On sol 199, Spirit completed a 6-hour early morning alpha particle X-ray spectrometer reading on Mastodon. After a midday nap to conserve energy, Spirit took pictures with the microscopic imager to create a mosaic of the rock abrasion tool hole. Spirit then placed the Moessbauer instrument in the hole and began a 20-hour overnight reading.

Sol 200, ending on July 26, was a busy day for Spirit. Spirit completed the overnight Moessbauer reading on the rock abrasion tool hole, took a midday nap, stowed the arm, bumped back to take pictures and readings of the hole with the panoramic camera and miniature thermal emission spectrometer, then drove about 52 feet (16 meters). Due to the nature of the terrain, the drive was done in 6-wheel mode to minimize errors (rather than the current standard 5-wheel mode to conserve the aging right front wheel). Engineers carefully targeted Spirit's drive to end in a location with favorable tilt to the north to point the solar panels toward the Sun, giving Spirit as much power as possible as the Sun hangs low in the sky during martian winter.

Spirit will continue to drive up the Columbia Hills and search for more rock outcroppings.

Daily Update - 7/27/04
Opportunity Pokes Around Pig
Opportunity Status for sol 174-176

On sol 174, Opportunity completed close-up examination of a rock target called "Arnold Ziffel" using the rover's microscopic imager, Moessbauer spectrometer and alpha particle X-ray spectrometer. All observations were successful.

Leaving Arnold Ziffel on sol 175, Opportunity backed up to capture an image the results of the close-up work, and then moved on down slope to a new target. This move will leave the rover about 13 meters (about 43 feet) down from the lip of the crater. The rover was put into deep-sleep, energy-saving status overnight from sol 175 to sol 176.

Sol 176, ending on July 23, was a driving day. Opportunity moved down the slope (and east) to a position to investigate a target called "Diamond Jenness." Everything executed as planned, leaving the rover in a great position to grind into the target with its rock abrasion tool.

The engineering team is looking into a concern about the driving surface. The downslope pavement requires close examination before the rover traverses, to ensure the sand covering the pavement is still capable of supporting Opportunity. Recent experience has shown up to 30 percent slip.

Daily Update - 7/26/04
Spirit Investigates "Wooly Patch"
Spirit Status for sol 194-197

On sol 194, Spirit took a large microscopic imager mosaic, consisting of 34 images at multiple positions, of a target called "Sabre" on an outcrop rock called "Wooly Patch." This was followed by a two-hour reading by the Moessbauer spectrometer and an overnight, seven-hour reading by the alpha particle X-ray spectrometer.

On sol 195, the rock abrasion tool dug a surprisingly deep hole in only two hours of grinding. The rock appears to be softer than what scientists and engineers have seen previously in Gusev Crater. The alpha particle X-ray spectrometer was placed in the rock abrasion tool hole at Sabre. However, due to uncertainties in how long the arm and grinding operations take, the sequence was terminated a few minutes too early and a planned overnight alpha particle X-ray spectrometer integration did not take place.

Spirit recovered the alpha particle X-ray spectrometer integration in the sol 196 plan. The sol began with a microscopic imager mosaic of the rock abrasion tool hole. The alpha particle X-ray spectrometer was put back in position in the hole, and reading lasting more than six hours was successfully performed, starting at about 4 a.m. Gusev time on sol 197.

The work on Sabre was completed with a very long, 21-hour Moessbauer integration, which was expected to be completed the morning of sol 198 (July 24). Before the integration was started on sol 197, a microscopic imager mosaic was taken of "Mammoth," the next rock abrasion tool target on Wooly Patch.

Daily Update - 7/26/04
Spirit Completes its 'Tune-up' and Begins Driving Backwards
Spirit Status for sol 184-189

On sols 184 and 185, Spirit cycled heaters and attempted to lubricate the right front wheel's drive motor. Spirit also performed very short test drives. Spirit's orientation on "Engineering Flats" had the rover in a slight southerly tilt, away from the Sun. This low Sun angle, coupled with the power required to energize the heaters, put quite a strain on the batteries. The state of charge of the batteries after the test was very low, so science observations were not performed during these two sols.

