Martian day, or sol, 1713 (Oct. 27, 2008), solar-array energy dropped to 207 watt-hours (that's enough energy to light a 100-watt bulb for slightly longer than two hours). The drop in energy was partly due to an increase in atmospheric dust believed to be related to distant dust storm activity. The same day, dust-related loss of visibility, known as Tau, reached a high of 0.69 before dropping to 0.60 on sol 1715 (Oct. 29, 2008).
Because of the limited solar energy, the energy used for driving comes, in part, from the rover's batteries. As solar energy improves, Spirit will have to dip less into the batteries for driving. Fortunately, temperatures are warmer now than in the depths of winter. As a result, the dip in battery reserves is not nearly as great as it would have been if Spirit also required more battery power for heating.
So far, rover drivers are pleased with Spirit's progress. The rover completed three upslope drives to achieve a northerly tilt of 21.8 degrees. Rover operators hope that a couple more budges will give Spirit a northward tilt of 20 degrees.
Eventually, if Spirit can drive all the way back on top of Home Plate, the rover will save a significant amount of time while heading out on the next science campaign. If necessary, Spirit still has the option of driving downslope.
Spirit is healthy, with all subsystems performing as expected as of sol 1715 (Oct. 29, 2008).
Sol-by-sol summary
In addition to measuring dust-related changes in atmospheric clarity each day with the panoramic camera and relaying data to Earth each evening via NASA's Odyssey orbiter, Spirit completed the following activities:
Sol 1709 (Oct. 23, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and surveyed the sky and ground with the instrument. Spirit then began inching uphill, and after the drive, took a single-frame image to document progress with the navigation camera.
Sol 1710: Spirit surveyed the horizon with the panoramic camera, drove, and acquired images with the hazard-avoidance cameras as well as a quarter-frame image of the spacecraft deck with the panoramic camera.
Sol 1711: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument.
Sol 1712: Spirit monitored dust on the panoramic-camera mast assembly and recharged the batteries..
Sol 1713: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. Spirit drove a bit farther upslope.
Sol 1714: Spirit acquired a single-frame, post-drive image with the navigation camera as well as images with the hazard-avoidance cameras.
Sol 1715 (Oct. 29, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. The rover then calibrated the spectrometer and began inching upslope again. After the drive, Spirit took a single-frame image with the navigation camera as well as images with the hazard avoidance cameras.
Odometry
As of sol 1715 (Oct. 29, 2008), Spirit's total odometry remained at 7,528.42 meters (4.68 miles).
sol 1702-1708, October 16-22, 2008: Mars Rover Gets Ready to Move
At Spirit's winter outpost on Mars, the atmosphere has been like the sky on many a clear day in Los Angeles. Smog is not noticeable and details are visible in the surrounding hills, though not with sparkling clarity.
For Spirit, the degree of clarity is especially important because it affects the rover's solar power levels. Lately, the rover has been on a "data diet" of limited atmospheric observations, each one typically generating less than a megabit of data.
One exception during the past week was a 5-by-1 mosaic of images that Spirit acquired to provide a wide-angle view of the rover's winter surroundings. This big-picture view will serve as a guide for putting together the many individual frames of the full-color, "Bonestell panorama" so they fit like the pieces of a jigsaw puzzle.
Spirit's top priority has been the transfer of data from the rover's flash memory files to Earth. Even with reduced activity, the downlink has been slow. When Spirit resumes driving as planned on sol 1709 (Oct. 23, 2008), these downlinks will become even more challenging.
A week ago, dust-related atmospheric murkiness, known as Tau, increased to 0.45. Since then, atmospheric clarity, solar power levels, and dust accumulation have remained steady. Energy from the solar arrays is about 236 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). The dust factor is about 0.33, meaning that only about one-third of sunlight reaching the solar arrays actually penetrates the coating of dust to generate electricity.
On Martian day, or sol, 1700 (Oct. 14, 2008), Spirit checked and adjusted the rover's measurements of Tau. Changes in Tau and the dust factor account for changes in solar energy production. In this instance, the recalibration raised Tau by 0.1 (meaning atmospheric dust levels worsened) and lowered the dust factor by 1 percent (meaning solar penetration was better than engineers thought). At the same time, an actual increase in atmospheric dust caused Tau to go up 0.05, for a total increase of 0.15. The higher dust levels drove down energy production by 18 to 20 watt-hours, compared to dust levels a couple of weeks ago.
The recalibration of Tau measurements is essential because it helps scientists measure changing amounts of dust on the camera lenses. Like drivers watching the road ahead, they need to know if the view is murky because the window is dirty or the atmosphere is hazy. To figure this out on Mars, they tell Spirit to measure Tau near noon when the Sun is overhead and again near sunset when the Sun is low in the sky. They also duplicate the measurements using both the panoramic and navigation cameras.
In preparation for the first roll of the wheels since hunkering down for the winter, Spirit stowed the robotic arm beneath the spacecraft deck. Plans call for the rover to try to climb back up onto "Home Plate" next week. Spirit will drive just far enough to change the northward tilt of the solar panels from 30 degrees to about 20 degrees. The change in position will keep the solar panels pointed toward the Sun. Should the rover be unable to climb the slope, Spirit will drive downhill onto flatter ground.
Spirit remains healthy, with all subsystems performing as expected as of sol 1708 (Oct. 22, 2008).
Sol-by-sol summary
In addition to measuring dust-related changes in atmospheric clarity each day with the panoramic camera and relaying data to Earth each evening via NASA's Odyssey orbiter, Spirit completed the following activities:
Sol 1702 (Oct. 16, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument.
Sol 1703: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument.
Sol 1704: Spirit recharged the batteries.
Sol 1705: Spirit acquired a 5-by-1 mosaic of images to provide a wide-angle, big-picture view of the Bonestell panorama.
Sol 1706: Spirit recharged the batteries.
Sol 1707: Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. The rover calibrated the miniature thermal emission spectrometer. Spirit stowed the robotic arm and its science instruments in preparation for the rover's first post-winter drive.
Sol 1708 (Oct. 22, 2008): Spirit took spot images of the sky for calibration purposes.
Odometry
As of sol 1708 (Oct. 22, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1695-1701, October 09-15, 2008: Getting Ready to Make the Next Move
In recent weeks, increasing solar power has enabled Spirit to complete more science activities. Spirit has finished the 360-degree, full-color view of its winter surroundings, known as the "Bonestell panorama," and acquired extra frames at super resolution to enhance details in the imagery. The rover also has documented seasonal changes in the atmosphere by measuring argon gas with the alpha-particle X-ray spectrometer.
The tradeoff has been that by funneling most available power into science activities, Spirit has not had much power for sending data to Earth. That is about to change, because Spirit's on-board memory is nearly full. Instead of sending data only every fourth day, Spirit will begin relaying data every day to NASA's Odyssey orbiter for transmission to Earth.
Rover operators will use the data to plan Spirit's first, post-winter drive to adjust the rover's position to keep the solar panels facing the Sun. The move will put the rover in optimum position before solar conjunction, when Earth and Mars will be on opposite sides of the Sun and communication will not be possible. Solar conjunction will take place on Martian days, or sols, 1745-1760 (Nov. 29-Dec. 15, 2008).
Meanwhile, Spirit is healthy, with all subsystems performing as expected as of sol 1700 (Oct. 14, 2008). Solar-array energy has been 242 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). After weeks of remarkably clear skies, atmospheric opacity or tau, a measure of the decrease in sunlight caused by atmospheric dust, has risen slightly to 0.294. Atmospheric dust levels remain low, but are beginning to trend upward and affect solar power levels. This increase is expected, as it has occurred at this time of year in each of the previous three Martian years.
The dust factor -- the percentage of light penetrating dust on Spirit's solar arrays -- has remained steady. Only 32 percent of the sunlight reaching the arrays penetrates the dust to generate electricity.
Sol-by-sol summary
In addition to making daily measurements of the amount of atmospheric dust preventing sunlight from reaching the rover's solar arrays, Spirit completed the following activities:
Sol 1695 (Oct. 9, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer, surveyed the sky and ground with the instrument, did survey work with the panoramic camera, and surveyed a surface target dubbed "Jules Verne" with the miniature thermal emission spectrometer.
Sol 1696: Spirit surveyed the sky and ground with the miniature thermal emission spectrometer and made some finishing touches to the lower edge of the full-color, 360-degree view of the rover's winter surroundings by acquiring 3 panels of images known as "Bonestell lower tiers" 1, 2, and 3.
Sol 1697: Spirit used the miniature thermal emission spectrometer to survey the sky, the ground, and a target known as "Stapledon." Spirit parked the panoramic camera mast assembly with the panoramic camera pointed below the horizon to minimize dust accumulation.
Sol 1698: Spirit took spot images of the sky for calibration purposes with the panoramic camera and spent much of the day recharging the battery.
Sol 1699: Spirit surveyed the sky at different elevations as well as the ground with the miniature thermal emission spectrometer and used the panoramic camera to survey the horizon and take thumbnail images of the sky on the rover's right (starboard).
Sol 1700: Spirit surveyed the sky and ground with the miniature thermal emission spectrometer and took spot images of the sky with the panoramic camera. Spirit relayed information from Mars to NASA's Odyssey orbiter for transmission to Earth.
Sol 1701 (Oct. 15, 2008): Spirit surveyed the sky and ground with the miniature thermal emission spectrometer and monitored dust accumulation on the panoramic-camera mast assembly.
Odometry:
As of sol 1700 (Oct. 14, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1690-1694, October 03-08, 2008: Spirit's Memory Is Getting Full
Taking advantage of recent improvements in battery power, Spirit has been rushing to complete top science activities before making a "sun-chasing" adjustment in position in late October. As a result, Spirit's on-board memory has been filling up dramatically as the rover relays data to Earth only once every four Martian days, or sols. In addition, transmissions are challenging because of the rover's position relative to NASA's Odyssey orbiter.
Rover operators plan to increase the flow of information to Earth via Odyssey to about three sessions per week starting on sol 1700 (Oct. 14). Even so, Spirit may need to go on a bit of a science diet over the next few weeks to free up sufficient memory for solar conjunction. That's the period when the Sun is between the Earth and Mars and blocks communications.
