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Daily Update - 8/31/04
Spirit has been etching into 'Ebenezer'
Spirit Status for sol 219-231

During sols 219 through 223, Spirit completed science observations at the "Clovis" rock outcrop. So Spirit packed up and slowly moved on. Winter is approaching and temperatures continue to drop. Power is always a major concern as available energy fluctuates between 300 and 400 watt-hours per sol, but Spirit continues the quest, climbing ever higher into the Columbia Hills. Spirit has climbed more than 13 meters (43 feet) in elevation from Hank's Hollow, at the base of Columbia Hills, but currently is at an elevation of 37 meters (121 feet) above its landing site on the plains of Gusev Crater!

On sol 224, operators became concerned that Spirit's batteries might be entering a very low state of charge, so Spirit shut down to charge the batteries.

Sol 225 was truly a mega-activity sol. Spirit awoke at 11:20 a.m., Gusev local solar time and stayed awake well past the afternoon communication session with NASA's Mars Odyssey orbiter without taking a nap. Spirit hasn't done that in a long time. The rover extended its arm and used its rock abrasion tool to brush seven circular patches on Clovis. After the first five brushings, the arm was moved out of the way and an image was taken of the circles. These five brushing circles resemble the Olympic rings.

After completing the brushing, Spirit performed a 30-minute reading with its alpha particle X-ray spectrometer, imaged the seven rings using its microscopic imager, stowed its arm and drove one meter (three feet) backward, farther off of the Clovis outcrop. Spirit's day was far from over. The rover performed post-drive observations with its navigation camera, observations with its miniature thermal emission spectrometer concurrent with the afternoon Odyssey pass, and panoramic camera observations before shutting down. Another gold medal performance for Spirit!

Total odometry after sol 225 was 3,605 meters (2.24 miles), a Mars record.

From sols 226-229, Spirit stopped at a rock dubbed "Ebenezer" for several sols of intense science. Ebenezer is roughly 8 meters (26 feet) from Clovis.

While at Ebenezer, Spirit was facing south of east, with its nose pitched up 21 degrees. This orientation was very favorable from a power perspective since the sun tracks to the north. Spirit's daily solar energy input increased about 10 percent as a result. Spirit also had a great view of the Gusev plain from this location.

On Sol 230, Spirit used the rock abrasion tool to brush a target on Ebenezer and took an overnight alpha particle X-ray spectrometer reading on the brushed area. On Sol 231, which ended on Aug. 27, the abrasion tool ground for two hours into the same spot it had brushed. An alpha particle X-ray spectrometer reading in the resulting hole began the morning of Sol 232.

Over the next few sols, the plan is for Spirit to drive to its next target, which is yet to be determined.

Daily Update - 8/30/04
Trying Traverses
Opportunity Status for sol 204-208

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.

Daily Update - 8/24/04
Opportunity Team Decides Against Dunes
Opportunity Status for sol 200-203

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.

Daily Update - 8/23/04
Spirit probes deeper into 'Clovis' outcrop.
Spirit Status for sol 209-218

Spirit continued work over the past nine sols at a rock called "Clovis." The rover used its rock abrasion tool, microscopic imager, alpha particle X-ray spectrometer, and Moessbauer spectrometer to probe deeper into the history of this rock. Clovis is the most altered rock encountered by Spirit to date. It is part of a rock outcrop located on the "West Spur" of the "Columbia Hills," roughly 55 meters (180 feet) higher than Spirit's landing site about 3 kilometers (2 miles) away.

Spirit also successfully performed a couple of communications tests with the European Space Agency's Mars Express orbiter last week. The tests demonstrated the two spacecraft's ability to work together to transmit data collected by the rovers to Earth via the Mars Express communications relay. NASA's Mars Odyssey and Mars Global Surveyor orbiters also have this capability. More than 85 percent of the data from the rovers has been transmitted to Earth via the Odyssey orbiter.

On sol 209, Spirit experienced an unexpected reboot of the flight software. This incident was not a threat to the spacecraft. It is a known bug in the system that the rover team is working around.

On sol 210, Spirit drove up steep terrain to reach the exact spot on Clovis for work with the science instruments at the end of the robotic arm.

Between sols 211 and 216, Spirit completed an alpha particle X-ray spectrometer reading of a spot on Clovis called "Plano," which had been brushed off using the rock abrasion tool. Spirit then placed the rock abrasion tool on Plano again and drilled for 2.5 hours, creating a hole 8.9 millimeters (0.4 inch) deep, which is a new record! Spirit also continued a campaign to capture a color 360-degree panoramic camera image from this location. Spirit captured additional segments of the panorama on sols 217 and 218.

On sol 217, Spirit took microscopic images of the rock abrasion tool hole, and then placed the alpha particle X-ray spectrometer in the hole for an early morning observation.

On sol 218, Spirit placed the Moessbauer spectrometer in the rock abrasion tool hole and started a 48-hour observation. This is a longer than normal integration time, with a goal of resolving in more detail the makeup of this highly altered rock.

Spirit remains in excellent health.

Daily Update - 8/18/04
Power Boost for Opportunity
Opportunity Status for sol 196-199

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 Moessbauer 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 Moessbauer 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.

