posted 02-05-2009 10:02 AM               

Spirit Resumes Driving

NASA's Mars Exploration Rover Spirit resumed driving Saturday after engineers gained confidence from diagnostic activities earlier in the week evaluating how well the rover senses its orientation.

Spirit drove about 30 centimeters (1 foot) Saturday, during the 1,806th Martian day, or sol, of what was originally planned as a 90-day mission. The rover team had commanded a longer drive, but Spirit stopped short after its right-front wheel, which no longer turns, struck a partially buried rock. The rover drivers prepared commands Monday for the next drive in a slightly different direction to get around that rock.

A diagnostic test on Sol 1805 provided an evaluation of how accurately Spirt's accelerometers sense the rover's orientation or attitude. The testing was a follow-up to Spirit's mistaken calculation of where to expect to see the sun on Sol 1802. The sol 1805 results indicate the accelerometers may have a bias of about 3 degrees. This would explain why Spirit pointed a camera about three degrees away from the sun's actual position on Sol 1802. However, the Sol 1805 test also showed that Spirit's gyroscopes are operating properly, which convinced engineers that the rover could safely resume driving. Only the gyroscopes are used for orientation information during driving.

Diagnostic tests last week also checked possible explanations for behavior for one period of activity on Spirit's Sol 1800, when the rover did not save information into its non-volatile flash memory, so the information was lost when the rover next powered down.

"We may not find any data that will explain what happened on Sol 1800, but there's no evidence that whatever happened then has recurred on subsequent sols," said Jacob Matijevic of the rover engineering team at NASA's Jet Propulsion Laboratory, Pasadena. One possibility is that a cosmic-ray hit could have temporarily put Spirit temporarily into a mode that disables use of the flash memory. The team intentionally used that mode -- relying only on volatile random-access memory -- during recovery from a memory problem five years ago on Spirit.

Spirit is just north of a low plateau called "Home Plate." It spent 2008 on a north-facing slope on the edge of Home Plate so that its solar panels stayed tilted toward the winter sun for maximum electrical output.

Spirit drove down off Home Plate on Jan. 6, 2009. It subsequently checked whether a patch of nearby soil, called "Stapledon," had a high concentration of silica, like a silica-rich patch of soil Spirit discovered east of Home Plate in 2007. The earlier discovery was interpreted as evidence left by a hot-spring or steam-vent environment. Examination with Spirit's alpha particle X-ray spectrometer confirmed silica at Stapledon. This indicates that the environment that deposited the silica was not limited to the location found earlier.

JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Exploration Rover project for the NASA Science Mission Directorate, Washington. Spirit and its twin, Opportunity, landed on Mars in January 2004 and have operated 20 times longer than their original prime missions.

posted 03-19-2009 10:05 AM               

One Mars Rover Sees a Distant Goal; The Other Takes a New Route

On a plain that stretches for miles in every direction, the panoramic camera on NASA's Mars rover Opportunity has caught a first glimpse on the horizon of the uplifted rim of the big crater that has been Opportunity's long-term destination for six months.

Opportunity's twin, Spirit, also has a challenging destination, and last week switched to a different route for making progress.

Endeavour Crater, 22 kilometers (14 miles) in diameter, is still 12 kilometers (7 miles) away from Opportunity as the crow flies, and at least 30 percent farther away on routes mapped for evading hazards on the plain. Opportunity has already driven about 3.2 kilometers (2 miles) since it climbed out of Victoria Crater last August after two years of studying Victoria, which is less than one-twentieth the size of Endeavour.

"It's exciting to see our destination, even if we can't be certain whether we'll ever get all the way there," said John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif., project manager for the twin Mars rovers, Opportunity and Spirit. "At the pace we've made since leaving Victoria, the rest of the trek will take more than a Martian year." A Martian year lasts about 23 months.