Spirit completed work on the 360-degree view of its winter surroundings, known as the "Bonestell panorama." The finished product includes a few select frames taken at super resolution for more detailed study. Spirit also completed another measurement of argon gas in the Martian atmosphere using the alpha-particle X-ray spectrometer. The measurements help scientists characterize seasonal airflows between the Martian poles.
In the past, rover operators have relied on "beeps" from Spirit to know if the rover received and activated command sequences from Earth. The beeps were X-band transmissions sent to Earth over Spirit's low-gain antenna. As power levels sank in the depth of winter, engineers discontinued the beeps to save energy. Recently, they attempted to start sending beeps again, only to find that the signal strength from the low-gain antenna was not great enough for Earth to hear. They decided to send a few beeps from Spirit's dish-shaped, high-gain antenna. Those transmissions were excellent. Rover planners have used them to get a rough estimate of the time drift in the rover's clock during the past nine months or so. The "timing beeps" show that the spacecraft clock has drifted 40 to 50 seconds from "Earth" time.
Spirit is healthy, with all subsystems performing as expected as of sol 1694 (Oct. 8, 2008). Solar-array energy dropped slightly during the past week to 255 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Tau, a measure of the amount of sunlight blocked by atmospheric dust, increased from 0.134 to 0.209. Historically, dust levels have been elevated at this time of year. Rover operators are keeping close tabs on atmospheric dust because of its potential impact on the rover's low power state.
Sol-by-sol summary
In addition to standard daily activities, which include using the panoramic camera (sometimes more than once) to measure the amount of atmospheric dust preventing sunlight from reaching the solar arrays, checking for drift (changes with time) in the miniature thermal emission spectrometer, and surveying the sky and ground with the instrument, Spirit completed the following activities:
Sol 1690 (Oct. 4, 2008): Spirit acquired column 23, part 3, and column 25, part 3 of the Bonestell panorama, a full-color, 360-degree view of the rover's winter surroundings made with all 13 color filters of the panoramic camera. Before relaying data to Odyssey to be transmitted to Earth, Spirit acquired four movie frames in search of clouds with the navigation camera.
Sol 1691: Spirit acquired column 27, part 3; column 26, part 3; column 24, part 3; and column 22, part 3 of the Bonestell panorama. The rover supplemented the usual, panoramic-camera measurements of atmospheric dust with measurements from the navigation camera. Spirit used the navigation camera to acquire a four-frame movie in search of Martian clouds.
Sol 1692: Spirit acquired column 20, part 3 of the Bonestell panorama as well as half of a super-resolution frame nicknamed "A" and later nicknamed "Hercules Joyner," in honor of a member of the all-black Tuskegee Airmen who served in World War II. The rover acquired a four-frame movie in search of clouds with the navigation camera.
Sol 1693: Spirit surveyed the sky at high Sun with the panoramic camera and acquired half of a super-resolution frame dubbed "General BO Davis," in honor of another Tuskegee Airman. The rover surveyed a target known as "Gernsback" with the miniature thermal emission spectrometer.
Sol 1694 (Oct. 8, 2008): After sending data to Odyssey, Spirit measured atmospheric argon with the alpha-particle X-ray spectrometer.
Odometry:
As of sol 1694 (Oct. 8, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1685-1689, September 28 - October 03, 2008: Spirit and Earth Stick Together
Spirit is poised to begin making more "phone calls" to Earth and engineers are preparing to contact Spirit more frequently as a result of improving solar power input on Mars. Though Spirit's energy levels are still low, they are improving significantly as Martian winter gradually fades into spring. The rover will use some of the energy to let engineers and scientists know how things are going on Mars.
Spirit stays in touch by transmitting data at UHF frequencies to NASA's Odyssey orbiter. Odyssey sends it to Earth. On the other end of the line, engineers send new activity plans to Spirit using X-band transmissions from Earth that go directly to the rover's dish antenna. More frequent communication allows greater operational flexibility as the rover gradually returns to a normal planning schedule and prepares to drive again in mid- to late October.
Spirit's first post-winter drive will be short, just far enough to adjust the rover's position so its solar panels remain tilted toward the Sun as it moves higher in the sky. The goal is to have Spirit in the best possible position before solar conjunction -- the time of year when the Sun passes between Mars and Earth and temporarily prohibits communication.
Meanwhile, Spirit has been working hard to complete the full-color "Bonestell panorama" of the rover's winter surroundings. After a long hiatus caused by power limitations, Spirit resumed making measurements of argon gas in the Martian atmosphere.
Spirit is healthy, with all subsystems performing as expected as of sol 1686 (Sept. 30, 2008). Solar-array energy increased to 262 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Skies remained clear, with tau, a measure of the amount of sunlight blocked by atmospheric dust, at 0.134. Historically, dust levels at this time of year have been higher. Rover operators are keeping close tabs on atmospheric dust because of its potential impact on the rover's power state.
Sol-by-sol summary
Spirit completed the following activities:
Sol 1685 (Sept. 28, 2008): Spirit listened for communications from Earth with the rover's low-gain antenna, checked for drift -- changes with time -- in the miniature thermal emission spectrometer, surveyed the sky and ground with the instrument, and measured atmospheric opacity caused by dust (tau) with the panoramic camera. Spirit monitored dust accumulation on the panoramic-camera mast assembly and acquired column 22, part 2, and column 24, part 2 of the so-called "Bonestell panorama," a full-color, 360-degree view of the rover's winter surroundings, created with all 13 color filters of the panoramic camera.
Sol 1686: Spirit received new instructions from Earth at X-band frequencies sent to the rover's high-gain antenna and spent three hours measuring argon gas in the Martian atmosphere with the alpha-particle X-ray spectrometer. Spirit relayed data to NASA's Odyssey orbiter to be transmitted to Earth.
Sol 1687: Spirit measured dust-related changes in atmospheric darkness with the panoramic camera and acquired column 23, part 2 and column 25, part 2 of the Bonestell panorama.
Sol 1688: Spirit checked for drift in the miniature thermal emission spectrometer, surveyed the sky and ground with the instrument, and measured atmospheric opacity caused by dust with the panoramic camera. Spirit acquired column 27, part 2 and column 26, part 2 of the Bonestell panorama. The rover supplemented panoramic-camera measurements of atmospheric dust with measurements from the navigation camera and acquired a four-frame movie in search of clouds with the navigation camera.
Sol 1689 (Oct. 3, 2008): Plans called for Spirit to measure dust-related changes in atmospheric darkness with the panoramic camera and acquire column 19, part 3 and column 21, part 3 of the Bonestell panorama. The rover was to assess atmospheric dust levels with the navigation camera and produce a four-frame, time-lapse movie of potential clouds passing overhead.
Odometry:
As of sol 1686 (Sept. 30, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1678-1684, September 21-27, 2008: Spirit Upgrades Calling Plan
Thanks to clear skies and longer Martian days, Spirit can accept three "collect phone calls" a week from Earth instead of two. The rover "pays" for each phone call, which is filled with new activities, with solar energy. As winter fades and sunlight increases with the coming Martian spring, Spirit can stay awake a little longer and accomplish more each day. For example, Spirit is making significant progress toward completing the 360-degree view of the north-facing slope where the rover has spent the past winter.
Spirit continues to phone home less frequently, however, sending news only every fourth Martian day, or sol. That's because the link to NASA's Odyssey orbiter occurs late in the Martian afternoon, when the rover's solar arrays are not generating much energy. The transmission relies almost completely on battery power. Spirit can "bounce back" from the current schedule by replenishing the battery after the Sun rises the next day, but more frequent downlinks remain problematic.
On sol 1680 (Sept. 23, 2008), Spirit completed the interplanetary equivalent of synchronizing watches. The rover sent a five-minute "timing beep" to Earth at X-band frequencies from its high-gain antenna. Antennas on Earth listened for the beep, which couldn't be detected by humans (if humans could hear microwaves, the beep would sound like a five-minute tone). By comparing the expected end time of the beep with the measured end time, rover operators estimated "drift" in Spirit's on-board clock. Currently, Spirit's clock lags by about 45 seconds, well within operational tolerance.
Spirit is healthy, with all subsystems performing as expected as of the report from NASA's Odyssey orbiter on sol 1678 (Sept. 21, 2008). Solar-array energy has increased ever so slightly from 255 watt-hours to 256 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Skies remain clear, with tau, a measure of the amount of sunlight blocked by atmospheric dust, at 0.14. The dust factor remains steady, with 32.3 percent of incoming sunlight actually penetrating dust on the solar arrays to generate electricity.
Sol-by-sol summary
In addition to taking daily measurements of dust-related changes in atmospheric opacity (tau), Spirit completed the following activities:
Sol 1678 (Sept. 21, 2008): Spirit acquired column 24, part 1 and column 25, part 1 of the so-called "Bonestell panorama," a full-color, 360-degree view of the rover's winter surroundings, using all 13 color filters of the panoramic camera. The rover checked for drift -- changes with time -- in the miniature thermal emission spectrometer and surveyed the sky and ground with the instrument. Spirit relayed data to NASA's Odyssey orbiter to be transmitted to Earth.
Sol 1679: Spirit completed the runout portion of the master sequence of commands and recharged the batteries.
Sol 1680: Spirit sent a five-minute timing beep to Earth to synchronize its clock with Earth's clocks. The rover completed the runout portion of the master sequence of commands and recharged the batteries.
Sol 1681 (Sept. 24, 2008): Spirit switched from planning 2 days a week to planning 3 days a week. The new schedule calls for more "up time" to accommodate more frequent uplinks from Earth and more science activities. Spirit checked for drift in the miniature thermal emission spectrometer and surveyed the sky and ground with the instrument. The rover acquired column 26, part 1; column 27, part 1; and column 18, part 2 of the Bonestell panorama, using all 13 filters of the panoramic camera.
Sol 1682: Spirit checked for drift in the miniature thermal emission spectrometer and surveyed the sky and ground with the instrument. Spirit took spot images of the sky for calibration purposes with the panoramic camera and recharged the batteries.
