Opportunity Updates: 2004

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sol 313-319, December 21, 2004: Back on the Plains

Opportunity examined tracks on its way to see its heat shield.


After six fruitful months exploring the interior of "Endurance Crater," the Opportunity rover has successfully climbed out of the crater onto the surrounding flatland of Meridiani Planum. Once out, the rover examined some of its own tracks that it had laid down prior to entering the crater. It compared them side-by-side with fresh tracks in order to observe any weathering effects in the intervening 200 sols. Opportunity is now making its way toward an engineering examination of its heat shield, which is located about 200 meters (220 yards) from the edge of Endurance. Now that the vehicle is on the relatively flat plain rather than tilted toward the Sun on the north-facing inner slope of the crater, electrical output from its solar array has declined by about 15 percent. Opportunity remains in excellent health as it begins a new phase of exploration.

Sol Details:

Sol 312 and 313 were planned in a single planning cycle. Opportunity was still inside Endurance Crater. On sol 312 the plan began with backing up and using the panoramic camera and miniature thermal emission spectrometer to observe a rock target called "Wharenhui," which had been treated with the rock abrasion tool on earlier sols. Subsequent commands were to turn cross-slope, drive 7 meters (23 feet), turn upslope, and drive an additional 6 meters (20 feet) uphill. Opportunity performed the drive perfectly, ending up approximately 5 meters (16.4 feet) from the rim of Endurance Crater. Opportunity's tilt went from 25 degrees pre-drive to 19 degrees post-drive.

Sol 313 was a restricted sol because results from the sol 312 drive were not available for planning sol 313. That meant that no driving or robotic-arm activities were permitted. So Opportunity performed about two hours of observations using the panoramic camera and miniature thermal emission spectrometer and then went to sleep in the early afternoon. The rover woke up to support late-afternoon and early-morning communication relays by the orbiting Mars Odyssey.

Sols 314 through 316 were planned in another single planning cycle. The plan was to complete the egress from Endurance Crater on sol 315, so sol 314 was another remote sensing sol. This would be the last full sol inside Endurance. Opportunity spent about two and a half hours observing with the panoramic camera and miniature thermal emission spectrometer. It also performed a nighttime observation with the miniature thermal emission spectrometer just before midnight. To ensure that Opportunity had adequate power, the early-morning communication-relay session with Odyssey was canceled and Opportunity went into a modified deep sleep after completing the late-night observation.

Sol 315 was the big day for Opportunity. The rover was finally going to leave Endurance Crater after spending 181 sols there! Opportunity was instructed to drive 7 meters (23 feet) up and out of the crater. It was a textbook drive. Everything went as planned and Opportunity had finally, successfully completed a long and detailed series of observations inside Endurance. Opportunity ended up on the plains of Meridiani ready to begin the next chapter of its adventures.

Sol 316 was the third sol of a three-sol plan, and because Opportunity had driven on sol 315, sol 316 was restricted to remote-sensing observations. The rover performed about two hours of remote sensing and went to sleep. Out on the plains, Opportunity went from a northerly tilt that is very good for solar exposure, to a southerly tilt that is not so good for solar exposure. The tilt was expected to be as high as 10 degrees, but Opportunity's actual tilt was about 5 degrees. Daily output from the solar panels went from 840 watt-hours in the crater, to 730 watt-hours on the plains.

Since the team continues to be operating in restricted sol mode, sols 317 and 318 were planned together as a two-sol plan. For sol 317, the science team elected to drive toward wheel tracks that Opportunity had made before entering Endurance Crater. The rover backed up about 5 meters (16.4 feet), performed some mid-drive imaging, and then continued another 10 meters (33 feet) to put the old rover tracks into the work volume of the robotic arm. Sol 318 was another remote-sensing sol, during which Opportunity imaged its still-distant heat shield and conducted a miniature thermal emission spectrometer observation of the tracks.

After the drive, both old and new tracks were directly in front of the rover. On sol 319 Opportunity captured microscopic imager mosaics of both types of tracks, then drove about 40 meters (131 feet) closer to the heat shield, which will be examined carefully in future sols. Sol 319 ended on Dec. 17.

sol 306-315, December 14, 2004: Out of 'Endurance'

Opportunity has finished its work inside "Endurance Crater" and climbed out. Before leaving, the rover examined a transition point between dark and light rock layers about 20 meters (about 66 feet) from the rim of the crater. Communication with Mars Odyssey has been good, so the backlog of onboard data has improved. The rover spent six months inside the stadium-sized crater to study layered bedrock exposed there. The exit drive on sol 315 put Opportunity completely outside the crater for the first time since sol 134. Opportunity continues to be in excellent health.

Sol details:

Sol 306 was the second sol of inspecting a rock target called "Paikea" with tools on the robotic arm. On the previous sol, Opportunity had cleaned the surface of Paikea with its rock abrasion tool brush. During sol 306, the rover observed the target with the panoramic camera and the microscopic imager, then ground away a patch of the rock's surface for about two hours with the rock abrasion tool. After the grind, the rover examined the fresh hole in the rock with the panoramic camera, hazard-avoidance camera and microscopic imager. This was followed by placement of the alpha particle X-ray spectrometer on the abraded area for later data collection. The rover woke at about 4:45 a.m. (local solar time) for a morning communication-relay pass with Odyssey on sol 307. Then it turned on the alpha particle X-ray spectrometer and gathered data until mid-morning.

Sols 307 through 309 were planned together as a three-sol plan. Sol 307 was similar to sol 306, with imaging, rock grinding, and overnight X-ray spectrometer measurements, this time targeted on "Wharenhui." Also, between 1:30 p.m. and 2 p.m. local solar time, Opportunity used its miniature thermal emission spectrometer and panoramic camera to make observations coordinated with a Mars Global Surveyor overflight. In the late morning of sol 308, the rover placed its Mössbauer spectrometer on the freshly drilled hole in Wharenhui, and then collected data nearly continuously for the next two sols. In order to provide sufficient energy for this extended integration, overnight communication passes for the early mornings of sols 309 and 310 were sacrificed.

The grinding activity on sol 307 was not as productive as hoped, so plans for the next couple of sols were revised. Because the team had to wait for retransmission of some rock abrasion tool data on sol 310, the sol was spent using the microscopic imager, placing the alpha particle X-ray spectrometer, and performing about an hour of remote-sensing observations.

Sol 311 was spent re-grinding Wharenhui. The plan was to grind another 3 to 4 millimeters (0.1 to 0.2 inches) into the rock. The grind went as planned, microscopic images were taken and the alpha particle X-ray spectrometer was placed in the hole. That spectrometer's integration was not started until the sol 312 early-morning Odyssey pass at 4:20 a.m. Mars local time.

The plan for sol 312 was to complete the alpha particle X-ray spectrometer integration begun in the early morning, perform about 45 minutes of observations with the panoramic camera and navigation camera, then drive about 12 meters (39 feet) toward the crater rim.

Total odometry after sol 311 was 1,766.07 meters (1.1 miles).

sol 292-298, December 06, 2004: Edging Out of 'Endurance'

Opportunity has completed its super-high-resolution imaging and other remote sensing operations from the base of "Burns Cliff," collecting more than 985 megabits of telemetry. Due to the large number of observations, the data management team has been working hard to manage available memory. Opportunity has now begun its journey out of "Endurance Crater." While in the crater, Opportunity has experienced drive slippage of up to 100 percent and tilts as high as 31.05 degrees. The rover was pushed to its traverse limits, but continued to perform all that was asked of it. Opportunity remains in excellent health. Solar power is nearly as high now as it was at the beginning of the mission.

Sol details:

Having made its closest approach to Burns Cliff, Opportunity continued its remote science campaign on sol 292. In the morning and early afternoon, the rover captured a portion of a color panorama plus images of targets called "Cushion" and "Bartlett." During these observations, Opportunity applied some of its excess energy to engage in an hour-long direct-to-earth communications session, downlinking an extra 10 megabits or so. Waking up the next morning at 7:18 local solar time, the rover heated cameras and actuators in advance of looking for clouds.

Sols 293 through 295 were planned together as a three-sol plan, continuing the panorama. Other observations included navigation camera imaging to fill holes in prior image coverage, panoramic camera atmospheric imaging while the Sun was high in the sky, and miniature thermal emission spectrometer imaging of targets "Ebony," "Ivory," and Cushion. Another direct-to-earth communications session was scheduled for midday on sol 293. On sols 293 and 294, the rover finished the remote science campaign, completing the panorama.

On sol 295, for the first time in 10 sols, Opportunity was on the move, beginning a trek out of Endurance Crater. The planned traverse had two parts, with the second leg to be driven only if the rover was on track after the first leg. Opportunity drove 3.6 meters (about 12 feet), determined that it was sufficiently close to a designated waypoint, and then continued for another 3.6 meters (about 12 feet). At the completion of the drive, the rover updated information about its attitude and position.

Opportunity continued its westward journey on sol 296, performing an 11-meter (36-foot) drive on flat rocky terrain that provides good traction for the rover. The drive succeeded as planned, leaving the vehicle perfectly in the middle of its intended path. Opportunity then performed two hours of post-drive observations. At this point, there appeared to be a possible shortcut out of the crater, just about 13 meters (about 43 feet) in front of Opportunity. If traversable, this early egress chute could shorten the vehicle's exit route by more than 30 meters (about 98 feet) and many sols. In response to this possibility, the team planned further investigation of the chute area.

Sols 297 through 299 and sols 300 through 302 were planned as two consecutive three-sol plans due to the Thanksgiving holiday on Earth. Commands for sols 297, 298 and 299 were uplinked on Tuesday (Nov. 23) and commands for sols 300 through 302 were uplinked the next day. The planning team went above and beyond to deliver six sol plans in two Earth days.

The plan for sol 297 included a drive west for about 13 meters (43 feet) to a relativity flat area. This location would afford a good view of the possible egress chute and allow the robotic arm to be deployed so the Mössbauer spectrometer could be placed on the filter magnet and perform four sols of data collection. The drive stopped early because Opportunity slipped more than anticipated and missed an intermediate waypoint. The drive covered 8.6 meters (about 28 feet). However, imaging after the drive allowed a detailed analysis of the possible shortcut.

To make an early exit, Opportunity would have had to cross terrain sloping 28 degrees. The opening of the chute is 1.14 meters (about 4 feet) wide, and there appears to be tall rock outcropping very close to the opening. On the route to the originally planned exit path at "Keratepe," where Opportunity entered the crater six months ago, the average slope is only 22 degrees and there are no large obstacles to avoid. So the decision was made to skip the shortcut and continue toward Karatepe.

Total odometry after sol 297 is 1736.22 meters (1.08 miles).

sol 285-291, November 23, 2004: Finishing Up in 'Endurance'

Opportunity has now reached the furthest point east in its travels inside "Endurance Crater." Rover drivers have determined that there is no safe path beyond the current position. Therefore, Opportunity is now in the midst of an intensive remote-sensing campaign, capturing a panorama of Burns Cliff plus super-resolution images and miniature thermal emission spectrometer observations of selected targets. When this campaign concludes, the rover will back away and head for a way out of Endurance Crater. Opportunity remains healthy and in an extremely advantageous solar array attitude.

Sol details:

The plan for 285 was to drive 1.5 meters (about 5 feet) east on firm rocky terrain ahead of the rover. The drive went as planned, covering 1.55 meters (5.1 feet). After integrating the results of this drive with an earlier study of Burns Cliff traversability, the team decided not to proceed farther. Opportunity has reached the easternmost point of its drive inside Endurance Crater. The rover is at the western edge of Burns Cliff and from this vantage point, it will perform super-high resolution imaging and other science observations.

Sol 286 was a restricted sol because the team did not know results of the sol 285 drive in time for planning sol 286. Opportunity recorded more than three hours of observations, took a nap, and then used afternoon and overnight communication sessions with Mars Odyssey. Solar exposure is excellent inside the crater, so Opportunity's power and battery state of charge continue to increase. The rover has not used deep-sleep mode in more than a week, and probably won't for the foreseeable future.

Sols 287 and 288 were planned together. Opportunity began super-high resolution imaging activities on sol 287. Starting at 11:15 local solar time, the rover performed the following activities: an hour of panoramic camera imaging, an hour of miniature thermal emissions spectrometer imaging and another hour of panoramic camera imaging. Sol 288 was almost exactly the same three-hour activity, but with the images targeted differently.

The Deep Space Network experienced a station transmitter problem on Saturday and Opportunity did not receive all of its two-sol uplink as planned. The rover received all except the last part of the sol 287 bundle, but none of the sol 288 bundle or data management bundle. Due to quick reaction by the weekend uplink team, bundles were successfully uplinked on Sunday, in time for execution of the sol 288 plan. The total effect of the missed Saturday uplink was a loss of about 30 minutes of science on the morning of sol 288.

Sols 289, 290 and 291 were very similar. Each was a continuation of the remote sensing campaign, with an additional panoramic camera observation. Sol 289 activities included observations of dunes and dust with the panoramic camera and miniature thermal emissions spectrometer. Also the panoramic camera was used for super-resolution imaging of "Whatanga," a contact boundary between two layers of rocks. For sol 290, in addition to the panoramic camera observation, Opportunity made several long-dwell observations of Burns Cliff targets with its miniature thermal emission spectrometer. Cloud observations on the morning of sol 290 produced a dramatic image. Sol 291 included a super-resolution observation of a target called "Bartlett."

The remote sensing campaign is generating a large volume of data at a time when, due to the rover's orientation, there is limited bandwidth available for downlink. As a consequence, Opportunity is operating with limited memory headroom, though still within planning guidelines. In order to improve the situation, the team took advantage of the Deep Space Network's 70-meter antenna availability and Opportunity's good energy state to plan a one-hour, direct-to-earth session in the middle of the day on sol 291. This resulted in the downlink of an extra 15 megabits of data.

sol 265-271, November 08, 2004: Journey toward 'Burns Cliff' Continues

Opportunity's trek towards "Burns Cliff" continues. The journey has been much more difficult than anticipated. The rover has experienced drive slippage of up to 100 percent. The plan is to attempt a couple of sols of up-slope, switchback driving and then review options to get to Burns Cliff.

The rover team celebrated Opportunity's 300-percent mission success anniversary on sol 270. The rover is showing no signs of slowing down despite its advanced age. Spacecraft health is excellent, and solar power is plentiful.

Sol details:

On sol 265 Opportunity began its drive away from a boulder called 'Wopmay.' The rover performed 45 minutes of remote observations and then attempted a 21-meter (69-foot) drive away from Wopmay. The drive stopped after 3.5 meters (11.5 feet). Opportunity experienced a drive and mobility goal error due to high current draw in the steering motors.

Sols 266, 267, and 268 were planned as a single 3-sol weekend plan. Due to the rover's heading at the end of sol 265, the morning uplink session on sol 266 was occluded by the panoramic camera, raising concern that we might fail to get the 3-sol command load to the spacecraft. To avoid this problem, the team instead chose to implement a high-priority communication window at 11:30 local solar time and to uplink all sequences at that time, activating the sol 266 master sequence by real-time command. This plan worked as designed, and all sequences got onboard.

The original plan for sols 266 and 267 was to place the alpha particle X-ray spectrometer on the filter magnet for extended integrations. However, Opportunity's position against a buried rock (informally named "Son of Bane") and the churning up of sandy terrain meant that we could not rule out the possibility of an unseen rock in the robotic arm's work volume. As a consequence, the arm deployment was cancelled, and the activities for sols 266-267 were limited to remote-sensing observations.

On sol 268, Opportunity drove away from Son of Bane. The rover turned and drove forward a short distance to get out of the hole it had dug for itself. It drove about 4.5 meters (about 15 feet) cross slope, and then began an up-slope drive designed to cover 9 meters (29.5 feet). Only about 0.4 meter (1.3 feet) of this last leg was achieved before the rover again encountered 100 percent slip.

Due to the large slippage and unsuccessful drive on sol 269, the day was used to take detailed images of the rover's position and to allow the rover mobility team to plan drive strategies for subsequent sols. Opportunity performed more than two hours of remote observations. The rover began a routine of forfeiting deep sleep for as many sols as the battery state of charge would allow. Solar exposure has been favorable enough to reduce the need for deep sleep. In an effort to reduce the backlog of onboard science telemetry that has not been downlinked, Opportunity will support early morning Mars Odyssey communication sessions as long as the battery state of charge is not impaired.

Sol 270 was the first sol dedicated to a potpourri of mobility maneuvers to gain a better understanding of the terrain on which Opportunity is driving. The rover completed the drive with no errors and achieved a positive elevation change of more than a meter (3.3 feet). Driving at a 45-degree angle to the slope appears to be the most productive operation.

With enthusiasm running high, the uplink team employed strategies of the drive from sol 270 to plan sols 271's drive. Opportunity was to drive up-slope at an angle heading east, towards Burns Cliff, as part of a longer switchback drive operation. But as has often been the case recently, the drive was not successful. Opportunity moved 0.78 meters in a beeline (about 2.6 feet) but experienced 100 percent slippage for most of the drive and ended up approximately 0.35 meters (1.1 feet) lower. Sol 271 ended on Oct. 28, PDT.

The result of this drive calls into question Opportunity's ability to reach Burns Cliff with the current approach. The team is assessing other possibilities.

Total odometry after sol 271 is 1664.43 meters (1.03 miles).

sol 258-264, October 22, 2004: Wave Goodbye to 'Wopmay'

Opportunity's health is excellent. Solar exposure continues to be very good. Opportunity spent its first night inside "Endurance Crater" on sol 134. To date, the rover has spent 130 sols in the crater, grinding 21 targets with the rock abrasion tool, performing 62 integrations with the Mössbauer spectrometer and 33 with the alpha particle X-ray spectrometer, and taking 115 observations with the miniature thermal emission spectrometer. Opportunity finally completed observations on the rock "Wopmay," and is ready to begin its trek towards "Burns Cliff" on the way to exiting Endurance Crater.