On sol 186, Spirit used its instrument deployment device, or robotic arm, to validate a new front hazard-avoidance camera model. This new model will improve the positioning accuracy of the tools on the arm. The arm attempted to place the Moessbauer spectrometer at nine different locations. Seven targets were hit, and two targets were missed. The engineering team planned to repeat this operation on the two missed positions on a later sol. Spirit also performed a test drive to characterize the results of the lubrication activity. The beginning orientation of the vehicle had the right front wheel facing the Sun, so the starting temperature was much warmer than the original baseline test drive. This temperature difference makes it hard to accurately compare the pre and post test-drive results. Analysis indicates there is approximately a 20 percent increase in wheel drive performance, but engineers cannot attribute this gain to the four-sol wheel heating operation alone. Spirit sat mostly motionless for the about the last 30 sols, and that allowed some lubrication to re-flow naturally. The bottom line is that the right-front wheel's performance has improved, but it is still drawing about twice as much current as any other wheel.

After the tune-up, Spirit was free to begin its drive away from Engineering Flats and head to higher ground and a better solar orientation. On sol 187, with its batteries very low, Spirit limped 8 meters (26 feet) to a location with a slightly better tilt toward the Sun and performed about 50 minutes of science observations.

On sol 188, Spirit continued to drive away from Engineering Flats. As a strategy for dealing with the right-front wheel, Spirit is now driving backwards and dragging its right front wheel when it is on relatively flat terrain. This strategy aims to extend the lifetime of the wheel's drive motor for use when it is needed most. Spirit performed its first backward test drive of 4 meters (13 feet) on this sol. Spirit also performed about an hour and a half of remote-sensing observations using the panoramic camera, navigation camera and miniature thermal emission spectrometer.

On sol 189, which ended on July 15, Spirit's battery state of charge increased due to a better tilt of the solar arrays toward the Sun. Spirit performed a precision 6-meter (20-foot), 6-wheel drive, then drove another 3 meters (10 feet) doing the wheel drag. Spirit also imaged an interesting rock outcrop. The outcrop was directly beneath the vehicle and extending northward.

Total odometry after sol 189 is 3,450 meters (2.14 miles). Vehicle heading is 184.8 degrees.

Daily Update - 7/26/04
Opportunity Lives High off the Hog
Opportunity Status for sol 170-173

Opportunity continued its exploration of "Endurance Crater" the past five sols, and is now roughly 11 meters (about 36 feet) into the crater. The only drive during this period was on sol 171, when the rover turned around, backed down across the slope, then turned towards a feature called "Razorback." Razorback is a vertical fracture in the local bedrock that may contain sediment deposits with clues about the water history in this area. The team's near-term plan is to follow Razorback farther down into the crater, at least another 7 meters (about 23 feet). Slopes at Opportunity's present location and immediately downward are in the 15- to 20-degree range, which is a comfortable range for driving.

Despite the gentler slopes, the slip is still difficult to predict, as evidenced by the sol 171 drive. In that series of maneuvers, the rover slipped roughly 20 centimeters (about 8 inches) more than expected. Opportunity ended up farther downslope than desired, with what appears to be a broken piece of Razorback within arm's reach. The decision was made to stay put and use the suite of science instruments on sols 173 and 174 to see if this rock, dubbed "Arnold Ziffel" (after a pig on the TV series, "Green Acres"), was different from the surrounding bedrock.

A minor concern about a temperature sensor on the rock abrasion tool that is functioning intermittently has been resolved. This sensor is used to determine the starting temperature of the tool's motors, which in turn is used to set motor control parameters. The rock abrasion tool team plans to use a nearby temperature sensor on the arm turret for the same purpose and is not expecting the loss of this temperature sensor to affect the rover's ability to use the tool.

Sol Highlights:
170 - Used panoramic camera to image Razorback and "Flatland" (a clean patch of bedrock nearby).
171 - Drive of 3.7 meters (about 12 feet). Total odometry is now 1,478 meters (just over nine-tenths of a mile). Used the miniature thermal emission spectrometer to analyze some nearby geologic features. Took a 360-degree navigation camera mosaic.
172 - Used the panoramic camera and miniature thermal emission spectrometer instruments to image the solar panels and the miniature thermal emission spectrometer instrument's calibration target as part of a continuing evaluation of dust accumulation. Turned on the rover inertial measurement unit during the afternoon Odyssey communication-relay pass as an experiment in support of our "teach your dog new tricks" campaign. If the inertial measurement unit does not adversely affect the communication, the team may be able to turn the rover during the communication relay sessions to increase the data return.
173 - Took a two-by-two microscopic imager mosaic of Arnold Ziffel, to be used on sol 174 (ending on July 21) for more accurate placement of the Moessbauer and alpha particle X-ray spectrometer instruments.