Sol 1683: Plans called for Spirit to listen for signals from Earth with the rover's low-gain antenna, check for drift in the miniature thermal emission spectrometer, survey the sky and ground with the spectrometer, and calibrate the spectrometer. Spirit was also to acquire column 18, part 3; column 18, part 4; and column 20, part 2 of the Bonestell panorama. The rover was to take color images of the external calibration target with the panoramic camera.
Sol 1684 (Sept. 27, 2008): Plans called for Spirit to check for drift in the miniature thermal emission spectrometer, survey the sky and ground with the instrument, and acquire column 19, part 2, and column 21, part 2 of the Bonestell panorama.
Odometry:
As of sol 1682 (Sept. 25, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
Twitter:
New calling plan: Spirit hears from Earth 3 times a week instead of 2. With longer days, Spirit stays awake longer and takes more pictures!
Spirit doesn't call home as often as her parents would like, but communications are improving. Spirit now takes 3 calls a week from Earth to Mars!
sol 1669-1677, September 12-20, 2008: Warming Up on Mars
With Martian winter on the wane, Spirit is using significantly less energy to stay warm. During the winter solstice, Spirit needed 90 watt-hours to run the heater. Now, the rover uses between 30 and 40 watt-hours. The reduced demand for power, more than the slow increase in solar-array input, has freed up energy for other things. In particular, Spirit has added more images to the 360-degree view of its winter surroundings, known as the "Bonestell panorama." The top tier, one of three tiers needed for the final image mosaic, is almost complete.
Plans called for Spirit to use the miniature thermal emission spectrometer for the first time in several months. The last time the rover used the instrument was on Martian day, or sol, 1558 (May 21, 2008). On sol 1675 (Sept. 18, 2008), Spirit's schedule of activities included calibrating the spectometer and using it to observe the sky and ground. Normally, scientists use the observations to measure temperatures at different heights and create a temperature profile of the ground and atmosphere. In this case, the purpose of the measurements is to verify that the spectrometer is still working after a long, cold period of disuse. The measurements will also enable scientists to estimate the amount of dust on the optics. They may or may not provide a useful temperature profile.
Spirit is healthy and all subsystems are performing as expected as of the most recent report from NASA's Odyssey orbiter on sol 1674 (Sept. 17, 2008). Solar-array energy has inched upward to 255 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Skies are clearer than last week, with tau, a measure of the amount of sunlight blocked by atmospheric dust, dropping to 0.141.
Sol-by-sol summary
In addition to taking daily measurements of dust-related changes in atmospheric opacity (tau), Spirit completed the following activities:
Sol 1669 (Sept. 12, 2008): Spirit recharged the batteries.
Sol 1670: Spirit received new instructions directly from Earth sent at X-band frequencies to the rover's high-gain antenna. The rover relayed data to NASA's Odyssey orbiter to be transmitted to Earth.
Sol 1671: Spirit acquired column 20, part 1 and column 21, part 1 of the full-color Bonestell panorama, using all 13 color filters of the panoramic camera. The rover took spot images of the sky for calibration purposes with the panoramic camera.
Sol 1672: Spirit recharged the batteries.
Sol 1673: Spirit recharged the batteries.
Sol 1674: Spirit received new instructions from Earth via the rover's high-gain antenna. The rover relayed data to Odyssey to be sent to Earth.
Sol 1675: Plans called for Spirit to acquire column 22, part 1 and column 23, part 1 of the Bonestell panorama and then verify that the miniature thermal emission spectrometer was still functional. This involved warming up the actuator, calibrating the instrument, measuring ground temperature, and measuring atmospheric temperatures at different heights. Plans also called for Spirit to calibrate the panoramic camera by taking images in darkness while the instrument was warm.
Sol 1676: Plans called for Spirit to recharge the batteries.
Sol 1677 (Sept. 20, 2008): Plans called for Spirit to recharge the batteries.
Odometry:
As of sol 1674 (Sept. 17, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1663-1668, September 06-11, 2008: Light Duty for Now
Spirit continues to conserve solar power while performing light science activities during the Martian winter. During the past week, Spirit studied the atmosphere and acquired two frames of the full-color image mosaic known as the "Bonestell panorama."
Spirit is healthy and all subsystems are performing as expected as of the relay of information from NASA's Odyssey orbiter on sol 1666 (Sept. 9, 2008). Solar-array energy and tau -- a measure of atmospheric opacity caused by suspended dust -- are holding steady at 245 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour) and 0.20, respectively.
Sol-by-sol summary
In addition to taking daily measurements of dust-related changes in atmospheric opacity (tau), Spirit completed the following activities:
Sol 1663 (Sept. 6, 2008): Spirit recharged the batteries.
Sol 1664: Spirit acquired column 18 of the Bonestell panorama, using all 13 color filters of the panoramic camera.
Sol 1665: Spirit recharged the batteries.
Sol 1666: Spirit recharged the batteries.
Sol 1667: Spirit received new instructions from Earth via the rover's high-gain antenna and relayed data to the UHF antenna on NASA's Odyssey orbiter to be transmitted to Earth.
Sol 1668 (Sept. 11, 2008): Spirit monitored dust accumulation on the panoramic-camera mast assembly and acquired column 19 of the Bonestell panorama.
Odometry:
As of sol 1666 (Sept. 9, 2008), Spirit's total odometry was 7,528.0 meters (4.7 miles).
sol 1657-1662, August 31-September 05, 2008: Spirit Continues Work on Winter Panorama
Spirit continues to conserve power during the waning Martian winter while performing light science activities. As power permits, Spirit continues to acquire the individual frames of an image mosaic known as the "Bonestell panorama," which will portray a full-color view of the rover's winter outpost.
Spirit is healthy, with all subsystems performing as expected as of the most recent report from Mars sent by NASA's Odyssey orbiter on sol 1658 (Sept. 1, 2008). Solar-array energy had increased slightly from 235 to 245 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Tau -- a measure of atmospheric opacity caused by suspended dust -- dropped from 0.274 to 0.218, meaning the skies were slightly clearer.
Sol-by-sol summary
In addition to taking daily measurements of dust-related changes in atmospheric opacity (tau), Spirit completed the following activities:
Sol 1657 (Aug. 31, 2008): Spirit acquired column 13, part 1 of the so-called "Bonestell panorama" of the rover's winter surroundings, using all 13 color filters of the panoramic camera.
Sol 1658: Spirit relayed data from Mars to NASA's Odyssey orbiter to be transmitted to Earth.
Sol 1659: Spirit received new instructions from Earth via the rover's high-gain, X-band antenna.
Sol 1660: Spirit recharged the batteries.
Sol 1661: Spirit recharged the batteries.
Sol 1662 (Sept. 5, 2008): Spirit recharged the batteries.
Odometry:
As of sol 1658 (Sept. 1, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1651-1656, August 25-30, 2008: Spirit Still Biding Time -- and Checking the Clock
To adjust for changes, known as "drift," in synchronicity between Spirit's clock and Earth-based clocks, engineers instructed Spirit to send a "timing beep" to Earth on Martian day, or sol, 1652 (Aug. 26, 2008). For a specifically scheduled duration of time, Spirit radiated a signal to Earth over its low-gain antenna. Rover operators listened for the signal, in order to make sure Spirit's clock and Earth clocks were in agreement.
Spirit continues to ride out the Martian winter by doing minimal activities in an attempt to save power. Spirit conducts science observations every three to four Martian days, known as sols. Every four sols, the rover sends data to NASA's Odyssey orbiter for transmission to Earth. Otherwise, Spirit mostly rests and recharges the batteries. This pattern of activity is not likely to change until sunlight on the rover's solar panels consistently generates 250 watt-hours (enough energy to light a 100-watt bulb for 2.5 hours) or more. Engineers do not expect that to happen until approximately mid-October, barring wind-related, dust-cleaning events between now and then.
Spirit remains healthy, with all subsystems performing as expected as of the downlink of information from NASA's Odyssey orbiter on sol 1650 (Aug. 24, 2008). Solar-array energy as of the same sol was 232 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Tau -- a measure of atmospheric opacity caused by suspended dust -- was 0.274. Spirit is approaching a time of year when the rover has historically seen increased atmospheric dust levels. Given the rover's already low power state, engineers will be on the lookout for dust-related changes in solar power.
Sol-by-sol summary
During the past week, Spirit completed the following activities:
Sol 1651 (Aug. 25, 2008): Spirit measured dust-related changes in atmospheric clarity (tau) with the panoramic camera. Spirit acquired column 17, part 1 of the so-called "Bonestell panorama" of the rover's winter surroundings, using all 13 color filters of the panoramic camera.
Sol 1652: Spirit received new instructions from Earth via the rover's high-gain, X-band antenna and transmitted the requested "timing beep" to Earth.
Sol 1653: Spirit recharged the batteries.
Sol 1654: Spirit measured dust-related changes in atmospheric clarity with the panoramic camera and acquired column 15, part 1 of the full-color Bonestell panorama. Spirit relayed data to NASA's Odyssey orbiter for transmission to Earth.
Sol 1655: Spirit recharged the batteries.
Sol 1656 (Aug. 30, 2008): Plans called for Spirit to receive a new set of instructions from Earth via the rover's high-gain antenna.
Odometry:
As of sol 1654 (Aug. 28, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1643-1650, August 16-24, 2008: Spirit Still Biding Time
Spirit continues to ride out the Martian winter by doing minimal activities to conserve power. The rover completes very light science observations every three to four Martian days, known as sols, and relays data to NASA's Odyssey orbiter to be transmitted to Earth every four sols. Otherwise, Spirit mostly sleeps. This pattern is not likely to change until sunlight on the rover's solar array consistently generates 250 watt-hours or more (enough energy to light a 100-watt bulb for 2.5 hours). Barring dust-cleaning winds, that is not expected to happen before about mid-October.
Spirit remains healthy, with all subsystems performing as expected as of the Odyssey downlink to Earth on sol 1646 (Aug. 19, 2008). Solar-array energy has dropped back to 229 watt-hours after recently reaching the high 230's. This drop is the result of an increase in tau -- a measure of atmospheric opacity caused by suspended dust -- from 0.19 to 0.29. Spirit is approaching a time of year when the rover has historically seen increased atmospheric dust levels. Given the rover's low power state, engineers will be watching this trend very closely.