Sol details:

On sol 258, Opportunity examined three targets ("Otter," "Jenny," and "Hiller") on Wopmay with its microscopic imager. Each of the observations was designed to produce a mosaic. They relied on touching the instrument's contact sensor to the uneven surface of Wopmay for each quadrant of each mosaic to ensure appropriate standoff distances for good focus.

Sols 259 through 261 were designed as a single three-sol weekend plan. During the morning of sol 259, arm operations continued with two more microscopic imager mosaics of the targets "Jet Ranger 2" and "Twin Otter." In the early afternoon, Opportunity placed its alpha particle X-ray spectrometer in a hover position approximately 1 centimeter (0.4 inches) above Otter. After a couple of naps and miniature thermal emission spectrometer observations, the rover went into deep sleep until the next morning.

The first part of a reading with the alpha particle X-ray spectrometer over Otter was performed for three hours in the morning of sol 260. During the same period, the rover made navigation camera, panoramic camera, and miniature thermal emission spectrometer cloud observations, then snapped images with the navigation and panoramic cameras in the drive direction. While performing an atmospheric observation with the panoramic camera, Opportunity collected extra images of the sky close to the Sun to allow observations of the dust accumulation on the camera's window.

In the early morning of sol 261, the reading with the alpha particle X-ray spectrometer resumed, continuing until about 11 a.m. local solar time and producing excellent spectra despite the standoff position of the sensor. Opportunity then collected Mössbauer data over Otter for another three hours. Several remote science observations were made over the course of the sol, including photometric measurements with the panoramic camera and targeted observations of Wopmay with the miniature thermal emission spectrometer and the panoramic camera observations.

On the morning of sol 262, Opportunity took a third photometric measurement and used the panoramic camera to study Wopmay, concluding the weekend plan. In the early afternoon, the rover made a final microscopic image of the target "Hercules" on Wopmay, then backed away as part of a plan to re-approach the back side of Wopmay for possible additional measurements. Navigation camera imagery of the back of Wopmay was collected in the afternoon, followed by extensive panoramic camera imaging the next morning. Unfortunately, due to slippage during the traverse, Opportunity didn't reach its desired vantage point, and the target was not in view.

For sol 263, a decision was made to delete the panoramic camera imagery without downlinking it, since on board memory was tight and we already have complete coverage of the part of Wopmay captured. The new plan was to continue the rover's drive toward the back of Wopmay, and repeat the imaging observations attempted in the sol 262 plan. But as Opportunity drove toward Wopmay, it encountered a hidden obstacle: a rock buried under the sand that resulted in 100 percent slip for a good part of the traverse. Once the rover was clear of the rock, it continued from a point much closer to Wopmay than anticipated. Rover planners estimated that, at the end of the traverse, Opportunity was within 30 centimeters (just under one foot) of Wopmay, uncomfortably close!

On sol 264, which ended on Oct 21, Opportunity backed away from Wopmay. The planned drive was 2.5 meters (8.2 feet) but the actual drive was 2.57 meters (8.4 feet). Opportunity is now in position to begin its drive toward Burns Cliff.

Total odometry after sol 264 is 1,638.57 meters (1.0181 mile).

sol 251-257, October 22, 2004: Welcome to 'Wopmay'

Opportunity continues to be in excellent health working inside of "Endurance Crater." The current cycle is to use the deep-sleep mode every second night and to support an early morning Odyssey communications pass on the non-deep-sleep nights. Opportunity is experiencing very good solar exposure, averaging more than 700 watt-hours per sol available from the solar arrays. Driving to a rock called "Wopmay" has proven to be more challenging than expected, with Opportunity experiencing drive slippage of more than 50 percent in a couple of instances.

Sol details:

For sol 251, the plan was to put Opportunity in final position at Wopmay, a convoluted and creviced rock of great interest to the science team. After remote-sensing observations in the morning, the rover drove toward Wopmay on its own, using its visual odometry software. Unfortunately, despite the rover planners' attempt to anticipate slippage during the traverse, the direction of the slippage differed from the prior sol, leaving the rover too close to Wopmay to permit deployment of its robotic arm. Opportunity conducted afternoon remote-sensing observations, then went into deep sleep.

Sols 252 through 254 were planned as a group, due to the rover team's switch to a five-day-a-week planning schedule. On the morning of sol 252, Opportunity performed remote sensing, including two photometry survey observations, a cloud-search movie and imaging of Wopmay with the panoramic camera using 13 filters. In the afternoon, the rover backed away from the target to reach a staging position for attempting to reach the most interesting part of Wopmay, the upper right lobe, on a drive after the rover team's weekend. Deep sleep was disabled, allowing Opportunity to support a Mars Odyssey pass in the early morning of sol 253.

Sols 253 and 254 were remote-sensing sols. On sol 253, the rover imaged its filter magnets and performed multiple observations with its miniature thermal emission spectrometer. Before the rover shut down for the night, it positioned the spectrometer for a middle-of-the-night observation. Opportunity woke up first at 10 p.m. local solar time to begin heating, then again at 11 p.m. for the actual observation, then slept until about 7 a.m. local solar time on sol 254. Upon waking, the rover began another day of remote science, including multiple observations of sky and ground with its miniature thermal emission spectrometer.

During planning for sol 255 it was decided that approaching Wopmay from directly uphill would be too risky due to concerns about vehicle stability, so the plan was revised to approach Wopmay very slowly from an angle and not to deploy the robotic arm with any pre-loading on the rock. This would minimize chances of the vehicle slipping or placing undue stress on the arm. So the plan for sol 255 was to back up the hill, away from Wopmay, and position Opportunity to begin the slow angular, downhill approach to Wopmay. The drive successfully covered 7.8 meters (about 26 feet), leaving Wopmay 3.4 meters (11 feet) away. Opportunity also performed about an hour of remote science observations before entering deep sleep for the night.

On sol 256 Opportunity continued its slow approach toward Wopmay. After receiving its morning uplink, Opportunity performed twenty minutes of panoramic camera observations, then crawled forward just over 2 meters (about 7 feet), taking three small steps and performing a turn in place. During these moves Opportunity experienced slippage as high as 54 percent. By the end of the drive, Wopmay was approximately 1.5 meters (about 5 feet) away. Opportunity performed another hour of post-drive remote science observations, took a nap, then used an afternoon communication session and early morning communications with Odyssey.

Sol 257, which ended on Oct. 14, was a final approach sol. During the morning Opportunity extended its arm to use its microscopic imager for an hour on soil targets just in front of Wopmay. The rover then stowed its arm and began the final approach toward Wopmay. The drive was commanded for rolling 30 centimeters (about 1 foot) with the expectation of approximately 50-percent slippage. The expected traverse was 45 centimeters (about 1.5 feet). The last few drives taxed the rover planners and they really came through! Opportunity is perfectly positioned to examine Wopmay with the rover's microscopic imager and alpha particle X-ray spectrometer.

Total odometry after sol 257 is 1,630.00 meters (1.0128 mile)!

sol 245-250, October 13, 2004: Working towards 'Wopmay'

Opportunity is in excellent health. The current pattern is to use the deep-sleep mode every second night, and to support an early morning Odyssey communications pass on the non-deep-sleep nights. Opportunity is experiencing good solar exposure, averaging more than 660 watt-hours per sol from the solar arrays. The rover is poised for final approach to "Wopmay," a fascinating creviced rock with a brain-like appearance.

Sol details:

Sol 245 was a restricted sol. Opportunity could perform only remote sensing. The rover took images in all directions with its navigation camera. It used its miniature thermal emission spectrometer for sky and ground observations. Then it went into deep sleep for the night of sol 245 into the morning of sol 246.

Sols 246 through 248 were planned in a single planning cycle as part of our 5-day-a-week schedule. The uplink team accomplished a Herculean task, successfully completing and uplinking three science-intensive sol plans despite some issues encountered during the day.

Opportunity began sol 246 by placing the Mössbauer spectrometer and starting a long reading with it on a target called "Void." While collecting the Mössbauer data, Opportunity also performed two hours of observations with its panoramic camera and its miniature thermal emission spectrometer. The Mössbauer integration was paused just before the afternoon communication session with Mars Odyssey. Deep sleep was disabled so that Opportunity could support an early morning communications session on sol 247 and restart the Mössbauer integration.

Sol 247 was day two of the long Mössbauer integration; the integration ran throughout the sol until early evening, at which time Opportunity again paused and entered deep sleep overnight. During the day, Opportunity also completed a series photometric observations with its panoramic camera.

On sol 248 Opportunity exited deep sleep and restarted the Mössbauer integration. During pre-uplink science activities in the early morning, the rover completed a sky observation pattern that planners call an itty-bitty cloud movie. In the martian afternoon, Opportunity ended the long Mössbauer integration and turned the tool turret on its arm to place the alpha particle X-ray spectrometer on Void. The X-ray instrument did not start taking data until early the next morning. Opportunity did not go into deep sleep overnight. Instead, it used an early morning Odyssey communications session and immediately afterwards started the alpha particle X-ray spectrometer integration.

Opportunity completed the alpha particle X-ray spectrometer integration on the morning of sol 249. The rover then performed a series of microscopic imaging activities, stowed the instrument deployment device and began driving toward its next target, Wopmay. The 19.98-meter (about 66-foot) drive went well, but with more slippage than expected. At the end of the drive, the nearest visible face of Wopmay was only 2 meters (about 7 feet) from the center of the rover; far enough not to have been a hazard during the drive, but closer than was predicted. Slip estimates indicate radial slippage as high as 64 percent. Opportunity used deep sleep overnight on sol 249.

On sol 250, which ended on Oct. 7, Opportunity performed the first part of a planned two-sol approach to Wopmay. This nearly 7-meter (23-foot) drive went well. The end of the drive incorporated conditional arcs to be executed only if the rover was in the appropriate position. The drive put the rover in very good position for the final approach on sol 251.

Total odometry after sol 250 puts Opportunity just over the one-mile mark: 1,611.99 meters (1.0016 mile)!

sol 238-241, September 30, 2004: Waking up from a Winter's Nap

After a well-deserved rest through solar conjunction, Opportunity is awake again and back to work. The conjunction was the period in mid-September when Mars was nearly behind the Sun from Earth's perspective, causing communications to be unreliable.

Sol details:

Sol 238
Opportunity completed instrument arm operations on a soil target called "Auk" by finishing a multi-sol Mössbauer spectrometer integration and collecting microscopic images of undisturbed soil. It then performing remote sensing observations on the next target, a rock called "Ellesmere." Once the morning activities were complete, Opportunity took a 90-minute nap then stowed the arm and drove backwards 0.34 meters (1.1 feet). The rover used an afternoon communications session on sol 238 and an early morning session on sol 239.

Sols 239 and 240
The planning session for sols 239 and 240 was extremely challenging for the uplink team. As the rover project transitions to five-day-a-week planning, the Opportunity team planned two sols of activities to be uplinked on sol 239. Adding to the complexity, the two sols' activities included difficult instrument arm placement activities. Rover planners rose to the occasion. The sol started with 45 minutes of microscopic imaging, then placement of the alpha particle X-ray spectrometer on a target area of Ellesmere called "No Coating." Opportunity performed a couple hours of remote sensing, used an afternoon communications session and then went into overnight deep sleep. On sol 240, Opportunity began taking a reading with the alpha particle X-ray spectrometer at 7:00 local solar time, then went back to sleep. After waking, it did an hour of remote sensing observations, completed the alpha particle X-ray spectrometer integration and collected more microscopic imager pictures. The rover then placed the alpha particle X-ray spectrometer on its next target, "Barbeau." Another hour of remote sensing completed the sol.

Sol 241
Opportunity finished its alpha particle X-ray spectrometer integration on Barbeau, collected more microscopic images, switched tools to the Mössbauer spectrometer and started that integration. The rover performed a mini deep sleep overnight. Sol 241 ended on Sept. 27.

Total odometry after sol 241 is 1,573.83 meters (0.98 miles - almost to the 1-mile mark).

sol 215-217, September 13, 2004: Spectrometers Sample Clean and Dirty Targets

On sol 215 Opportunity completed a reading with its Mössbauer spectrometer of a target called "Kirchner," where a wire brush on the rover's rock abrasion tool had scrubbed a circular patch on the surface of a rock called "Escher." The rover also made some remote-sensing observations then then set up for using its alpha particle X-ray spectrometer on Kirchner early the following morning. However, an image from the rover's hazard-avoidance camera revealed that the doors of the alpha particle X-ray spectrometer had not completely opened. The door is a tricky mechanism; incomplete openings and closings have occurred before, and the team continues to work on approaches to more reliably maneuver the door.

On sol 216 the rover successfully acquired early morning alpha particle X-ray spectrometer data on Kirchner. Despite the incomplete opening of the instrument's dust doors, the spectra look good. No repeat of the integration will be necessary. The rover also used the Mössbauer spectrometer to examine another brushed target, "EmilNolde," on Escher. This reading was planned to run into the evening then later, following a deep sleep, to resume in the early morning of sol 217. The Mössbauer placement went fine. The rover was commanded to close and reopen the alpha particle X-ray spectrometer doors and this went well. The doors are now properly open and ready for action on sol 217.

On sol 217, which ended on Sept. 3, Opportunity used its rock abrasion tool to brush a target called "Otto Dix," and used its microscopic imager to look at the brushed area. Then the rover was commanded to place the alpha particle X-ray spectrometer on EmilNolde, precisely on a "dirty" portion of that target (an area that was not very well cleared away by the brush action a few sols ago). The plan was to collect data with the alpha particle X-ray spectrometer in the evening, perform a move in the middle of the night to a cleanly brushed portion of EmilNolde and integrate again until morning. These two integrations will be used to discern the differences between the "clean" and "dirty" portions of the target. A 100-megabit afternoon downlink through Mars Odyssey on sol 217 showed that all activities went well through the placement of the alpha particle X-ray spectrometer on the "dirty" part of EmilNolde.

sol 211-214, September 09, 2004: RAT is Rearin' to Go!

Opportunity is healthy and continuing to explore a rock called "Escher" on the southwestern slope of "Endurance Crater."

Sol 211: Opportunity awoke from deep sleep at 7 a.m. local solar time. It re-enabled survival heaters on its miniature thermal emission spectrometer and re-started a Mössbauer spectrometer examination of a target called "Kirchner." The rover made observations with its panoramic camera and its miniature thermal emission spectrometer from about 11 a.m. to 2 p.m. local solar time, focusing on getting thermal inertia measurement of the dunes at different times of day. A planned tool change to the alpha particle X-ray spectrometer in the afternoon failed due to a sequencing error in retracting the Mössbauer spectrometer from the surface. A conditional sequencing check prevented the overnight alpha particle X-ray spectrometer integration from occurring as desired in such fault cases.

Sol 212: A calibration of the rock abrasion tool calibration was completed successfully. The tool is healthy and ready for action! An aggressive plan acquired 80 microscopic images of the rock Escher. As part of the team's efforts to increase operational flexibility, a test was conducted involving operating the miniature thermal emission spectrometer in parallel with arm operations. Unfortunately, this resulted in some corrupted data from the miniature thermal emission spectrometer due to vibrations as the rover arm moved. The rover used its Mössbauer spectrometer in the afternoon before going into deep sleep overnight.

Sol 213: Opportunity awoke from deep sleep and re-started the Mössbauer integration. The rover performed some remote sensing during the day and then changed tools to the alpha particle X-ray spectrometer for an overnight integration. Later it completed a midnight thermal inertia observation with the miniature thermal emission spectrometer, which required an hour of actuator preheating.

Sol 214: Opportunity completed the alpha particle X-ray spectrometer observation and successfully used the rock abrasion tool to brush clean two targets on Escher ("EmilNolde" and "Kirchner_RAT"). Then it made observations with its microscopic imager, hazard-avoidance camera and panoramic camera. The Mössbauer spectrometer was then positioned on Kirchner_RAT, where it analyzed the rock's mineral composition until the rover went into deep sleep overnight. Sol 214 ended on Aug. 31.

sol 209-210, August 31, 2004: 'Look Mom, no pebble!'

Sol 209 activities for Opportunity focused on recharging its batteries and downlinking data through both an afternoon communications link with NASA's Mars Odyssey orbiter and an overnight Odyssey pass (early morning sol 210). The rover also made some remote sensing observations. The sol 209 plan was constructed without benefit of the sol 208 downlink (due to the restricted nature of the planning at this point in the cycle of Mars days progressing relative to Earth days). For that reason, activities were limited to remote sensing, which did not depend upon knowledge of the exact position of the rover. All went fine, and about 165 megabits of data were returned through relay by Odyssey.

On sol 210, which ended on Aug. 27, the rover was commanded to image the rock abrasion tool in a variety of positions to get better knowledge of a pebble that appeared to be jammed between rotors in an earlier image. Then the rover used its microscopic imager to survey several spots on a rock called "Escher." In addition, it took panoramic camera images for assembling into a mosaic of the dune field at the bottom of "Endurance Crater." The diagnostic images of the rock abrasion tool brought good news with the revelation that there is no longer a pebble jammed between the grind bits! Apparently, sometime after the last previous images of the tool were acquired on sol 200, the pebble fell out, perhaps due to thermal cycling or vehicle motion. The team will proceed next with diagnostic actions to confirm that the abrasion tool is functioning normally again. Those activities are planned for sol 212.

sol 204-208, August 30, 2004: Trying Traverses

Sol 204 was planned as a rather circuitous 6-meter (about 20-foot) traverse to the vicinity of a target called "Shag" on one side of a rock called "Ellesmere." The route was necessary to avoid a significant rock hazard close to the rover's position. Unfortunately, due to the steep slopes and lack of traction when driving in this terrain, the rover experienced up to 50 percent slip during parts of its traverse. It ended up more than 50 centimeters (about 20 inches) downslope from the planned final position. This left the rover close to the edge of its safe terrain zone.

