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NASA Mars Rover Spirit
The robot has been silent for over a year now, but made revolutionary contributions to space science in its time

After six years of active exploration and one year of silence on Mars, NASA has finally decided to call it quits for one tough robot that has been put to rest.

Spirit, a golf cart-sized, solar-powered robot geologist that was sent to Mars in 2004, spent six long years traveling the Martian surface. But after enduring many harsh winters on Mars, Spirit finally fell silent last year, and will be removed from the mission next week. 

In January 2004, Spirit and its twin, Opportunity, were parachuted onto opposite sides of Mars for what was supposed to be a three-month expedition. The robots were designed to scale craters and hills while drilling into rocks along the way. The robots would then record data to their flash memory, which would be sent to deep space antennas in California, Australia and Spain. 

Spirit and Opportunity were very popular back on Earth. People would follow their journey through every crater and rock, eager to hear what was found on the Red Planet. 

But the robots were more than just machines feeding NASA scientific feedback. They seemed to take on different personalities, with Opportunity being the overachiever and Spirit being the troublesome and sometimes misguided sibling. When the robots first landed on Mars, Opportunity ended up in an ancient lakebed that was rich with water-forming materials, showing that Mars, which is now a dry planet, was once wet and tropical billions of years ago. Spirit, on the other hand, landed in a crater named Gusev that was the size of Connecticut and possessed very little evidence of a watery past for Mars.

Not long after landing, Spirit began sending "nonsense data" back to Earth and fell into critical condition, but NASA engineers were able to bring Spirit back to health. 

But Spirit's time on Mars was not frivolous by any means. In 2005, it managed to climb a mountain the height of the Statue of Liberty, and was even the first to record Martian dust devils. It also discovered a patch of "nearly pure silica" on the Home Plate section of Mars.

But in 2006, Spirit showed signs of complications once again. One of its front wheels stopped spinning, which made Spirit travel backward and drag the bum wheel. It also started to "forget" to save data to its flash memory. Then, in April 2009, Spirit got stuck in a sand pit, and engineers were unable to get it out. Spirit was forced to remain stuck there until the present time, but in the early days of its self-inflicted solitary confinement, Spirit was still able to send data back about rocks within reach.

Engineers blame the harsh Martian winters for Spirit's continuous problems. At times, Spirit's internal temperature was minus 67 degrees Fahrenheit, and engineers had no way of tilting the robot toward the low winter sun, which would have warmed Spirit through its solar panels.

In January 2010, NASA officially announced the end of Spirit's career. It was a stationary spacecraft at that point, and began to fall silent. For over a year, orbiting spacecraft attempted to provoke any sign of life from Spirit, but there was no such luck. 

NASA plans to make one last effort to make contact with the robot Wednesday, and a final farewell is planned next week after Memorial Day. Engineers expect the farewell to be "more like an Irish wake than a funeral" in celebration of Spirit's long life and revolutionary contributions to space science. 

Over its six years of activity, Spirit traveled 4.8 miles.

"This is a story of perseverance," said Jim Bell, a mission scientist at Arizona State University. "Spirit got a lot of bum breaks, including almost dying early on and wheel problems."

While Spirit's journey is over, the exploration of Mars is not. Opportunity is still scaling Mars' surface at full health, and has traveled 18.5 miles since landing in 2004. It is now journeying toward a crater called Endeavour, which is less than three miles away from its present location. NASA expects the robot to make it to the crater's rim by the end of the year. 

In addition, NASA plans to send a Mini Cooper-sized mega-rover onto Mars in Summer 2012 to accompany Opportunity in its exploration. 

Spirit's farewell will be broadcasted next week on NASA TV.



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RE: it goes like a lightning
By kattanna on 5/25/2011 3:03:00 PM , Rating: 5
its all about energy. or the lack of it in this case. if they could have been equipped with a RTG power source

http://en.wikipedia.org/wiki/Radioisotope_thermoel...

it could have driven around the clock without having to stop at night and then waiting for the battery to fully recharge the next day before venturing further out.

but too many ignorant fear mongers who style themselves as "environmentalists" make sure that doesnt happen.


RE: it goes like a lightning
By FITCamaro on 5/25/2011 3:17:53 PM , Rating: 4
In the words of Eric Cartman

God damn HIPPIES!


RE: it goes like a lightning
By omnicronx on 5/25/2011 3:57:29 PM , Rating: 2
Was that specifically stated as the reason though? As pretty much all probes have made use of them, and so will new Mars Science Laboratory set to launch this year.


RE: it goes like a lightning
By Master Kenobi (blog) on 5/25/2011 5:55:00 PM , Rating: 2
The only probes that end up with RTG power sources are ones that go beyond the asteroid belt as Solar power is impractical at those distances. Anything closer can be several different types but I agree that for planetary missions on Mars, RTG is the best bet and most bang for our buck. Orbiting relay satellites can utilize solar.