Sol-by-sol summary
During the past week, Spirit completed the following activities:
Sol 1643 (Aug. 16, 2008): Spirit monitored atmospheric darkness caused by dust with the panoramic camera. Spirit acquired column 15, part 2 of the so-called "Bonestell panorama," using all 13 filters of the panoramic camera.
Sol 1644: Spirit recharged the batteries.
Sol 1645: Spirit recharged the batteries.
Sol 1646: Engineers on Earth transmitted a new plan of activities at X-band frequencies directly to Spirit's high-gain antenna. Spirit relayed data to NASA's Odyssey orbiter for transmission to Earth.
Sol 1647: Spirit monitored atmospheric opacity with the navigation camera and acquired column 17, part 2 of the "Bonestell camera," using all 13 color filters of the panoramic camera.
Sol 1648: Spirit recharged the batteries.
Sol 1649: Plans called for Spirit to continue to rest and recharge the batteries.
Sol 1650 (Aug. 24, 2008): Spirit was to receive a new plan of activities transmitted at X-band frequencies directly to Spirit's high-gain antenna. The rover was scheduled to relay data to NASA's Odyssey orbiter for transmission to Earth.
Odometry:
As of sol 1642 (Aug. 15, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1635-1642, August 08-15, 2008: Spirit Standing By
Though Spirit is using less energy to run heaters as Martian winter slowly gives way to spring, dust on the rover's solar arrays continues to block sunlight. Presently about one-third -- 34 percent -- of sunlight reaching the arrays is penetrating the layer of dust to generate electricity. This is a primary reason why Spirit's third winter on the red planet has been more difficult than the first two.
Energy has been steady, averaging 235 watt-hours daily (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Tau, a measure of atmospheric dust, and the dust factor, a measure of the amount of dust on the solar arrays, have also been steady at 0.197 and 0.340, respectively. The Tau measurement indicates that 80 to 82 percent of direct sunlight makes it through the atmosphere and reaches the array (the rest is scattered or absorbed, though scattered light also contributes to Spirit's energy).
Currently, Spirit spends one of every four Martian days, or sols, taking science images. The slight energy increase isn't yet sufficient to allow more activity.
Spirit remains healthy and all subsystems are normal as of the latest downlink of information from the Odyssey orbiter on sol 1638 (Aug. 11, 2008).Sol-by-sol summary
In addition to measuring atmospheric dust with the panoramic camera, Spirit completed the following activities:
Sol 1635 (Aug. 8, 2008): Spirit implemented the runout portion of the master sequence of commands already on board the rover, then received new instructions from Earth via the rover's high-gain antenna. The rover recharged the batteries.
Sol 1636: Spirit implemented the runout portion of the master sequence of commands already on board the rover and recharged the batteries.
Sol 1637: Spirit woke up and listened for potential transmissions from Earth at X-band frequencies using the rover's broad-beam, low-gain antenna. Spirit acquired column 13, part 2 of the so-called "Bonestell panorama," using all 13 filters of the panoramic camera.
Sol 1638: Spirit woke up and listened for signals from Earth at X-band frequencies using the low-gain antenna. Spirit completed the runout portion of the master sequence of commands on board the rover and relayed data to NASA's Odyssey orbiter for transmission to Earth.
Sol 1639: Spirit woke up and listened for signals from Earth using the rover's low-gain antenna. Engineers on Earth transmitted a new plan of activities at X-band frequencies to the rover's high-gain antenna. Those plans called for Spirit to spend the day surveying the horizon and monitoring the dune field known as "El Dorado" with the panoramic camera.
Sol 1640: Plans called for Spirit to complete the runout portion of the master sequence of commands on board the rover. Spirit was to wake up and listen for signals from Earth using the low-gain antenna and recharge the batteries. To save energy, Spirit was not directed to measure atmospheric opacity, known as Tau.
Sol 1641: Plans called for Spirit to complete the runout portion of the master sequence of commands on board the rover. Spirit was to wake up and listen for signals from Earth using the low-gain antenna and recharge the batteries. Spirit was not scheduled to measure atmospheric opacity.
Sol 1642 (Aug. 15, 2008): Plans called for Spirit to wake up and listen for signals from Earth using the low-gain antenna. Later, the rover was to relay information to Odyssey about the past four sols of activity.
Odometry:
As of sol 1638 (Aug. 11, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1628-1634, August 01-07, 2008: Waiting Out the Winter
Spirit's battery levels are slowly edging upward, thanks to a slight decrease in atmospheric dust (Tau) and a gradual increase in sunlight as winter gives way to spring.
Early in the week, Spirit spent two Martian days carrying out contingency plans following a temporary delay in data transmission from Earth. Spirit implemented the so-called "runout" portion of an earlier master sequence on sols 1628 and 1629 (Aug. 1-2, 2008). Subsequent relays of new instructions from Earth on sols 1629 and 1632 (Aug. 2 and Aug. 5, 2008) went off without a hitch.
Spirit remains healthy, with all subsystems performing as expected as of sol 1630 (Aug. 3, 2008).
Sol-by-sol summary
In addition to using the panoramic camera to make daily measurements of dust-related changes in atmospheric clarity, Spirit completed the following activities:
Sol 1628 (Aug. 1, 2008): Spirit implemented the runout portion of the master sequence of commands already on board the rover.
Sol 1629: Upon awakening, Spirit continued to implement the runout portion of the master sequence sent earlier. Spirit then received new instructions directly from Earth via the rover's high-gain antenna.
Sol 1630: Spirit acquired column 13 of the "Bonestell panorama" using all 13 color filters of the panoramic camera. The rover relayed fresh data from Mars at UHF radio frequencies to NASA's Odyssey orbiter to be transmitted to Earth.
Sol 1631: Spirit recharged the batteries.
Sol 1632: Spirit received new instructions from Earth via the rover's high-gain antenna.
Sol 1633: Spirit acquired six freeze frames for a time-lapse movie in search of Martian clouds using the navigation camera. The rover took spot images of the sky for calibration purposes with the panoramic camera and monitored dust on the panoramic-camera mast assembly.
Sol 1634 (Aug. 7, 2008): Spirit transmitted fresh data to Odyssey to be relayed to Earth.
Odometry:
As of sol 1634 (Aug. 7, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1621-1627, July 25-31, 2008: With Batteries Charged, Spirit is Ready for More Science
Spirit has fully recovered from a recent rundown in battery power. Energy has improved to levels not seen since sol (Martian day) 1604 (July 7, 2008). The hit in battery energy was primarily the result of data transmissions taking place later in the day, when less solar energy was available.
During the past week, rover planners eliminated the late communications sessions. Spirit is not scheduled to have another one until sol 1636 (Aug. 9, 2008). To mitigate the impact that one will have on power, rover planners plan to shorten the duration of data transmission from 20 minutes to only 10 minutes. This will allow sufficient time to get new instructions on board the rover while minimizing battery drain.
A transmitter problem thwarted data transmission on sol 1625 (July 29, 2008). The uplink from Earth was to have loaded activity plans and maintenance instructions for sols 1626, 1627, 1628 and 1629 (July 30-Aug. 2, 2008). The sequences already on board Spirit were designed with built-in contingency plans to handle just such an event. As a result, while Spirit continues the "runout" portion of the earlier master sequence, rover operators will send a new set of commands for sols 1630, 1631 and 1632 (Aug. 3-5, 2008) on sol 1629 (Aug. 2, 2008).
Spirit remains healthy, with all subsystems performing as expected as of sol 1626.
Sol-by-sol summary
In addition to using the panoramic camera to make daily measurements of dust-related changes in visibility, Spirit completed the following activities:
Sol 1621 (July 25, 2008): Spirit recharged the batteries.
Sol 1622: Spirit received instructions from Earth via the rover's high-gain antenna and relayed data to NASA's Odyssey orbiter via the rover's UHF antenna.
Sol 1623: Spirit acquired images of sand formations with the rear hazard-avoidance and navigation cameras. The rover took six, time-lapse, movie frames in search of clouds with the navigation camera, as well as images of the sky (called "sky flats") for calibration purposes.
Sol 1624: Spirit recharged the batteries.
Sol 1625: Spirit took spot images of the sky for calibration purposes with the panoramic camera and acquired movie frames in search of clouds with the navigation camera.
Sol 1626: Spirit completed a horizon survey with the panoramic camera and relayed data to Odyssey for transmission to Earth.
Sol 1627 (July 31, 2008): Spirit recharged the batteries.
Odometry:
As of sol 1626 (July 30, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1615-1620, July 19-24, 2008: Time to Recharge the Batteries
Spirit is recovering from a recent rundown in battery power. Over the last two weeks, Spirit's battery levels have steadily dropped by about 18 percent. The decrease appears to be a result of transmitting data to Earth later in the day and staying awake longer to accommodate extra science activities.
When Spirit sends transmissions late in the day, there's not enough sunlight left to recharge the batteries. As a consequence, each late uplink has contributed to an energy deficit.
Barring sudden changes in Martian temperature or atmospheric dust levels, engineers expect it may take as long as two weeks to recharge the batteries enough to resume work on the Bonestell panorama and other science activities.
Spirit remains healthy and all subsystems are operating as expected as of Martian day, or sol, 1618 (July 22, 2008).
Sol-by-sol summary
In addition to daily, panoramic-camera measurements of atmospheric opacity caused by dust, Spirit completed the following activities:
Sol 1615 (July 19, 2008): Spirit received new instructions from Earth via the rover's high-gain antenna.
Sol 1616: Spirit monitored dust accumulation on the panoramic-camera mast assembly.
Sol 1617: Spirit recharged the batteries.
Sol 1618: Spirit received instructions from Earth over the rover's high-gain antenna and relayed data to Earth via NASA's Mars Odyssey orbiter.
Sol 1619: Spirit took spot images of the sky for calibration purposes with the panoramic camera and acquired movie frames in search of clouds with the navigation camera.
Sol 1620 (July 24, 2008): Spirit recharged the batteries.