Daily Update - 8/16/04
Abrading 'Axel Heiberg'
Opportunity Status for sol 192-195

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 Moessbauer 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.

Daily Update - 8/12/04
Aiming for 'Axel Heiberg'
Opportunity Status for sol 190-191

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.

Daily Update - 8/11/04
Spirit Investigating 'Clovis' Outcrop
Spirit Status for sol 205-208

Over the last few sols, Spirit struggled mightily to reach a rock outcrop called "Clovis," overcoming the challenge of rough, steep terrain and subsequent backsliding. The site is near the crest of the "West Spur" of "Columbia Hills."

On sol 205, Spirit attempted to reach Clovis by climbing out of the sandy hollow in which it was sitting. Unfortunately, on a slope of more than 20 degrees, slippage caused Spirit to dance around the outcrop. The drive was finally cut off by a time-of-day limit on rover mobility.

The plan for sol 206 was designed to accommodate up to a 50 percent slip and still reach the outcrop target. However, due to challenging terrain near Clovis, Spirit again did not end up exactly where scientists and engineers wanted it to go. For part of its traverse, Spirit slipped about 125 percent, actually losing ground in its attempt to move uphill.

Late in the sol, internal software experienced a timing problem in which two instrument-related commands were given at nearly the same time, temporarily precluding further operation of the miniature thermal emission spectrometer and camera mast on Spirit.

Sol 207 became a recovery sol. While the timing issue was being analyzed, engineers decided not to use the mast, panoramic cameras, navigation cameras, Moessbauer spectrometer, alpha particle X-ray spectrometer, or the miniature thermal emission spectrometer. On the bright side, since the problem did not affect communications, a communications experiment with the European Space Agency's Mars Express orbiter was successfully conducted in the early morning hours of sol 208.

By sol 208, which ended on Aug. 3, Pacific Time, the mast had been declared usable. Operators commanded Spirit to drive 7.5 meters (25.6 feet) to Clovis, using a route avoiding the steepest terrain that had created problems for the rover in earlier sols.

Spirit is examining Clovis. This outcrop will likely be the subject of Spirit's most intensive investigation to date.

Daily Update - 8/9/04
Opportunity Turns to Talk to Odyssey
Opportunity Status for sol 188-189

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.

Daily Update - 8/6/04
'Tuktoyuktuk's' Turn
Opportunity Status for sol 186-187

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 Moessbauer spectrometer and acquired a 7-hour Moessbauer 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.

Daily Update - 8/3/04
Opportunity Sees Double.
Opportunity Status for sol 181-185

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 Moessbauer 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 Moessbauer 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.

Daily Update - 8/3/04
The Quest for the Top of the Hills Continues
Spirit Status for sol 201-204

Mars has seasons like the Earth does, but the seasons are twice as long due to Mars' larger orbit around the Sun. Right now, Mars is approaching northern summer. That also means that it's approaching southern martian winter at the same time. So Spirit is headed for winter, being 14 degrees south of the equator. Because martian winter is setting in, solar array energy continues to be a concern for Spirit. If Spirit parks with a northerly tilt, the rover will see between 350 and 380 watt-hours of energy, but if Spirit stops on flat ground or with a southerly tilt, solar energy is as low as 280 watt-hours. So engineers make a concerted effort to find the north-facing islands along Spirit's path.

On Sol 201, Spirit was commanded to drive 98 feet (30 meters) across terrain that was pretty steep. Spirit accomplished 8.2 feet (2.5 meters) then stopped due to an excessive tilt angle of 25.6 degrees. Engineers had set the maximum tilt angle limit at 25 degrees. Spirit did complete pre-drive science observations and post-drive imaging.

On sol 202, Spirit repeated the drive plan from sol 201 with the maximum tilt angle set to 32 degrees. This time the rover completed the drive as planned, traveling 83.6 feet (25.5) meters up the hill. Spirit then performed post-drive imaging.

On sol 203, scientists' hope was to find rock outcropping in this location, but none were found. So the decision was made to continue the drive up the hill to find a better rock outcrop. Spirit performed another six-wheel, 62-foot (19-meter) drive. This drive was completed successfully; however, at the end of the drive, Spirit drove into a small hollow. As a result, Spirit was pitched 15 degrees toward the southwest, and ended up with a southerly tilt.

Planning for sol 204 was very exciting due to the late downlink of information from sol 203. Very late in the planning cycle, available power on sol 204 was reduced from 370 watt-hours to 288 watt-hours. Ouch! Pre-drive observations were cut back to 17 minutes, during which the motors were heated for driving. Spirit drove only 0.82 feet (0.25 meters). Because the drive was so short, the power situation is not as bad as it could have been.

Total odometry after sol 204, which ended on July 30, is 2.21 miles (3,565.57 meters). Total elevation above the plains of Gusev Crater is estimated to be 30 feet (9 meters).

Over the next few sols, scientists and engineers hope to make it to "Clovis" rock outcrop and to recharge the batteries.

Daily Update - 8/2/04
Opportunity Sees Double.
Opportunity Status for sol 177-180

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 Moessbauer spectrometer reading of the deepened hole.

On sol 179 the rover completed the Moessbauer 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.

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