Spirit News Archive - Updates on the efforts to free the Spirit rover.
The rover team has begun driving Spirit backward as next technique for attempting to extricate the rover from the sand trap where it is embedded. The first two backward drives produced about 6.5 centimeters (2.6 inches) of horizontal motion and lifted the rover slightly.
Spirit performed the first backwards drive (toward the south) on Sol 2045 (Jan. 14, 2010). Until then, all drives since extrication attempts began two months earlier had been with forward driving, with Spirit facing northward. The rover first entered its present location driving backward in April 2009. The backward driving in recent days includes the additional technique of steering the wheels side-to-side before performing each step. The hypothesis for the wheel steering is two-fold. The process clears out material in front of the wheel and allows material to slough off the face of the wheel trench and provide traction under the wheel. Also, the flat surface of the wheel's side "kicks" against loose material, like a swimmer's frog kick or breast stroke, to provide some push. This Sol 2045 drive included enough wheel rotations to move the rover backward about 30 meters (98 feet) in six steps of 5 meters (16 feet) each, if the rover were in a situation with good traction. However, as Spirit is in a sand trap, the drive moved the rover backward a total of just over 3 centimeters (1.2 inches) and raised it in altitude just over 1 centimeter (0.4 inch). This is the first time the rover has climbed since extrication attempts began.
Northerly tilt also improved by just over a degree. The explanation here is that the rover's rear wheels are climbing, raising the back of the rover. Images from the rear hazard avoidance camera confirm this. A tilt toward the north would be favorable for energy production in the coming Martian winter, as it would gain more sunshine on the solar array.
A second backward drive was commanded on Sol 2047 (Jan. 16, 2010). It was also six steps of 5 meters backward with the steering "frog kicks." The rover moved about 3.5 centimeters (1.4 inches) backward and climbed 0.3 centimeters (0.1 inch). However, this time the northerly tilt deteriorated by over a degree, undoing the prior drive's improvement. The explanation here is that the rover yawed counterclockwise, swinging the angled solar arrays away from north. But the rear wheels continued to climb, suggesting that the middle wheels are gaining traction. The rover is now about 3.5 centimeters (1.4 inches) south of the point where it started extrication two months ago, meaning the backward driving has already covered all of the distance achieved with forward driving and then some. Spirit is still down about 3 centimeters (1.2 inches) in altitude since extrication started. It is important to remember that the right-rear wheel is still non-functional, along with the right-front wheel.
On Sol 2050 (Jan. 19, 2010), Spirit was commanded to drive further backwards. Partway through the drive, the rover's left middle wheel stalled. Activities planned for coming sols include getting more diagnostic information about that wheel stall. Even with four working wheels, Spirit would have a very difficult path to extrication. And the rover needs a much better northerly tilt to assure winter survival.
As for other techniques to consider for extrication, the rover team has examined the two options that would use the robotic arm: pushing with it and re-sculpting the terrain by the left-front wheel. The assessment of pushing with the arm reveals that only about 30 newtons of lateral force could be achieved, while a minimum of several hundreds of newtons would be needed to move the rover. Further, such a technique risks damaging the arm and preventing its use for high-priority science from a stationary rover. The other technique of re-sculpting the terrain and perhaps pushing a rock in front of or behind the left-front wheel is also assessed to be of little to no help and, again, risks the arm. There is also a large risk of accidentally pushing the rock into the open wheel and jamming.
The list of remaining maneuvers being considered for extricating Spirit is becoming shorter. Results are being analyzed Wednesday, Jan. 13, from a drive on Sol 2143 (Jan. 12, 2010) using intentionally very slow rotation of the wheels. Earlier drives in the past two weeks using wheel wiggles and slow wheel rotation produced only negligible progress toward extricating Spirit.
The right-front wheel has not rotated usefully since Sol 2117 (Dec. 16, 2009). With the right-rear wheel also inoperable since Sol 2099 (Nov. 28, 2009), Spirit now drives with only four wheels.
Pending results of the latest drive, the rover team is developing plans for their final few attempts, such as driving backwards and using Spirit's robotic arm to sculpt the ground directly in front of the left-front wheel, the only working wheel the arm can reach. Such activities may take several sols to implement, but time is getting short as winter approaches and the team needs to focus on Spirit's winter survival.
The amount of energy that Spirit has each day is declining as autumn days shorten on southern Mars. If NASA does determine that the rover will not be able to get away from its current location, some maneuvers to improve the tilt toward the winter sun might be attempted.
Spirit's drive on Sol 2120 (Dec. 19, 2009) included commands for using all six wheels. However, the right-front wheel rotated less than 2 degrees and the right-rear wheel did not rotate at all. The other four wheels completed enough rotations to drive about 10 meters (33 feet), but produced no measurable forward motion by the rover.
The rover team plans to command further driving this week while continuing to assess the possibility of getting more motion from the right-front wheel.
Spirit's right-front wheel, which had stopped operating in March 2006, revolved with apparently normal motion during the first three of four driving segments on Sol 2117 (Wednesday, Dec. 16) but stopped early in the fourth segment of the drive.