Daily Update - 7/26/04
Spirit is Driving Backwards on Five Wheels
Spirit Status for sol 190-193

On Sol 190, Spirit completed remote sensing and a 13-meter (43-foot) drive, which included driving on 5 wheels to minimize further degradation of the actuator on the sixth, aging, right front wheel. During the 5-wheel portion of drive, visual odometry was used to accurately estimate the rover position. The drive ended with a short 6-wheel drive to achieve the desired position. This approach worked well, and engineers will continue to do 5-wheel driving to preserve the right front wheel actuator life while still achieving the desired position.

On Sol 191, Spirit took pictures with the microscopic imager and used the Moessbauer spectrometer on soil, then successfully completed another 10-meter (33-foot), 5-wheel drive to the north. (As Spirit is driving backwards to 'drag' the right front wheel, the robotic arm is effectively now in the back of the rover.)

On Sol 192, Spirit turned east off of a planned northerly traverse route to investigate a potential rock outcropping. The 17-meter (56-foot) drive, which included two sections of 5-wheel driving, landed Spirit right on top of the outcrop. Unfortunately, the drive left the rover at a bad tilt angle for solar energy, decreasing the available energy.

On Sol 193, which ended on July 19, Spirit completed a series of microscopic images and a short Moessbauer reading on the outcrop. Spirit then moved into a better position to use the rock abrasion tool and to improve the tilt toward the Sun for solar energy.

In the upcoming sols, Spirit will use the rock abrasion tool and other science instruments to investigate Wooly-Patch. Then it will resume driving up the "Columbia Hills" to look for more outcrops.

Daily Update - 7/20/04
Opportunity Multi-Tasks on the Slopes of 'Endurance Crater'
Opportunity Status for sol 166-169

Sol 166:
Sol 166's tasks for Spirit included imaging of possible traverse paths inside "Endurance Crater," then the start of a long period of data collection by the Moessbauer spectrometer on a target called "Dahlia." All went as planned.

Sol 167:
Sol 167 saw completion of the Moessbauer spectrometer's long integration at Dahlia, acquisition of some microscopic imager pictures, and placement of the alpha particle X-ray spectrometer on the capture magnet, which is one of the two magnets on the front of the rover deck. In the early morning hours of sol 168, the alpha particle X-ray spectrometer collected data at this magnet. The composition of material sticking to the magnet is what interests scientists.

Sol 168:
On sol 168, the rover lifted the alpha particle X-ray spectrometer off the capture magnet and replaced it with the Moessbauer spectrometer for the start of a long integration with that instrument. These complementary measurements of the material on the capture magnet should provide insight into the composition and magnetic properties of the dust around the rover. Remote-sensing activities were also performed.

Sol 169:
On sol 169, the rover drove deeper into the crater. A judgment had been made that the terrain in front of the rover would be no more difficult to traverse than terrain the rover had already crossed. Further, the science team was very interested in some geologic features about 3 to 4 meters (about 10 to 13 feet) down the slope, next to and including a rock called "Knossos." The rover stowed its arm and trundled down the nearly 30-degree slope, arriving on a more-level area exactly where engineers intended. The rover is now below the steepest part of the inner slope in this part of the crater.

Up to this point, Opportunity had not been commanded to take any images during an ultra-high-frequency (UHF) relay session with orbiting spacecraft. Testing prior to launch suggested that there could be electromagnetic interference that would degrade the telemetry link, so operations had carefully kept those activities separate. However, time could be used more efficiently if the rover could simultaneously take images and communicate. As an experiment, the rover was commanded to take navigation camera and panoramic camera images while transmitting on sols 167 and 168, respectively. The quality of data sent during use of the navigation camera has been analyzed, and there seems to have been no ill effect. Data is still being analyzed from the transmission during use of the panoramic camera. The UHF relay session returned the expected amount of data. In both cases, no degradation of images was expected or seen. Based on this experiment, the engineering team will consider lifting the restriction against imaging during a UHF session.