For sol 205, the team shifted its objective from Shag to another target, "Auk," on the other side of Ellesmere. Auk, though farther from the rover's current position, was of higher scientific priority, in safer terrain, and more accessible to the rover arm. To avoid the significant slip observed during turns in place, the traverse was planned as a tight-radius turn covering 1.6 meters (5.2 feet). Mindful of the uncertainties inherent in navigating in this terrain, planners designed the traverse to cover only a portion of the total distance to Auk. This proved to be prudent, since the rover again ended up slipping more than 50 percent during most of its drive, with little progress away from dangerous terrain. On the bright side, analysis of the drive indicated that the rover was getting better traction during its last moves.

On sol 206 the rover was commanded to perform a drive to turn away from its cross-slope orientation and move upslope toward Auk. The drive succeeded. After the slips of the sol 205 traverse, this traverse managed nearly all of the desired yaw response to get the rover pointed uphill and then found good traction to deliver the rover more than a meter (3.3 feet) farther upslope. Serendipitously, the rock directly in front of the rover at the end of the drive proved to be so interesting to the science team that efforts were redirected to study it. The rock was dubbed "Escher."

On sol 207 the team entered restricted planning. This happens when the timing of the rover's sol on Mars and our day in the California time zone get out of sync due to the nearly 40-minute difference in length of Earth days and Mars sols. The afternoon downlink arrives at JPL too late in the day to plan the next sol unless the team works through the night. Instead of staying up all night, the team plans with restrictions that forbid rover movement or arm activity on a sol immediately following a sol on which the rover has moved. This gives additional time for the data to become available so that planners can use up-to-date knowledge about the rover's position and orientation.

So, rather than any driving on sol 207, Opportunity conducted remote-sensing work, including atmospheric observations and panoramic camera imaging of several features.

For sol 208, which ended on Aug. 25, Opportunity drove again. It bumped forward to put Escher well within the arm's work volume. The sol also included panoramic camera imaging of Escher and of a trench created by Opportunity's prior wheel movements in the vicinity. Opportunity slept deeply on the night of sol 208 for the second night in a row. The purpose of successive deep sleeps was to align the deep-sleep nights with poorer overnight Mars Odyssey passes, leaving the rover ready to take advantage of higher-volume passes on alternate nights.

sol 200-203, August 23, 2004: Opportunity Team Decides Against Dunes

On sol 200 Opportunity was commanded to perform some remote sensing and some rock abrasion tool diagnostics in response to an activity that faulted out on sol 199. During these diagnostics on sol 200, the tool failed to respond as desired to a command to calibrate the grind motor. Analysis of this event suggests that there is a piece of debris (probably a rocky chunk of Mars) trapped between the grind bit and the brush bit. The rover team believes that it can be freed by turning the bits in reverse, but they are still evaluating the best approach to remedy the situation. There are several options available. The team decided to continue the investigation of this anomaly while pressing on with other objectives.

On sol 201 the rover was commanded to stow its arm and drive to a position about 12 meters (about 39 feet) clockwise around the crater. The intent is to head towards a dune tendril that reaches out of the bottom of the crater and may be accessible without having to drive into terrain that is too sandy for the rover to safely traverse. The drive went very well, and the rover ended up in the expected place.

On sol 202 the rover was commanded to proceed a little ways downslope. Team members were not able to command the drive the rover as far as they might have liked because they did not get all the data they hoped to get in the afternoon downlink pass on sol 201. The terrain around the rover is heavily coated with sand and dust, so each traverse requires careful evaluation to make sure there is enough rock material to drive on with confidence. From the images available, the team determined it could safely command only about a 1-meter (3.3-foot) drive. This drive proceeded as expected. At the end of the drive, panoramic camera images were acquired directly in front of the rover and out to the dune tendril. These images will be used to assess traversability to this sandy feature.

On sol 203 the team decided to scratch the approach to the dune tendril and, instead, headed the rover back towards "Axel Heiberg" and another target named "Ellesmere" for some soil observations. The terrain between the rover and the dune tendril did not present clear evidence of rocky plates to give the rover sufficient traction. Rather than spend more time in an attempt to scout further for an approach path, the decision was made to abandon the quest for the dune tendril. A drive of approximately 14 meters (46 feet) positioned the rover where it will be able to zero in on Ellesmere next. There was an apparent combination of slip or induced heading change, or both, due to the sandy terrain, which resulted in the rover ending up about 3 meters (about 10 feet) farther left than expected. This also caused Opportunity to unintentionally run over a patch of fine soil with some small dune-like ripples in it. The team will be assessing this traverse error, but it is par for the course when driving this far on such sandy, sloped terrain.

sol 196-199, August 18, 2004: Power Boost for Opportunity

Opportunity is healthy and continuing to investigate a rock outcrop dubbed "Axel Heiberg" on the southern slope of "Endurance Crater." The rover's solar energy input has risen above 610 watt-hours the last few sols, which is more than it has experienced since about sol 100. The additional power may be the result of less hazy skies.

On sol 196, Opportunity completed an overnight reading with the Mössbauer spectrometer on a hole into Axel Heiberg where the rock abrasion tool gnawed off the rock's outer surface on sol 193. Then the rover bumped back about half a meter (about 1.6 feet) to position itself for reaching an interesting vein feature. After the bump, Opportunity made observations of the abraded hole with its miniature thermal emission spectrometer and panoramic camera data to complete the remote sensing of that target.

Opportunity completed a microscopic imager mosaic of the vein feature called "Sermilik" on sol 197. The rover also acquired panoramic camera and miniature thermal emission spectrometer data of sand spots to identify future targets for the rover arm. Overnight deep sleep was used to conserve power.

On sol 198, Opportunity awoke from deep sleep and used heaters to warm the panoramic camera mast assembly in preparation for morning cloud, sky and ground imaging and miniature thermal emission spectrometer observations. It made a daytime Mössbauer inspection of a 3-centimeter (1.2-inch) chuck of vein material that was apparently broken off from the vein when the rover backed up. This was followed by a tool change to the alpha particle X-ray spectrometer before sleep. Opportunity awoke for an early morning Mars Odyssey communications pass and turned on the alpha particle X-ray spectrometer for a nearly 6-hour integration.

Opportunity's planned abrading of a target called "Jiffypop" failed on sol 199. The preparatory seek-scan process successfully found the rock surface, but a motor stall prevented any further activity by the rock abrasion tool. Planned microscopic imager pictures of the target area and remote sensing were acquired successfully.

The stall of the rock abrasion tool on sol 199 is under investigation. Sol 200 activities will focus on diagnostic imaging and motor actuations to confirm the health of the tool. Another issue being reviewed is the failure of the alpha particle X-ray spectrometer doors to close fully on sol 199. This has been seen several times before, and in this case the rover team did not have positive confirmation that doors were properly latched open. Plans for sol 200, ending Aug. 16, include door opening and closing on the alpha particle X-ray spectrometer.

sol 192-195, August 16, 2004: Abrading 'Axel Heiberg'

On sol 192, Opportunity drove down slope in "Endurance Crater" to reach a rock dubbed "Axel Heiberg." The rover arrived in position to approach a particular point for work in this area with its instrument deployment device (the rover arm). Favorable geometry for an overnight communications pass with Mars Odyssey motivated the team to keep the rover out of deep sleep mode and take advantage of the pass. About 115 megabits of data were returned in this overnight pass.

The rover started sol 193 with some cloud imaging at about 8:45 a.m., local solar time. This required some heating of the camera mast motors and bearings. The observations were acquired, though one of the heaters apparently did not heat as planned. Engineers believe a thermostat controlling that heater had already opened. This rendered the heating circuit inoperable so that even though the heater switch was commanded on and off correctly, the heater itself never got powered. This probably resulted in use of the mast actuator at lower-than-intended temperatures. Rover team members are investigating this, and in the meantime they will not command the rover to perform mast activities at that time of morning.

After the early morning activities, the rover was commanded to approach a target on Axel Heiberg for grinding with the rock abrasion tool. The drive was designed and executed to compensate for slip, and the result was very precise. The rover also made additional remote-sensing observations, then it went into a deep sleep for the night to save energy.

On sol 194 the rover took microscopic imager pictures of a spot on Axel Heiberg, and then performed a grind with the rock abrasion tool to get access to subsurface chemistry. The grind went well, but the targeting was a little off (the hole was about 6 centimeters - about 2.4 inches - to the left of the intended target.) After some investigation it was determined that there is an error in the way one of the ground tools represented the commanded position. This error has existed previously, but the team has never detected it to be this large. It is now being fixed. The exact positioning of the rover and the arm, and the nature of the activity all combined to make the error particularly large in this instance. After the grind, the rover placed the alpha particle X-ray spectrometer on the hole to measure the rock's elemental composition early the next morning.

On sol 195, which ended on Aug. 11, the rover acquired post-grind microscopic images and placed the Mössbauer instrument on the hole to take a reading all afternoon, plus an additional reading after wakeup on the morning of sol 196. The rover also made remote-sensing observations, including images to help assess where it might drive next.

sol 190-191, August 12, 2004: Aiming for 'Axel Heiberg'

Opportunity continues its voyage farther into "Endurance Crater" with a near-term drive goal of a rock outcrop dubbed "Axel Heiberg," and a possible later destination at the foot of "Burns Cliff" on the south side of the crater.

Sol 190 - Opportunity completed a 3.4-meter (about 11-foot) drive towards Axel Heiberg. The slope was steady at about 17 degrees and slippage during the drive was about 16 percent, as predicted. The rover took images for use in planning future drives and made observations with its miniature thermal emission spectrometer. Controllers employed the microscopic imager to help with diagnosing the cause of error messages from that instrument received last week.

Sol 191 - Opportunity successfully drove another 5 meters (about 16.4 feet) closer to Axel Heiberg, leaving about 5 meters (about 16.4 feet) to go. The drive included a short backup at the end to check for uphill-drive slippage, which was within acceptable limits. Deep sleep was used overnight.

The team continues to acquire microscopic imager diagnostic images at different times of day to see if temperature might be a contributing factor to the errors seen from that instrument last week. So far, no more errors have occurred.

sol 188-189, August 09, 2004: Opportunity Turns to Talk to Odyssey

Sol 188 was devoted to finishing an examination of a target patch called "Tuktoyuktuk" where the rover's rock abrasion tool had ground the surface coating off of a rock called "Inuvik." Opportunity then drove partly up-slope and partly cross-slope as both a mobility test and the start of a traverse to the next target. It slipped down-slope about as much as expected, a good result. The rover's current terrain consists of rocky plates lightly covered with sand and soil, plus some deeper sandy patches between the plates. The sandy patches result in more slip and sometimes cause the vehicle to yaw a little (as more slip on one side of the vehicle than the other causes it to turn). The overall tilt of the rover is about 18 degrees.

On sol 189 the rover drove about 4 meters (13 feet) eastward across the inner slope of the crater. The drive went well despite substantial down-slope slip. Slippage averaged about 33 percent, with a peak of about 56 percent on one half-meter (1.6-foot) drive segment, but the rover team expected that and compensated in advance for it. The team then asked the rover to conduct a series of turns in place during the communications relay pass with the Mars Odyssey orbiter to optimize the communications link. The idea was to keep Odyssey in the sweet spot of the rover's ultra-high-frequency antenna pattern as the orbiter swept across the sky. The total data return was about 135 megabits. The best possible return predicted by models if the rover had just sat in one orientation was about 115 megabits.

The next target the scientists would like the rover to approach, "Axel Heiberg," is a rocky outcrop about 18 meters (59 feet) away to the east and a bit deeper in the crater.

sol 186-187, August 06, 2004: "Tuktoyuktuk's" Turn

The rock abrasion tool has been keeping busy at Opportunity's position about 22 meters (72 feet) inside of "Endurance Crater" while rover handlers are preparing for Opportunity's next traverse.

Sol Highlights:
186 - After a night of deep sleep, Opportunity started the sol with imaging of the sky in search of clouds and using its miniature thermal emission spectrometer for observations of the sky and ground. In the afternoon, the rover took microscopic images of a target called "Tuktoyuktuk," then used its rock abrasion tool to gnaw a hole 7.7 millimeters (0.3 inch) deep into that target. The robotic arm moved the alpha particle X-ray spectrometer into position for reading of the composition of the freshly exposed interior of the rock.
187 - Opportunity woke for an early morning Mars Odyssey communications relay session. After that, the rover started the alpha particle X-ray spectrometer reading, which lasted until 9:00 a.m. local solar time. Opportunity then took a long nap as the uplink command window was delayed until 1:00 p.m. local solar time due to launch of NASAs Messenger mission to Mercury. In the afternoon, Opportunity rotated its tool turret from the alpha particle X-ray spectrometer to the Mössbauer spectrometer and acquired a 7-hour Mössbauer reading before beginning deep sleep.

The rover team is addressing some concerns about rover slippage and about error messages from the microscopic imager. An uphill driving test is planned for sol 188 to gain better understanding of a 40-percent slip observed in a repositioning maneuver on sol 185. This will aid planning for a potential drive clockwise across the inner slope of the crater toward rocks called the "Arctic Islands" and the base of "Burns Cliff." Diagnostic work is also planned for sol 188 about the error messages generated during use of the microscopic imager.

sol 181-185, August 03, 2004: Opportunity Finishing Up at 'Karatepe'

Opportunity is completing an intensive survey of the "Karatepe" region that began 50 sols ago when the rover first ventured into "Endurance Crater." The rover currently sits about 20 meters (about 66 feet) inside the stadium-sized crater. The investigation at an area dubbed "Inuvik" at a target called "Tuktoyuktuk" (named for a small village in the Canadian arctic) will likely be the rover's last in this region. The rover planning team is contemplating the next traverse which will move Opportunity around the interior of the crater, first to some outcroppings dubbed the "Arctic Islands," then possibly to "Burns Cliff," roughly 80 meters (about 262 feet) from the rover's current position. Opportunity continues to perform very well, a testament to all those who worked so hard to get it to Mars and to those who operate it daily.

Some concerns that are being addressed are slippage, an error message from the microscopic imager and pointing errors with the front hazard-avoidance cameras.

The drive on sol 185 included a short backup, during which the rover experienced a 40 percent slip. Typical slips when driving uphill have been in the 15- to 20-percent range. More evaluation of what happened on this and other drives will be needed before any general conclusions can be made about traversability in this region. The overall slope in this area is 15 degrees, which is 10 degrees below the general threshold of concern for rocky terrain. Sol 185 ended on Aug. 1.

There have been four instances of a warning message in the last ten sols that indicate a problem getting data from the microscopic imager. The messages indicate that the data was corrupted, and that a retry was necessary to receive the data without error. In all cases, the retry succeeded in transferring the data. This problem has not been seen before on either vehicle.

The new front hazard-avoidance camera models may need some more tweaking. Pointing errors were greater than expected on two recent placements of the instrument deployment device (robotic arm). The error is such that rover planners can still confidently place the instruments, provided that a 2-centimeter (0.8-inch) offset can be safely tolerated. If more precision is needed, planners must first use the microscopic imager to survey the target, then wait one sol before placing any instruments.

Sol highlights:
181 - A very accurate drive placed the target "Mackenzie" squarely in Opportunity's work volume.
182 - A two-hour hour rock abrasion tool (RAT) operation at Mackenzie was followed by an observation with the Mössbauer spectrometer. On this sol, Opportunity took panoramic camera images during the abrasion tool operation for the first time. The images were normal. Being able to use the panoramic camera and abrasion tool in parallel is one of the items on the "teach your dog new tricks" list, an effort to help the rover multi-task. The rover went into deep sleep this sol.
183 - Opportunity completed the Mössbauer observation of the RAT hole at Mackenzie, then placed the alpha particle X-ray spectrometer on the hole for an observation to start at 4 a.m. the next morning. (This instrument works best when very cold).
184 - The rover took microscopic imager pictures of the Mackenzie RAT hole, stowed the arm, then backed up to observe the hole with the panoramic camera and the miniature thermal emission spectrometer. The rover drove forward roughly 8 meters (26 feet) to Inuvik, using visual odometry to gauge the amount of slip. The drive left Opportunity to the right of the intended location because the rover slipped towards the fall line of the crater, causing the vehicle to effectively arc to the right. Deep sleep was invoked.
185 - Opportunity performed a short maneuver to get Tuktoyuktuk into the arm's work volume. Slippage was greater than expected during the uphill part of that move, so Opportunity ended up with only the upper part of the target in the work volume. That turned out to be good enough to perform a full set of arm work, which is planned for sols 186 through 188. The rover took panoramic camera images of the area between Inuvik and the Arctic Islands for the purposes of evaluating that drive. It turned the inertial measurement unit on again during the afternoon communications relay. This is another item on the "new tricks" list that, if successful, will allow rover planners to turn the vehicle during communication passes to optimize the data return. The rover again used deep sleep.

sol 177-180, July 30, 2004: Opportunity Sees Double

Opportunity marked its 180th sol on Mars without pausing to celebrate. Originally slated for missions of 90 sols each, both Spirit and Opportunity have passed the double-mission milestone and are continuing their phenomenal journeys of discovery.

On sol 177 Opportunity performed a two-hour rock abrasion tool grind on the target "Diamond Jenness," then took the resulting hole's picture with the microscopic imager. Surface debris and the bumpy shape of the rock apparently contributed to a shallow and irregular hole, only about 2 millimeters or .08 inches deep, not enough to take out all the bumps and leave a neat hole with a smooth floor. The alpha particle X-ray spectrometer examined the rock's composition in the abraded area during early morning of sol 178.

The team decided that sol 178 would be used to grind into "Diamond Jenness" again in hopes of deepening the hole. The sequence went extremely well with the rock abrasion tool grinding almost an additional 5 millimeters (about 0.2 inches). The rover then started a Mössbauer spectrometer reading of the deepened hole.

On sol 179 the rover completed the Mössbauer integration, gathered some remote-sensing data, then positioned the alpha particle X-ray spectrometer on the abraded hole for an early-morning integration at cold temperature on sol 180. This double integration of the hole (once on sol 178 at an intermediate depth and then a second one at full depth) will give the science team a unique opportunity to evaluate how the composition changes with depth.