The rover's right-rear wheel, which stalled nearly three weeks ago, remained immobile during the entire Sol 2117 drive. The other four wheels all drove forward in this part of the continuing attempt to extricate Spirit from the sand trap where it is embedded. The sol's total commanded motion was 10 meters (33 feet) worth of wheel rotations. The resulting movement of the rover was about 2 millimeters (0.08 inch) forward and 4 millimeters (0.16 inch) downward. That ratio of forward to downward is well below what would be necessary over longer distance for extrication. Part of the downward motion on Sol 2117 resulted from the right-front wheel digging in as it rotated about 10 times.
Engineers are analyzing results from the Sol 2117 drive and from electrical tests conducted prior to the drive. Movement of the right-front wheel for about 3.5 minutes was a surprise, despite an indication from an electrical-resistance test on Sol 2113 (Saturday, Dec. 12) that some motion might be possible by the long-disused wheel. It is not clear whether the wheel will work again, since it stopped during the final drive segment. It is also not clear whether extrication from the sand trap would be possible even with an operable right-front wheel.
The drive conducted on Sol 2117 had been planned for one sol earlier, but was delayed after analysis of the Sol 2113 test led to discovery of a new electrical issue on Spirit. Engineers learned that a persistent voltage now exists between the rover electric ground and the rover chassis where no voltage should exist. This condition might be related to problems with the right-rear wheel.
Spirit ran diagnostic tests related to this grounding issue on Sol 2117 prior to driving and during the drive. The single-point ground showed a sustained minus 5 volts that increased to minus 25 volts whenever any of the six wheel-driving motors or four wheel-steering motors were powered. This suggests the unusual electrical behavior is associated with the rover motor controller board since the behavior is seen with all 10 motors associated with that electronics board. The rover has other motors not related to the wheels, but the persistent voltage has not been associated with any of those.
The plan ahead is to perform another set of low-voltage tests on the three right-side wheels and then command another four-step forward drive. This drive would not use the right-front wheel in conjunction with the others, but that wheel would be driven briefly by itself after each step to gain more information about its possible usefulness.
Diagnostic tests were run on Spirit's right-rear wheel and right-front wheel on Sol 2113 (Dec. 12, 2009). The right-rear wheel, which stalled during a drive two weeks earlier, continued to show no motion in the latest tests and exhibited very high resistance in the motor winding. The right-front wheel, which stopped operating on Sol 779 (March 13, 2006), surprised engineers by indicating normal resistance and turning slightly during a resistance test for that wheel.
Small motion is expected during an electrical resistance test for an operating actuator, but the right-front actuator was expected to be non-operational. The right-front wheel was last checked just after its apparent failure in 2006 and at that time indicated an open circuit. Although no clear theory for failure had been established, the failure was generally regarded as permanent. It is important to remember that the Sol 2113 test of the right-front wheel was only a rotor resistance test, and no conclusions can be drawn at this point without further testing.
The plan for Spirit on Sol 2116 (Dec. 15) is to command a drive. This drive will further investigate functionality of the right-front and right-rear wheels. The results are expected Wednesday.
Results of diagnostic tests on Spirit's right-rear wheel on Sol 2109 (Dec. 8, 2009) continue to indicate a troubled wheel, which may leave the rover with only four operable wheels.
The Sol 2109 plan included a check of the grind motor of Spirit's rock abrasion tool (RAT) because it shares the same motor controller as the right-rear wheel. It also included rotor resistance tests on the right-rear motor at three temperatures using opposite voltage polarity from earlier tests, backward and forward commanded motion of the right-rear wheel, and a check of rotor resistance on all other operating wheels. The RAT motor appears okay, although a more exhaustive test will be tried later. The right-rear wheel rotor resistance tests continue to show very elevated resistance, although not as high as in previous tests, and exhibiting a curious voltage-dependent effect. No motion of the right-rear wheel occurred during the backward commanded motion. The forward motion was not executed since the initial backward motion did not occur. The rotor resistances on all the other operating wheels are nominal.
The plan ahead, still being developed, will likely include more rotor resistance tests, an attempt to apply higher voltage to the right-rear wheel to see if any movement will occur, and a check of the right-front wheel to confirm its status and to see if it may offer insight into the right-rear wheel's condition. Further ahead, steering tests will be considered to explore an external jam as a possible explanation.
Concurrent with this, the project is exploring whether any meaningful rover motion would be possible with only four operable wheels. Spirit lost the use of its right front wheel in 2006.
Because of the current rover tilt, the environmental conditions and dust accumulation on the solar arrays, Spirit is at risk of inadequate power for surviving through the next southern Mars winter, which reaches solstice on May 13, 2010. Even if extrication is not possible, some limited rover motion may be able to improve rover tilt and increase the chance of winter survival.
A series of diagnostic tests on Spirit's right-rear wheel on sols 2104 and 2105 (Dec. 3 and 4) investigated stalls that occurred on Sol 2099 (Nov. 28) and earlier. The rover team cannot draw any conclusions at this point, but the results are not encouraging, and further tests are planned.