Daily Update - 7/16/04
Spirit Gets Into Position for a Tune-Up
Spirit Status for sol 181-182

Sol 181:
On sol 181 the plan for Spirit was to deploy the instrument deployment device for microscopic imaging, then perform a two-hour Moessbauer integration. The rover was to conduct miniature thermal emission spectrometer and navigation camera observations of rover-disturbed soil. After this, the rover was to drive to a relatively flat area dubbed "Engineering Flats." This was to prepare for a multi-sol engineering activity to heat, and ideally re-lubricate, the right-front wheel actuator. After the drive, Spirit was to take a 360-degree navigation camera panorama, followed by miniature thermal emission spectrometer observations during the communications session with NASA’s Mars Odyssey orbiter. Unfortunately, as Spirit began to execute the sol 181 plan, the onboard software predicted an instrument deployment device collision. This prevented further arm functions and the drive.

Sol 182:
On Sol 182, rover planners quickly determined the cause of the instrument deployment device error and continued to plan for sol 182 as normal. The intent for sol 182 was to complete the activities originally intended for sol 181. The sol 182 plan executed nominally, placing Spirit squarely in the middle of Engineering Flats.

Daily Update - 7/15/04
Spirit Reaches 180 Sols!
Spirit Status for sol 179-180

On sol 179, Spirit woke up at a new location and spent the day performing remote sensing with the miniature thermal emission spectrometer, including an overnight observation.

Sol 180 marked a grand accomplishment for Spirit. The rover has survived two times the original planned mission duration of 90 sols. On this notable sol, the rover continued with remote sensing, performing miniature thermal emission spectrometer observations on disturbed soil and rover tracks. Spirit then looked at the targets "Cookie Cutter" and "Julienned" with the panoramic camera. Because of power and timing issues, Spirit was not able to complete intended microscopic imaging, Moessbauer spectrometer, and alpha particle X-ray spectrometer measurements at this site. These operations were moved into the sol 181 plan. Total odometry after sol 180 is 3414 meters (2.1 miles).

Daily Update - 7/15/04
Opportunity Reading Rocks Within its Reach
Opportunity Status for sol 159-163

Opportunity has not moved (intentionally or otherwise) since its stabilizing maneuver on sol 158. The rover has been using the instruments on its arm and mast to study the rocks at its current location, which is in the sixth layer encountered on the way into "Endurance Crater." Opportunity remains in excellent health. Deep sleep has been invoked every other night to save energy; the miniature thermal emission spectrometer continues to operate nominally despite temperatures as low as -53 degrees Celsius (-127 degrees Fahrenheit) on some nights.

Opportunity is due for a set of "corrective lenses" (new hazard-avoidance camera models) after the trial run of new camera models is complete on Opportunity's twin rover, Spirit. In the meantime, the rover team has been using microscopic imager mosaics to locate targets when the hazard-avoidance camera-based targeting is not sufficient.

The mechanical team is investigating an anomaly involving the door on the alpha particle X-ray spectrometer. The spectrometer has two contact switches; one that indicates its doors are open, another that indicates it is fully in contact with its target. For the purpose of opening the alpha particle X-ray spectrometer doors on sol 161, engineers placed the spectrometer on the compositional calibration target, a rock disc with a known composition that is located on the underbelly of Opportunity. It is used to calibrate the Moessbauer instrument periodically. The team expected both contact switches to trip on that move; only the in-contact switch tripped. The next sol, when the spectrometer was removed from its rock target, a front hazard-avoidance camera image indicated that the doors were fully open. A subsequent move to close the doors resulted in only partial closure. The team tried again to open, then close the doors and was successful, with the doors fully open, then fully closed during that maneuver. The door-open contact switch, however, once again did not trigger as expected during that maneuver. Since the team is still able to safely open and close the alpha particle X-ray spectrometer doors, full use of the instrument is not compromised.

