Tag: Spirit Rover

Mission managers for the Mars Exploration Rover program announced this week that the Spirit rover will likely never rove again on Mars. But that doesn’t mean her life is over. However, with the rover virtually immobile and stuck in a sand trap, she currently is in a very vulnerable and potentially “deadly” situation as winter approaches on Mars’ southern hemisphere. Pointing the rover’s solar panels towards the sun is critical if the rover is to survive, and the rover team has just a handful of drives to make it so. And the winters are long and harsh on Mars. “The temperatures will be colder than anything Spirit has experienced before,” said John Callas, project manager for the MER mission. “This is a much more difficult and dangerous situation for Spirit, and we’re heading into a regime where vehicle is going to get colder than it ever has.”

What is Spirit facing, and what are her odds?

“Spirit will be experiencing decreasing power levels, and we will likely see energy levels that will drop below 160 watt hours,” said Callas, which is the level of power the rover needs to maintain so it can communicate daily with Earth. “If we can’t maintain that level, that will trip a low power fault where the rover shuts down or hibernates, taking the necessary steps to preserve as much power as possible. Everything is turned off except the master clock, and all the photons that hit solar arrays go into charging the batteries.”

In this low-power fault, a timer wakes the rover up occasionally to check battery levels, and if there is enough power, Spirit will wake up enough to see how charged the batteries are and attempt to communicate with Earth. “Spirit will be like a polar bear hibernating, possibly for several months, maybe on the order of 6 months that the rover will be in this state,” said Callas. “It won’t be like the Phoenix lander where it shuts down virtually completely. The rover will still be electrically active, but not with enough power to be awake each day.”

Callas predicted it will be in the March-April time frame here on Earth when they run out of ability to communicate with rover because there won’t be enough power.

Normally the rover stays warm enough simply by being “on” and running, like running your car in the winter to warm it up. But since rover will be deeply sleeping, temperatures on the rover will drop.

Callas and his team are concerned that temperatures on the rover will get very cold. Based on past winters, they expect about -40 to -50 C temperatures on Mars during the depths of winter. The electronics on the rover can withstand -40 degrees C when operating and -50 c when the rover is idle. But these standards are for a brand-new out-of-the-box rover, Callas said, not a 6 year-old rover with electronics have gone through many different temperature cycles.

Ironically, the fumaroles or steam vents that likely created the very scientifically rich “Troy” area where Spirit sits would have made it a “hot spot” on Mars. But, of course, the fumaroles are no longer active.

The rovers do have three 1-watt Radioisotope Heater Units (RHUs) which are tiny thermal heating units used to keep motors and batteries warm on the rover, so Spirit’s important insides will not get as cold as the outside.

But power from the solar panels is very important for keeping the computer and other electronics active, and right now, the position of the solar panels is not at all optimal.

“Our primary mission is to get solar panels pointed toward sun improve her chances,” said rover driver Ashley Stroupe. “Ideally the solar panels should be pointed toward the sun, to maximize the energy the rover receives. If we can get enough power to keep the rover warm, that will shorten the amount of time Spirit may have to be in a low power state.”

In upcoming drives, the team will try to get left rear wheel of the rover lifted up, by driving backward and improving its northerly tilt. Spirit is sitting in a small crater with the rim behind her, so as it moves backwards, it is slowly climbing up on the rim, tilting the rover. “On the last drive we saw 1-2 degree improvement in tilt,” Stroupe said on Tuesday. “So we’re going to do as much improvement as we can by continuing to drive backward. We can an also attempt to rotate the rover in place, so that the roll isn’t pointed as much towards the south as it is now.”

Each degree of tilt towards the north gains 5 watt hours of improvement. One upside is that the solar panels are currently fairly free of dust accumulation.

When the rover attempts to wake up each day, it will be at about noon local time on Mars, when the electronics will have warmed up because of sunlight.

But there’s the possibility the team might not hear from the rover for months.

“We have to be prepared to go through a period like this,” said Callas. “We may not hear from rover, and it will be frustrating and challenging for the team, but we’ll have to be disciplined about this, and hopefully when power resumes we can resume communication in the spring.”

“That’s a very complex problem,” Callas told Universe Today at the Tuesday’s press conference. “The rover will actually experience two levels of fault protection. The rover takes action based on hearing from Earth, and if we go too long without talking to the rover, it trips an up loss timer. We only keep about 6 weeks of communication tables on the rover, so that likely will have run out. All these things make for a complex recovery effort for the rover. It is hard to say how long we would try, because we would have to try many things before we exhaust the list of things we can do.”

Callas didn’t want to give odds if Spirit will make it through the winter. “Spirit’s best chance for survival is when we can stay in contact with her,” he said. “As long as we can maintain communication with rover we can look out for trouble, and advise her on how to best reapportion her limited resources.”

MER PI Steve Squyres said not having a roving rover is a “poignant moment” for the team. “We built the rovers to drive around, so we have shifted our focus to a different class of activities. It is a change and one we’ll have to adapt to. But this is a much better way that having an abrupt end to the mission, which would preclude doing the kind of science we’re looking forward to.” (Read more about the science Spirit can do in our earlier article)

“We have hope that Spirit will survive this cold dark winter that Spirit has ahead of her,” Squyres said.

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The Spirit rover’s driving days are likely over, as efforts to extricate the rover have been curtailed. “We do not believe that Spirit is extractable,” said Doug McCuistion, director of NASA’s Mars Exploration Program. But mission managers stressed that today is not a day of loss at this point, as they hope to continue to make some exciting scientific observations. However, the rover needs to be tilted to gather as much sunlight as possible in order to survive the Martian winter. John Callas, project manager for the MER mission told Universe Today at today’s press briefing that time is short. “We estimate about three weeks of driving activity, and we can’t drive every day,” he said. “So there are just a handful of drives left before there is insufficient power to continue.”