On sol 180, which ended on July 27, the rover stowed its arm and drove back up the slope about 1.5 meters (about 5 feet), then turned a little to the right to go back down about 0.5 meters (about 1.6 feet). The drive up was to gain a vantage point from which to image the abraded hole in "Diamond Jenness" with the panoramic camera and to evaluate characteristics of the driving on this particular terrain. The drive back down and to the right served to position the rover for potentially proceeding farther into the crater (avoiding a sandy patch to its left). It also left the rover at a better angle for communications in the afternoon. The drive went well, with less slip that anticipated, reinforcing the team's confidence in driving back up out of the crater on some future sol.

In general, the rover continues to perform well, benefiting from a predominantly northward tilt and the greater solar-array energy that affords. The Mars Odyssey orbiter continues to perform as the rover's primary source of data return. The location on the slope of "Endurance Crater" and intensive use of the instrument arm hinder rover drivers from orienting Opportunity optimally for the radio relays to Odyssey. The level of communication is acceptable for now and the team expects that, some sol, Opportunity will venture back out of the crater to explore to new places. When the rover is on flatter ground, the team can optimize communications with Odyssey more often.

sol 174-176, July 27, 2004: Opportunity Pokes Around Pig

On sol 174, Opportunity completed close-up examination of a rock target called "Arnold Ziffel" using the rover's microscopic imager, Mössbauer 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.

sol 170-173, July 26, 2004: Opportunity Lives High off the Hog

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 Mössbauer and alpha particle X-ray spectrometer instruments.

sol 166-169, July 20, 2004: Opportunity Multi-Tasks on the Slopes of 'Endurance Crater'

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 Mössbauer spectrometer on a target called "Dahlia." All went as planned.

Sol 167 saw completion of the Mössbauer 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.

On sol 168, the rover lifted the alpha particle X-ray spectrometer off the capture magnet and replaced it with the Mössbauer 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.

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.

sol 159-163, July 15, 2004: Opportunity Reading Rock Within its Reach

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 Mössbauer 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 Mössbauer 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 Mössbauer 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 Mössbauer integration at the same location. The Mössbauer 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 Mössbauer 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.

sol 154-158, July 07, 2004: Opportunity Tests its Mettle on Slopes of 'Endurance Crater'

Sol 154 consisted of Opportunity completing activities on the target "Kettlestone," including a long Mössbauer 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.

sol 150-153, July 01, 2004: Ravenous Rock Abrasion Tool

On Sol 150, Opportunity completed Mössbauer 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 Mössbauer 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 Mössbauer spectrometer and integrated until mid-afternoon. When the Mössbauer 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 Mössbauer 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).

sol 144-149, June 29, 2004: Rock Abrasion Tool Hops from 'Virginia' to 'London'

While Opportunity is hard at work inside "Endurance Crater," engineers at JPL are busy testing engineering models in the Lab's simulated martian environment. A tilt platform is being used to determine Opportunity's ability to climb back up over the "curb" below its current location.

On sol 144, Opportunity completed the Mössbauer spectrometer integration on the rock abrasion tool hole on the "Cobble Hill" area. Microscopic images were also collected.

Sol 145 was a busy day, with the rover collecting more post-rock abrasion tool Cobble Hill and pre-"Virginia" microscopic images. The tool then bored a 4.3-millimeter (0.17 inches) hole in Virginia. Deep sleep mode was invoked for the overnight hours.

Sol 146 was used to examine the newly-abraded hole with the microscopic imager and the alpha particle X-ray spectrometer.

On sol 147 the rover performed a long Mössbauer spectrometer integration on Virginia and completed some remote sensing from its location in the crater. After relaying the data through both Mars Global Surveyor and Mars Odyssey, Opportunity went into deep sleep mode for the night.

"London" was Opportunity's target on sol 148. The rock abrasion tool ground a 4.5-millimeter (0.18 inches) hole in the rock. The alpha particle X-ray spectrometer was then placed on the hole for integration.

On sol 149 the rover continued to scrutinize London with the alpha particle X-ray spectrometer and the microscopic imager. A Mössbauer spectrometer integration was initiated and will be completed on sol 150. Deep sleep mode was invoked for the overnight hours.

sol 141-143, June 22, 2004: Edging Down 'Endurance'

Opportunity is showing no signs of middle age as it continues to work in "Endurance Crater." The rover has spent the last few sols inching farther down into the crater, making observations and pushing the limits. Managing resources as the rover's tilt angle changes is challenging and keeps the rover planning team very busy.

On sol 141 Opportunity completed post-rock abrasion tool Mössbauer spectrometer observations on the rock called "Tennessee." Having spent the last four sols investigating Tennessee, Opportunity stowed its arm and moved deeper into Endurance Crater. A 0.70-meter (2.3 feet) drive positioned the vehicle to begin observations on the first contact point, a transition between two different geologic layers. As it turns out, after arriving at the rover's new location and taking images, there appears to be not one contact point, but three contact points all within reach of the arm. Opportunity then performed 2.5 hours of remote observations using the panoramic camera and miniature thermal emission spectrometer. The rover then went into deep sleep mode for the night.

On sol 142 Opportunity begin another series of microscopic imager observations on three different targets: "Bluegrass," "Siula Grande" and "Churchill." The rover then performed alpha particle X-ray spectrometer and Mössbauer spectrometer integrations overnight.

On sol 143 Opportunity again used its rock abrasion tool, but not without some consternation from the uplink team. In order to grind using the rock abrasion tool, a minimum of force must be used to push the tool onto the target. With the vehicle tilted 23.2 degrees, there was concern that applying too much force could cause the vehicle to lose traction on the slope and slide farther into the crater, possibly damaging the arm. Concerns were pacified when the rock abrasion tool operation worked flawlessly, abrading approximately 3 millimeters (about 0.12 inches) into the rock called "Cobble Hill."

sol 138-140, June 18, 2004: Diggin' into 'Tennessee'

Opportunity spent sol 138 grinding an 8.12-millimeter (0.32 inch) hole into the rock target called "Tennessee." It took the rover 2 hours and 4 minutes to complete this grind, which is the deepest yet of the mission. After all this hard work, the rover went into a deep sleep for the night.

On sol 139, Opportunity used the microscopic imager to analyze the hole in Tennessee. The rover also performed both a daytime Mössbauer spectrometer observation and an overnight alpha particle X-ray spectrometer integration on the abraded surface.

Opportunity was busy finishing up some miniature thermal emission spectrometer observations of Tennessee on sol 140 and then began a long Mössbauer integration that ran for the entire sol. Opportunity enjoyed some more deep sleep after these activities and will finish up the last of the Tennessee observations the morning of sol 141.

sol 134-137, June 15, 2004: Exploring Endurance

Opportunity is becoming accustomed to its new sloped home inside "Endurance Crater." There are positives and negatives to the rover's new position and orientation. The solar array is oriented toward the northeast, which maximizes solar power in the morning and also warms the high gain antenna actuator faster, so heating is no longer required before the morning communications session. On the downside, the UHF communications sessions have degraded slightly at this orientation.

On sol 134, Opportunity drove 3.9 meters (about 13 feet) into Endurance Crater, then backed up 1.4 meters (4.6 feet), remaining inside the crater. Drive slippage and vehicle tilt was as predicted by the engineering team. An hour's worth of remote sensing completed the sol. Opportunity then performed deep sleep overnight into the morning of sol 135.

On sol 135, Opportunity drove 1.3 meters (4.3 feet) deeper into Endurance Crater to a position that was about the deepest point it reached on sol 134. This short drive was intended to allow for detailed imaging of the first likely target for the instrument arm, a rock called "Tennessee." The drive went exactly as planned, leaving Opportunity with a final tilt of -19.44 degrees and a heading of 62.5 degrees. The rover then performed almost two hours of remote sensing, then set up for another night of deep sleep.

Sol 136 was spent performing a series of panoramic camera and miniature thermal emission spectrometer observations from sol 135's final location. The miniature thermal emission spectrometer performed atmospheric measurements and an overnight observation during the early morning pass by NASA's Mars Odyssey orbiter. Part one of a planned ingress (entry) survey campaign with the panoramic camera was initiated.

On sol 137, Opportunity approached the rock target referred to as Tennessee. Opportunity drove 1.19 meters (3.9 feet) deeper into Endurance Crater, placing Tennessee perfectly within the instrument arm's reach. The rover is in position to perform the first series of arm operations starting on sol 139. Deep sleep mode was again invoked overnight from sol 137 to sol 138. The plans for the coming sols include grinding into Tennessee with the rock abrasion tool and investigating it with the rover's spectrometers.

Total odometry after sol 137 is 1,466.16 meters (more than nine-tenths of a mile)!

sol 130-133, June 10, 2004: Opportunity Takes A Dip

On sol 130 Opportunity traversed a total of about 45 meters (about 147.6 feet). About 39 meters (about 127.9 feet) of that was counter-clockwise along the edge of "Endurance Crater," and 6 meters (about 19.7 feet) toward the crater rim. The sol ended with the rover about 10 meters (32.8 feet) from the crater rim. The traverse ended up about 1 meter (about 3.3 feet) short of what was commanded due to a slightly uneven patch of ground that the rover seemed to run across near the end of the drive. Driving over this tripped a suspension limit that rover planners had set to help prevent inadvertently driving into difficult terrain. Deep sleep was again invoked for the night of sol 130 to 131.

On sol 131 the rover successfully traversed up the slope to the crater edge, took a detailed set of images and then backed off a little to optimize its orientation for the rover's communications passes. These images will aid in the project's assessment of traversing on the interior slopes of Endurance Crater in this vicinity. Deep sleep was not invoked on this night, in favor of relaying data to Mars Odyssey in the early morning on sol 132.

On sol 132 the rover re-approached the crater rim at the location and orientation most advantageous for the "pre-dip" into the crater. This approach was designed to just crest the edge of the crater and leave the rover roughly level (with the front two wheels in the crater). The drive executed beautifully.

On sol 133 the rover executed the first real "dip" into Endurance Crater. The intent was to go far enough in that all wheels would be on the slope of the crater, and then come all the way back out, proving that the rover was capable of getting back out before going very deep. The other main objective was to gather information on the degree and nature of any slip that would be experienced while traversing the crater wall. The execution went extremely well, with slips and disturbance of the terrain well below acceptable levels, giving the team confidence that the rover is capable of going deeper. The engineering team will continue to characterize the variety of slopes and materials that Opportunity will encounter deeper in the crater.

sol 127-129, June 10, 2004: To Ingress or Not to Ingress

Engineers and scientists on the Mars Exploration Rover project continue to contemplate the safety and viability of a trek into "Endurance Crater."

After a "deep sleep" overnight, Opportunity began its 127th sol with a three and one-half hour nap. Upon awaking, the rover drove 50 meters (164 feet) on a directed drive, turned to face Endurance Crater and took images using its front hazard-avoidance cameras. Opportunity then performed 45 minutes of remote sensing using the panoramic camera and miniature thermal emission spectrometer. The rover then supported an afternoon and overnight Mars Odyssey data pass.

Foregoing deep sleep over the sol 127 night, sol 128 was spent approaching the crater rim. The drive took about 10 minutes and moved Opportunity 13.4 meters (44 feet), coming to rest about 5 meters (16.4 feet) from the lip of the crater. The remainder of the day was spent supporting two afternoon Odyssey passes. The rover then underwent its sixth deep sleep cycle into the morning of sol 129.

On sol 129, it was decided that Opportunity was not in the most advantageous location for entering the crater. The rover was commanded to move approximately 50 meters (164 feet) back along the crater rim, close to the rock called "Lion Stone." After a 4.5-meter (14.7 feet) bump toward the rim and some navigation and hazard-avoidance camera images, the rover backed up 4.5 meters (14.8 feet) and then drove 8 meters (26.2 feet) toward Lion Stone. Power limited the total drive duration. Instead of utilizing the deep sleep mode overnight into sol 130, Opportunity again supported two Odyssey passes that returned a large volume of data to Earth.

After sol 129, Opportunity's odometer read 1,395.91 meters (4,579.76 feet).

Sols 130 and beyond will see Opportunity drive farther toward the possible point of ingress (entry).

sol 123-127, June 10, 2004: Opportunity Sols 123-127 Mission Update

On Opportunity's 123rd sol the rover completed an alpha particle X-ray spectrometer activity and performed a Mössbauer spectrometer read on the target called "McDonnell." The rover also acquired microscopic images before repositioning to set up for instrument deployment device (arm) work on the target referred to as "Pyrrho." This interesting rock on the Endurance rim has a braided ripple pattern. After more remote sensing, Opportunity successfully went into "deep sleep" mode to conserve energy overnight and into the morning of sol 124.

Awakening from deep sleep on sol 124, Opportunity performed miniature thermal emission spectrometer activities, proving that the instrument was, once again, able to survive the cold martian night without its heater running. The rover also acquired 75 microscopic images and performed a Mössbauer integration on Pyrrho before executing another repositioning to put the target rock called "Diogenes" within the instrument arm's work volume. This short drive was perfect and set the scene for rover planners to access nearly any point on this rock filled with intriguing disc-shaped cavities. Opportunity again took advantage of the deep sleep mode overnight into the morning of sol 125.

On Sol 125, the rover acquired 76 microscopic images on Diogenes. Very little else was done on this sol, as rover planners opted not to enter deep sleep in favor of waking up for the morning Mars Odyssey pass on Sol 126. Because it performed extensive instrument arm work and stayed awake for two Odyssey passes, the rover drained a fair amount from its battery.

Sol 126 was a very active sol, beginning with a quick placement of the Mössbauer instrument on Diogenes. The rover then napped for about two hours while the Mössbauer performed its integration. Upon waking, the rover stowed its arm and began a mobility test and preparation activity that will aid rover planners should they decide to traverse down steep rocky slopes in Endurance Crater. This set of activities included a draw-bar pull activity where the front rover wheels are locked and dragged back across rocks by driving the other four wheels backwards for about one meter (3.3 feet). The draw-bar pull is intended to give insight into the friction between the wheels and the rock surface at this site. The other mobility preparation activity was to scuff each wheel on the surface by driving one wheel at a time for a few rotations in each direction (with all the other wheels locked). This "pawing at the ground" activity was intended to scrub off the anodized layer on the surfaces of the wheels, which will allow for better grip. After these mobility activities, Opportunity traversed about 72 meters (236.2 feet) west around the crater towards "Karatepe." This very busy day also included relaying about 190 Megabits of data through Odyssey with two back-to-back afternoon passes. All this was made possible by having the option of deep sleep to save energy overnight, which Opportunity took full advantage of overnight into sol 127.

The plan for the coming sols involves approaching the rim of Endurance and imaging potential entry points to aid in the decision of whether or not to enter the crater.

sol 115-116, May 25, 2004: Opportunity on the Edge

On Sol 115 Opportunity drove 11.7 meters (38.4 feet), coming to rest about 3 meters (10 feet) from the edge of "Endurance Crater," as intended. Rover planners had commanded Opportunity to go 10 centimeters (3.9 inches) farther, but the rover decided to stop when it "saw" the edge of the crater in the navigation camera images. This was actually a more conservative response than necessary, as it would have been safe to complete the drive. Rover planners are looking into changing the way they send commands to prevent this over-conservatism next time.

Opportunity used its navigation camera to acquire images showing its proximity to the crater. On Sol 116 Opportunity turned slightly to the right and crept a little closer to the edge of Endurance Crater to get into just the right position to set up camp for a few sols. The rover executed this 1.5 meter (4.9 feet) traverse as planned, ending up facing northwest with a total tilt of about 8 degrees pitched "nose-up". From this position, Opportunity will make many observations with the panoramic camera and mini thermal emission spectrometer to fully characterize the parts of the crater that can be seen from here. Opportunity now sits only about 1 meter from the edge of the crater, and there is a sloping drop-off of about 40 degrees dead ahead.

sol 112, May 18, 2004: A Sol for Rest and Recharging.

Opportunity is healthy, but feeling a bit sluggish today. The rover's 40-meter (131 feet) traverse along the southern edge of "Endurance Crater" on sol 111, and a sol 112 error with a Deep Space Network command transmission have resulted in a low battery state of charge.

The sol 111 drive put Opportunity on an 8-degree slope that tilted the rover away from the Sun and limited the amount of direct sunlight that could reach the solar panels.

To help the battery recover to its normal state of charge, rover planners had built a sol 112 plan that deleted two of the three UHF windows. Unfortunately, a Deep Space Network configuration error prevented the command load from reaching Opportunity on sol 112 and, as expected in such cases, the rover executed the onboard run-out sequence, which included an hour of remote sensing and the three on-board UHF communication windows.

Sol 113 will be a sol for sleep and recharging for Opportunity. On sol 114, the rover will do some limited remote sensing in the morning, but will generally take it easy over the next few sols in order to fully charge the batteries. The limited activity over the next few sols will focus on moving towards the Endurance Crater rim and a new position for panoramic camera imaging.

sol 107-111, May 17, 2004: Opportunity Digs, Scuffs, and Cruises.

On sol 107, Opportunity successfully drilled a hole into "Lion Stone" with the rock abrasion tool. Since the surface of the rock was fairly uneven, the tool had to work through some high spots before getting a good bite on the rock for a full circular hole. Sol 107 ended at 6:44 a.m. May 13 PDT, with a nighttime integration of the alpha particle X-ray spectrometer to reveal elemental composition of the inner part of the rock.

On Sol 108, which ended at 7:24 a.m. May 14, PDT, the rover finished up its work on Lion Stone by analyzing the rock abrasion tool hole with the Mössbauer spectrometer and taking microscopic images to create a mosaic of the hole. Opportunity then moved away from Lion Stone and continued traversing counterclockwise around the crater. Opportunity drove 32 meters (105 feet) to the top of a small ridge for a better view of where to drive on Sol 109.

On Sol 109 and sol 110, which ended at 8:04 a.m. May 15, PDT, and 8:43 a.m. May 16, PDT, respectively, Opportunity drove about 41 meters (135 feet) each sol. Opportunity ended the drive on May 16 with a "scuff" of the soil and rocks under the front wheel. This scuff action produced an interesting dislodged plate of some kind. The scientists will be making some additional observations of different pebbles on the ground in the sol 111 plan.