Odometry:
As of sol 1618 (July 22, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1608-1614, July 11-18, 2008: A Juggling Act
Winter planning for Spirit requires human operators to perform a complex juggling act to maintain overall rover health. They must manage engineering activities, such as receiving science and engineering data from Mars and sending new operation plans from Earth, as well as try to fit in science observations when possible. But they must also give the rover sufficient downtime between these activities to recharge the batteries. In recent months, the team's juggling skills have continued to improve.
Meanwhile, Mars has been helping out with steady temperatures and low levels of atmospheric dust, providing stability when it comes to allocating energy for heating and predicting the amount of sunlight reaching the rover's solar panels to generate electricity. Solar energy has been steady between 225 watt-hours to 230 watt-hours, of which about 65 to 75 watt-hours is required for heating the batteries and the miniature thermal emission spectrometer.
The overall state of charge on the battery has dropped slightly as a result of the timing of engineering and science activities. To restore the state of charge, the rover team will be making adjustments in upcoming plans.
Spirit is healthy and all subsystems are performing as expected as of sol 1610 (July 13, 2008).
Sol-by-sol summary
During the past week, in addition to making daily measurements of atmospheric opacity caused by dust with the panoramic camera, Spirit completed the following activities:
Sol 1608 (July 11, 2008): Spirit received new instructions from Earth via the rover's high-gain antenna.
Sol 1609: Spirit acquired column 17, part 3 of the so-called "Bonestell panorama" using all 13 color filters of the panoramic camera. The rover acquired six, time-lapse, movie frames in search of clouds with the navigation camera.
Sol 1610: Spirit relayed science and engineering data to NASA's Odyssey orbiter for transmission to Earth.
Sol 1611: Spirit received instructions from Earth over the rover's high-gain antenna and sent a timing beep to Earth at X-band frequencies.
Sol 1612: Spirit acquired column 15, part 3 of the full-color Bonestell panorama.
Sol 1613: Spirit recharged the battery.
Sol 1614 (July 18, 2008): Spirit relayed science and engineering data to Odyssey for transmission to Earth.
Odometry:
As of sol 1610 (July 13, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1601-1607, July 04-10, 2008: Solar Energy Evens Out
A week after the winter solstice, NASA's Mars rover Spirit is experiencing stable solar energy levels of between 225 watt-hours and 230 watt-hours. (One hundred watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Spirit continues to perform light science activities every three to four Martian days, or sols. Science activities this week included acquiring additional frames of the so-called "Bonestell panorama" of Spirit's overwintering locale.
The rover continues to relay data to NASA's Odyssey orbiter every four sols. The reduced level of activity has allowed Spirit to maintain a healthy battery charge despite the low level of solar energy input.
Spirit is healthy and all subsystems were performing as expected as of the downlink of fresh data from Odyssey on Sol 1606 (July 9, 2008).
Sol-by-sol summary
During the past week, Spirit completed the following activities:
Sol 1601 (July 4, 2008): Spirit assessed atmospheric dust levels based on the darkness of the sky with the panoramic camera.
Sol 1602: Spirit assessed atmospheric dust, monitored the dune field known as "El Dorado," and took spot images of the sky for calibration purposes with the panoramic camera. The rover relayed data to Odyssey for transmission to Earth.
Sol 1603: Spirit recharged the battery and measured atmospheric dust opacity with the panoramic camera.
Sol 1604: Spirit received a new activity plan from Earth via the rover's high-gain antenna and assessed atmospheric dust levels with the panoramic camera.
Sol 1605: Spirit again gauged atmospheric dust levels and also surveyed the horizon with the panoramic camera. The rover acquired Column 16, Part 4 of the Bonestell panorama, using all 13 color filters of the panoramic camera.
Sol 1606: Spirit assessed atmospheric dust with the panoramic camera and sent fresh data to Odyssey for transmision to Earth.
Sol 1607 (July 10, 2008): Spirit recharged the battery and measured atmospheric dust with the panoramic camera.
Odometry:
As of sol 1606 (July 9, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1594-1600, June 27-July 03, 2008: Biding Time
Spirit continues to ride out the Martian winter by doing minimal activities to conserve power. The rover conducts very light science activities every three to four Martian days, or sols, and relays data to NASA's Odyssey orbiter for transmission to Earth every 4 sols. The rest of the time, Spirit mostly sleeps.
As it has been some time since Spirit's operators were able to synchronize the spacecraft clock to Earth time, they wished to determine how far the spacecraft clock had drifted (how much it had changed over time). Synchronization of the clock is a process that requires a power-intensive, two-way, X-band communications link. When the power situation allowed it, they decided to perform an X-band "beep" (a five-minute, low-gain communication session) to estimate the amount of drift. The transmission of plans to do so on sol 1594 (June 27, 2008) were not detected by the ground station. Engineers hoped to make another attempt on sol 1604 (July 7, 2008).
Spirit is healthy and all subsystems were performing as expected as of the Odyssey downlink on sol 1598 (July 1, 2008). Solar-array energy has been steady within the range of 225 watt-hours to 230 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour).
Sol-by-sol summary
During the past week, Spirit completed the following activities:
Sol 1594 (June 27, 2008): Plans called for Spirit to perform a five-minute "beep" at X-band frequencies after relaying data to Earth via the Odyssey orbiter.
Sol 1595: Spirit recharged the battery and measured atmospheric dust opacity, known as Tau, using the panoramic camera.
Sol 1596: Spirit recharged the battery and measured atmospheric dust opacity with the panoramic camera.
Sol 1597: Spirit recharged the battery and measured atmospheric dust opacity with the panoramic camera.
Sol 1598: Spirit received new instructions from Earth via the rover's high-gain, X-band antenna and relayed data to Odyssey at UHF frequencies for transmission of the latest Martian data to Earth. The rover measured atmospheric darkness caused by suspended dust particles with the panoramic camera.
Sol 1599: Spirit conducted light remote sensing.
Sol 1600 (July 3, 2008): Spirit recharged the battery and again measured atmospheric dust with the panoramic camera.
Odometry:
As of sol 1598 (July 1, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1587-1594, June 20-27, 2008: Here Comes the Sun
With this week's passage of the longest night and shortest day of the year, also known as the winter solstice, Spirit's solar power levels should slowly but steadily increase. The winter solstice occurred on Martian day, or sol, 1591 (June 24, 2008, Pacific time).
In fact, Spirit's solar array energy and battery state of charge have already improved in recent days to the point where rover operators have begun adding some planning features back into the rover's schedule. The first change, adopted as of sol 1592 (June 25, 2008), was to return to a planning schedule covering every 3 or 4 sols. The plans themselves remain quite spartan at this time. In particular, rover operators are still planning to have Spirit relay data to Earth only every 4 sols. To do this, the rover sends data to NASA's Odyssey spacecraft, in orbit above Mars. To save power, engineers are keeping the data relays short in duration. Spirit has begun measuring dust-related atmospheric darkness every sol instead of every other sol.
Because it has been some time since engineers have been able to synchronize the spacecraft clock to Earth time, they decided to determine how much the clock had "drifted" -- that is, changed with time. To do this usually requires a power-intensive, two-way, X-Band communication session. This time, to save energy, they decided to perform an X-band "beep," a five-minute communication session using the rover's low-gain antenna, on sol 1594 (June 27, 2008). Accuracy will not be as good, but they expect to get an estimate of drift that is accurate to within about a minute.
Spirit is healthy and all subsystems are performing as expected as of the Odyssey downlink on sol 1590 (June 23, 2008). Solar array energy has been steady at 230 watt-hours, enough energy to light a 100-watt bulb for 2.5 hours.
Sol-by-sol summary
During the past week, Spirit completed the following activities:
Sol 1587 (June 20, 2008): Spirit recharged the battery.
Sol 1588: Spirit recharged the battery and received new instructions direct from Earth via the rover's high-gain dish antenna. Spirit measured atmospheric dust opacity, known as Tau, with the panoramic camera.
Sol 1589: Spirit recharged the battery.
Sol 1590: Spirit recharged the battery, measured atmospheric opacity caused by dust with the panoramic camera, and relayed data to Odyssey for transmission to Earth.
Sol 1591: Spirit recharged the battery and received a backup relay of commands from Earth via the rover's high-gain antenna.
Sol 1592: Spirit recharged the battery and conducted light remote sensing.
Sol 1593: Spirit recharged the battery.
Sol 1594 (June 27, 2008): Plans called for Spirit to send data to Odyssey for relay to Earth and transmit a five-minute signal to Earth to allow spacecraft operators to estimate drift in the spacecraft clock.
Odometry
As of sol 1586 (June 19, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1580-1586, June 13-19, 2008: Battery Power on the Rise
Spirit's battery is recharging nicely now that rover planners have reduced the frequency of communications to and from the rover during the darkest days of Martian winter. Most measures of battery health are showing an increase of about 2 amp-hours in the battery state of charge (an amp-hour is equivalent to the amount of charge flowing for one hour from a current of 1 amp). The minimum state of charge has improved from 10.92 amp-hours to 12.97 amp-hours, the maximum from 16.77 amp-hours to 18.17 amp-hours, which is fairly close to the battery's full capacity of 19.5 amp-hours.
Because battery energy increased sufficiently, the team added 12 minutes of remote sensing science to Spirit's to-do list for Sol 1586 (June 19, 2008). Spirit was to monitor atmospheric dust with the panoramic camera as well as dust on the panoramic-camera mast assembly and acquire seven, time-lapse movie frames in search of clouds with the navigation camera. Engineers anticipate that the additional activities will have no significant effect on the battery's state of charge.
Skies remain remarkably clear. Solar array energy is up slightly, averaging 229 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Atmospheric darkness caused by dust (known as Tau) increased by an insignificant amount, going from an average of 0.193 the previous week to 0.205 this week. The dust factor, the fraction of sunlight hitting the arrays that penetrates the dust layer, also rose insignificantly, from 0.349 to 0.352.
Rover planners are generating new activity plans for Spirit only once a week to minimize uplink time and therefore the length of time the rover must stay awake. Spirit relays data to Earth only every fourth sol to minimize battery usage.