Callas added that around the March-April time frame will be the last images and data the rover can transmit before going into hibernation for the winter.

Spirit has been embedded in a sandtrap for 10 months, and the rover team has been engaged in an ambitious process to extricate the rover. They’ve encountered numerous setbacks, including the loss of use of an additional wheel, making it a four-wheeled rover. (Spirit’s right front wheel has not worked for a couple of years, now the right rear wheel has lost functionality).

Pointing the rover’s solar panels towards the sun is critical if the rover is to survive. In past winters, the movable rover has been able to be positioned to allow for maximum sun-gathering but the current embedding of the rover has left it with an unfavorable tilt, 9 degrees to south, when they really want a level rover — or even better — tilted to north.

Rover driver Ashley Stroupe said the rover is now pitched flat and rolled to left. “We want to try to pitch it forward and roll right for best winter survival.”

The last few drives were aimed at trying to improve the rover’s position, and were mildly successful.

“We’ve aimed toward improving northerly tilt,” said Stroupe. “Spirit is sitting in a small crater with the rim behind her, so as it moves backwards, it is slowly climbing up, providing more tilt. On the last drive saw 1-2 degree improvement in tilt.”

In recent drives, the rover has moved approximately 20 centimeters. The team can also attempt to rotate the rover in place, so that the roll isn’t pointed as much towards the south as it currently is.

Should they be successful, and if the rover survives the winter, the science team has some exciting prospects of continuing science with Spirit.

“We have hope that Spirit will survive this cold dark winter that she has ahead of her,” said MER principal investigator Steve Squyres. “The bottom line is we’re not giving up on Spirit.”

Squyres said they are most excited about tracking the radio signal from Spirit in order to determine if Mars has a solid or liquid core. “This is something totally new, something we’ve never done,” Squyres said. “If we can accurately determine the rover’s motion in space in three dimensions, we can see the motions of Mars in orbit and track it precisely, then we can characterize the wobble very precisely. The way Mars wobbles depends on its internal structure. If Mars has a solid core of iron, will wobble one way but if it has a liquid molten core it will wobble another way. We should be able to do this by tracking the stationary rover for six months.”

Squyres said the team is finding new tricks on how to use a stationary rover. Additionally, they should be able to characterize the odd soil at the Home Plate region, and characterize the interactions between the atmosphere and the surface of Mars.

“We’re not giving up on Spirit and we’ll keep squeezing as much science out of the rover as we can,” Squyres said. “We feel there is a lot of really exiting science yet ahead.”

Source: Press briefing

In just a few days, the Spirit rover will celebrate six incredible years on Mars. But JPL put out a press release today, as well as the video above, saying the outlook for Spirit’s survival is not good. Being stuck in a sand trap with wheels that aren’t working well are challenges to Spirit’s mobility that could prevent the rover team from using a key survival strategy — positioning the rover’s solar panels to tilt toward the sun to collect power for heat to survive the severe Martian winter. “The highest priority for this mission right now is to stay mobile, if that’s possible,” said Steve Squyres, principal investigator for the rovers.

I’m still holding out hope, however, that the rover team will work another miracle, and that 2010 will be another happy year for Spirit on Mars — see the image below created by Stu Atkinson.

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But if mobility is not possible, the next priority is survival. To to that, the rover team will attempt 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.

Source: JPL

Could it be true that the old gimpy wheel on the Spirit rover is making a comeback? The right-front wheel, which stopped operating way back on Sol 779 (March 13, 2006), surprised engineers by indicating normal resistance and turning slightly during a resistance test for that wheel. Spirit, which has been stuck in soft soil for several months, recently got bad news that the right rear wheel also stopped working (Nov. 21), leaving her with just four of six wheels operational. Engineers conducted tests on Dec. 12 and the right rear wheel continued to show no motion and exhibited very high resistance in the motor winding. Just for fun (I’m assuming) engineers also test the right front wheel – the wheel that Spirit has limped with in coming down from the top of Husband Hill and making the trek across Gusev Crater to the Home Plate region where she currently sits. In surprises of all surprises, the old gimpy wheel showed signs of life.

Diagnostic tests were run on Spirit’s right-rear wheel and right-front wheel on Sol 2013 (Dec. 12, 2009). The recently stalled right-rear wheel continued to show no motion. Engineers expected nothing from the right front wheel. The last time it was checked was just after its apparent failure in 2006 and at that time indicated an open circuit. JPL says that although no clear theory for failure had been established, the failure was generally regarded as permanent.

JPL also says 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, which will test the functionality of both the right-front and the right-rear wheels. The results are expected Wednesday.

Spirit continues to surprise….stay tuned!

Mission managers sent the drive commands to the Spirit rover at 4 a.m. EST (0900 GMT) today, — Nov. 17, 2009 and Sol 2088 for the rover — but the data back from the rover indicates the rover stopped less than one second after it began moving its wheels when the rover automatically sensed more lateral tilt than permitted. A tight limit on vehicle roll and pitch of less than 1 degree change was set for this first drive, and as the rover began its first move, it sensed that its roll was outside the allowed limit and safely stopped the drive. Those driving the rover say they are 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. The team hopes to completion their planning of the next drive on Wednesday, Nov. 18, with possible wheel movement again on the 19th (Sol 2090)

At last week’s press conference about the attempt to extricate Spirit from the Martian sand trap, the rover team stressed this procedure could take weeks or months, with the likelihood of not being successful.

Learn more about the process in this video footage of the rover testing and planning teams.

Source: Free Spirit