The recent tests included rotor-resistance tests at three temperatures and a one-radian (about 57 degrees) forward motion test. The resistance tests indicate anomalously high resistance in the motor winding at all three temperatures. However, a curious transition from anomalously low resistance to high resistance was observed very briefly on the very first resistance test. The resistance remained high for the balance of all the testing. Control measurements on the left-rear wheel showed normal resistance for that actuator motor. For the forward wheel motion test, the right-rear wheel stalled immediately and did not produce any motion.
The plan ahead is to explore a set of hypotheses: possible motor failure, possible internal gearbox jam, possible external jam (e.g., a rock in the wheel). Commands being developed for Spirit's activities on sols 2109 and 2110 (Tuesday and Wednesday, Dec. 8 and 9) will include more diagnostics to explore these hypotheses.
Spirit's right-rear wheel stalled again on Sol 2099 (Nov. 28, 2009) during the first step of a two-step extrication maneuver. This stall is different in some characteristics from the stall on Sol 2092 (Nov. 21). The Sol 2099 stall occurred more quickly and the inferred rotor resistance was elevated at the end of the stall. Investigation of past stall events along with these characteristics suggest that this stall might not be result of the terrain, but might be internal to the right-rear wheel actuator. Rover project engineers are developing a series of diagnostics to explore the actuator health and to isolate potential terrain interactions. These diagnostics are not likely to be ready before Wednesday. Plans for future driving will depend on the results of the diagnostic tests.
Before the Sol 2099 drive ended, Spirit completed 1.4 meters of wheel spin and the rover's center moved 0.5 millimeters (0.02 inch) forward, 0.25 millimeters (0.01 inch) to the left and 0.5 millimeters (0.02 inch) downward. Since Spirit began extrication on Sol 2088, the rover has performed 9.5 meters (31 feet) of wheel spin and the rover's center, in total, has moved 16 millimeters (0.63 inch) forward, 10 millimeters (0.39 inch) to the left and 5 millimeters (0.20 inch) downward.
On Sol 2095 (Tuesday, Nov. 24), Spirit performed a set of diagnostic actions related to a stall of the right-rear wheel on the previous drive, three days earlier. The diagnostics showed a fully functioning wheel free of obstruction. The rover was commanded forward with 1.5 meters (4.9 feet) of wheel spin. The rover moved 2.1 millimeters (0.08 inch) forward, 1.1 millimeters (0.04 inch) to the left, and 0.3 millimeters (0.01 inch) down.
The cumulative results from Sols 2088 to 2095 (Nov. 17 to 24) are 8.1 meters (27 feet) of commanded motion, 15.7 millimeters (0.6 inch) of forward progress, 9.9 millimeters (0.4 inch) of movement to the left, and 4.8 millimeters (0.2 inch) of sinkage.
The plan for a drive during the long holiday weekend is another two-step drive, with each step 2.5 meters (8.2 feet) of commanded wheel spin. All wheels will be straight and run at the same speed. Results of this commanded drive will be analyzed Monday, Nov. 30.
Spirit experienced a wheel stall with the right-rear wheel during the second step of a two-step drive on Sol 2092 (Saturday, Nov. 21). This is not the same wheel that stalled on Sol 1899 (May 6), the left-middle wheel. On Sol 2092, the right-rear wheel did not experience a hard stall like what was seen on Sol 1899. Instead, it stalled because the wheel's progress fell behind the expected rotation rate. The rover had completed about 4 meters (13 feet) of commanded wheel spin before the stall terminated the drive. The center of the rover moved about 4 millimeters (0.2 inch) forward, 3 millimeters (0.1 inch) to the left and about 3 millimeters (0.1 inch) down. The rover suspension stayed within the tighter limits set for the drive, and there was only a fractional change in rover tilt.
The plan ahead for today, Nov. 23, is to sequence a set of diagnostics to explore the right rear wheel stall. The diagnostics will include a rotor resistance test, a possible steering test, a small backward rotation of just the right-rear wheel and a short (about 1 meter, or 3 feet) forward commanded motion of the rover. Resumption of the extrication driving would be no sooner than Wednesday.
Because the first extrication drive for Spirit, on Sol 2088 (Nov. 17), stopped as soon as it began due to an exceeded tilt limit, the plan for an extrication drive on Sol 2090 (Nov. 19) will essentially be a repeat of the first drive plan, but with improved rover attitude knowledge. The updated attitude knowledge comes from the rover's measurement of its tilt on Sol 2088.
In the Sol 2090 plan, the rover will be instructed to drive straight ahead in two steps. Each step will be a commanded wheel motion of about 2.5 meters (8.2 feet). As before, not much actual motion of the rover is expected. At the conclusion of the commanded motion, the rover will collect three frames from its microscopic imager for a mosaic of the rover underbelly. The rover's panoramic camera will take images of the middle wheels, the navigation camera will take pre-drive and post-drive images for visual odometry, and the front and rear hazard-avoidance cameras will take supporting images.