The image with portions of Endeavour's rim faintly visible can be seen online.

v Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the rovers' science instruments, said, "We can now see our landfall on the horizon. It's far away, but we can anticipate seeing it gradually look larger and larger as we get closer to Endeavour. We had a similar experience during the early months of the mission watching the Columbia Hills get bigger in the images from Spirit as Spirit drove toward them."

Both rovers landed on Mars in January 2004 to begin missions designed to last for three months. Both are still active after more than five years.

For the next several days, the rover team plans to have Opportunity use the tools on its robotic arm to examine soil and rock at an outcrop along the route the rover is taking toward Endeavour.

"We're stopping to taste the terrain at intervals along our route so that we can watch for trends in the composition of the soil and bedrock," Squyres said. "It's part of systematic exploration."

The pause for using the tools on the arm also provides two other benefits. Opportunity's right-front wheel has been drawing more electric current than usual, an indication of friction within the wheel. Resting the wheel for a few days is one strategy that has in the past helped reduce the amount of current drawn by the motor. Also, on March 7, the rover did not complete the backwards-driving portion of its commanded drive due to unanticipated interaction between the day's driving commands and onboard testing of capabilities for a future drive. The team is analyzing that interaction before it will resume use of Opportunity's autonomous-driving capabilities.

Meanwhile, on March 10, the rover team decided to end efforts to drive Spirit around the northeastern corner of a low plateau called "Home Plate" in the inner basin of the Columbia Hills, on the other side of Mars from Opportunity. Spirit has had the use of only five wheels since its right-front wheel stopped working in 2006. Consequently, it usually drives backwards, dragging that wheel, so it can no longer climb steep slopes.

Callas said, "After several attempts to drive up-slope in loose material to get around the northeast corner of Home Plate, the team judged that route to be impassable."

The new route to get toward science targets south of Home Plate is to go around the west side of the plateau.

Squyres said, "The western route is by no means a slam dunk. It is unexplored territory. There are no rover tracks on that side of Home Plate like there are on the eastern side. But that also makes it an appealing place to explore. Every time we've gone someplace new with Spirit since we got into the hills, we've found surprises."

JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Exploration Rovers for the NASA Science Mission Directorate, Washington.

posted 04-13-2009 06:57 PM               

Spirit Healthy but Computer Reboots Raise Concerns

The team operating NASA's Mars Exploration Rover Spirit is examining data received from Spirit in recent days to diagnose why the rover apparently rebooted its computer at least twice over the April 11-12 weekend.

"While we don't have an explanation yet, we do know that Spirit's batteries are charged, the solar arrays are producing energy and temperatures are well within allowable ranges. We have time to respond carefully and investigate this thoroughly," said John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif., project manager for Spirit and twin-rover Opportunity. "The rover is in a stable operations state called automode and taking care of itself. It could stay in this stable mode for some time if necessary while we diagnose the problem."

Spirit communicated with controllers Friday, Saturday and Sunday, but some of the communication sessions were irregular. One of the computer resets apparently coincided in timing with operation of the rover's high-gain dish antenna.

The rover team has the advantage of multiple communication options. Spirit can communicate directly with Earth via either the pointable high-gain antenna or, at a slower data rate, through a low-gain antenna that does not move. Additionally, communications can be relayed by Mars orbiters, using the UHF (ultra-high frequency) transceiver, a separate radio system on the rover.

"To avoid potential problems using the pointable antenna, we might consider for the time being just communicating by UHF relay or using the low-gain antenna," Callas said.

Spirit finished its three-month prime mission on Mars five years ago and has kept operating through multiple mission extensions.

The rover's onboard software has been updated several times to add new capabilities for the mission, most recently last month. The team is investigating whether the unexpected behavior in recent days could be related to the new software, but the same software is operating on Opportunity without incident.

"We are aware of the reality that we have an aging rover, and there may be age-related effects here," Callas said.