RE: it goes like a lightning
By B on 5/25/2011 6:47:52 PM , Rating: 5
From wikipedia: The Mars Science Laboratory (MSL) (aka Curiousity) is a United States space administration (NASA) mission with the aim to land and operate a rover named Curiosity on the surface of Mars. It is scheduled to launch on November 25, 2011 and land on Mars on August 6, 2012.

The Curiosity rover will be powered by radioisotope thermoelectric generators (RTGs), as used by the successful Mars landers Viking 1 and Viking 2 in 1976 Radioisotope power systems are generators that produce electricity from the natural decay of plutonium-238, which is a non-weapons-grade form of that radioisotope used in power systems for NASA spacecraft. Heat given off by the natural decay of this isotope is converted into electricity, providing constant power during all seasons and through the day and night, and waste heat can be used via pipes to warm systems, freeing electrical power for the operation of the vehicle and instruments.

The RTG system is designed to produce 125 watts of electrical power at the start of the mission and 100 watts after its minimum lifetime of 14 years.[26][27] The MSL will generate 2.5 kilowatt hours per day compared to the Mars Exploration Rovers which can generate about 0.6 kilowatt hours per day.


RE: it goes like a lightning
By Solandri on 5/26/2011 12:11:25 PM , Rating: 2
Viking 2 was lost after about 3.6 years due to a battery failure. Viking 1 was lost after 6.3 years when a command inadvertently overwrote part of its antenna pointing software. Its RTG was still fine, and expected to last for a decade or more.

Interestingly, Spirit lasted 6.2 years, and Opportunity is still going strong after 7 years. So while there are high expectations for Curiosity, there's still a good chance some other component failure will kill it before it exceeds Spirits lifespan.

That said, having constant power from the RTGs will mean it can operate 24/7 instead of having to shut down at night and during winter. So it will get a lot more useful work done in a shorter amount of time than the MERs.


RE: it goes like a lightning
By delphinus100 on 5/25/2011 6:48:53 PM , Rating: 2
This isn't just about radioactive material. (Though the PR problem can't be ignored, either)

Every space probe has specific mass, volume, and power limits, working all the way back to the launcher, that you can't just 'make bigger.'

Putting an RTG (or anything else with a greater-than-zero mass and volume) on board, would mean taking one or more experiments off the rovers to fit it in, partially defeating the purpose of the whole mission. Go ahead, you tell the Principal Investigator(s) hat their experiment(s) have to be dropped. I'll watch...

And speed of light delays in control being what they are, you need to plan every move carefully, anyway. Just because you can drive 'around the clock' doesn't mean you should.

Both machines greatly exceeded their design lifetimes, especially as physical maintenance was impossible. Enjoy and move on...


RE: it goes like a lightning
By dcollins on 5/25/2011 7:59:51 PM , Rating: 2
Where did you get the notion that environmentalists had anything to do with that decision? I think they used solar panels in order to reduce weight. The next generation Mars Rover is much larger so the additional weight is justified.


RE: it goes like a lightning
By randomly on 5/26/2011 10:18:58 AM , Rating: 2
The new RTG powered Mars Science Laboratory doesn't drive all night either, it stops to recharge it's batteries at night. The power demands of the motors exceed the power available from the RTG so the MSL uses batteries much like Spirit and Opportunity do.

The big advantage is reliable power and heat. Power is not dependent on dust storms, dust accumulation, or sun angle like the MERs were. It can operate at full capacity in shadow and winter time. The MERs were sometimes stuck for 5 months at at time during the Martian winter waiting for solar power to be strong enough to move the rover. It was crucial to retain enough battery power to keep the internal systems from freezing at night. On the MSL waste heat from the RTG is used to keep the systems warm. Dust accumulation on the solar panels also cut solar power considerably. Dust storms were another big threat not just from the threat of dust accumulation but the airborne dust blocked out most of the sunlight for weeks at a time.
http://www.nasa.gov/images/content/182691main_mer-...

The major drawback of RTGs is cost. They are very expensive, not only in materials cost, but assembly, testing, and safety procedures and safety qualification of everything down the line, especially the launch vehicle.

The Solar powered MER rovers cost about $820 Million, the RTG powered MSL cost is at $2.3 Billion.

Within the budget window for Spirit and Opportunity and the original plan for only a 90 day mission, solar was a much cheaper (and lighter weight) solution. The much more expensive Flagship class MSL is designed for a 2 year mission.

The other major problem with RTGs is the very limited supply of Plutonium-238. After the launch of the MSL later this year the total world stockpile will be less than 20Kg, and there is no longer any facility that can produce it. As a reference point MSL uses about 4kg, New Horizons (the Pluto probe) uses 7.8 kg, the Cassini probe (Saturn)uses 32.7 kg.

Any probe to Jupiter or beyond must use RTG power, as sunlight is too faint at that distance to use solar.

RTG or no RTG all comes down to money, people with anti-nuclear sentiments actually have little to do with it. RTG's are designed to be extremely robust. A launch failure dropped one in the ocean off the town I grew up in, they recovered it from the bottom of the ocean, refurbished it and flew it again.


"I modded down, down, down, and the flames went higher." -- Sven Olsen

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