These commands will be transmitted to Spirit early Thursday morning, Nov. 19. The results from the drive are expected to be received on the ground later Thursday via a Mars orbiter relay. Because of limited data volume available in the rover relay pass, the data downlink will likely be insufficient for the project to conduct a complete analysis of the drive that same day.
The preliminary results from the first extrication drive for Spirit on Sol 2088 (Nov. 17, 2009) indicate the rover stopped less than 1 second after it began, sensing more vehicle lateral tilt than permitted.
A tight limit on vehicle roll and pitch of less than 1 degree change was set for this first drive. As the rover began its first move, it sensed that its roll was outside the allowed limit and safely stopped the drive.
The project is starting cautiously, setting initial parameters with very tight limits with the knowledge that these hair triggers may stop the rover frequently. As the project gains confidence with extrication, these limits may be relaxed. From this limited drive the team now has a more accurate measurement of vehicle roll and pitch that will be used for subsequent drive planning. Analysis is continuing. Completion of planning for the next drive will be no sooner than Wednesday, Nov. 18.
The attempt to extract Spirit from the Martian sand trap is expected to take weeks or months, with uncertain probability of success.
Today (Monday, Nov. 16), driving commands are being prepared to instruct Spirit to attempt to drive forward. These are the first driving commands since Spirit became embedded in a Martian sandtrap approximately six months ago. These commands will be transmitted to Spirit at 1 a.m. PST (4 a.m. EST) Tuesday, Nov. 17.
The rover will be instructed to drive straight ahead (north) in two steps. Each step will be a commanded wheel motion of about 2.5 meters (8.2 feet). At the conclusion of the commanded motion, the rover will collect a three-frame Microscopic Imager mosaic of the rover underbelly. Spirit will also collect Pancam images of the middle wheels, pre-drive and post-drive visual odometry (Visodom), Navcam images, and supporting front and rear Hazcam images. The rover will drive with the robotic arm (Instrument Deployment Device) already deployed in the "fishing stow" position, like Opportunity, so it can take Microscopic Imager images without having to stow and un-stow the arm before and after each drive.
The team expects to spend all day Tuesday analyzing the drive results before the next drive attempt, possibly on Wednesday, Nov. 18. It is expected, at least initially, that little actual motion of the rover will be observed.
The attempt to extract Spirit from the Martian sandtrap is expected to take weeks or months, if it is at all possible. The next status update will be issued Tuesday, Nov. 17.
PASADENA, Calif. -- NASA will begin transmitting commands to its Mars exploration rover Spirit on Monday as part of an escape plan to free the venerable robot from its Martian sand trap.
Spirit has been lodged at a site scientists call "Troy" since April 23. Researchers expect the extraction process to be long and the outcome uncertain based on tests here on Earth this spring that simulated conditions at the Martian site.
"This is going to be a lengthy process, and there's a high probability attempts to free Spirit will not be successful" said Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters in Washington. "After the first few weeks of attempts, we're not likely to know whether Spirit will be able to free itself."
Spirit has six wheels for roving the Red Planet. The first commands will tell the rover to rotate its five working wheels forward approximately six turns. Engineers anticipate severe wheel slippage, with barely perceptible forward progress in this initial attempt. Since 2006, Spirit's right-front wheel has been inoperable, possibly because of wear and tear on a motor as a result of the rover's longevity.
Spirit will return data the next day from its first drive attempt. The results will be assessed before engineers develop and send commands for a second attempt. Using results from previous commands, engineers plan to continue escape efforts until early 2010.
"Mobility on Mars is challenging, and whatever the outcome, lessons from the work to free Spirit will enhance our knowledge about how to analyze Martian terrain and drive future Mars rovers," McCuistion said. "Spirit has provided outstanding scientific discoveries and shown us astounding vistas during its long life on Mars, which is more than 22 times longer than its designed life. "
In the spring, Spirit was driving backward and dragging the inoperable right front wheel. While driving in April, the rover's other wheels broke through a crust on the surface that was covering a bright-toned, slippery sand underneath. After a few drive attempts to get Spirit out in the subsequent days, it began sinking deeper in the sand trap. Driving was suspended to allow time for tests and reviews of possible escape strategies.
"The investigations of the rover embedding and our preparations to resume driving have been extensive and thorough," said John Callas, project manager for Spirit and Opportunity at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We've used two different test rovers here on Earth in conditions designed to simulate as best as possible Spirit's predicament. However, Earth-based tests cannot exactly replicate the conditions at Troy."
Data show Spirit is straddling the edge of a 26-foot-wide crater that had been filled long ago with sulfate-bearing sands produced in a hot water or steam environment. The deposits in the crater formed distinct layers with different compositions and tints, and they are capped by a crusty soil. It is that soil that Spirit's wheels broke through. The buried crater lies mainly to Spirit's left. Engineers have plotted an escape route from Troy that heads up a mild slope away from the crater.
"We'll start by steering the wheels straight and driving, though we may have to steer the wheels to the right to counter any downhill slip to the left," said Ashley Stroupe, a JPL rover driver and Spirit extraction testing coordinator. "Straight-ahead driving is intended to get the rover's center of gravity past a rock that lies underneath Spirit. Gaining horizontal distance without losing too much vertical clearance will be a key to success. The right front wheel's inability to rotate greatly increases the challenge."