Opportunity is driving along the south edge of Endurance Crater, with a southward tilt of about 8 degrees. The Sun is now at higher latitudes (south hemisphere winter is coming), so a southward tilt robs the rover of total solar array energy. This is making it more difficult to perform many activities. In a couple of sols when Opportunity drives to flatter ground near the crater edge to take the next large panorama, the energy situation is expected to improve.

Opportunity has driven a total of 1,170 meters (3,839 feet or 0.7 miles).

sol 103-106, May 13, 2004: Crater Cruise

On Sol 103, Opportunity traversed approximately 13 meters (about 43 feet) farther south along the eastern rim of "Endurance Crater," reaching the beginning of the "Karatepe" area. On sol 104, the rover approached "Lion Stone," a rock at the crater's edge that stands about 10 centimeters tall (about 4 inches) and is about 30 centimeters long (12 inches). This brought Opportunity's total mission odometry to 1,054meters (3,458 feet)!

On Sol 105, Opportunity acquired a series of microscopic images of Lion Stone and the surrounding soil.

The rover then went on to collect a short Mössbauer integration on the rock during the day, performed a tool change to the alpha particle X-ray spectrometer in late afternoon, and acquired that integration in the early morning of Sol 106. That sol also included additional microscopic images and a successful "bump" maneuver to reposition the rover so the top of Lion Stone was in position for the rock abrasion tool on Sol 107. Remote sensing was also acquired during the two sols, including panoramic camera images of the heatshield that protected Opportunity during its toasty trip through the martian atmosphere. The heatshield impacted approximately 250 meters (about 820 feet) south of Endurance Crater.

Plans for Sol 107 are to perform a rock abrasion tool grind on Lion Stone with subsequent microscopic images and alpha particle X-ray spectrometer overnight integration. The tentative plan for Sol 108 is to leave Lion Stone and begin traverse to observation position 2 on the southeastern rim of Endurance Crater.

sol 101-102, May 10, 2004: 'Deep Sleep' Gives Opportunity More Energy to Cruise the Crater

Opportunity awoke on sol 102 from its first "deep sleep." This set of activities was initiated to conserve the energy that is being used by the instrument arm's stuck-on heater switch. During deep sleep, rover planners power off the main electronics at night and open the switches that supply battery power to the main power bus, and in turn nearly all the secondary electronics. In particular this removes power input to the Rover Power Distribution Unit, which normally supplies power to the stuck-on heater. With the Rover Power Distribution Unit input turned off, the heater cannot burn any energy either. In the morning, when the sun strikes the solar panel array, the Battery Control Board resets and connects the batteries to the main power bus again. At this time, the stuck-on heater again draws power, but this will only be for a few hours in the morning instead of all night.

The most vulnerable instrument to the cold martian nights is the miniature thermal emission spectrometer. With a cutoff of the power electronics, its heater cannot keep it warm overnight. Data returned on sol 102 showed the temperature reached -46 degrees Celsius (-50.8 degrees Fahrenheit), a bit warmer than the spectrometer's lowest proven temperature for functionality, -50 degrees Celsius (-58 degrees Fahrenheit).

Rover planners commanded Opportunity to take a drive during the afternoon of sol 102 to the south, along the edge of the crater toward a dark rock in the vicinity.

More remote sensing was conducted, including miniature thermal emission spectrometer measurements that confirmed the instrument is still functioning normally after deep sleep.

Wake-up songs for the sols were "Morning has Broken" by Cat Stevens; "Hallelujah Chorus" from George Frideric Handel's Messiah; and "Dazed and Confused" by Led Zeppelin.

sol 98-99, May 06, 2004: An Eyeful at 'Endurance'

Opportunity continues to gaze at the incredible "Endurance Crater" from its vantage point on the western rim. Remote sensing, including gathering of imagery of two potential traverse targets just inside the northern edge and southwestern edge of the crater, will continue on the rover's 100th sol.

sol 94-97, May 03, 2004: Opportunity Arrives at 'Endurance Crater'

After a 50-meter (164-foot) drive on sol 94, which ended at 10:10 p.m. April 29 PDT, and the final approach of 17 meters (56 feet) on sol 95, which ended at 10:49 p.m. April 30 PDT, Opportunity arrived on the western rim of "Endurance Crater" and began surveying the spectacular new view.

Opportunity sits about half a meter (1.6 feet) outside the edge of the crater with a positive pitch of 4.7 degrees, meaning the rover is slightly tilted with its head up. The western side of the crater rim slopes down in front of Opportunity with an angle of about 18 degrees for about 17 meters (56 feet).

Sols 96 and 97, which ended at 11:29 p.m. May 1 PDT, and 12:08 a.m. May 3 PDT respectively, focused on remote sensing of Endurance Crater and the interesting features in and around it.

All systems are healthy and Opportunity's batteries are near a full state of charge.

The plan for sols 98 and 99, which end at 12:48 a.m. May 4 PDT and 1:28 a.m. May 5 PDT respectively, is to take advantage of Opportunity's current vantage point and take high-resolution miniature thermal emission spectrometer readings of the far crater wall.

sol 92-93, Apr 29, 2004: Opportunity Edges Its Way Toward 'Endurance'

Opportunity spent sols 92 and 93, which ended at 8:51 p.m. PDT on April 27 and 9:30 p.m. PDT on April 28 respectively, edging its way closer to "Endurance Crater." A total drive of 106 meters (347.8 feet) left the rover just 70 meters (229.7 feet) from the rim.

The pattern for these two sols has been to take pre- and post-drive remote sensing observations and imaging in the crater direction between midday energy-conserving naps.

By sol 95, Opportunity will make the final approach to Endurance Crater.

sol 90-91, Apr 27, 2004: Opportunity Achieves Mission Success!

With 811.57 meters (a little over one half of one mile) on its odometer, 12,429 images downloaded and a record for the longest one-sol drive under its belt, Opportunity completed its prime mission. Finishing 90 sols of surface operations since landing day marked completion of the last of the official success criteria for Opportunity's prime mission.

On sol 90, the rover continued with the multi-sol panoramic camera and miniature thermal emission plains photometry observations. The alpha particle X-ray spectrometer was busy collecting data on the soil targets "Nougat" and "Fred Ripple."

On sol 91, Opportunity completed more remote sensing and took a Mössbauer spectrometer read on Fred Ripple. The rest of the sol was spent driving. A 40-meter (131.2 feet) drive in the southeasterly direction left Opportunity only 160 meters (about 525 feet) from the rim of "Endurance Crater."

sol 88-89, Apr 27, 2004: Finishing Up at 'Fram'

On Opportunity's 88th sol, which ended at 6:12 p.m. PDT on April 23, the rover team decided that although "Fram Crater" was an intriguing depression, the potential hazards and the time involved in investigating it made it more of a tour stop than a destination.

With the goal of "Endurance Crater" in mind, the rover finished its investigation of the rock called "Pilbara." A final Mössbauer spectrometer measurement was taken, and then the miniature thermal emission spectrometer studied the recently carved rock abrasion tool hole.

The rover then successfully drove out onto the nearby plains for a photometry experiment (measurement of light detectable by the human eye). The 33-meter (about 108 feet) south-easterly drive ended with a front wheel "scuff" mark in the soil.

On the rover's 89th sol, which ended at 6:52 p.m. PDT on April 24, the microscopic imager photographed a soil target called "Nougat" within the scuff. A Mössbauer spectrometer reading of the target followed.

The photometry experiment continued on this sol along with miniature thermal emission spectrometer remote sensing.

sol 87, Apr 23, 2004: Opportunity Reviews Rock Abrasion Tool Hole

Opportunity spent its 87th sol, which ended at 5:33 p.m. PDT on April 22, gathering compositional information from the depression ground into "Pilbara" on sol 86. The Mössbauer spectrometer examined the hole before the alpha particle X-ray spectrometer was placed there. The microscopic imager shot close-ups of Pilbara's new impression.

Data were also gathered by the miniature thermal emission spectrometer.

This set of activities should nearly complete a very detailed look at representative rocks and soil from "Fram Crater," which can then be compared to the "Eagle Crater" rocks and soils.

sol 86, Apr 23, 2004: Rock Abrasion Tool Pesters 'Pilbara'

Opportunity's 86th sol, which ended at 4:53 p.m. PDT on April 21, was another record-breaker! A nearly two-and-a-half hour grind produced an impressive 7.2 millimeter (about 0.28 inches) hole in the rock called "Pilbara."

The plan for the rest of the sol called for placing the alpha particle X-ray spectrometer on the new impression to determine the elemental composition of the exposed area. It was determined, however, that the rover position would not allow for a safe integration of the instrument. Rover planners amended the plan for the sol so the rover would back up and reposition itself for a safe placement of the spectrometer after the rock abrasion tool completed the grind.

On sol 87 the rover will analyze the rock abrasion tool hole with the alpha particle X-ray and Mössbauer spectrometers.

sol 85, Apr 21, 2004: Finally at 'Fram'

Opportunity got an up-close look at the rocky nature of "Fram Crater" as it approached the crater on sol 85, which ended at 4:13 p.m. PDT on April 20. After some morning remote sensing, the rover drove to the target rock dubbed "Pilbara," near the crater rim.

The wake-up song was "Take Me Out to the Ball Game!" by Jack Norworth in honor of all the baseball-related target names chosen this sol.

Plans called for Opportunity to grind into Pilbara with its rock abrasion tool on sol 86.

sol 84, Apr 19, 2004: On the Way to 'Fram Crater'

Opportunity began sol 84, which ended at 3:34 p.m. PST on April 19, with some remote sensing observations and analysis with the microscopic imager and Mössbauer spectrometer. At 13:13 Mars Local Solar time, Opportunity began a 25-meter (82 feet) drive toward "Fram Crater," taking images of its surroundings on the way. At the conclusion of the drive the rover acquired more remote sensing.

Opportunity will spend sol 85, which ends at 4:13 p.m. PST on April 20, 2004, using the instruments on its instrument deployment device to investigate a rock target at Fram Crater.

sol 81-82, Apr 17, 2004: Record-Setting Drive

Three days after switching to new software with mobility-enhancing features, NASA's Opportunity shattered the record for a single day's driving on Mars. The rover covered 140.9 maters (462 feet) during its 82nd sol on Mars, ending at 2:15 p.m. PDT, Saturday, May 17. That is about 40 meters farther than either the best previous one-day drive, by Opportunity two weeks ago, or the total distance covered by NASA's smaller Sojourner rover during its entire three-month mission in 1997.

The first 55 meters (180 feet) was done as a "blind" guided drive based on images acquired previously. Speed during that session averaged 120 meters (394 feet) per hour. For the rest, Opportunity used autonomous navigation, watching for obstacles, choosing its own path, and averaging 40 meters (131 feet) per hour. After the drive, the rover took forward-looking images for planning the next drive.

On the previous martian day, sol 81, Opportunity awoke with its alpha particle X-ray spectrometer on a soil target called "Beagle Burrow" inside a trench the rover had dug on sol 73. The rover removed the instrument arm, stowed it, then backed up to image the trench before driving toward a crater nicknamed "Fram Crater." Opportunity then completed a 7.5-meter (24.6-foot) drive to a trough to image a rock outcrop within it with the panoramic camera. After a bit of guided driving, the rover set out using its autonomous navigation. The sol 81 drive totaled more than 40 meters (131 feet).

Nearly reaching the second of four waypoints on the way to Fram Crater, the rover imaged its new surroundings to identify any future driving hazards. An afternoon nap preceded sol 81's final science session, atmospheric observations with the miniature thermal emission spectrometer and the panoramic camera.

Rover controllers devoted sol 82 to driving after some morning atmospheric observations and a quick look back with the panoramic camera. The record-setting run took three hours -- a good time for a marathon. It brought Opportunity to within about 90 meters (295 feet) of Fram Crater. It also took Opportunity over the 600-meter threshold, a criterion that had been set for at least one of the Mars Exploration Rovers to achieve in order for the mission to be called a success. Opportunity has now traveled 627.7 meters (0.39 mile). Spirit passed the 600-meter threshold two weeks ago.

Rover wake-up music for sol 82 was "I Would Walk 500 Miles," by Less Than Jake (originally by the Proclaimers).

For sol 83, ending at 2:54 p.m. PDT, Sunday, April 18, another drive day is planned for Opportunity, with a goal of getting the rover close to Fram Crater. Scientists then plan to use Opportunity for some investigations of that location.

sol 80, Apr 15, 2004: A Taxing Day at the Trench

Opportunity spent sol 80, which ended at 12:55 p.m. PDT on April 15, examining the trench it dug on sol 73. The rover's microscopic imager got close-up views of the targets called "Jeff's Choice," "RipX," "Jack Russell," "Beagle Burrow" and "NewRipX" in the trench.

The navigation and panoramic cameras shot images in Opportunity's drive direction toward "Endurance Crater."

The rover's spectrometers gathered data at several of the soil targets. Atmospheric data was collected by the miniature thermal emission spectrometer and panoramic camera.

In the coming sols, Opportunity will make its way to "Fram Crater," a waypoint on the path to Endurance Crater.

sol 79, Apr 14, 2004: Opportunity Wakes with New "Brainpower"

Waking up to the Ramones' "Teenage Lobotomy," Opportunity began operating with new flight software on its 79th sol on Mars, which ended at 12:16 p.m. PDT on April 14.

Yestersol, the rover took daytime readings with its Mössbauer spectrometer on "Jeff's Choice" -- a soil target in the tailings of the trench that the vehicle dug on Sol 73. This sol, the rover performed a free-air integration of its alpha particle X-ray spectrometer. This procedure measures the effect of the Mössbauer's radiation source on the alpha particle X-ray spectrometer's sensor, allowing the science team to subtract out the Mössbauer influence for an accurate calibration.

In the coming sols, Opportunity will examine the trench with its microscopic imager and alpha particle X-ray spectrometer.

sol 78, Apr 12, 2004: Opportunity Stands Down for Flight Software Update

Opportunity began a four-sol stand-down on sol 75, which ended at 8:58 a.m. PST on April 9, 2004. During this time, the rover will receive a flight software update that should make its remaining martian days even safer and more productive. The upload will run through sol 78 with a rover re-boot on sol 79, Tuesday, April 13.

Opportunity is currently parked near the trench it dug on its 73rd martain sol. It will remain there for the duration of the flight software update. To keep the battery charge high, engineers are not planning to integrate the rover spectrometers on a target in the trailings of the trench during the flight software update.

The flight software update package includes three key changes. First is an update to the autonomous navigation software that will allow both rovers to travel longer distances autonomously. The current autonomous navigation software sometimes gets stuck when it detects a hazard that it can't navigate around. The new version will allow the rovers to turn in place to find the best possible path.

The second part of the flight software update will allow the rovers to recover more easily from an anomaly like the one that occurred on Spirit's sol 18. Although operational processes and software have already been updated to prevent something like this from ever happening again, engineers have included additional safety nets in the software that would allow the rovers to autonomously react to a similar anomaly and recover to a more stable state.

The third portion of the update is specific to Opportunity and is intended to mitigate against energy loss associated with the stuck heater on Opportunity's instrument deployment device. The fix allows rover planners to put the rover in a deep sleep mode, where the batteries are totally removed from being able to power the stuck switch. Therefore, with no power reaching the stuck heater switch, the Opportunity rover battery will not be drained. Rover controllers will not initiate the deep sleep capability on Spirit unless it becomes necessary.

sol 73, Apr 08, 2004: Trough Tour Continues

Opportunity was on the move again on sol 73, which ended at 7:39 a.m. PST on April 7. The rover toured and examined the trough remotely.

Opportunity woke up to "Let the Good Times Roll" by B.B. King - a nod to Spirit's successful primary mission of 91 sols and a call for more good times during the coming sols.

sol 72, Apr 07, 2004: Traveling Around the Trough

"The Wanderer" by Dion and the Belmonts woke Opportunity on its 72nd sol, which ended at 7:39 a.m. PST on April 7. The rover drove around the sinuous trough in a long dogleg pattern. Remote sensing to examine the crevice was conducted on the 50-meter (164 feet) drive to its ultimate position for the sol, at the northeast extreme of "Anatolia."

On sol 73, the rover will perform a trenching operation in the soil. During the following sol, the instrument's arm will be placed on the trenched area.

The planned flight software upload will begin on Opportunity's 75th sol.

sol 70, Apr 06, 2004: 100-Meter Dash

Opportunity "dashed" away from the rim of its "Eagle Crater" landing-site on sol 70, which ended at 6:20 a.m. PST on April 5. The roughly 100-meter (about 328 feet) drive led the rover to a target area dubbed "Anatolia," along a sinuous crack in the plains of Meridiani Planum defined by deep impressions in the sand sprinkled with Eagle Crater-like rocks. In the coming sols Opportunity will further investigate the rocks in this "mini-outcrop."

Before leaving the vicinity of Eagle Crater, Opportunity performed a maneuver on "Bounce" rock lightheartedly called "crush and go" by the rover engineers. In order to gather further information about the rock's hardness, the intentional drive over Bounce was an attempt to fracture it. The science team is awaiting images from the rover's rear hazard avoidance camera to see the results.

An appropriate tune - "Truckin'" by The Grateful Dead - woke Opportunity this sol.

sol 68-69, Apr 05, 2004: Bidding Adieu to 'Bounce'

Over the weekend, Opportunity completed its observations at "Bounce Rock" rock and prepared for its trek toward "Endurance Crater."

On sol 68, which ended at 4:00 a.m. PST on April 3, the rover backed away from Bounce, then re-approached the rock in preparation for an alpha particle X-ray spectrometer read on the right side of it. The wake-up tune chosen for the sol was "Got to Go Back" by Van Morrison.

