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Daily Update - 11/23/04
Finishing Up in 'Endurance'
Opportunity Status for sol 285-291
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.
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.
Daily Update - 11/18/04
Three hundred sols and counting!
Spirit Status for sol 292-305
Spirit remains in excellent health and has survived more than 300 martian days on the red planet.
With the Sun still relatively low on the horizon in the early spring season on Mars, rover drivers are forced to seek driving routes that keep the rover and its solar panels tilted northward for energy reasons. That constraint, plus the rocky terrain, will challenge rover drivers in the coming weeks.
Over the last few weeks, the electrical "brakes" on Spirit's right-front and left-rear steering actuators (motors) apparently failed to disengage during drive attempts. The most likely cause of this anomaly is the buildup of insulating material on the electronic relay contacts that indicate that the brakes are disengaged. To help ensure successful future drives, engineers decided to permanently ignore the "brake-disengaged" indicator. If their theory is correct, the brake will actually be disengaged despite the "failure-to-disengage" indication. If they are wrong, a fuse in the brake circuit will safely blow when they attempt to move the steering actuators. In either case, driving operations will not be adversely affected.
A few sols ago, Spirit's engineering team discovered an electric-circuit grounding problem between the rover chassis and the power bus return. This incident occurred at the exact time the Spirit team was performing an inspection of the instrument deployment device, or robotic arm. The inspection sequence commanded one of the arm joints to a position beyond where it had previously been. That particular joint, joint number 5, is the rover arm turret, which rotates the four rover arm instruments into position. This coincidence may indicate that the joint 5 move somehow created the electrical short; it could also just be coincidence. The mechanical team has not found any reason to suspect a failure in the joint 5 cabling. To be safe, the engineering team has constrained the use of joint 5 on Spirit and Opportunity to avoid this extreme position. The constraint is not expected to significantly impact normal operations. The apparent short may also be the result of a failed measurement circuit. The short, if real, has no immediate effect on the rover, but does remove one layer of protection against effects of future shorts should they occur.
Between sols 292 and 298, Spirit completed its studies of the rock called "Uchben" and drove west about 2 meters (almost 7 feet) to a rock called "Lutefisk."
Between sols 299-303, Spirit finished its investigation of Lutefisk. Lutefisk, a rock with some interesting nodules, lies a site roughly 40 meters (131 feet) above and 2700 meters (1.67 miles) away from Spirit's landing site on the Gusev plain. Team members should know more about the chemistry of Lutefisk and its nodules when they receive results from the alpha particle X-ray spectrometer and Moessbauer spectrometer.
For coming sols, Spirit is in an exploration and discovery mode, continuing the rover's ascent towards "Machu Picchu" in the Columbia Hills. Spirit will stop at interesting rocks along the way.
Daily Update - 11/8/04
Journey toward 'Burns Cliff' Continues
Opportunity Status for sol 265-271
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.
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).
Daily Update - 11/2/04
The engineering team is keeping Spirit moving.
Spirit Status for sol 285-291
Spirit employed its full instrument suite on Sols 285 through 291 to study "Uchben," an interesting rock encountered on the way into the Colombia Hills. The engineering team continued to diagnose and study work-arounds for a problem with the steering brake relay. An anomaly related to electric-circuit grounding came to light during this period and is also being studied by the engineering team. Neither problem has hampered Spirit's daily operations. Spirit is otherwise healthy and ready to continue its trek further into the Columbia Hills.
The engineering team has been studying recovery options for steering brakes that apparently failed to release on two previous sols. On Spirit and Opportunity, dynamic braking is accomplished using a relay switch to place a short across the motor windings of an actuator that is not being used. If that actuator starts to move unexpectedly, the motor acts as a generator and the short provides an electrical load that slows the motor down. The same principle is used to generate electrical energy for hybrid cars when the brakes are applied. Thanks to forethought on the part of the rover design team, it is possible to disable the dynamic braking function using ground commands. Those commands deliberately and safely blow a fuse that is in line with the brake relay circuit. The absence of the braking function for the steering actuators in question (right front and left rear steering) will not affect the accuracy of our drives or the rover's safety when we are stopped. Until this problem is fully resolved, we will continue to drive with the right front and left rear steering actuators disabled, using tank-like steering.
Regarding the grounding anomaly, the engineering team regularly receives telemetry that tells them the voltage difference between "rover chassis" and "power bus return". The rover chassis is the conductive structure of the rover akin to an automobile chassis. The power bus return is a collection of wires designed to carry current back to the rover power source (battery or solar array). Ideally, all rover current flows in a loop from the battery or solar array, returning by way of the power bus return wires. No current is supposed to flow in the rover chassis though, in reality, some leakage paths exist that allow current to return by way of the rover chassis. When these currents flow across the circuitry that separates the rover chassis and power bus return, they create a small voltage that is measured and reported in telemetry. Until sol 287, the reported voltage was typically in the range of 0.6 to 0.8 volts. On Sol 287, that voltage dropped to 0 volts. The 0 volt reading could indicate that there is a problem with the measurement circuit, or it could indicate that power bus return and rover chassis are now shorted (making direct contact). The rover can operate when the chassis and power bus return are shorted together or when they are separated from each other by electrical circuitry. In the shorted case, however, the rover is more susceptible to permanent damage if another short occurs somewhere else. Engineers are looking at when the short indication occurred for clues about its possible root cause.
On 285, Spirit continued systematic atmospheric observations on this and all sols during this period using the miniature thermal emission spectrometer and panoramic camera. The rock abrasion tool was employed to drill a shallow hole at "Koolik," a location on the rock Uchben.
On sol 286, Spirit took microscopic images of the Koolik rock abrasion tool hole and placed the alpha particle X-ray spectrometer on Koolik for an overnight observation. The alpha particle X-ray spectrometer works best when cold.
During sols 287 through 289, Spirit placed the Moessbauer spectrometer on the Koolik rock abrasion tool hole for several observations over the Earth weekend. The Moessbauer spectrometer radiation source has weakened significantly since landing, through normal decay, so longer integration times are now required to get acceptable data.
On sol 290, Spirit performed tests to diagnose the root cause of the indication that steering brakes had failed to release, but the tests were inconclusive. Spirit then used the rock abrasion tool to brush "Chiikbes," another location on Uchben. Spirit placed the alpha particle X-ray spectrometer on Chiikbes for an overnight observation.
On sol 291, which ended on Oct. 28, Spirit took microscopic images of the Chiikbes brush site, and then placed the Moessbauer spectrometer on Koolik to improve the data from that location.