Spirit has been examining its Martian surroundings with tools on its robotic arm and its camera mast. The rover's work at Troy has augmented earlier discoveries it made indicating ancient Mars had hot springs or steam vents, possible habitats for life. If escape attempts fail, the rover's stationary location may result in new science findings.
"The soft materials churned up by Spirit's wheels have the highest sulfur content measured on Mars," said Ray Arvidson a scientist at Washington University in St. Louis and deputy principal investigator for the science payloads on Spirit and Opportunity. "We're taking advantage of its fixed location to conduct detailed measurements of these interesting materials."
Spirit and its twin rover landed on Mars in January 2004. They have explored Mars for five years, far surpassing their original 90-day mission. Opportunity currently is driving toward a large crater called Endeavor.
NASA's JPL manages the rovers for NASA's Science Mission Directorate in Washington.
For updates about Spirit's progress, visit: http://www.nasa.gov/rovers or http://marsrovers.jpl.nasa.gov/home/index.html
Until Oct. 24, NASA's Mars Exploration Rover had gone more than six months without an episode of amnesia-like symptoms like those that appeared on four occasions earlier this year.
In these amnesia events, Spirit fails to record data from the day's activities onto the type of computer memory -- non-volatile "flash" memory -- that can retain the data when the rover powers down for its energy-conserving periods of "sleep." The reappearance of this behavior in recent days might delay the start of planned drives by Spirit geared toward extricating the rover from a patch of soft soil where its wheels have been embedded since April.
Spirit sent data Oct. 24 through Oct. 27 indicating that the rover was not using its flash memory. The rover also has alternate memory (volatile, random-access memory) where data can be saved for communicating to Earth if the communication session comes before the next sleep period. Spirit remains in communication with Earth, maintaining good power and temperatures.
"We still don't have information about what causes these amnesia events," said Mars Exploration Rover Project Manager John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "If they are intermittent and infrequent, they are a nuisance that would set us back a day or two when they occur. If the condition becomes persistent or frequent, we will need to go to an alternate strategy that avoids depending on flash memory. We would only get data collected the same day and any unsent data from an earlier day would be lost. The total volume of data returned by the rover is expected to be about the same."
This week, an independent panel of robotics experts has been reviewing the rover team's tests and plans for getting Spirit away from the site called "Troy," where the rover's wheels broke through a crusty, dark surface layer and became embedded in bright, loose material that had been hidden underneath.
Spirit has worked on Mars for more than 69 months in what was originally planned as a three-month mission.
Engineers using test rovers on Earth to prepare for extracting the sand-trapped Spirit rover on Mars have added a new challenge to their preparations.
Until last week, the engineers commanding and assessing drives by the test rovers were usually in the same room as the sandbox setup simulating Spirit's predicament, where they can watch how each test goes. That changed for the latest preparation, called an operational readiness test.
The team members commanding drives by a test rover last week stayed away from the building with the sandbox. They assessed the results of each commanded drive only from the images and other data communicated from the test rover, the same way the team does for daily operations of the rovers that are on Mars.
"We conducted this round of testing under more flight-like conditions to test the team's ability to make very complex extraction driving decisions using only the data sent back from the rover," said Mars Exploration Rover Project Manager John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The test began on Oct. 12 and ran five days on an accelerated schedule of two Martian days' worth of commanding every day. The rover team also operated both Spirit and its twin, Opportunity, while conducting this readiness test at JPL.
Spirit became embedded in soft soil at a site called "Troy" five months ago, more than five years into a mission on Mars that was originally scheduled to last for three months. The rover team suspended further driving attempts with Spirit while evaluating possibilities from tests performed at JPL simulating the Troy situation.
Current plans call for an independent panel to review Spirit driving plans in late October, following analysis of results from the readiness test. Unless that review recommends any further preparations, Spirit will probably begin extraction moves within two weeks after the review.
Spirit has spent much of its time at Troy actively examining its surroundings, including analysis of layered soil at the site. In September, a new issue began affecting operations. Data from Spirit indicated that a brake on the motor that rotates the rover's dish-shaped high-gain antenna was not working correctly. The team has been getting more diagnostic data and developing a work-around strategy similar to work-arounds already used for rover-motor brakes that showed similar symptoms earlier.
For more updates, please visit the Free Spirit site: http://www.jpl.nasa.gov/freespirit/
Tests on Earth simulating Spirit's predicament on Mars have reinforced understanding that getting Spirit to rove again will be very difficult.
To supplement the tests at NASA's Jet Propulsion Laboratory in Pasadena, Calif., the rover team is refining a detailed computer model of rover mobility, calibrated with results from testing and measurements from Mars.
"The computer modeling will allow us to connect the results from tests performed in Earth gravity with what to expect from the rover in Mars gravity," said JPL's John Callas, project manager for Spirit and its twin, Opportunity.