Opportunity made observations with its miniature thermal emission spectrometer during the martian morning. Then it took set of microscope images before backing away from the rock. More images were taken from that vantage point before Opportunity made a 10-degree turn in place and drove the 0.85 meters (2.8 feet) back to Bounce.

On sol 69, which ended at 5:40 a.m. PST on April 4, Opportunity completed its instrument arm work on Bounce. It also examined soil targets with its microscopic imager and Mössbauer spectrometer. The wake-up song for the sol was "Little Maggie" by Tom Adams, chosen for the soil target named "Maggie."

In coming sols Opportunity will make progress in a 750-meter (nearly a half mile) drive to Endurance Crater. The rover team plans to make pit stops along the way at scientifically interesting sites and will pause other activities for a few sols while the rover gets new flight software.

sol 67, Apr 02, 2004: 'Bounce' Barraged by Instruments

In recognition of changing the instruments on its arm nine times, David Bowie's "Changes" woke Opportunity on its 67th sol on Mars, which ended at 3:21 a.m. PST on April 2.

The rover continued to examine "Bounce" with the microscopic imager and the Mössbauer and alpha particle X-ray spectrometers.

During the martian morning, the Mössbauer spectrometer was turned off before atmospheric science was conducted with the miniature thermal emission spectrometer and the panoramic camera.

The afternoon hours were dedicated to intensive study of a handful of targets on Bounce, including the impression ground by the rock abrasion tool on sol 66.

Opportunity will continue to investigate Bounce for the next two sols and then begin its journey toward "Endurance Crater."

sol 66, Apr 01, 2004: Biting into 'Bounce'

Opportunity's rock abrasion tool ground into "Bounce" for just over two hours, producing a 6.44-millimeter (0.25 inch) hole that will allow the rover's spectrometer's to analyze the rock's chemical composition.

Bon Jovi's "Bounce" woke Opportunity on its 66th sol, which ended at 2:41 a.m. PST on April 1. The martian morning began with the alpha particle X-ray spectrometer observing a target called "Glanz2" on Bounce. Miniature thermal emission spectrometer measurements of the ground and sky followed.

The rock abrasion tool was then placed on the target dubbed "Case." After the grind, the Mössbauer spectrometer was placed on the hole for an overnight integration.

In the afternoon, the rover also had time to complete more atmospheric science with its panoramic camera and miniature thermal emission spectrometer.

In the coming sols, Opportunity will remain parked at the intriguing Bounce rock to continue its investigations.

sol 65, Mar 31, 2004: Opportunity 'Back in the Saddle'

Opportunity resumed science operations after waking to Aerosmith's "Back in the Saddle" on its 65th sol, which ended at 2:02 a.m. PST on March 31. During the martian morning, the miniature thermal emission spectrometer and panoramic camera studied the atmosphere. "Bounce" rock was imaged by the panoramic camera.

Opportunity's instrument arm was then deployed to get a close-up view of "Bounce" using the microscopic imager. The rock abrasion tool team used some of these images to identify the exact target for next sol's grinding operation. The Mössbauer spectrometer was then placed on a designated target on the rock for an overnight integration.

In the afternoon, Opportunity took navigation and panoramic camera images and completed more miniature thermal emission spectrometer science.

Next sol, the rover's rock abrasion tool will grind into Bounce.

sol 64, Mar 30, 2004: Opportunity Takes a Breather

On Opportunity's 64th sol, which ended at 1:22 a.m. PST on March 30, the rover team analyzed the results of engineering activities run to investigate an error message they received from the rover on sol 63.

A problem with a secondary memory file was isolated and resolved. Just as an ordinary computer disk can have corrupted sections, a corrupted file in an area where rover commands are addressed and stored has been identified. Engineers have identified the location of the problem within the memory and figuratively fenced it off, containing it and preventing it from harming any future command sequences. This minor issue has not impeded the rover from resuming normal science operations on the next sol.

The wake-up song chosen for Opportunity on this quiet sol was "Stand" by REM.

The rover is currently at the rock dubbed "Bounce." Opportunity met this rock once before; while still cloaked in its protective lander and airbags, the rover bounced on the rock while on its way to a safe landing in "Eagle Crater." Miniature thermal emission spectrometer observations have shown Bounce is rich in hematite. In the coming sols, the rover's other spectrometers will examine the rock before the rock abrasion tool grinds into a designated target.

sol 60, Mar 26, 2004: Opportunity and 'The Lion King'

On sol 60, which ended at 10:44 p.m. PST on March 25, NASA's Mars Exploration Rover Opportunity had a quiet day continuing its research around the exterior of Eagle Crater.

Opportunity changed tools from the Mössbauer spectrometer to the alpha particle X-ray spectrometer around 11:30 Local Solar Time. In addition to the tool change, Opportunity's panoramic camera took a comprehensive color high-resolution panorama. The rover team dubbed it the "Lion King Panorama" because it is a look around Opportunity's domain from a high vantage point -- much like the view from "Pride Rock" in "The Lion King" movie. The large panorama essentially filled the remaining flash memory volume onboard the spacecraft, requiring a plan for sol 61 that minimizes data collection. The miniature thermal emission spectrometer also collected remote sensing data.

The wake up song for sol 60 was "The Circle of Life" by Elton John in honor of the Lion King panorama.

The plan for sol 61, which will end at 11:23 p.m. on March 26 PST, is to drive north to an area with dark material.

sol 59, Mar 25, 2004: Browsing Bright Material

Opportunity spent sol 59, which ended at 10:04 p.m. PST, placing the Mössbauer spectrometer on the bright material it approached yestersol, and conducting more remote sensing observations.

This relatively light workload allowed the rover to recover energy for the next sol's activities. Those will include completing an alpha particle X-ray spectrometer read on the same soil target and initiating the panoramic mosaic image from the rover's current position.

The wake-up tune for the sol was "59th Street Bridge Song (Feeling Groovy)" by Simon and Garfunkel.

sol 58, Mar 24, 2004: Back to Bright Material

The song "Come on Home" by Lambert, Hendricks and Ross beckoned Opportunity back toward its landing site crater to an area of bright material. The rover also began to image a panoramic mosaic of the plains on this sol, which ended at 9:25 p.m. PST on March 23.

Over the martian night, Opportunity will again wake up to take miniature thermal emission spectrometer measurements.

In the coming sols, the rover will use its spectrometers to investigate the bright material area and then move on to a specific target in the area dubbed "Bright Spot."

sol 57, Mar 22, 2004: Opportunity Leaves the Nest

After a slightly slippery start yestersol, Opportunity made it out of "Eagle Crater"on sol 57, which ends at 8:45 p.m. PST on March 22. The drive along the crater's inner slope that was initiated on the last sol continued this sol until Opportunity exited its landing-site crater. Images from the navigation camera confirm that the rover is about 9 meters (about 29.5 feet) outside of the crater.

The rover also conducted remote sensing observations between naps this sol. After completing the drive out of the crater, the navigation camera imaged Opportunity's brand new view of the plains of Meridiani Planum.

During the martian night, rover planners will awaken Opportunity to take miniature thermal emission spectrometer observations of the ground and the atmosphere.

The song chosen to motivate Opportunity to move up and out of the crater was "If You Don't Get it the First Time, Back Up and Try it Again" by the JBs and Fred Wesley.

sol 56, Mar 21, 2004: Try Again to Exit Crater

NASA's Opportunity tried driving uphill out of its landing-site crater during its 56th sol, ending at 10:05 p.m. March 21, PST, but slippage prevented success. The rover is healthy, and it later completed a turn to the right and a short drive along the crater's inner slope. Controllers plan to send it on a different route for exiting the crater on sol 57.

Earlier on sol 56, Opportunity successfully examined a patch of soil dubbed "Brian's Choice" with its Mössbauer spectrometer, alpha particle X-ray spectrometer and microscopic imager. Following the drive, it made observations with its navigation camera and miniature thermal emission spectrometer. Wake-up music for the sol was "Fly Like an Eagle," by the Steve Miller Band.

sol 54, Mar 20, 2004: Sightseeing at Sweet Spots

Opportunity flipped 115 meters (377.3 feet) on its odometer during the latest drives along the current soil survey campaign, surpassing the total drive distance of 1997's Sojourner rover. After performing a "touch and go" sequence at the third soil target south of the Challenger Memorial Station, Opportunity moved east to its fourth target. There the rover used its wheels to dig a trench that will be studied in coming sols.

The sol, which ended at 6:46 p.m. PST on March 19, started with brief alpha particle X-ray and Mössbauer spectrometer measurements on the soil target known as "Coconut2." These were followed by two sets of microscopic imager shots of Coconut2 and "ChocolateChip." The rover then stowed its arm and drove.

Remote sensing with the miniature thermal emission spectrometer and the panoramic camera remote sensing was performed before, during, and after the drive and trenching activities. Also, Opportunity took additional images with its navigation camera imaging in preparation for next sol's drive to the final site inside the crater.

To prepare for the trenching on this sol, the wake-up song was "I Feel The Earth Move" by Carole King.

sol 53, Mar 18, 2004: Two Down, Three to Go

On sol 53, which ends at 6:07 p.m. PST on March 18, Opportunity first completed the alpha particle X-ray spectrometer work from yestersol and then continued to study the second soil survey target with the Mössbauer spectrometer.

Following an afternoon nap, the rover used its microscopic imager to get close-up views of the soil. Opportunity then made its way to the third soil target, which involved a 5-meter (about 16 feet) drive. The alpha particle X-ray spectrometer was then positioned to examine the magnet arrays. Preparations were also made to conduct a miniature thermal emission spectrometer observation of the martian sky at dawn on the next sol.

"Ice Cream Man" by John Brim woke Opportunity this sol to remind it of the possible sweet treats that await at targets referred to as "Chocolate Chip" and "Coconut" in the neighborhood dubbed "Mudpie."

The soil survey will continue in the coming sols.

sol 52, Mar 17, 2004: Scrutinizing the Soil

Sol 52, which ended at 5:27 p.m. PST on March 17, was a full day for Opportunity, punctuated by short naps. The rover arm was deployed on the first of five targets in the rover's current soil survey. The soil was examined by all the rover's spectrometers and the panoramic camera.

In the afternoon, the rover moved about 6 meters (about 20 feet) to the second soil target, performing several remote observations along the way. Closing out the sol, Opportunity's alpha particle X-ray spectrometer began to inspect the capture magnets on the front of the rover. Clues about Mars' watery history are present even in the smallest dust grains that settle on these magnet arrays.

Images of Opportunity's "scuff" experiment on the rock "Carousel" reached Earth this sol. Scientists are currently examining the results.

In honor of Opportunity's 52nd sol on Mars, engineers chose "Rock Lobster" by the B52s as a wake-up tune.

In the coming sols, the rover will travel to the final targets in the soil survey.

sol 51, Mar 16, 2004: "Scuff and Go"

Opportunity reached the first of five targets in its current soil survey on the rover's 51st sol on Mars. The sol, which ended at 4:47 p.m. PST on March 16, began with a salute to the rover's intended target on the southern face of the crater where it has been exploring since its early sols on Mars. "Song of the South" by Alabama was chosen to wake Opportunity for a busy sol that involved a 15-meter (49.2 feet) u-shaped drive toward the soil target.

Before the rover ventured away from the outcrop that has been the focus for the majority of its mission, alpha particle X-ray spectrometer observations were completed on the red rind dubbed "Shark's Tooth." The arm was stowed before Opportunity "scuffed" the rock "Carousel" with its front left wheel. Results of the experiment were imaged as Opportunity backed up and prepared for its drive away from the outcrop.

Backing down towards the center of the crater and then arcing around the Challenger Memorial Station, Opportunity ultimately drove back up the slope to a position fairly close to the rim. On its way to the current soil target, the rover was also able to image the trench it previously dug on sol 23 from a different angle.

In the coming sols, Opportunity will use the instruments on its arm to examine all five soil targets identified for the soil survey.

sol 50, Mar 15, 2004: Finishing up at the Outcrop

On sol 50, which ended at 4:08 p.m. PST on March 15, Opportunity got closer to completing its observations of the rock outcrop. The rover arm, with the alpha particle X-ray spectrometer at the ready, was placed on the rock called "Shark's Tooth" for a 30-minute observation. The microscopic imager then took a series of pictures of the targets "Enamel 1" and "Lamination." The focus then switched back to "Shark's Tooth" for an examination by the Mössbauer spectrometer.

The song chosen to awaken Opportunity was "The Dentist" by Bill Cosby, in honor of the toothy targets in "Shark's Cage."

The sol also included many panoramic camera observations of targets with creative names like "Patio Rug," "Anaconda Snake Den," "West Zen Garden" and "Garter Snake."

The next sol calls for a final experiment at the outcrop called "scuffing." "Scuffing" essentially turns one of the rover wheels into a tool to scrape a rock to help determine its hardness. The rock "Carousel" will be scraped by Opportunity's front left wheel. After that experiment, the rover will begin its trans-crater traverse to five soil survey targets, the first of which will lead Opportunity up the sandy southern face of the crater.

sol 48, Mar 14, 2004: Shark Ahead

NASA's Opportunity finished inspecting the "Berry Bowl" site and drove 10 meters (33 feet) toward a new target during its 48th sol on Mars, which ended at 2:50 p.m. Saturday, PST.

The rover used all four tools on its arm during the morning, ending with a brushing by the rock abrasion tool, then post-brushing examinations with the microscope and alpha particle X-ray spectrometer. This closed out three sols of work at "Berry Bowl" to compare the composition of targets with and without groups of the BB-sized spherules believed to have formed while the local environment was wet.

Opportunity then stowed its arm and drove toward an area dubbed "Shoemaker's Patio" at the southwestern end of the outcrop the rover has been studying since it arrived on Mars. This informal name pays tribute to the late geologist Dr. Eugene Shoemaker of the U.S. Geological Survey. Opportunity's more specific target is a rock called "Shark's Tooth" at the near edge of the patio. The drive did not quite put that target within reach of the robot arm. Activities of the sol also included atmospheric observations with the panoramic camera and miniature thermal emission spectrometer, plus post-drive imaging with the navigation camera.

Mission controllers at JPL chose John Williams' "Jaws: Main Title and Fist Victim" as the wake-up song for sol 48.

Plans for sol 49, ending at 3:28 p.m. Sunday PST, call for finishing the approach to "Shark's Tooth" after a morning examination of the ground right in front of the rover. Inspection of "Shark's Tooth" with tools on the robotic arm is planned for sol 50.

sol 47, Mar 12, 2004: Aiming for Shark's Tooth

On sol 47, which ended at 2:10 p.m. PST on Friday March 12, Opportunity awoke to "No Particular Place to Go" by Chuck Berry in recognition of the stay at "Berry Bowl." Engineers also played "That's Amore" by Dean Martin in honor of the Phobos moon's transit across the sky.

Opportunity finished remnants of activities from the past sol's research at "Berry Bowl." The sol started with the hazard avoidance camera taking a picture of the "Berry Bowl" area as a context picture. The miniature thermal emission spectrometer then performed some "sky stares" of the atmosphere. At 11:30 Local Solar Time, the robotic arm started moving. It picked up the alpha particle X-ray spectrometer and moved to a new location nearby, then switched to the Mössbauer spectrometer. Both spectrometers are searching for clues about the chemical composition of the mysterious "blueberries."

Later, Opportunity took panoramic camera images of the suite magnet on the rover itself, which is collecting atmospheric dust samples to understand why the martian dust is so magnetic. The panoramic camera also took images of a target dubbed "Fool's Silver," which contains an interesting angular feature in the outcrop.

After all the morning's hard work, Opportunity took a short siesta to rest and recharge. Opportunity reawakened a few hours later to take more images of the atmosphere with the miniature thermal emission spectrometer and panoramic camera. Those were taken in the same locations as the morning measurements to compare the atmospheric data throughout the sol.

At 15:40 Local Solar Time, Opportunity took about a dozen images of the Sun to catch the eclipse by the martian moon, Phobos. Opportunity once again shut down for a nap and woke up at 4:53 Local Solar Time, sol 48, for a tool change and a communications session with the Odyssey orbiter. While the rover was awake for the Odyssey pass, the rover heated up the robotic arm, which had chilled to almost -80 degrees Celsius (-112 degrees Fahrenheit). The motors cannot move at that frigid temperature, so the rover arm heated for 32 minutes to surpass the operational temperature of 40 degrees Celsius (104 degrees Fahrenheit). As the rover arm quickly cooled, the heat lasted long enough (5 minutes) for the arm to twist its wrist and change instruments from the Mössbauer spectrometer back to the alpha particle X-ray spectrometer.

The rest of the plan for sol 48, which will end at 2:49 p.m. PST on Saturday, March 13, is to perform quite a few complicated maneuvers. Opportunity plans to brush an area with the rock abrasion tool, analyze the brushed area with the spectrometers, then drive 10 meters (33 feet) along the slippery slopes of the outcrop to "Shark's Tooth" in "Shoemaker's Patio."

sol 46, Mar 11, 2004: Berry Nice News

On sol 46, which ended at 1:30 p.m. PST on Thursday, March 11, Opportunity awoke at 9:20 Local Solar Time to two songs in honor of researching the mysterious "blueberries" with the instruments on the robotic arm. The wake-up songs were "Berry Nice News" by Raffi and "Huckling the Berries" by Country Cooking.

Opportunity performed a series of activities including microscopic imaging of the berries and placing the Mössbauer spectrometer on the berries to analyze their chemical composition. The miniature thermal emission spectrometer later made multiple atmospheric observations. After a short nap to conserve energy, Opportunity awoke in the afternoon to perform some additional remote sensing observations and to transmit data to Earth via the Odyssey orbiter.

Later in the evening Local Solar Time, Opportunity collected data with its alpha particle X-ray spectrometer at two locations.

The plan for sol 47, which will end at 2:10 p.m. PST on Friday, March 12 is to continue analyzing the blueberries and the "Berry Bowl." By early next week, Opportunity will drive to a new area dubbed "Shoemaker's Patio."

sol 45, Mar 10, 2004: Halfway Mark

On sol 45, which ended at 12:50 p.m. PST on Wednesday, March 10, Opportunity awoke to ''Eclipse" by Pink Floyd in recognition of the transit of the martian moon, Phobos. A second song, "Meet Me Halfway" by Kenny Loggins, was played because Opportunity is halfway through its primary 90-sol surface mission.