In the past five weeks, Spirit has made 119 meters (390 feet) of progress going counterclockwise around a low plateau called "Home Plate" to get from the place where it spent the past Martian winter on the northern edge of Home Plate toward destinations of scientific interest south of the plateau. On March 10, after several attempts to get past obstacles at the northeastern corner of Home Plate, the rover team decided to switch from a clockwise route to the counterclockwise one. Subsequent events have included Spirit's longest one-day drive since the rover lost use of one of its wheels three years ago, plus detailed inspection of light-toned soil exposed by the dragging of the inoperable wheel.

Halfway around Mars, meanwhile, Opportunity has continued progress on a long-term trek toward Endeavour Crater, a bowl 22 kilometers (14 miles) in diameter and still about 12 kilometers (12 miles) away. Last week, a beneficial wind removed some dust from Opportunity's solar array, resulting in an increase by about 40 percent in the amount of electrical output from the rover's solar panels. JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Science Mission Directorate, Washington.

posted 05-12-2009 04:21 AM               

Soft Ground Puts Spirit in Danger Despite Gain in Daily Energy

The five wheels that still rotate on NASA's Mars Exploration Rover Spirit have been slipping severely in soft soil during recent attempts to drive, sinking the wheels about halfway into the ground.

The rover team of engineers and scientists has suspended driving Spirit temporarily while studying the ground around the rover and planning simulation tests of driving options with a test rover at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

"Spirit is in a very difficult situation," JPL's John Callas, project manager for Spirit and its twin rover, Opportunity, said Monday. "We are proceeding methodically and cautiously. It may be weeks before we try moving Spirit again. Meanwhile, we are using Spirit's scientific instruments to learn more about the physical properties of the soil that is giving us trouble."

Both Spirit and Opportunity have operated more than five years longer than their originally planned missions of three months on Mars and have driven much farther than designed. The rover team has so far developed ways to cope with various symptoms of aging on both rovers.

Spirit has been driving counterclockwise from north to south around a low plateau called "Home Plate" for two months. The rover progressed 122 meters (400 feet) on that route before reaching its current position.

In the past week, the digging-in of Spirit's wheels has raised concerns that the rover's belly pan could now be low enough to contact rocks underneath the chassis, which would make getting out of the situation more difficult. The right-front wheel on Spirit stopped working three years ago. Driving with just five powered wheels while dragging or pushing an immobile wheel adds to the challenge of the situation.

Favorably, three times in the past month, wind has removed some of the dust accumulated on Spirit's solar panels. This increases the rover's capability for generating electricity.

"The improved power situation buys us time," Callas said. "We will use that time to plan the next steps carefully. We know that dust storms could return at any time, although the skies are currently clear."

Behavioral problems that Spirit exhibited in early April -- episodes of amnesia, computer resets and failure to wake for communications sessions -- have not recurred in the past three weeks, though investigations have yet to diagnose the root causes.

Wheel slippage during attempts to extricate NASA's Mars Rover Spirit from a patch of soft ground during the preceding two weeks had partially buried the wheels by the 1,899th Martian day, or sol, of the Spirit's mission on Mars (May 6, 2009).

posted 05-19-2009 11:32 AM               

Mars and Earth Activities Aim to Get Spirit Rolling Again

NASA's rover project team is using the Spirit rover and other spacecraft at Mars to begin developing the best maneuvers for extracting Spirit from the soft Martian ground where it has become embedded.

A diagnostic test on May 16 provided favorable indications about Spirit's left middle wheel. The possibility of the wheel being jammed was one factor in the rover team's May 7 decision to temporarily suspend driving Spirit after that wheel stalled and other wheels had dug themselves about hub-deep into the soil. The test over the weekend showed electrical resistance in the left middle wheel is within the expected range for a motor that has not failed.

"This is not a full exoneration of the wheel, but it is encouraging," said John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif., project manager for Spirit and its twin rover, Opportunity. "We're taking incremental steps. Next, we'll command that wheel to rotate a degree or two. The other wheels will be kept motionless, so this is not expected to alter the position of the vehicle."