Spirit became embedded in soft soil at a site called "Troy" in early May, more than five years into a mission on Mars that was originally scheduled to last for three months. The rover team suspended further driving attempts with Spirit while evaluating possibilities from tests performed at JPL simulating the Troy situation.
An additional round of testing was added to the September schedule to gain more detailed assessment of how to move Spirit while avoiding putting the rover's center of gravity directly over a rock that is touching or nearly touching the rover's underbelly. Other added tests are using a lighter-weight test rover than the one used for most of the testing this summer. A complete "dress rehearsal" test of the extrication strategy judged to hold the best chance of success is planned in the test setup at JPL before the team commands Spirit to begin driving. That test and subsequent review of its results are expected to take several weeks. Moves by Spirit will not begin before October, according to current plans.
"We are proceeding very cautiously and exploring all reasonable options," Callas said. "There is a very real possibility that Spirit may not be able to get out, and we want to give Spirit the very best chance."
A dust storm that had reduced the electrical output from Spirit's solar panels by nearly half during late August still has some lingering effects on the skies above Spirit.
For more updates, please visit the Free Spirit site: http://www.jpl.nasa.gov/freespirit/
The amount of electricity generated by the solar panels on Spirit has been declining for the past several Martian days, or sols, as a regional dust storm moved southward and blocked some of the sunshine at Spirit's location. The team operating the rover has responsively trimmed Spirit's daily activities and is keeping an eye on weather reports from observations by NASA's Mars Reconnaissance Orbiter.
Spirit's solar panels generated 392 watt-hours during the mission's Sol 2006 (Aug. 24, 2009), down from 744 watt-hours five sols earlier, but still generous compared with the 240 watt-hours per sol that was typical before a series of panel-cleaning events about four months ago.
"We expect that power will improve again as this storm passes, but we will continue to watch this vigilantly," said JPL's John Callas, project manager for Spirit and its twin, Opportunity. "Spirit remains power positive with healthy energy margins and charged batteries. The weather prediction from the Mars Color Imager team is that the storm is abating, but skies will remain dusty over Spirit for the next few sols."
Recent images from the Mars Color Imager camera on Mars Reconnaissance Orbiter showed this regional storm becoming less extensive Monday even as it shifted southward so that its southern edge covered the Gusev Crater area where Spirit is working. Malin Space Science Systems in San Diego, which operates that camera, provides frequent weather updates to the rover team. Weekly reports are posted at http://www.msss.com/msss_images/latest_weather.html .
Meanwhile, in JPL's In-Situ Instrument Laboratory, the rover team is continuing testing of strategies for getting Spirit out of a patch of soft soil where it is embedded on Mars. On Sol 2005 (Aug. 23, 2009) Spirit used its panoramic camera to examine the nature of how soil at the site has stuck to the rover's middle wheels. The team has also used Spirit's rock abrasion tool as a penetrometer to measure physical properties of the soil around Spirit by pressing into the soil with three different levels of force. The team is aiming to start sending drive commands to Spirit in September.
A second, lighter-weight test rover has entered the testing setup at JPL where rover team members are assessing strategy for getting Spirit out of soft soil where it is embedded on Mars.
The rover team has begun using a test rover that does not carry a science payload or robotic arm, as do Spirit and Opportunity on Mars, and the primary engineering test rover at JPL. While the primary test rover's weight on Earth is greater than Spirit's weight on Mars, the second rover is even lighter on Earth and closer to the weight of Spirit on Mars.
Making comparisons between motions of the two test rovers in duplicated drives will aid the rover team in interpreting effects of differing gravity on rover mobility. The testing team plans to run such comparisons both in the soft, fluffy material being used to simulate the soil at Spirit's current location and also on coarser, crushed rock that offers better traction.
"There is no perfect Earth analog for Spirit's current situation," said JPL's John Callas, project manager for the twin Mars Exploration Rovers. "There's less gravity on Mars, little atmosphere, and no moisture in the soil where Spirit is. It is not anything like being stuck in sand or snow or mud on Earth. Plus, since the rover moves only about as fast as a tortoise, you cannot use momentum to help. No rocking back and forth as you might do on Earth."
The comparison experiments with the two test-rover siblings to Spirit and Opportunity precede a planned "dress rehearsal" long-duration test of driving as far in the test setup as the distance that Spirit would need to achieve on Mars to escape its predicament at the site called "Troy."
The team has also made further assessments of the position of a rock underneath Spirit relative to the rover's center of gravity. Part of the strategy for getting Spirit free will be to avoid getting in a position with the center of gravity directly over a rock touching the rover.
For more updates, please visit the Free Spirit site: http://www.jpl.nasa.gov/freespirit/
Mars rover team members are planning a long-duration experiment with the test rover at JPL beginning next week. This test will check whether favorable motion seen in earlier tests can be sustained to gain as much distance in the sandbox as Spirit would need to complete on Mars to escape its predicament.
The team expects to drive the test rover for several hundred meters, or yards, worth of wheel rotations over the course of a week or more without starting over. Steering direction will be changed several times during the run. Earlier tests have run for one or two days. In between tests, the team resets the sandbox to simulate Spirit's current starting position at the Mars location called "Troy."
