Mars Rover "Spirit" In Danger

Riding with Robots writes "Just days after announcing that the Mars Phoenix Lander has met its icy demise, NASA reports that a dust storm has left the rover Spirit on the edge of power failure. During one recent Martian day, the robotic geologist's solar array produced only 89 watt hours of energy, the lowest output by either rover in their nearly five years on Mars. Mission managers are taking steps to protect the hardy, battle-worn spacecraft, but the agency describes Spirit's status as 'vulnerable.'"

Comments

Re:It's been a good run

[UnknowingFool]

Both rovers were designed for a 90 Mars day (sol) mission. The difference between Earth days and Mars days is that sols are 24.6 hours long. Opportunity is on Sol 1710 or so and Spirit is on Sol 1730. Both rovers have lasted almost 20 times longer than originally designed.

Re:Anonymous Coward

[UnknowingFool]

NASA probably thought of that, but the issue is how practical any wiper system would be. Unlike automobile wipers, there's no air or water supply to remove the dust. Adding a system to compress air would have added unacceptable weight to the rover and every little bit counts (even if would work reliably under Mars conditions). A water system would have been out of the question. A waterless/airless system then depends on the material you would use. Such a material would have be softer than the panels or they would damage them; however, a softer material (rubber, polypropylene, polyethylene) probably would not survive the extreme conditions of Mars.

And that's just the survivability aspects. Now factoring the usability aspects: Some sort of arm would have to be long enough to reach all the panels. None of the rovers arms can extend that far so they would have to have been modified. This might add weight and complexity.

Probably the biggest reason why NASA didn't put one in was the rovers were designed for 90 sol missions. Having them last 5 years is a bonus. Along the way, the Rover team has dealt with the problems that have come with extending the mission beyond the original parameters: wheels no longer work, tools no longer function, dust storms limit power usage, etc. This is one issue that they knew would eventually cause the rovers to cease functioning after a few years.

Re:Winter?

[ScottMaxwell]

Isn't this just an effect of reduced sunlight during winter? Or is Spirit near the equator / other hemisphere? I know the Phoenix shutdown is at least partly due to seasonal changes

Time of year plays into it, certainly; this would be less worrisome at the height of summer. But it's not quite the dead of winter, either (solstice was something like 150 sols ago), so it could be worse.

Spirit is a little farther from the equator than her twin sister, Opportunity, so winters hit her somewhat harder than they hit Opportunity anyway. (Phoenix is at something like 60 degrees N latitude -- much farther than either rover.) On top of that, she was pretty well dust-covered already, thanks to a previous dust storm and the regular old ongoing dust-deposition process -- dust was blocking about 70% of the light hitting her solar arrays before this storm hit.

It's possible for this to turn out to be good news. Dust storms are caused by (and, in a classic feedback loop, cause) high winds, so it's possible that the winds will actually clean Spirit off and she'll end up better than she was before. Keep your fingers crossed.

Putting it in perspective.

[DerekLyons]

The Planetary Society blog has a composite picture of Spirit from two years ago and today which shows starkly just how much dust has accumulated.

Not to be pedantic but...

[mykepredko]

The two rovers were not designed to work for 90 days.

They were guaranteed to work for 90 days.

The various components were designed to work no matter what they experienced for 90 days on the Martian surface.

I suspect that they were designed for the worst possible set of circumstances for 90 days which has allowed them to operate for the much longer time in the actual environment which is more benign than the worst case scenario.

Regardless of the semantics of the 90 days, the time the two robots have been operating is still an amazing achievement and everybody involved should be very proud.

myke

Re:Not to be pedantic but...

[iamlucky13]

They were indeed designed to work for almost the worst conditions expected for 90 days, based on what prior landers saw. If you read Dr. Steven Squyre's book Roving Mars (which I highly recommend for any space nerd, even though he wrote it several years too early), he describes at several points how worried they were that dust accumulation was going to kill these things before 90 days were up.

After talking about wipers, blowers, vibrators, etc. they concluded the best course of action was to just size the panels to produce the minimum required amount of electricity for operations after 90 days of worst-case dust accumulation. An added bonus of this approach was plenty of power to play around with early in the mission (and part of why they've done so well now). Accomplishing this ended up being a huge problem, however, and I think the power team spent weeks trying to figure out a geometery that would provide the needed amount of surface area, but not get in the way of all the other parts while folding down small enough to fit inside the tetrahedral lander platform. They finally got a break when they figured out a set of winglet-like tabs that unfolded from the back of an already folded section of panel.

The result didn't just solve the problem, it looked freaking awesome. Earlier renders of the rovers had them being nearly square or hexagon shaped, as opposed to the swept-back fighter wing look they have as built. Heck, Steve Jobs is probably even jealous of how sexy the MER's look, and they aren't even trying.

Re:Pedantic griping on the units

[compro01]

Which is why they are using Watt-hours, which are a unit of energy equal to 3600 joules (1 Joule=1 Watt-second).