Sol Summaries:

sol 159: The operations team planned this sol's activity a day in advance so that they could a enjoy a much-deserved holiday on July 4th, resulting in a relatively quiet sol on Mars for Spirit. The sol's activities included daily miniature thermal emission spectrometer and panoramic camera atmospheric observations. A calibration of the miniature thermal emission spectrometer vertical scan mirror actuator was also conducted. The vertical scan mirror actuator operates like a periscope, allowing the miniature thermal emission spectrometer to target things vertically from the ground to the sky.

sol 160: Opportunity forfeited deep sleep overnight from sol 159 to sol 160 to take advantage of an optimal communication window with Mars Odyssey. We used the microscopic imager to take a mosaic of the "Drammensfjorden" location on the rock "Millstone," which is in layer "F" of Endurance Crater. The microscopic images were taken to enable the accurate placement of the rock abrasion tool on sol 161. The Moessbauer spectrometer was then placed on the compositional calibration target (CCT). This was the first such use of the CCT and was done partially out of concern that the instrument's behavior might be affected by the rover's present tilt of roughly 25 degrees. The rover team put Opportunity into a deep sleep the night of sol 160.

sol 161: The rover awoke from deep sleep to make some early morning atmospheric observations, including another attempt to image clouds. Later that morning the Moessbauer instrument was stopped and removed from the CCT. The rock abrasion tool was then used on the target Drammensfjorden, creating a 6.3mm (a quarter of an inch)-deep hole during the two and one-half hour sequence. The day ended with more atmospheric observations and a placement of the alpha particle X-ray spectrometer on the abraded rock abrasion tool hole.

sol 162: Opportunity woke up in the wee hours of sol 162 for an Odyssey communication session and to start the alpha particle X-ray spectrometer observation. The alpha particle X-ray spectrometer collected data from the hole in Drammensfjorden until 10:30 a.m. local solar time. The data indicated that the alpha particle X-ray spectrometer doors were fully open, despite the failure of the door-open switch to trigger when the doors were opened on the CCT. The rover then took a series of microscopic images of the rock abrasion tool hole before starting a Moessbauer integration at the same location. The Moessbauer integrated until the team invoked deep sleep at 7p.m. local solar time, and was restarted after deep sleep at 7a.m. the next sol.

sol 163: Rover engineers stopped the Moessbauer then successfully opened and closed the alpha particle X-ray spectrometer doors for diagnostic purposes. The rover arm was then stowed and the rover began a two-sol panoramic camera science survey of areas upslope from our current position.

Daily Update - 7/9/04
Spirit Tries Out Visual Odometry
Spirit Status for sol 175-178

On sol 175, Spirit analyzed the new targets "Breadbox" and "Sourdough" with its panoramic camera and miniature thermal emission spectrometer. Spirit then got an up-close look at Breadbox with the microscopic imager, and deployed the Moessbauer spectrometer on Sourdough for an overnight integration. In the middle of the martian night, Spirit did a tool change to the alpha particle X-ray spectrometer and completed a five-hour integration before the sol 176 plan began.

Spirit spent sol 176 getting a battery re-charge and a front hazard avoidance camera calibration. The evening of sol 176, engineers commanded Spirit to wake up and enable the panoramic camera mast actuator heater so they could determine when the thermostat turns the heater on. The heater turned on when expected, which will allow Spirit to conduct a night-time miniature thermal emission spectrometer observation in a few sols.

On sol 177, Spirit successfully performed a series of observations on an interesting and shiny feature called "String of Pearls." The rover acquired two microscopic images of the target and an overnight integration with the Moessbauer spectrometer and alpha particle X-ray spectrometer. As Mars' southern winter approaches, Spirit's energy resources become increasingly limited. Overnight tool changes and their associated heating take a big toll on the limited energy budget, and require some preparation and recovery to keep up Spirit's battery charge.

Spirit began sol 178 by stowing the robotic arm and then backing up 1.5 meters (about 5 feet) from "Hank's Hollow" in order to properly place the miniature thermal emission spectrometer to get a good view of "Pot of Gold" and nearby rover tracks. Engineers also took this opportunity to use visual odometry for the first time on Spirit. This is a technique in which the rover takes successive images of its surroundings during a drive and then matches features in those images on-board to compute how far and in what direction it has moved. Both the drive and the test went well, and ground verification showed that the matching worked quite nicely with the features in this terrain. Visual odometry will be important if and when Spirit starts driving on five wheels, since the actual drives can and will be rather different than what is commanded. The rover can use the visual odometry estimates while driving to compensate for the slipping and yawing that engineers expect with five-wheel driving.