In addition to estimating the amount of scattering and absorption of sunlight by atmospheric dust, Spirit received one transmission of new instructions direct from Earth to the rover's high-gain antenna on Sol 1581 (June 14, 2008). Spirit sent two transmissions of data to Earth via Odyssey on sols 1582 and 1586 (June 15 and June 19, 2008). Data from the sol 1582 downlink showed that the backup uplink on sol 1584 (June 17, 2008) was not needed and the communications link was shortened to save energy.
Spirit remains healthy and all subsystems were performing as expected as of the downlink to Earth via NASA's Odyssey Mars orbiter on sol (Martian day) 1582 (June 15, 2008).
Sol-by-sol summary
During the past week, Spirit completed the following activities:
Sol 1580 (June 13, 2008): Spirit recharged the battery and measured atmospheric opacity caused by dust (Tau) using the panoramic camera.
Sol 1581: Spirit recharged the battery and received new instructions direct from Earth to the rover's high-gain dish antenna.
Sol 1582: Spirit soaked up the sunlight to recharge the battery, assessed atmospheric darkness caused by dust particles with the panoramic camera, and sent data to NASA's Odyssey orbiter for transmission to Earth.
Sol 1583: Spirit recharged the battery.
Sol 1584: Spirit recharged the battery, surveyed atmospheric dust with the panoramic camera, and received new commands from Earth over the rover's high-gain antenna.
Sol 1585: Spirit recharged the battery.
Sol 1586 (June 19, 2008): Plans called for Spirit to recharge the battery, conducted remote sensing, and send data to Odyssey for relay to Earth.
Odometry
As of sol 1578 (June 11, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1574-1579, June 06-12, 2008: New Tricks for an Old Rover
To conserve energy and protect one of the on-board spectrometers, spacecraft operators have established the first major change to planning for the Mars Exploration Rover mission since the end of the primary mission, which lasted for 90 days in early 2004.
Spirit's scientists have declared that their highest priority for the winter is preserving the miniature thermal emission spectrometer, an instrument that identifies minerals in rocks from a distance. To do this, the rover heats the instrument overnight and into the morning of every sol. These heaters have been running longer as winter temperatures have dropped and are now averaging about 55 watt-hours per sol.
Heating for Spirit's batteries has increased as well and is now averaging 29 watt-hours per sol. Together, the two heaters account for 84 watt-hours or about 37 percent of Spirit's total energy usage. Everything else, including on-board computers and memories, radios, cameras, sensors and actuators, gets by on about 140 watt-hours -- enough energy to run a microwave oven for a scant 7 minutes.
In response, rover operators have further reduced Spirit's activity levels. The rover now transmits data to Odyssey to be relayed to Earth only every fourth sol. Instead of spending 20 minutes each sol using the rover's high-gain antenna to listen for new instructions from Earth, Spirit spends five minutes listening for instructions using the low-gain antenna on all but two sols per week.
Rover operators create new activity plans once a week, on Fridays, that cover seven sols at a time. Because Spirit isn't engaged in activities that require rover operators to have new images or other data for planning, the rover does not have to relay data to Odyssey just before a planning day. Despite changes to multiple procedures and software tools, the transition has been remarkably smooth.
For the time being, Spirit is basically just hanging out, charging the batteries.
Recent Events
Initially, the uplink team deleted virtually all science activities except for tau measurements of atmospheric dust. They then limited transmission of rover data to NASA's Odyssey orbiter, which consumes about 30 watt-hours, to every other sol. Still, the batteries continued to use more energy than they could replenish.
Prior to this change, Spirit received new plans three times a week and listened for new instructions for 20 minutes every sol. The 20-minute, high-gain-antenna communication window was costing the rover a lot of unnecessary awake time. On the other hand, engineers on Earth needed Spirit to be awake for at least 15 minutes every sol. By changing some of the unneeded 20-minute communication windows to shorter, five-minute, low-gain-antenna communication windows, and by having the windows overlap with the required awake time, Spirit's operators have shortened the overall awake time from 39 minutes to 16 minutes and saved another 15 watt-hours per sol.
Engineers have also gotten more strategic about how they communicate with Spirit. They send a new activity plan to Spirit every week (after the Friday planning session). Because Odyssey downlinks happen only every fourth sol, they can't guarantee they'll have a communication from Odyssey showing whether an uplink actually made it to the rover. So they send the same activity plan a second time. If the first uplink is successful, software on the rover automatically changes the second, high-gain communication window to a five-minute, low-gain window, saving 15 watt-hours. When this occurs, the second uplink fails and flight software generates a bunch of warnings, known as event reports. The warnings tell engineers that the plan is on board. If the first uplink fails, the instructions to change the second uplink window don't take place.
Why do engineers do the planning on Fridays? A new schedule of communication opportunities, called a "strategic load," goes into effect every other Friday. Rover operators plan activities on Friday so they can include the strategic load in the uplink.
The new strategy is working. Battery states of charge are up about two amp-hours (an amp-hour is a measure of electrical current flowing for one hour) above the rather scary levels of two weeks ago and other indicators of battery health are similarly improving. Spirit now has some margin of protection against further increases in heating power or unpleasant changes in the Martian environment. One concern is the possibility that thin, water-ice clouds could form overhead during the Martian winter. Such clouds are nearly invisible without image enhancement but they're thick enough to noticeably lower solar array energy. Fortunately, there's been no evidence of water-ice clouds so far.
Turning the Corner
The Martian winter solstice will be on June 25, 2008 (sol 1591). During the winter solstice, the Sun is as low in the sky as it ever gets. From there, it will rise higher each sol until the summer solstice in May 2009. For Spirit, solar power levels are expected to increase in a few weeks. Unlike Earth, where the coldest temperatures arrive 4-6 weeks after the solstice, Martian temperatures will begin to rise again almost immediately -- but slowly, very, very slowly.
With little dust overhead, Spirit is seeing very little additional dust settling out on the rover's solar arrays. The dust factor, a measure of the proportion of sunlight penetrating the coating of dust on the solar arrays, has remained almost unchanged at 0.349 (meaning that 34.9 percent of the sunlight, direct and scattered, that reaches the arrays penetrates the dust layer to generate electricity).
Energy has been steady, averaging about 226 watt-hours each Martian day, or sol, and varying by only a couple of watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). This is due in large part to a clear and stable atmosphere.
Tau, a measure of dust in the atmosphere, has ranged from 0.178 to 0.207 and averaged 0.193. As a result, between 81 percent and 84 percent of the sunlight reaching Mars continues down through the atmosphere to Spirit's solar array. (The remaining 16 percent to 19 percent is either scattered or absorbed by dust particles in the atmosphere. The portion of sunlight that's scattered also contributes to Spirit's solar array energy.)
A Tau this low means the skies above Spirit are remarkably clear. Not only that, Tau has decreased by an average of about 0.01 per week over the last month. (Though scattering and absorption are different and not exactly comparable, a clear mountain day on Earth has a Tau of 0.1-0.2.)
Spirit is healthy and all subsystems are performing as expected as of the Odyssey downlink on Sol 1578 (June 11, 2008). The next planned Odyssey downlink will be on Sol 1582 (June 15, 2008).
What Do You Say When You Call Home?
One of the key ways engineers monitor Spirit is through "event records." These are messages generated by the flight software -- basically, the rover's operating system -- telling Earth how Spirit is doing and why. Most modern operating systems store such information in log files; Spirit transmits it over long distances.
Spirit's event records come in five "flavors." Activity event records note that some event has occurred. Command event records log the issuance and success or failure of commands. Warning event records indicate unexpected events. Fault event records indicate more serious problems the flight software must address, usually by disabling further use of some device or capability. Fatal event records indicate problems so severe they invoke the fault protection features of the operating system. At that point, the whole rover is "disabled" and goes into so-called "safe" mode by shutting down all activities while waiting for instructions from home.
Whether such warnings indicate a problem depends on the context. For example, every time a motor stalls (stops turning while still powered), Spirit's flight software generates a warning event record. Sometimes, the stall is intentional. For example, engineers calibrate the position of an actuator by slowly driving it into a mechanical "hardstop" at a known position. When the hardstop is reached, the motor stalls and issues a warning event record. If one of the motors stalls unexpectedly, that same event record could indicate a problem.
It's like easing into a parking space until your wheels hit the parking bumper. The resulting jolt says you are correctly parked. On the other hand, a similar jolt could mean a fender bender, depending on the context.
Spirit's operators are sending two copies of new command sequences and then sending it twice again on a backup uplink one or two sols later. Data relays are so sparse, they don't always know if the first attempt succeeded and want to minimize the risk of not getting a new sequence on board.
Typically, the first attempt is successful and the second is rejected. Flight software generates event records telling engineers that the rover received the files correctly and copied them into the primary and secondary file systems. The software then rejects the same files later because their names conflict with existing files of the same name.
Rover operators don't actually read all the event reports in text form. An identification number encodes the "flavor" of the event report and a time tag called SCLK for "spacecraft clock" translates the time into readable format. Ground software decodes these and a few other parameters and converts them into readable words.
Sol-by-sol summary
Spirit completed the following activities:
Sol 1574 (June 6, 2008): Spirit recharged the batteries, listened to instructions from Earth for five minutes using the low-gain antenna, measured atmospheric opacity caused by dust using the panoramic camera, and relayed data to the Odyssey orbiter as it passed overhead.
Sol 1575: Spirit recharged the batteries and listened to instructions from Earth for 20 minutes using the high-gain antenna.
Sol 1576: Spirit recharged the batteries, listened to instructions from Earth for five minutes using the low-gain antenna, and measured atmospheric opacity caused by dust using the panoramic camera.
Sol 1577: Spirit recharged the batteries and listened to instructions from Earth for five minutes using the low-gain antenna.
Sol 1578: Spirit recharged the batteries, listened to instructions from Earth for five minutes using the low-gain antenna, measured atmospheric opacity caused by dust using the panoramic camera, and relayed data to Odyssey during the overhead pass of the orbiter.
Sol 1579 (June 12, 2008): Spirit recharged the batteries and listened to instructions from Earth for five minutes using the low-gain antenna.