Opportunity used the rock abrasion tool brush to sweep off the dirt in and around the hole at "Mojo 2" in the "Flat Rock" area. Opportunity then took five microscopic images of the freshly brushed "Mojo 2."

The miniature thermal emission spectrometer took measurements at three locations on the surface of Mars, and then pointed upwards to observe the atmosphere in four different directions. The panoramic camera was also busy taking images of the magnets around the rock abrasion tool area, "Mojo 2" post brushing, and a new area called "Slick Rock."

The plan for sol 46, which will end at 1:30 p.m. PST on Thursday, March 11, is to use the science instruments on the end of the robotic arm on the area dubbed "Berry Bowl."

sol 44, Mar 09, 2004: Back to the Grind

On Opportunity's 44th sol, ending at 12:10 p.m. PST on Tuesday, March 9, the rock abrasion tool ground a 3.1 millimeter-deep (just over one-tenth of an inch) hole in the "Mojo 2" target on "Flatrock." Yesterday, diagnostic testing determined a voltage adjustment was necessary to overcome some mechanism "stickiness" in the routine during which the rock abrasion tool finds the highest point in the target area.

The routine worked perfectly on this grind with the new voltage setting. After one hour and five minutes of successful grinding, the rock abrasion tool grind motor stalled, probably while grinding into one of the spherules also known as "blueberries." These objects are known to obstruct the grinding tool and cause it to terminate its sequence.

Late in the martian morning, the Mössbauer spectrometer was placed on the hole, followed later by the alpha particle X-ray spectrometer. The miniature thermal emission spectrometer took two long atmospheric measurements. The panoramic camera was busy taking images of the hole as well as surrounding target areas.

The wake-up songs were "Try (Just a Little Bit Harder)" by Janis Joplin for the rock abrasion tool's second attempt at "Mojo 2," and "X-ray Eyes" by Kiss for the alpha particle X-ray spectrometer.

sol 43, Mar 08, 2004: More Mojo

On sol 43, which ended at 11:31 a.m. PST on Monday, March 8, Opportunity awoke to ''You Can Look (But You Better Not Touch)" by Bruce Springsteen in recognition of the fact that the rock abrasion tool grind did not touch the surface of its rock target on sol 42.

Using a combination of microscopic images, hazard avoidance camera images, and rock abrasion tool tests on sol 43, Opportunity's engineering team discovered that the grind motor of the rock abrasion tool on Mars stalled prematurely during what's called the "seek/scan" phase when the rock abrasion tool instrument searches for the rock face. This resulted in no contact during the actual grind activity on sol 42. The most likely causes of the stall are dust and dirt accumulations and temperature variations on the instrument. The tests also confirmed that engineers can safely increase the motor voltage on the instrument to prevent a future stall.

In the process of conducting the rock abrasion tool activities, Opportunity placed the Mössbauer spectrometer on "Mojo 2," a target on "Flat Rock."

The remainder of the sol included preparations for the future target in this area, dubbed "Berry Bowl," taking pictures with the panoramic and navigation cameras. Opportunity also took ground and atmospheric measurements with the miniature thermal emission spectrometer.

The plan for sol 44, which ends at 12:10 p.m. PST on Tuesday, March 9 is to grind into "Mojo 2" using the rock abrasion tool and then to research the rock's chemical composition using the alpha particle X-ray spectrometer and the Mössbauer spectrometer.

sol 42, Mar 07, 2004: No Hole This Time

NASA's Opportunity attempted to grind a shallow hole into a target called "Flat Rock" during its 42nd sol on Mars, ending at 10:51 a.m. Sunday, PST. However, the operation of the rover's rock abrasion tool produced almost no discernable impression on the rock. All indications are that the tool is healthy. Controllers plan to run some diagnostic tests during sol 43 (ending at 11:31 a.m. Monday, PST) to aid with tuning parameters for a second grinding attempt on the target on sol 44.

Opportunity observed the Sun with its panoramic camera on sol 42 as a practice run for future imaging of Mars' moon Phobos passing in front of the Sun. The alpha particle X-ray spectrometer was placed against "Flat Rock" for an overnight reading to identify the chemical elements present.

Wake-up song for the sol was "Break on Through (to the Other Side)," by The Doors.

sol 41, Mar 06, 2004: Precision Driving after Mid-Sol Science

In its 41st sol on Mars, ending at 10:02 a.m. Saturday, PST, NASA's Opportunity inspected a rock target called "Wave Ripple" with tools on its arm, then drove to a new target. The new target, "Flat Rock," is in the "Slick Rock" area near the south end of the outcrop that the rover has been examining for weeks.

Although the rover wheels slip some in the local soil and the drive traversed a slope of 10 to 11 percent, Opportunity and engineers at JPL navigated the trip so well that a planned final approach to the target on sol 42 could be cancelled. The target is within the work volume of Opportunity's robotic arm. The drive was done in a series of one-meter (3.3-foot) segments making up a U-shaped path to the south and west. Each segment included a correction for slippage.

Before starting the drive, Opportunity used its microscope for 50 images of "Wave Ripple," and examined the composition of the rock with its alpha proton X-ray spectrometer and its Mössbauer spectrometer.

Rover controllers spun Willie Nelson's "On the Road Again" as the sol's wake-up song, and used a compressed planning schedule as practice for procedures that might become standard after the 90-sol prime mission.

Plans for sol 42, ending at 10:51 a.m. Sunday, PST, include using the rock abrasion tool at "Flat Rock."

sol 40, Mar 05, 2004: Opportunity Fit At Forty

After 40 good days on the surface, Opportunity is showing no signs of middle age.

On sol 40, which ended at 9:32 a.m. PST, March 5, 2004, Opportunity finished a set of overnight alpha particle X-ray spectrometer measurements at "Last Chance" and completed a morning set of panoramic camera and miniature thermal emission spectrometer remote sensing observations. At 11:30 Local Solar Time, engineers retracted the alpha particle X-ray spectrometer off the target, took a final set of 24 microscopic images, and stowed the arm for driving.

Opportunity then scored another first by successfully using visual odometry to navigate autonomously on Mars. During a drive along the crater wall, the vehicle properly identified wheel slippage on the steep slope of the crater wall using features in the navigation camera imagery. This effectively provided a mid-course correction that landed the science and engineering team exactly at the target location where they want Opportunity to do work using the instruments on the rover arm on sol 41.

The plan for sol 41, which will end at 10:12 a.m. PST, March 6 will be to take microscopic images of an area dubbed "Wave Ripple" in the "Last Chance" area, followed by a traverse to "Slick Rock" in the "Berry Bowl" area.

sol 39, Mar 04, 2004: An Armada of Arm Moves

On sol 39, which ends at 8:52 a.m. PST on Thursday, March 4, Opportunity awoke to "Bad Moon Rising" by Creedence Clearwater Revival in honor of the eclipse caused by the martian moon Deimos.

The science and engineering team built a whopping 490 commands to accomplish the most complex robotic arm operations on Mars yet. Opportunity took three mosaics on the area dubbed "Last Chance," using the microscopic imager, creating 128 images in over 200 arm moves. Each "frame" of these mosaics required multiple microscopic images. There are two reasons for this. First, the microscopic imager does not have auto-focus, so the team needed to have Opportunity take and return multiple images at each location at different distances from the rock to get at least one in focus. A second reason is that the team needed Opportunity to take an extra image at a slightly different angle for each frame to create the right conditions to build stereo and computer-generated graphics of the "topography" of the rock area up close.

After about two-and-a-half hours of microscopic imager maneuvers, the robotic arm placed the Mössbauer spectrometer on a location at "Last Chance" called "Makar." Opportunity also used the panoramic camera to watch the rare solar crossing of the sun by the moon Diemos and took images of the sky in coordination with the European Space Agency's orbiter at Mars, Mars Express.

The plan for sol 40, which will end at 9:32 a.m. PST on Friday, March 5 is to continue taking microscopic images of the "Last Chance" area, then drive to a new location dubbed "The Dells."

sol 38, Mar 03, 2004: Opportunity Hits Pay Dirt

On sol 38, which ended at 8:13 a.m. PST on Wednesday, March 3, Opportunity awoke to "Have You Ever Seen the Rain?" by Creedence Clearwater Revival in honor of the confirmation that liquid water once flowed through the rocks at Meridiani Planum.

In the morning of sol 38, Opportunity observed the atmosphere with the panoramic camera and miniature thermal emission spectrometer. Then, the rover turned the miniature thermal emission spectrometer to stare at the ground for science observations. Later, Opportunity took stereo microscopic images and Mössbauer spectrometer readings of the soil target dubbed "Pay Dirt."

In the early afternoon Local Solar Time, Opportunity stowed the rover arm, took a panoramic camera image of "Last Chance," and drove a very short distance of 0.4 meters (16 inches) toward "Last Chance" to prepare for the deployment of the robotic arm.

The proposed plan for sol 39, which will end at 8:52 a.m. PST on Thursday, March 4, is to start the morning by taking images of a rare solar transit of the martian moon, Deimos. The solar transit of Deimos causes a solar eclipse only twice per Mars year (one Mars year equals roughly two Earth years). Later in the sol, Opportunity is scheduled to take a microscopic panorama of the layers in the "Last Chance" rock formation.

sol 37, Mar 02, 2004: Let's Go to 'Last Chance'

On sol 37, Opportunity woke up at 9:35 Local Solar Time to "Let's Go" by the Cars. Opportunity completed the miniature thermal emission spectrometer and panoramic camera surveys of the rock abrasion tool holes at "Guadalupe" and "McKittrick," then drove 4.25 meters (14 feet) to "Last Chance," ending the sol at 7:33 a.m. PST on Tuesday, March 2.

With the moves of a tango dancer, the drive was another intricate study in, and challenge of, driving on a slippery, steep slope.

The rover was directed to: turn right, go forward, turn right, take images of "Last Chance," turn right, go forward, turn left, go forward, turn right, take images of "Big Bend," go straight, turn left and go straight! Due to the challenges of driving and pirouetting on such a steep slope (as steep as 22 degrees) the rover found it difficult to maintain a perfectly straight course, and Opportunity came up shy and right of the "Last Chance" target by about 30 centimeters (about one foot).

The plan for sol 38, which will end at 8:13 a.m. PST on Wednesday, March 3 is to do a short drive again to get within arm's reach of "Last Chance." Once in place, Opportunity will use the science instruments on the end of the robotic arm to analyze "Last Chance."

sol 36, Mar 01, 2004: Moving On

Opportunity woke up to Sting's "Rock Steady" on its 36th sol on Mars, which ended at 6:54 a.m. PST on Monday, March 1. The rover completed an overnight alpha particle X-ray spectrometer measurement on "Guadalupe," retracted its arm, placed the Mössbauer spectrometer on the calibration target and then stowed its arm.

A series of backward drives - away from the "El Capitan" site in the outcrop - were then conducted.

The rover also got in some remote sensing, including miniature thermal emission spectrometer observations and panoramic camera imaging of the holes created by the rock abrasion tool. In addition, the panoramic camera took images of a crater to the east.

The plan for the next sol involves several short drives in the direction of the "Last Chance" target in the "Big Bend" area of the outcrop.

sol 35, Feb 29, 2004: "Guadalupe" Under the Microscope

During its 35th sol on Mars, ending at 6:14 a.m. Sunday, PST, Opportunity manipulated the microscopic imager at the tip of its arm for eight observations of the fine textures of an outcrop-rock target called "Guadalupe." The observations include frames to be used for developing stereo and color views.

Opportunity also used its Mössbauer spectrometer and, after an overnight switch, its alpha particle X-ray spectrometer to assess the composition of the interior material of "Guadalupe" exposed yestersol by a grinding session with the rock abrasion tool.

The panoramic camera up on the rover's mast captured a new view toward the eastern horizon beyond the crater where Opportunity is working, for use in evaluating potential drive directions after the rover leaves the crater.

Jimmy Cliff's "I Can See Clearly Now," was played in the mission support area at JPL as Opportunity's sol 35 wake-up music.

Plans for sol 36, ending at 6:54 a.m. Monday, PST, called for finishing the close-up inspection of "Guadalupe," then backing up enough to give the panoramic camera and miniature emission spectrometer good views of the area where the rock interior has been exposed by grinding.

sol 34, Feb 28, 2004: Scratch and Sniff

Opportunity remains healthy and active. During its 34th sol on Mars, which ended at 5:34 a.m. Saturday, PST, the rover used its rock abrasion tool for the second time. It ground the surface off a patch of rock at a site called "Guadalupe" in the outcrop the rover has been examining. The rover looked at the patch with its microscope both before and after the grinding session. Then it placed its Mössbauer spectrometer against the newly exposed interior material of the rock for a long reading of data that scientists use to identify what iron-containing minerals are present in the target.

Opportunity also used its miniature thermal emission spectrometer during the sol to assess the composition of an outcrop feature dubbed "Shoemaker Wall." It took images of "Guadalupe" with its panoramic camera before and after the use of the rock abrasion tool.

Wake-up music played in the mission support area at JPL for sol 34 was "Dig In," by Lenny Kravitz.

For sol 35, ending at 6:15 a.m. Sunday, PST, plans call for continuing use of tools on the robotic arm to examine the rock interior exposed by the "Guadalupe" grind.

sol 33, Feb 27, 2004: Biting Blueberry Hill

On sol 33, which ended at 4:55 a.m. Friday, February 27, Opportunity reached its second rock abrasion tool target site, and it's ready to take the next bite of Mars.

Opportunity woke up a little late on sol 33 to conserve energy. The wake-up song was 'Blueberry Hill' by Fats Domino, in honor of the hill in front of the rover.

Opportunity took an early afternoon 360-degree panorama and an extra observation of the area to the east with its navigation camera, while the Mössbauer instrument completed the measurements it began on sol 32.

The microscopic imager also took three sets of observations of the hole created by the rock abrasion tool on sol 30. Opportunity later took stereo images of the rock area named "Maya" and took pictures of an area called "Half-Dome." Both the panoramic camera and the miniature thermal emission spectrometer observed the sky.

In between science measurements, Opportunity stowed its instrument arm and drove a 15-centimeter (6-inch) "bump" to reach its next rock abrasion tool target. Final shutdown was at 2:37 Local Solar Time, with a brief wakeup at 4:10 Local Solar Time to transmit data to the Mars Odyssey orbiter as it flew over the rover.

The plan for the weekend is to grind into the upper part of "El Capitan" dubbed "Guadalupe" and to take extensive measurements of the new hole using the microscopic imager and two spectrometers.

sol 32, Feb 26, 2004: New Communications Plan

On sol 32, which ended at 4:15 a.m. Thursday, February 26, Opportunity awoke to "Let It Be" by the Beatles. Opportunity's day was focused on getting a second Mössbauer instrument measurement of the hole created by the rock abrasion tool at the "McKittrick" rock site. The Mössbauer can detect spectral signatures of different iron-bearing minerals.

The data from the first Mössbauer spectrum of "McKittrick" was received on Earth Wednesday afternoon. The alpha proton X-ray spectrometer data from yestersol at this target was retransmitted to Earth again Wednesday to get missing packets of data that were not received during the first data communications relay. Opportunity also snapped pictures of the rock areas named "Maya" and "Jericho" with the panoramic camera and took miniature thermal emission spectrometer measurements of the sky and "El Capitan" throughout the sol.

The amount of power Opportunity is able to generate continues to dwindle due to the decreasing amount of sunlight (energy) reaching the solar panels during the martian seasonal transition to winter. Because of this, the engineers are adjusting the rover's daily communications activities. To minimize power use for communications sessions, engineers began a new "receive only" morning direct-from-earth communication relay. This lower-power communication mode was successful. Opportunity will continue with this approach to maximize the available power for driving and science activities as Mars moves farther away from Earth and the Sun in its elliptical orbit.

In conjunction with the morning communications session change, engineers added a second afternoon Mars Odyssey orbiter relay pass, which uses less power in transmitting data volume than direct-to-Earth communication. This additional Odyssey pass more than compensated for the elimination of the morning direct-to-Earth downlink. Engineers also continue to effectively use rover "naps" throughout the day to maximize energy savings.

The plan for sol 33, which ends at 4:55 a.m. Friday, February 27, is to take a very short trip (10 to 20 centimeters or 4 to 8 inches) towards the next rock abrasion tool target site, "Guadalupe."

sol 31, Feb 25, 2004: Opportunity Gets an Attitude Adjustment

On sol 31, which ended at 3:36 a.m. Wednesday, February 25, Opportunity awoke to "Rock Around the Clock" by Bill Haley and his Comets. At 1:00 a.m. Local Solar Time, Opportunity sent data to Earth via the Mars Global Surveyor orbiter and then sent another whopping 145.6 megabits of data at 3:30 a.m. Local Solar Time via the Mars Odyssey orbiter.

During the morning hours, Opportunity collected data with the alpha particle X-ray spectrometer for five hours and took measurements with its miniature thermal emission spectrometer from inside its newly formed hole that was created on sol 30 by the rock abrasion tool. Later, Opportunity retracted and closed the door of the alpha particle X-ray spectrometer and swapped the Mössbauer spectrometer into the hole made by the abrasion tool for a leisurely 24-hour observation.

Opportunity also updated its "attitude knowledge," which fine-tunes the rover's information about its exact location and position on Mars. Updating the attitude knowledge allows the rover to more accurately point the high gain antenna toward Earth, which increases the communications capabilities. The attitude adjustment also enables scientists and engineers to point instruments onboard Opportunity more precisely at targets of interest, such as particular rocks and patches of soil. To adjust the attitude knowledge, engineers have the rover turn the panoramic camera to the Sun and watch the Sun travel across the sky for 15 minutes. The rover is then smart enough to take the Sun movement data collected from the panoramic camera to calculate its own location in the universe…..on Mars. The rover gathers attitude knowledge errors over time as it drives and uses the robotic arm extensively, but it only needs an attitude adjustment about once a week or after driving long distances.