Daily Update - 7/7/04
Opportunity Tests its Mettle on Slopes of 'Endurance Crater'
Opportunity Status for sol 154-158

Sol 154 consisted of Opportunity completing activities on the target "Kettlestone," including a long Moessbauer integration, some microscopic images and placement of the arm for a little early morning alpha particle X-ray spectrometer integration to occur on the morning of Sol 155. The rover then went to sleep.

Sol 155 began with an early morning Mars Odyssey UHF relay of about 60 megabits of data, followed by a completion of the alpha particle X-ray spectrometer integration on Kettlestone. The rover then performed a calibration activity with the arm, consisiting of moving the arm into about 20 different poses and imaging each pose with the front hazard-avoidance cameras. From the stereo images and the reported position of the arm, the rover team will be able to update models and better target the instruments onto surface features in the future. Some miniature thermal emission spectrometer activity was conducted midday, and then the rover drove backwards about 1 meter (3.3 feet). The drive backwards served two purposes: first, it positioned the rover to image the most recent rock abrasion tool holes with the panoramic camera and miniature thermal emission spectrometer; secondly, it gave the team an opportunity to evaluate driving back up over the "curb" that was considered so difficult before traversing on sol 150. The drive back up over the curb went very well. Slip was estimated at around 11 percent, admirable for such a traverse.

On sol 156, due to an incorrect time conversion, the rover team failed to get the intended command load to the spacecraft at the right time. As a result, the spacecraft executed a backup set of minimal activities and returned about 80 megabits of data through Odyssey in the afternoon.

On sol 157 the rover acquired some images of the rock abrasion tool holes from previous sols. Then it drove down the hill to approach the next target. It drove beautifully and achieved its goal location. However, due to the large slopes (final rover tilt was 28.6 degrees), Opportunity ended the drive with the right rear wheel apparently slightly above the terrain (not touching anything). Even in this state the rover appears to be stable, but the team will likely take action on the next sol to get the suspension squared up (six wheels touching) before proceeding with preparations to grind with the rock abrasion tool again. On the night of sol 157 to 158 the rover gave up deep sleep in order to preserve an exceptional morning Odyssey pass.

The very early morning of sol 158, the rover woke up to chat with the Odyssey spacecraft and returned over 100 megabits of data! The rover then started the day's activities early with an attempt to image clouds around 8:30 in the morning. It then went back to sleep until about 10:30. After the morning uplink, it acquired some microscopic images of the new target area, then stowed its arm to allow a small mobility maneuver to get all six wheels squarely planted on the ground. This seemed to go as planned and reduced the total tilt of the vehicle to only 26.4 degrees, but did not appreciably change its position. This left the rover, as desired, in position to perform science investigations on the next targets of interest.

Daily Update - 7/2/04
Moving On From 'Pot-of-Gold'
Spirit Status for sol 171-174

On sol 171, Spirit continued its investigation in "Hank's Hollow" and the rock target "Pot-of-Gold." The rover successfully completed observations of the abraded area with the microscopic imager and alpha particle X-ray spectrometer.

On sol 172, Spirit looked at the sky with the miniature thermal emission spectrometer and panoramic camera. The rover also acquired some thermal inertia observations of nearby soil with the miniature thermal emission spectrometer. Spirit finished up its Pot-of-Gold observations with some microscopic images and a final long Moessbauer integration of the abraded surface.

On sol 173, Spirit performed atmospheric observations with the miniature thermal emission spectrometer and panoramic camera. The rover also took some panoramic camera context images for the sol 172 thermal inertia observations. The rover finished the day's work by stowing the instrument deployment device and doing a "bump-back" to the "Bread Box" target. One last panoramic camera shot of Pot-of-Gold ended up a bit overexposed and will need to be retaken.