Odometry:
As of sol 1578 (June 11, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1567-1573, May 30-June 5, 2008: Not Quite Hibernation
To save energy, engineers on Earth are sending new instructions to Spirit once every seven Martian days, or sols, with an additional 10 sols of "runout" instructions in the event of an interruption in communications.
The reason for the reduced workload is that rover engineers are trying to avoid having the state of charge in Spirit's battery go below 8.0 amp-hours (an amp-hour is equivalent to the amount of charge flowing for one hour from a current of 1 amp). By doing so, they hope to avoid a low-power fault condition, during which the rover goes to sleep until it senses that it has enough energy to wake up and communicate with Earth.
Spirit has come close to tripping a low-power fault a couple of times recently, but for the most part, the minimum battery state of charge has hovered around 8.5 amp-hours. Should the battery state of charge drop below that level, engineers would have to consider another course of action, such as further reducing the load or turning off the heater to the miniature thermal emission spectrometer, one of Spirit's scientific instruments.
Rover operators selected Friday as the day for building weekly activity plans for Spirit, because it naturally fits within the two-week cycle of updates to communications "windows" -- opportunities to transmit to and receive data from the rover via NASA's Odyssey spacecraft in orbit above Mars.
Spirit received the first seven-sol plan without a glitch. Preliminary reports indicate power and battery levels remain somewhat steady, but the team will be monitoring those numbers closely.
To further reduce Spirit's workload, engineers could continue to curtail communications via Odyssey as well as direct-from-Earth transmissions to the rover's high-gain antenna. Another approach would be to build activity plans lasting 14 sols, using only one high-gain uplink every two weeks for sending new plans to Spirit (with backups to make sure the rover receives them). Because the high-gain uplinks occur during peak solar power levels on the rover, reducing their frequency would not save as much energy as using fewer Odyssey transmissions.
The other downside is that, while a 14-sol plan would reduce the load on Spirit's battery, it would also result in receiving data less often from the spacecraft. Rover planners could try to listen for direct-to-Earth transmissions indicating potential problems, such as low-power faults or spacecraft clock issues. Still, listening for an indication of trouble does not compare to getting fresh data on a regular basis, making longer planning cycles undesirable.
Spirit is healthy and all subsystems are performing within normal range. Current solar array energy has been around 223 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).
Sol-by-sol summary
During the past week, Spirit completed the following activities:
Sol 1567 (May 30, 2008): Spirit received new commands from Earth and recharged the batteries.
Sol 1568: Spirit measured atmospheric opacity caused by dust (Tau) with the panoramic camera, sent data to NASA's Odyssey orbiter to be relayed to Earth, and recharged the batteries.
Sol 1569: Spirit soaked up the sunlight to recharge the batteries.
Sol 1570 (June 2, 2008): Spirit measured atmospheric opacity caused by dust (Tau) with the panoramic camera, sent data to NASA's Odyssey orbiter to be relayed to Earth, and recharged the batteries.
Sol 1571: Spirit received new commands from Earth and recharged the batteries.
Sol 1572: Spirit measured atmospheric opacity caused by dust (Tau) with the panoramic camera and recharged the batteries.
Sol 1573 (June 5, 2008): Spirit recharged the batteries.
Odometry:
As of sol 1570 (June 2, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1559-1566, May 22-29, 2008: Energy Levels Reach Record Low
Energy production reached a record low for Spirit this past week. On Sol 1560 (May 23, 2008), solar array input was 220 watt-hours (enough energy to light a 100-watt bulb for two hours and 12 minutes). On sol 1563, Spirit expended the highest amount of energy yet on running heaters to maintain minimum temperatures for batteries (30.6 watt-hours) and the miniature thermal emission spectrometer (54.0 watt-hours). Activity levels on Spirit have been kept low this week to compensate for the reduced energy production.
As was the case last week, Spirit had insufficient energy to transmit data to Earth each day. As a result, the operations team selected which Martian days, or sols, would be used for data downlinks to Earth.
Uplinks of communications from Earth have also been curtailed. Spirit typically has a daily communications window when the rover wakes up and points its High-Gain Antenna toward Earth and listens for new commands. By passing up on some of these uplink opportunities, the rover is able to stay awake for shorter periods of time each sol. Rover operators still have the ability to send new commands if necessary.
Despite low energy levels, Spirit continues to be in good health. The rover continues to conduct atmospheric observations, especially measurements of atmospheric opacity. As explained in last week's report, these Tau measurements of the amount of dust in the atmosphere provide valuable data for science and operations planning because they affect the amount of solar energy that reaches the rover's solar panels.
All subsystems are performing as expected.
Sol-by-sol summary:
In addition to receiving direct-from-Earth instructions over the rover's high-gain antenna, Spirit completed the following activities:
Sol 1559 (May 22, 2008): Spirit received new commands from Earth, measured atmospheric opacity caused by dust (Tau) with the panoramic camera and sent data to NASA's Odyssey orbiter to be relayed to Earth.
Sol 1560: Spirit again measured atmospheric dust with the panoramic camera and recharged the batteries.
Sol 1561: Spirit received new commands from Earth. The rover measured atmospheric darkness caused by dust with the panoramic camera.
Sol 1562: Spirit recharged the batteries.
Sol 1563: Spirit measured atmospheric dust with the panoramic camera and transmitted data to Odyssey.
Sol 1564: Spirit received new commands from Earth.
Sol 1565: Spirit recharged the batteries.
Sol 1566 (May 29, 2008): Spirit measured atmospheric opacity caused by dust with the panoramic camera and sent data to Odyssey to be relayed to Earth.
Odometry:
As of sol 1566 (May 29, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1552-1558, May 15-21, 2008: Some Data Fly First Class, Others Fly Coach and Standby
Lately, Spirit has begun assigning seating priorities to data traveling to Earth. The highest-priority, critical data are like first-class passengers who get to board first, followed by other critical data, who fly coach. These data are guaranteed a seat because they must be returned to Earth to enable engineers to plan the next round of activities.
Non-critical data are like standby passengers. They get to board only if there's room after all the critical data have been seated.
The reason for the seating arrangement is that Spirit's energy levels are so low that the rover has to miss out on some opportunities to transmit data to NASA's Odyssey orbiter, which relays data from the rover to Earth. Odyssey usually passes overhead twice a day, once in the very early morning and again in the afternoon. Spirit hasn't had enough energy to stay awake for a very-early-morning pass in nearly a year, and now is missing some afternoon passes as well.
Uplinks to Odyssey use more energy than the solar arrays have been able to provide, even during peak output at noon. Because Odyssey overflights occur late in the afternoon, they require even more battery power. By deleting some of the Odyssey passes, Spirit saves energy, though doing so limits the amount and "freshness" of the data.
In addition, not all Odyssey passes are created equal. When Odyssey passes directly overhead, communication is excellent, enabling transmission of a large volume of data. When the orbiter is lower in the sky (nearer the horizon), communication can be harder and data volumes smaller.
Last week, a combination of deleted communication links and low data volumes created a problem. The rover wasn't transmitting Tau measurements of sunlight-blocking dust in the Martian atmosphere. Spirit can go a few days without updating Tau measurements, but the longer engineers on Earth go without an update, the greater their uncertainty about actual conditions on Mars. To improve the timeliness of the data, they assigned a much higher priority to new Tau measurements. Spirit used the new priority on Sol 1555 (May 18, 2008).
Overall, Spirit remains healthy and all subsystems are performing as expected.
Energy production was down slightly during the past week, dropping from the previous week's average of 231 watt-hours to an average of 229 watt-hours (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Instead of remaining constant, energy declined by a watt-hour or two each Martian day, or sol. By the end of the week, power levels were down to 226 watt-hours.
Spirit has been a bit more active, using a little more battery energy and lowering the battery voltage. The lower voltage explains the lower energy production, because environmental factors such as Tau and the dust factor have remained nearly constant.
Tau, a measurement of the loss of sunlight as it passes through the atmosphere, averaged 0.23 the previous week and 0.24 this past week. The 0.01 change represents random fluctuations and is not significant. In both cases, 79 percent of the sunlight hitting Mars' atmosphere reached Spirit's solar arrays.
Spirit measures Tau by taking pictures of the Sun and calculating its brightness. A bright Sun means a low Tau, a dimmer Sun means a higher Tau. The time of day when Tau is measured makes a difference. A noontime Tau measures sunlight through the minimum depth of atmosphere. A sunset Tau measures sunlight as it travels along a slanting path through a thicker swath of atmosphere. By combining the measurements, the rover cancels out losses of sunlight caused by dust on the camera lens.
Tau measures direct sunlight only. As on Earth, dust both blocks and scatters light, and the scattered light changes direction and makes the whole sky seem to "glow." On Earth, the glow is bluish and causes the sky to appear blue. On Mars, the glow is pinkish. Without scattered light, the sky would look pitch black. Scattered light provides some of the rover's solar energy.
Spirit's other measure of energy loss is the dust factor, or the percentage of sunlight reaching the solar arrays that penetrates the dust to make electricity. The average dust factor dropped from 36 percent to 35 percent during the past week, though this, too, was not statistically significant.
Besides foregoing some of the Odyssey uplinks, Spirit has begun eliminating occasional higher-frequency links, known as X-band windows, as well. A communications window is a specific time interval when either the X-band or UHF radio is to be used to send data. When no communications window is active, the system defaults to using the X-band receiver with the low-gain antenna. Because the X-band receiver is always on when the rover is awake, Spirit doesn't save energy simply by deleting a communcations window but is able to wake up later in the day, reducing overall energy use.
On Sols 1557 and 1558 (May 20-21, 2008), Spirit reset the on-board system of fiber-optic gyroscopes and solid-state accelerometers that help the rover keep track of where and how it moves. Known as the inertial measurement unit, the system measures changes in the rover's orientation (yaw, pitch, and roll) and changes in the rover's location. (Activity plans run from roughly noon of one sol to noon of the next sol.)
Because each measurement has a small error, the sum of the measurements can accumulate a significant error (called "drift"). Normally, engineers correct this error by finding the Sun and comparing its actual position to where it would be if the inertial measurement system measurements were exact. Staying up to do that correction (called a "quick fine attitude") takes more energy than Spirit can spare and isn't necessary. Because Spirit hasn't moved since the last time the rover completed a quick fine attitude, engineers are able to use the values measured at that time.