Based on test results, the team might begin sending driving commands to Spirit during the second week of September. Any progress by Spirit toward getting out of the soft soil where it is embedded is expected to be slow. With its right front wheel disabled since 2006, Spirit's success at getting out of the sand trap is not guaranteed. Both Spirit and Opportunity have operated on Mars more than five years longer than their initially planned missions of three months.
During the weeks of testing at JPL designed to identify the best escape strategy, Spirit has been productively using the tools on its robotic arm to analyze multiple layers of soil at Troy.
For more updates, please visit the Free Spirit site: http://www.jpl.nasa.gov/freespirit/
A review on Aug. 6 of test results to date yielded a decision to conduct further checkouts in an augmented testing set-up on Earth before beginning to send driving commands to Spirit for attempting to get out of the loose soil where the rover has partially embedded itself.
The ample power available to Spirit due to wind cleaning dust off of its solar panels has removed the initial urgency for getting the rover moving toward a winter haven site. The rover science team has not completed the analysis the soil layers at Spirit's current location. And the review pointed to additional types of position measurements and analysis that could make further testing useful in mapping the strategy for freeing Spirit.
No specific date has been set for Spirit to resume driving.
Visit the Free Spirit web site for more updates: http://www.jpl.nasa.gov/freespirit/
Mars rover engineers at JPL are winding down testing of different escape maneuvers using a test rover in a sand box filled with soil to mimic the Martian surface. It is possible that in early August the first extraction attempts with Spirit rover, which is dug-in on Mars, might take place.
This week, longer-duration test runs continued, and the team drove the rover several meters, or yards, forward and uphill in a crab-like position. These long-duration drives will continue through the end of next week.
Meanwhile, observations from the Mars Climate Sounder instrument on NASA's Mars Reconnaissance Orbiter indicate to scientists that a large regional storm is developing. Right now the dust storm is not near Spirit or its twin, Opportunity, but scientists will continue to monitor it as it develops. Since Mars is still in the dust storm season, it is possible (and perhaps even probable) that the storm will continue to grow over the next few days.
› Visit the Free Spirit website
Mars rover team members have begun a new phase of testing at JPL -- using longer-duration experiments -- in their preparations for driving Spirit again on Mars.
They have completed assessments of individual maneuvers, using the test rover in a box of sloped, soft soil that simulates conditions at the patch of Martian ground called "Troy," where Spirit's wheels have dug themselves hub-deep. Tests beginning today are using combinations of the individual maneuvers and longer-duration drives. These tests will evaluate a full escape strategy for Spirit.
With the test rover temporarily removed from the box on Friday, July 24, the rover team members renewed the test setup. They tamped the soil in the uphill half of the box with more pressure than the soil on the downhill side. This was done to offer a closer simulation to the conditions at Troy, where Spirit's wheels have not churned up the soil as much on the uphill side.
At Troy, meanwhile, Spirit is continuing to use all of its tools to examine the environment around it.
The team that operates rovers on Mars is using a test rover in southern
California to assess maneuvers the Mars rover Spirit might use to get out
of soft, loose soil where its wheels have sunk hub-deep. A live videocast
and chat from NASA's Jet Propulsion Laboratory, Pasadena, Calif., will give
viewers a chance to ask questions of rover team members working to get
Spirit rolling again.
The live event will air on the "NASAJPL" channel available on Ustream Web TV at: http://www.ustream.tv/channel/nasajpl on Thursday, July 23, beginning at 3 p.m. PDT (6 p.m. EDT and 2200 UTC).
Spirit and its twin, Opportunity, landed on Mars in January 2004 for what were planned as three-month missions to study sites on opposite sides of the planet. Both are still active and returning streams of scientific information. Spirit has not driven since May 6, 2009, when it had become partially embedded in the soil. To minimize the risk of worsening Spirit's predicament, operators decided to conduct a series of experiments with a test rover before driving Spirit again.
Participants in the July 23 event include:
-- John Callas, project manager for NASA's Mars Exploration Rovers, Spirit and Opportunity.
-- Ashley Stroupe, JPL rover planner, deputy lead for "Free Spirit" testing
Viewers may submit questions over Ustream or via Twitter. Twitter users may send their questions to @NASAJPL using the hashtag #FreeSpirit. In addition, if you are unable to take part in the live chat, you may submit questions in advance to firstname.lastname@example.org and watch the archived video at a later time.
Information about Spirit and Opportunity is available at http://www.nasa.gov/rovers. Updates about testing of possible maneuvers for freeing Spirit are at http://www.jpl.nasa.gov/freespirit .
JPL is managed for NASA by the California Institute of Technology, Pasadena.
As the Mars rover team uses testing at JPL to evaluate possible ways to drive Spirit out of loose soil on Mars, the team is finishing tests of individual "building block" maneuvers and is about to begin stringing some of those together.