On sol 174, Spirit began the day acquiring atmospheric observations with the mini thermal emission spectrometer and panoramic camera. The rover then imaged the drive direction with the panoramic camera. Last but not least, Spirit took a look at a disturbed area of soil called "Bright Tracks" with the panoramic camera to help scientists learn more about the very bright material found here.

During the next 15 or more sols, rover planners will perform a "3,000 meter tune-up" on Spirit before the rover embarks on a climb up the hills.

The tune-up will include a number of elements including:

A front hazard avoidance camera calibration where a series of robotic arm poses and hazard avoidance camera images will be used to refine the rover planners' ability to target objects using stereo hazard avoidance camera images. The team is currently experiencing a 2 to 3 centimeter (slightly less or slightly greater than an inch) error in predicted versus actual target locations in the vicinity of the instrument deployment device.

Spirit's first deep sleep. Deep sleep is a mode that leaves the rover completely un-powered overnight, saving the energy that would be spent powering rover electronics and survival heaters that are normally on even when the rover is napping. Spirit needs deep sleep to save energy in the coming sols. Since deep sleep is potentially harmful to the mini thermal emission spectrometer instrument because its survival heater is not powered, rover planners have identified two observations that must be completed before the first deep sleep is attempted. Opportunity has been using deep sleep for several weeks now.

A right front wheel lubrication. Spirit's right front wheel continues to draw roughly twice the current of the other wheels. Spirit will drive to "Engineering Flats," a relatively flat, hazard-free area where rover planners will execute a series of diagnostic drive tests and heating sequences over the course of four to five sols. The intent is that the heating will re-flow the lubricants in this actuator, correcting the problem. Engineering Flats is roughly 7 meters (nearly 23 feet) from Spirit's current location.

Engineering tests of visual odometry. Visual odometry uses navigation camera images taken during a drive to determine the rover's location. This rover feature has been improved and is ready for trial runs now. Rover planners would like to use it on a regular basis to get Spirit where they want it to go more quickly. Due to slippage, Spirit sometimes needs two or more sols to make a short approach when using the blind drive technique.

Daily Update - 7/1/04
Ravenous Rock Abrasion Tool
Opportunity Status for sol 150-153

On Sol 150, Opportunity completed Moessbauer spectrometer observations in the rock abrasion tool hole on the rock "Tennessee" (hole number 3). The rover then stowed its arm, drove 0.55 meters (1.8 feet) backwards, turned to 40 degrees and then drove 1 meter (3.3 feet) forward. That was a net forward motion of 0.45 meters (1.5 feet) down-crater. This drive enabled Opportunity to reach two targets in the fifth distinct layer (E) of "Endurance Crater." The night of sol 150 into morning of sol 151, Opportunity did not do a deep sleep.

It was time to get to work again drilling another rock abrasion tool hole on sol 151. Opportunity began the sol by performing panoramic camera images, then it unstowed its arm and used the microscopic imager to capture the next drilling target, "Grindstone." After using the microscopic imager, Opportunity spend two hours grinding and created another precise hole. Upon completing the grinding operation, Opportunity placed the Moessbauer in the hole and performed a long integration. Opportunity did a mini-deep sleep operation overnight from sol 151 into the morning of sol 152. The miniature thermal emission spectrometer reached a chilly -51 degrees Celsius overnight.

On sol 152, Opportunity completed the observations on the hole on Grindstone. When the rover woke up from deep sleep at 7:00a.m. local solar time, it turned on the Moessbauer spectrometer and integrated until mid-afternoon. When the Moessbauer integration was complete, the rover switched tools to place the alpha particle X-ray spectrometer in the hole.

On sol 153 Opportunity ended the alpha particle X-ray spectrometer integration, and set its sights on still another rock abrasion tool target. This time Opportunity stretched its arm out just a little farther down into the crater to a target called "Kettlestone." Grinding again for just over two hours, Opportunity successfully created the fifth hole on the slopes of Endurance Crater. The last two grind operations took place on a slope of -25.6 degrees. Just as on sol 151, after completing the drilling operation, Opportunity placed the Moessbauer spectrometer in the new hole and collected data late into the night. Shutting down late at night, Opportunity deep slept until 7:00a.m. local solar time on sol 154.

Total odometry after sol 153 was 1468.46 meters (0.91246 mile)