Another reason to suspend driving is the possibility that the wheels' digging into the soil may have lowered the body of the rover enough for its belly pan to be in contact with a small mound of rocks. The rover team is using Opportunity to test a procedure for possible use by Spirit: looking underneath the rover with the microscopic imager camera that is mounted on the end of the rover's arm. This might be a way to see whether Spirit is, in fact, touching the rocks beneath it.

NASA's Mars Odyssey orbiter is also aiding in the Spirit recovery plan. As a result of winds blowing dust off Spirit's solar panel four times in the past month, Spirit now has enough power to add an extra communication session each day. The Odyssey project has made the orbiter available for receiving extra transmissions from Spirit. The transmissions include imaging data from Spirit's examinations of soil properties and ground geometry.

Rover team members are using that data and other information to construct a simulation of Spirit's situation in a rover testing facility at JPL. The team is testing different materials to use as soil that will mimic the physical properties of the Martian soil where Spirit is embedded. Later, the team will test maneuvers to get the rover free. Weeks of testing are anticipated before any attempt to move Spirit.

posted 07-28-2009 11:49 AM               

I always wondered if these are capable of operating for years why does NASA start the mission with a potential life of 90 (I believe) days?

Are they simply understating the potential lifespan to make themselves look good?

posted 07-28-2009 08:58 PM               

quote:

---

Originally posted by jimsz:
These two machines are amazing...

Are they simply understating the potential lifespan to make themselves look good?

---

There are a lot of unknowns in engineering these machines. The Martian environment is brutal, with huge temperature variations every day and nighttime temperatures as cold or colder than anything we experience on Earth. Some components may be expected to last longer than others just by the nature of the materials they're made out of and what they're expected to do. For example, the solar panels aren't subject to much except dust deposits (which we've seen repeatedly on both rovers). However, components that move run the risk of the wires eventually breaking from repeated use.

Age catches up with the rovers in other ways, too. The cobalt-57 radiation source in the Mössbauer spectrometers has a half-life of 271 days. As a result of the rovers being in transit to Mars for half a year, and then on the surface for more than 5 years, it now takes weeks to run a Mössbauer integration that used to take a couple of hours at the beginning of the mission.

posted 08-11-2009 09:24 AM               

Meteorite Found on Mars Yields Clues About Planet's Past

NASA's Mars Rover Opportunity is investigating a metallic meteorite the size of a large watermelon that is providing researchers more details about the Red Planet's environmental history.

The rock, dubbed "Block Island," is larger than any other known meteorite on Mars. Scientists calculate it is too massive to have hit the ground without disintegrating unless Mars had a much thicker atmosphere than it has now when the rock fell. An atmosphere slows the descent of meteorites. Additional studies also may provide clues about how weathering has affected the rock since it fell.

Two weeks ago, Opportunity had driven approximately 180 meters (600 feet) past the rock in a Mars region called Meridiani Planum. An image the rover had taken a few days earlier and stored was then transmitted back to Earth. The image showed the rock is approximately 60 centimeters (2 feet) in length, half that in height, and has a bluish tint that distinguishes it from other rocks in the area. The rover team decided to have Opportunity backtrack for a closer look, eventually touching Block Island with its robotic arm.

"There's no question that it is an iron-nickel meteorite," said Ralf Gellert of the University of Guelph in Ontario, Canada. Gellert is the lead scientist for the rover's alpha particle X-ray spectrometer, an instrument on the arm used for identifying key elements in an object. "We already investigated several spots that showed elemental variations on the surface. This might tell us if and how the metal was altered since it landed on Mars."

The microscopic imager on the arm revealed a distinctive triangular pattern in Block Island's surface texture, matching a pattern common in iron-nickel meteorites found on Earth.

"Normally this pattern is exposed when the meteorite is cut, polished and etched with acid," said Tim McCoy, a rover team member from the Smithsonian Institution in Washington. "Sometimes it shows up on the surface of meteorites that have been eroded by windblown sand in deserts, and that appears to be what we see with Block Island."