The individual maneuvers, such as turns in place or crablike slant moves, may be combined to get Spirit's wheels away from the spots where they have sunk into the soil. Some of the tests in a JPL sandbox simulating Spirit's predicament have moved the test rover slightly -- on the order of a centimeter, or half an inch, of shift in position. This position change was achieved after enough wheel turns to have driven the rover the equivalent of tens of meters or yards on firmer ground. The testing evaluates how each maneuver shifts the test rover's orientation and tilt.
A live webcast from the testing site at JPL, supplemented by simultaneous Internet chat to take public questions, is planned for Thursday, July 23. The live event will air on the "NASAJPL" channel available on Ustream Web TV at: http://www.ustream.tv/channel/nasajpl on Thursday, July 23, beginning at 3 p.m. PDT (6 p.m. EDT and 2200 UTC). For more information, see http://www.jpl.nasa.gov/news/news.cfm?release=2009-113 .
The Mars rover team is using a test rover at JPL to assess various extraction techniques that might get Spirit out of the loose soil of "Troy" on Mars. One of the maneuvers being run with the test rover involves turning the rear wheels toward the left while the left-front wheel is turned toward the right, and driving forward to pivot around the inoperable right-front wheel.
Engineers and scientists on the rover team are evaluating several repeats of this forward-right-arc maneuver in the sandbox at JPL as part of a weeks-long series of tests to identify maneuvers that might help Spirit.
Meanwhile Spirit is using abundant power from its solar panels, recently cleaned by Martian winds, to examine the composition of soil layers at Troy and make daytime and nighttime observations.
› Visit the Free Spirit website
Engineers checking possible rover movements to get Spirit out of the "Troy" sand trap on Mars are evaluating how a comparable rover at JPL fares in a crablike backward drive, with all four corner wheels turned 60 degrees toward the right.
This is the fifth of 11 maneuvers on the current testing list. Others ahead are crabbing backward with wheels turned 20 degrees to the right, a tight forward right arc, a clockwise turn in place, a counterclockwise turn in place, crabbing forward with wheels turned to the left, and driving while steering. Some of the maneuvers might be repeated.
The team is learning how the test rover reacts to various motions in a test sandbox built to simulate Spirit's situation at Troy. The steps eventually sent as driving commands to Spirit may be a combination of some of the 11 maneuvers being tested.
› Visit the Free Spirit website
On firm ground, NASA's Mars Exploration Rovers can make crablike moves by turning all four steerable wheels to the same side angle, then rotating the wheels either forward or backward. The rover team is experimenting with variations of those maneuvers in a test sandbox at JPL as part of its work to identify the best way to get Spirit out of the loose soil where the rover has become embedded on Mars.
By Friday morning, July 10, the team had tested crabwalk patterns driving forward in the test sandbox with the wheels turned at 60 degrees to the right and 20 degrees to the right. The angle of motion was upslope in the testing setup that simulates Spirit's predicament on Mars. Together with earlier experiments evaluating straight-forward and straight-backward driving, the latest actions completed four out of 11 maneuvers that the team has on its current testing list. Next, engineers plan to test backward (downslope) crabbing with wheels turned 60 degrees to the right.
› Free Spirit page
Engineers used straight-backward driving of a test rover on Earth on Wednesday, July 8, as they evaluate maneuvers that might be useful for getting Spirit out of a sandtrap on Mars. They had tested straight-forward driving first, then refreshed the sandbox setup simulating Spirit's situation before beginning the backward tests. Weeks of further testing and analysis are expected before engineers identify the best moves to command Spirit to perform. Meanwhile, Spirit is using its science instruments to examine the environment surrounding the rover on Mars.
› Free Spirit page
Using a test rover in a sandbox at JPL with special soil simulating Spirit's predicament on Mars, engineers are assessing possible maneuvers for getting Spirit out and onto firmer ground. They began on Monday, July 6, with the simplest maneuver on their list of options: driving forward with all five operable wheels. In the first set of tests, the wheels turned enough to cover tens of meters, or yards, if there had been no slippage. The test rover moved slightly forward and sideways downslope. Weeks of further testing and analysis of results are expected before engineers identify the best moves to command Spirit to make.
› Free Spirit Page
Engineers placed a rock underneath the test rover at NASA's Jet Propulsion Laboratory, Pasadena, Calif., on July 1, 2009, to more closely simulate Spirit's predicament on Mars. After becoming embedded in soft soil, Spirit used the microscopic imager at the end of its arm last month to look under its own belly for the first time. The resulting view (at http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20090603a.html) confirmed a rock beneath the rover touching its underbelly. With a rock now placed similarly in the test sandbox, testing in the next few weeks will evaluate possible extraction moves for Spirit.
For all Spirit updates, go to http://www.jpl.nasa.gov/freespirit/ .
After several days of preparing a sloped area of soft, fine soil to simulate Spirit's current sandtrap on Mars, the rover team drove a test rover into the material on June 30, 2009. The test rover became embedded in the soil, as planned. The rover team will use this setup at NASA's Jet Propulsion Laboratory, Pasadena, Calif., during the next few weeks to test possible extraction moves Spirit might use on Mars.
For all Spirit updates, go to http://www.jpl.nasa.gov/freespirit/ .