Around 12:15 pm Local Solar Time, Opportunity went to sleep to recharge its batteries from its strenuous rock abrasion tool activities on sol 30, but reawakened briefly at 4 p.m. Local Solar Time and again in the evening to send data to Earth via additional overflights by the Mars Global Surveyor and Odyssey orbiters.

The plan for sol 32, which ends at 4:15 a.m. Thursday, February 26, is to take another unique set of Mössbauer measurements to look at the rover-created hole in a different spectrum. The goal is to then crawl slightly forward on sol 33 to position Opportunity to use the rock abrasion tool on the upper target of the El Capitan/McKittrick area.

sol 30, Feb 24, 2004: A Beautiful Grind

On sol 30, which ended at 2:56 a.m. Tuesday, February 24, Opportunity performed its first rock abrasion tool operation on a rock target known as 'McKittrick Middle Rat' at the El Capitan site inside the crater. The tool shaved the rock over a period of two hours, grinding into a total depth of about 4 millimeters (.16 inches).

The auspicious day began with the song 'Rock'n Me' by Steve Miller and some miniature thermal emission spectrometer sky surveys and sky stares to study the atmosphere. After completing these activities, Opportunity took a short siesta to recharge its batteries. The rover has been doing a lot of science work at night, and the season on Mars is changing to winter, so the rover has less energy to work with than it did earlier in the mission. The martian days are getting shorter and the sun angle is not allowing either rover to power up the solar panels as much as in the past.

Opportunity woke up from its nap at 11:30 Local Solar Time on Mars to run through the series of commands required to retract the alpha particle X-ray spectrometer and close its doors; take several microscopic images of another nearby rock abrasion tool target called 'Guadalupe;' flip the wrist; take a microscopic image of "McKittrick Middle Rat;" and place the rock abrasion tool on its target to run at 13:00 Local Solar Time.

After the abrasion tool was retracted, a series of microscopic images of the scene were taken, and the alpha particle X-ray spectrometer was successfully placed into the abrasion tool's hole late in the day.

Some additional panoramic camera, miniature thermal emission spectrometer readings, and hazard avoidance camera imagery was completed through the day.

The plan for sol 31, which will end at 3:36 a.m. Wednesday, February 25, is to continue getting long Mössbauer readings of the rock abrasion tool hole and to prepare the tool for more work again on sol 33 or 34.

sol 28, Feb 22, 2004: Busy Microscope at "El Capitan"

On sol 28, which ended at 1:38 a.m. Sunday, PST, Opportunity moved its arm repeatedly to make close-up inspections the "El Capitan" part of the street-curb-sized outcrop in the crater where the rover is working. Opportunity took 46 pictures with its microscope, examining several locations on "El Capitan" at a range of focal distances. It also placed its Mössbauer spectrometer and its alpha particle X-ray spectrometer on the rock target to assess what minerals and what elements are present.

Controllers chose the song "I am a Rock," performed by Paul Simon and Art Garfunkel, as Opportunity's sol 28 wake-up music. The sol's activities included observations by the miniature thermal emission spectrometer and the panoramic camera, as well as the use of the tools on the arm.

The arm's complex maneuvers totaled 25 minutes of actual arm movement. Rover planners' success in accomplishing them drew a round of applause in the Mission Support Area at JPL during the afternoon downlink from Mars.

During the martian night, early on sol 29, Opportunity woke up and moved its arm again to switch from the Mössbauer spectrometer to the alpha particle X-ray spectrometer. Additional close-up inspections are planned for later in sol 29, which ends at 2:17 a.m. Monday. Plans for sol 30 feature the use of the rock abrasion tool to grind through the surface at one target on "El Capitan."

sol 27, Feb 21, 2004: Supersized Science

On sol 27, ending 12:57 a.m. Saturday, PST, Opportunity successfully "supersized" the measurements of the "El Capitan" area with the panoramic camera, miniature thermal emission spectrometer, and microscopic imager. The rover team is analyzing "super resolution" and "super spectral" observations from the science instruments and currently locating the best spots to place the rock abrasion tool.

Opportunity also drove 33 centimeters (13 inches) closer to "El Capitan" to better poise the robotic arm for use of the rock abrasion tool sometime over the next four or five sols, which will be the first use of the rock abrasion tool by Opportunity.

On sol 28, ending at 1:38 a.m. Sunday, PST, plans call for Opportunity to take extensive microscopic images of "El Capitan," which is a rich science target because it has multiple layers and varied textures on the upper and lower areas of the rocks, implying multiple changes in the geologic history of this area.

The Mars Odyssey orbiter is scheduled to fly over Opportunity during sol 28 with increased data communications capabilities to 256 kilobits per second, which is five times the speed of normal home computer modems.

sol 26, Feb 20, 2004: Enter the Rock Abrasion Tool

On sol 26, which ended at 12:18 a.m. Friday, February 19, PST, Opportunity successfully obtained one final Mössbauer spectrometer reading of the trench, stowed the rover arm, and drove 15 meters (50 feet) to the "El Capitan" area. The drive was Opportunity's longest yet and required the vehicle and planners to skirt the trench and avoid the lander.

The plan for sol 27, which will end at 12:57 a.m. Saturday, PST, is to first "supersize" the measurements of the "El Capitan" area with the panoramic camera, miniature thermal emission spectrometer, and microscopic imager. The mineralogy and geology teams have requested a minimum of three hours worth of "super resolution" and "super spectral" observations for the science instruments to get the most comprehensive coverage of this interesting site, which has varying textures and layers of dirt and rock.

After a short siesta in the early afternoon, Opportunity will drive 30 centimeters (12 inches) to sneak a bit closer to the rocks in "El Capitan" to get ready for the rock abrasion tool to do its work. After the drive, the Opportunity team plans to take a picture of the martian sky with the panoramic camera and miniature thermal emission spectrometer. If time permits, Opportunity will attempt to aim its cameras toward the heat shield in the far distance.

Over the weekend, Opportunity plans to find the perfect spot to use the abrasion tool and set it loose to grind away on "El Capitan," which will be the first use of the rock abrasion tool by Opportunity.

sol 25, Feb 19, 2004: Stutter Stepping to El Capitan

On sol 25, which ended at 11:38 p.m. Wednesday, February 18, PST, Opportunity used the microscopic imager and alpha particle x-ray spectrometer to study the chemical makeup of the wall and floor area within the rover-made trench. Due to time constraints, Opportunity was unable to take a picture of the heat shield in the distance.

Sol 25's wake-up music was "Fascination" by Human League.

The plan for sol 26, which will end at 12:18 a.m. Friday, PST, is to back away from the trench, obtain one grand finale Mössbauer spectrometer reading of the trench, pick up and stow the rover arm, then turn and drive 9 meters (30 feet) to the El Capitan area. Opportunity will make a few intentional "stutter steps" on its way to El Capitan, stopping to take a few front hazard avoidance camera images and navigation camera images to plan for final approach and robotic arm activities.

Opportunity will stop a couple of meters (about 6 or 7 feet) short of El Capitan to take images with its panoramic camera and gather science measurements with its miniature thermal emission spectrometer. On sol 27, Opportunity will make a short, closer approach to El Capitan to poise itself to use the rock abrasion tool and other instruments on the rover arm.

sol 24, Feb 18, 2004: Peering into the Hole

On sol 24, which ended at 10:59 p.m. Tuesday, PST, Opportunity used science instruments on its robotic arm to examine the hole it dug with its right front wheel on sol 23. The trench is about 50 centimeters (20 inches) long by 20 centimeters (8 inches) wide by 10 centimeters (4 inches) deep.

Sol 24's wake-up music was "Trench Town Rock" by Bob Marley.

The plan for sol 25, which will end at 11:38 p.m. Wednesday, PST, is to continue examining the walls and floor of the trench for clues about the history of Mars. Opportunity will also peek at its right front wheel with the panoramic camera to see what materials got stuck on the wheel from the trenching activity. Then, Opportunity will use the panoramic camera high on the rover's mast to check out a former piece of itself -- the heat shield, which is sitting off in the distance. The heat shield protected the rover during cruise and during descent through the atmosphere on Jan. 4, 2004, PST.

sol 23, Feb 17, 2004: Can You Dig It?

The Opportunity rover successfully dug an 8-centimeter (3.1 inch) trench on Mars using its right front “paw” or wheel on sol 23, which will end at 10:19 p.m. Monday, PST. Sol 23's wake-up music was “Spinning Wheel” by Blood, Sweat, and Tears, in honor of the right front wheel.

Opportunity also made observations with the navigation camera to help prepare for the drive to a target of interest within the outcrop named “El Capitan” later this week.

The plan for sol 24, which will end at 10:59 p.m. Tuesday, PST, is to thoroughly examine the freshly exposed layers of dirt and ground inside the rover-made hole. Opportunity will use its microscopic imager, Mössbauer spectrometer, and alpha particle X-ray spectrometer to take parallel science measurements and compare with those with measurements made on sol 22 during pre-trench activities.

sol 22, Feb 16, 2004: Check Before Digging

Opportunity spent much of sol 22, which ended at 9:39 p.m. Sunday, PST, making a thorough "before" examination of the spot selected for digging a ditch the next sol.

Also, Opportunity completed upward-looking observations before, during and after Mars Global Surveyor flew overhead looking down. Opportunity and Global Surveyor have similar infrared sensing instruments: the miniature thermal emission spectrometer on the rover and the (full-size) thermal emission spectrometer on the orbiter. Coordinated observations of looking up through the atmosphere with one while looking down through the atmosphere with the other were designed to provide a more complete atmospheric profile than either could do alone.

Sol 22's wake-up music was "Invisible Touch" by Genesis. In preparation for digging, Opportunity examined the trenching site with its microscopic imager, its Mössbauer spectrometer and, overnight, its alpha particle X-ray spectrometer.

The plan for sol 23, which will end at 10:19 p.m. Monday, PST, is to dig a trench with alternating forward and backward spinning of Opportunity's right front wheel in order to see what's below the surface. Inspections of the resulting hole are planned for sol 24 and the morning of sol 25.

sol 21, Feb 15, 2004: Dig this Place

Opportunity completed its longest drive so far -- about 9 meters or 30 feet -- during its 21st sol on Mars, which ended at 9 p.m. Saturday, PST. The rover finished the drive with its first U-turn, arriving at a location selected for the mission's first trenching operation. Plans call for examining the hematite-rich surface of this location, called "Hematite Slope," during sol 22, then spinning one wheel to dig below the surface on sol 23.

Controllers at JPL chose "Send Me on My Way," by Rusted Root, and "Desert Drive," by Tangerine Dream, as Opportunity's wake-up music for sol 21. The rover worked a long day. It awoke earlier than usual for an early morning observation with its panoramic camera. It made additional observations from its new location just before finishing the drive, and again after finishing the last bit of the drive. Then it was woken after dark to make the mission's first nighttime observations with its infrared sensor, the miniature thermal emission spectrometer.

sol 20, Feb 14, 2004: Rover Says "No"

During Opportunity's 20th sol on Mars, which ended at 8:20 p.m. Friday, PST, the rover told mission controllers "no." Opportunity received commands in the morning to use the microscopic imager at the end of its arm, but the onboard computer judged the requested arm movement to be unacceptable and refused the command.

This was the proper precaution for the rover to take. The arm maneuver had been tested with a simulation at JPL, and engineers subsequently worked on a solution to make the ground testing more accurately predict the rover computer's response to the particular arm-movement conditions involved.

However, with the arm left extended, rather than stowed, after the arm-movement command was refused, the rover also could not make the drive that had been planned for the sol. That drive, to a site selected for soil examination and trenching, was postponed until sol 21, which ends at 9:00 p.m. Saturday, PST.

Observations by the panoramic camera and miniature thermal emission spectrometer were completed successfully on sol 20. The sol's wake-up music was "I Like Dirt," by the Red Hot Chili Peppers, and "Pioneers of Mars," by Karen Linsley and Lloyd Landa.

sol 19, Feb 12, 2004: Intending to Trench

During its 19th sol on Mars, which ends at 7:41 p.m. Thursday, PST, Opportunity climbed to Waypoint Charlie, where it will complete its initial survey of the outcrop nicknamed "Opportunity Ledge."

The flight team at JPL chose 'Here I Go Again' by Whitesnake as Opportunity's wake-up music.

The plan for sol 20, which will end at 8:20 p.m. Friday, PST, is to do a "touch and go," meaning Opportunity will touch the soil with its instrument arm around the outpost area Charlie, then stow the arm and drive. It will head for an area of soil that the rover's miniature thermal emission spectrometer indicates is rich in hematite. Over the following few sols, engineers intend to use one of Opportunity's wheels to spin into the soil and "trench" a shallow hole so scientists can check what's below the surface early next week. Knowing more about the hematite distribution on Mars may help scientists characterize the past environment and determine whether that environment provided favorable conditions for life.

Scientists and engineers will pore over the data collected along Opportunity Ledge this week to target a return trip to the most interesting science locations along the outcrop later next week.

sol 18, Feb 12, 2004: Extended Tour

Opportunity had a couple of little hiccups on sol 18, February 11, which ends at 7:01 p.m. Wednesday, PST. The wrist on the real rover arm would not point as far vertically as the engineering rover's wrist did on Earth during a model test the night before. Because of this, the arm on Mars did not stow, and the rover did not move on to waypoint Charlie. The rover also automatically stopped use of the mast due to the fact that it believed a requested pointing position was in an area beyond its limits. Engineers solved both problems on sol 18. All systems are go for Opportunity to complete the tour of the outcrop by heading to outpost Charlie on sol 19, Thursday, February 12.

sol 17, Feb 11, 2004: Three-Day Tour

On its 17th sol on Mars, which ended at 6:21 p.m. Tuesday, PST, Opportunity completed its study of the target area named Bravo. Opportunity is on a three-day tour of the outcrop, taking pictures and measurements to build what geologists call a "base map," which will help them decide what specific spots they want to target for more thorough investigation with their science instruments.

sol 16, Feb 09, 2004: Slip Sliding Away

Opportunity appears to have experienced slips during 50 percent of a drive on sol 15, so for sol 16, engineers played a lighthearted wake-up call: Paul Simon's "Slip Sliding Away." Regardless of the loose soil, Opportunity made it across 4 meters (12 feet) today and is positioned to continue observing parts of the outcrop up close tomorrow. In coming sols, Opportunity will "shoot and scoot," meaning the rover will shoot pictures of the terrain and acquire new scientific measurements of the rocks, then scoot up, down, and across the inside of the crater.

sol 15, Feb 08, 2004: Opportunity Gets a Closer Look at the Outcrop

On Opportunity's 15th sol on Mars which ends at 5:02 p.m. Sunday, PST, the rover took microscopic images of a rock in the outcrop and nearby soil. The rock is called Stone Mountain (formerly called "Snout") and the target area for the microscope is called Robert E. The day's activities also include examination of Robert E with the alpha particle X-ray spectrometer and the Mössbauer spectrometer. Opportunity's panoramic camera and navigation camera were used to get pictures of the outcrop from the rover's current position.

In the coming sols, the plan is to move along the outcrop to examine other points along it.

sol 14, Feb 07, 2004: Opportunity Succeeds with First "Touch and Go"

Opportunity performed her first "touch and go" maneuver on the rover's 14th sol on Mars, which ended at 4:23 p.m. Saturday, PST. The activity included deploying the arm, taking microscopic images of the soil in front of the rover, re-stowing the arm and finishing its drive to Stone Mountain.

The panoramic camera and miniature thermal emission spectrometer instruments were used to make observations both before and after the "touch and go" sequence.

sol 13, Feb 06, 2004: Driving to "Snout"

On Opportunity's 13th sol on Mars, which ended at 3:43 p.m. Friday, the Mars Rover Opportunity was awakened by engineers at JPL playing the Beach Boys song, “Little Honda,” with lyrics about various gear shifts. Images from the rover's rear hazard identification camera indicated that some fine-tuning was needed for a planned 1.5 meter drive to a target called "Snout" at the northeastern end of a rock outcrop in the inner wall of the landing-site crater. Adjustments were made, and new commands were sent to Opportunity. The rover is now tilted at nearly 13 degrees, pointing uphill. On its 14th sol, Opportunity will take microscopic images of the soil, then stow its arm and complete the short drive to Snout.

sol 12, Feb 05, 2004: Opportunity Passes Her Driver's Test!

"Just like you would want to perfect your parallel parking abilities before trying to make it to an appointment on a tight schedule in a big city, engineers tested Opportunity's ability to maneuver on Mars on sol 12, which ended Thursday. She passed with flying colors!" reported Mark Powell, Science Downlink Coordinator. Engineers commanded Opportunity to do a little dance, making three arcs -- two to the left and one to the right. Opportunity then did a 30-degree turn in place where you can see the most radical track curves in the image. For its grand finale drive, Opportunity proceeded straight for 1.8 meters (5.9 feet), completing a total traverse of 3.54 meters (10.6 feet).

The plan for sol 13 is to do a 1.1 meter (3.6 feet) drive straight toward the outcrop and take some more pancam and mini-TES instrument images of the outcrop area.

Scientists have decided to wait to trench for a few days until they can drive to an area with a higher concentration of hematite.

Watch a related video: Rover Navigation 101: Autonomous Rover Navigation

sol 11, Feb 04, 2004: Opportunity to "Stow and Go"

Opportunity woke up on sol 11 to Duran Duran's "Please Tell Me Now" and successfully completed a 24-hour observation of the soil with the Mössbauer instrument at "Tarmac." The arm rotated to place the APXS instrument on the same patch of soil and observations with that instrument are underway. Scientists are busy trying to determine what geologic processes formed the spherical grains seen through the eyes of the Microscopic Imager. The plan for sol 12 is to stow the arm and go for a 3 meter (9 foot) drive to the right of the outcrop where they hope to trench on sol 14.