Opportunity found a smaller iron-nickel meteorite, called "Heat Shield Rock," in late 2004. At about a half ton or more, Block Island is roughly 10 times as massive as Heat Shield Rock and several times too big to have landed intact without more braking than today's Martian atmosphere could provide.

"Consideration of existing model results indicates a meteorite this size requires a thicker atmosphere," said rover team member Matt Golombek of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Either Mars has hidden reserves of carbon-dioxide ice that can supply large amounts of carbon-dioxide gas into the atmosphere during warm periods of more recent climate cycles, or Block Island fell billions of years ago."

Spectrometer observations have already identified variations in the composition of Block Island at different points on the rock's surface. The differences could result from interaction of the rock with the Martian environment, where the metal becomes more rusted from weathering with longer exposures to water vapor or liquid.

"We have lots of iron-nickel meteorites on Earth. We're using this meteorite as a way to study Mars," said Albert Yen, a rover team member at JPL. "Before we drive away from Block Island, we intend to examine more targets on this rock where the images show variations in color and texture. We're looking to see how extensively the rock surface has been altered, which helps us understand the history of the Martian climate since it fell."

When the investigation of Block Island concludes, the team plans to resume driving Opportunity on a route from Victoria Crater, which the rover explored for two years, toward the much larger Endeavour Crater. Opportunity has covered about one-fifth of the 19-kilometer (12-mile) route plotted for safe travel to Endeavour since the rover left Victoria nearly a year ago.

Opportunity and its twin rover, Spirit, landed on Mars in January 2004 for missions originally planned to last for three months. Both rovers show signs of aging but are still very able to continue to explore and study Mars.

posted 09-25-2009 10:49 AM               

18 months ago - I did two things. I found the HiRISE DEM's and I figured out how to use them. However, time and hardware move on and I thought the 3rd martian birthday of Spirit and Opportunity was a good excuse to revisit the techniques involved and try and improve where I could, on that work of 2008. Whilst I don’t think the end results are much improved, they are a bit different. I’ve made it a little hazier to mark the moderate dust storm that helped to blow out the 3 birthday candles. An intro credit page to avoid it being badly credited and described if it’s repeated elsewhere has been bolted onto the beginning, and a map has been bolted onto the end. A sound track courtesy of creative commons music. And most importantly, Spirit in her current predicament, up to the wheel-hubs in dusty sandy hate inducing Mars soil.

This then is my Columbia Hills, 2.0. My 130 second tribute to the teams that worked to produce data that documents our exploration.

posted 11-12-2009 12:26 PM               

NASA to Begin Attempts to Free Sand-Trapped Mars Rover

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," McCuisition 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.

posted 12-05-2009 10:50 AM               

The latest discovery is that Spirit is stuck on the boundary of a sulfate rich soil deposit. Sulfates are minerals formed by steam vents, so this important new information about the history of water on Mars.

Sandtrapped Rover Makes a Big Discovery

Homer's Iliad tells the story of Troy, a city besieged by the Greeks in the Trojan War. Today, a lone robot sits besieged in the sands of Troy while engineers and scientists plot its escape.

Welcome to "Troy" – Mars style. NASA's robotic rover Spirit is bogged down on the Red Planet in a place the rover team named after the ancient city.

So why aren't scientists lamenting?

"The rover's spinning wheels have broken through a crust, and we've found something supremely interesting in the disturbed soil," says Ray Arvidson of the Washington University in St. Louis...

posted 12-15-2009 05:54 PM               

Unexpected Wheel-Test Results

Diagnostic tests were run on Spirit's right-rear wheel and right-front wheel on Sol 2013 (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 2013 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.

posted 12-18-2009 07:51 AM               

Right-Front Wheel Rotations

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.

posted 12-31-2009 12:22 PM               

NASA's Mars Rover Has Uncertain Future as Sixth Anniversary Nears

NASA's Mars rover Spirit will mark six years of unprecedented science exploration and inspiration for the American public on Sunday. However, the upcoming Martian winter could end the roving career of the beloved, scrappy robot.