Sol-by-sol summary:
In addition to receiving direct-from-Earth instructions over the rover's high-gain antenna, Spirit completed the following activities:
Sol 1552 (May 15, 2008): Spirit checked for drift (changes with time) in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. The rover transmitted data to Odyssey during its afternoon pass.
Sol 1553: In the morning, Spirit acquired column 14, part 1 of the full-color "Bonestell panorama," using all 13 filters of the panoramic camera. Spirit measured atmospheric opacity caused by dust (Tau) with 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.
Sol 1554: In the morning, Spirit watched the sky for clouds with the navigation camera and acquired spot images of the sky for calibration purposes with the panoramic camera. Later, the rover measured atmospheric dust with the panoramic camera. Spirit checked for drift in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument.
Sol 1555: In the morning, Spirit surveyed the external calibration target with the miniature thermal emission spectrometer, acquired six movie frames in search of clouds with the navigation camera, measured atmospheric dust with the navigation camera, and watched for dust devils. Spirit completed its first critical-priority Tau measurement of atmospheric dust and relayed data to the Odyssey orbiter.
Sol 1556: Spirit conducted no morning science activities and did not receive X-band radio instructions direct from Earth. The rover spent the day recharging the batteries.
Sol 1557: Spirit measured atmospheric dust opacity with 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 transmitted data to Odyssey in the afternoon.
Sol 1558 (May 21, 2008): First thing in the morning, Spirit reset the inertial measurement unit and scanned the sky for clouds with the navigation camera. Later, the rover measured atmospheric dust opacity. Spirit checked for drift in the miniature thermal emission spectrometer and completed a mini-survey of the sky and ground with the instrument. Plans for the next morning called for Spirit to acquire column 16, part 1 of the full-color Bonestell panorama.
Odometry:
As of sol 1557 (May 20, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles).
sol 1546-1551, May 09-14, 2008: Rover Hindered by Moon over Madrid
Though Martian skies have been quite clear, the Moon recently prevented Spirit from having a clear view of Earth. Such events are rare, but during the past week, a lunar occultation prevented instructions from Earth from reaching the rover. In fact, they are so rare that the mission has never before had its communications blocked by a lunar occultation. There have been only two lunar occultations since the rover landed, but because they last only about 30 minutes, there is only a slight chance that they might interfere with a 20-minute uplink from Earth. If Spirit is on an energy-saving communications diet, as it is now, interference is even less likely. Spirit will not see another lunar occultatation at least through the end of 2009.
At first, mission planners thought that light rainfall at NASA's Deep Space Network station near Madrid, Spain, might have absorbed the microwaves used to transmit the instructions. But the rain in Spain wasn't enough to stop the uplink. They also wondered if something was amiss at the station or on board the rover but found nothing wrong. Then someone had a brilliant idea: Where was the Moon? Sure enough, the Moon was directly between Spain and Spirit during the failed uplink on sol 1547 (May 10, 2008).
Winter Wattage
Overall, Spirit remains healthy and all subsystems are performing as expected. Power values have remained remarkably steady and energy has averaged 231 watt-hours, varying by only a single watt-hour (100 watt-hours is the amount of energy needed to light a 100-watt bulb for one hour). Tau, a measure of atmospheric opacity, was 0.23 (resulting in 79 percent of direct sunlight passing through the atmosphere). The other 21 percent was either absorbed or scattered. (The scattered portion contributes to power levels but is not part of the tau measurement.)
The dust factor, too, has been steady at 0.36, meaning that only 36 percent of the sunlight that reaches the rover has been penetrating the dust to make electricity. It is this dust that has made life difficult for Spirit.
Mars passed its aphelion -- the farthest point from the Sun in its orbit -- on Sol 1549 (May 12, 2008) at 10:00 a.m. Local Solar Time, which happened to be 5:14 a.m. Pacific Daylight Time. In the southern hemisphere, where Spirit is located, Mars will be at its winter solstice -- the same day as the summer solstice in the red planet's northern hemisphere -- on Sol 1591 (June 24, 2008) at 22:13 LST (10:30 p.m. Pacific Daylight Time). The winter solstice is effectively the "peak" or mid-point of winter, when the Sun is lowest in the northern sky. Weather conditions for Spirit are expected to improve after that time.
Mars Time
Local Solar Time (LST) is like ordinary civil time on Earth. Sixty Mars seconds make a Mars minute, 60 Mars minutes make a Mars hour, and 24 Mars hours make a Mars day, or sol. Because a sol is as long as 24.66 Earth hours, Mars time intervals are 24.66/24 or 1.027 (2.7 percent) longer than corresponding time intervals on Earth. And, as on Earth, Martian time varies depending on location. Instead of universal time (UTC) or Pacific Daylight Time (PDT), Local Solar Time denotes the time at each rover's site. And just as different locations on Earth can be in different time zones, the rovers are in different time zones denoted "LSTA" or "LSTB."
Sequencing Blackout
Because Spirit is a robot, it needs to be told what to do and when to do it. The time-tagged series of commands for each sol's activities is known as a "sequence." Because it's hard to prepare more than three sequences in a single planning session, the rover's operators limit advance planning to no more than three sols at a time.
Shortly before planning Spirit's schedule of activities for sols 1547-1549 (May 10-12, 2008), engineers learned that their normal uplink session for sol 1550 (May 13, 2008) was needed by another mission. Because it was too late to adjust the sequencing plan and they couldn't create a four-sol plan, they decided to let sol 1550 be a "runout sol," during which the rover conducts very limited and standardized activities while awaiting a new set of instructions. If no new sequences arrive, the rover drops into "automode," waking up only for pre-programmed information exchanges, known as communication windows.
Spirit's operators expected the rover to attempt a standard "handover" from the old sequence for Sol 1549 (May 12, 008) to a new sequence for Sol 1550 (May 13, 2008) and then execute another runout for sol 1549 and attempt a handover to the sequence for sol 1551 (May 14, 2008), which by then would be on board the spacecraft.
Things don't always go as expected. The uplink of instructions on Sol 1547 (May 10, 2008) failed and the sequences for sols 1547-1549 did not get on board. Spirit began executing the runout on sol 1546 (May 9, 2008). Because this occurred on a weekend and the rover was safe, rover operators decided to wait until Monday to retransmit the sequences.
Again, things didn't go as expected. As a result of a lot of complexity, the sequences weren't transmitted on Sol 1549, either! All this time, Spirit continued to execute the sol 1546 runout, trying to hand over first to the Sol 1547 sequence, then the Sol 1548 sequence, and finally the Sol 1549 sequence. None were on board. Finally, after the third attempt, the Sol 1546 sequence ran out and Spirit dropped into automode on Sol 1549 at 11:51 LST.
Spirit remained in automode until the Sol 1551 sequence arrived along with a real-time activate command. The activate command started the Sol 1551 sequence and Spirit was resumed normal operations.
Interestingly, rover operators had planned to delete communications with the Odyssey orbiter to save energy. But Spirit didn't receive those instructions and went ahead and sent data to Earth on sols 1547 and 1549 (May 10 and May 12, 2008). Given the low level of activity during runout and automode, power levels were not adversely affected.
Robotic Arm Hibernation
To conserve power, Spirit's operators originally planned to stow the robotic arm in a winter hibernation position on Sol 1547. It turned out the arm would have been too cold to move without heating and team members had concerns about heating the robotic arm. Rover operators postponed the hibernation date to sol 1551 (May 14, 2008), when startup time would be later in the morning and temperatures would be warmer. They transmitted commands to move the arm. Confirmation wnould have to wait until sol 1552 (May 15, 2008).
The arm will remain in hibernation for several months. Members of the science team considered leaving the Mössbauer spectrometer in place on the soil until they realized they wouldn't have enough power to use it. They were also concerned about the possibility that a joint could fail. If that happened, they couldn't drive the following spring. They chose Spirit's winter hibernation position because it preserved the rover's ability to continue driving if the robotic arm "froze" in place, with the alpha-particle X-ray spectrometer in position to acquire atmospheric argon measurements. (Argon is a trace gas in the atmosphere. By measuring it, scientists can infer changes in barometric pressure).
With the arm in hibernation, Spirit will be ready for the worst of winter. The rover will still be active, acquring more frames of the "Bonestell panorama" as well as other images and measurements, but activity levels will decrease as the winter solstice approaches. Engineers think they may be able to support limited science activities every sol or two.
Sol-by-sol summary:
In addition to receiving direct-from-Earth instructions over the rover's high-gain antenna, Spirit completed the following activities:
Sol 1546 (May 9, 2008): Spirit measured atmospheric opacity caused by dust -- known as tau -- with the panoramic camera, checked for drift (changes with time) in the miniature thermal emission spectrometer, and completed a mini-survey of the sky and ground with the spectrometer. Spirit did not relay data to Odyssey.
Sol 1547: In the morning, Spirit acquired column 16, part 2 of the Bonestell panorama, using all 13 filters of the panoramic camera, and monitored dust accumulation on the panoramic-camera mast assembly. The attempted uplink of a new sequence of activities to the rover was unsuccessful, causing Spirit to execute runout activities. The rover relayed data to Odyssey.
Sol 1548: In the morning, Spirit spent 10 minutes measuring atmospheric opacity caused by dust with the panoramic camera and again conducted runout activities, which included sending data to Odyssey and spending 10 minutes the next morning assessing atmospheric dust with the panoramic camera. The rover did not, as planned, acquire thumbnail images of the sky or complete a horizon survey with the panoramic camera.
Sol 1549: Spirit conducted runout activities and dropped into automode.
Sol 1550: Spirit remained in automode. The rover's only activity was the transmission of data to Odyssey.
Sol 1551 (May 14, 2008): Spirit was to move the robotic arm to the winter hibernation position. The rover was not instructed to communicate with Odyssey.
Odometry:
As of sol 1551 (May 14, 2008), Spirit's total odometry remained at 7,528.0 meters (4.7 miles)
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).
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. Odyssey, 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).
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).