Spirit successfully landed on the Red Planet at 8:35 p.m. PST on Jan. 3, 2004, and its twin Opportunity arrived at 9:05 p.m. Jan. 24, 2004. The rovers began missions intended to last for three months but which have lasted six Earth years, or 3.2 Mars years. During this time, Spirit has found evidence of a steamy and violent environment on ancient Mars that was quite different from the wet and acidic past documented by Opportunity, which has been operating successfully as it explores halfway around the planet.

A sand trap and balky wheels are challenges to Spirit's mobility that could prevent NASA's rover team from using a key survival strategy for the rover. The team may not be able to position the robot's solar panels to tilt toward the sun to collect power for heat to survive the severe Martian winter.

Nine months ago, Spirit's wheels broke through a crusty surface layer into loose sand hidden underneath. Efforts to escape this sand trap barely have budged the rover. The rover's inability to use all six wheels for driving has worsened the predicament. Spirit's right-front wheel quit working in 2006, and its right-rear wheel stalled a month ago. Surprisingly, the right-front wheel resumed working, though intermittently. Drives with four or five operating wheels have produced little progress toward escaping the sand trap. The latest attempts resulted in the rover sinking deeper in the soil.

"The highest priority for this mission right now is to stay mobile, if that's possible," said Steve Squyres of Cornell University in Ithaca, N.Y. He is principal investigator for the rovers.

If mobility is not possible, the next priority is to improve the rover's tilt, while Spirit is able to generate enough electricity to turn its wheels. Spirit is in the southern hemisphere of Mars, where it is autumn, and the amount of daily sunshine available for the solar-powered rover is declining. This could result in ceasing extraction activities as early as January, depending on the amount of remaining power. Spirit's tilt, nearly five degrees toward the south, is unfavorable because the winter sun crosses low in the northern sky.

Unless the tilt can be improved or luck with winds affects the gradual buildup of dust on the solar panels, the amount of sunshine available will continue to decline until May 2010. During May, or perhaps earlier, Spirit may not have enough power to remain in operation.

"At the current rate of dust accumulation, solar arrays at zero tilt would provide barely enough energy to run the survival heaters through the Mars winter solstice," said Jennifer Herman, a rover power engineer at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The team is evaluating strategies for improving the tilt even if Spirit cannot escape the sand trap, such as trying to dig in deeper with the wheels on the north side. In February, NASA will assess Mars missions, including Spirit, for their potential science versus costs to determine how to distribute limited resources. Meanwhile, the team is planning additional research about what a stationary Spirit could accomplish as power wanes.

"Spirit could continue significant research right where it is," said Ray Arvidson of Washington University in St. Louis, deputy principal investigator for the rovers. "We can study the interior of Mars, monitor the weather and continue examining the interesting deposits uncovered by Spirit's wheels."

A study of the planet's interior would use radio transmissions to measure wobble of the planet's axis of rotation, which is not feasible with a mobile rover. That experiment and others might provide more and different findings from a mission that has already far exceeded expectations.

"Long-term change in the spin direction could tell us about the diameter and density of the planet's core," said William Folkner of JPL. He has been developing plans for conducting this experiment with a future, stationary Mars lander. "Short-period changes could tell us whether the core is liquid or solid," he said.

In 2004, Opportunity discovered the first mineralogical evidence that Mars had liquid water. The rover recently finished a two-year investigation of a half-mile wide crater called Victoria and now is headed toward Endeavor crater, which is approximately seven miles from Victoria and nearly 14 miles across. Since landing, Opportunity has driven more than 11 miles and returned more than 132,000 images.

posted 01-14-2010 04:46 AM               

Just a Few More Approaches to Try for Extrication

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.

posted 01-21-2010 06:24 PM               

• NASA's Opportunity roves Mars (2010)
  
• NASA's Spirit stationary Mars mission (2010)