'Something' Cleaning Mars Rover

bluenirve writes "'Something' has been cleaning the solar panels of the Mars rover Opportunity. "NASA's Mars rover Opportunity seems to have stumbled into something akin to a carwash that has left its solar panels much cleaner than those of its twin rover, Spirit. A Martian carwash would account for a series of unexpected boosts in the electrical power produced by Opportunity's solar panels.""

Nitrogen

[panxerox]

I've always wondered why they never put a little bottlie of compressed nitrogen on the rover with nozzels pointed at the panels. Press a switch on earth and pffftt! dust be gone!

I don't know why

[eclectro]

they just didn't put a windshield wiper with a mister on the rovers.

Then there would be water on Mars!

Re:Wind maybe?

[Control Group]

The reason wind isn't the obvious answer it seems like is that the Martian atmosphere is so thin. I remember seeing (on Discovery HD, IIRC) a wind tunnel simulation NASA was doing to study dust devils on Mars. They set up the chamber at Martian atmospheric pressure, then cranked up a fan to blow some insanely high wind speed. The fine dust on the floor didn't even budge; there just wasn't enough air to make anything happen.

The only way they were able to replicate the observed dust devil effects was to toss larger pebbles into the chamber, kicking the dust up into the wind.

Anyway, the point is that wind is still the most probable cause, but it's not quite the obvious slam-dunk that it superficially seems.

Design

[FiReaNGeL]

NASA engineers decided not to put wipers on the solar panels, because it would have been too much trouble / added too much weight. I guess they're pretty happy with their decision now, with the 'unexpected' cleaning events...

Re:would wind work

[MightyMartian]

> We had gusts up to 98mph earlier this week and my car looks as dirty as ever

I suspect the dirt that's covering your car is not much like the particulate on the rovers.

dust devils?

[jokach]

The article states:
And the researchers suspect the shape of the crater may encourage the development of dust devils or other wind patterns that could help scrub the panels.

The tornado like winds that can be caused by dust devils is something that was discussed by NASA back in April and surely seems like the real answer:

http://www.space.com/scienceastronomy/dust_devils_ 040420.html [space.com]

I'm not sure why they think its such a mystery now ...

Re:hmmm...

[Jester99]

You would think they would have built a wiper to sweap the dust off, or maybe some high pressure air hose or fan. Or thy could have added an ability to vibrate the dust off.

I got to ask a NASA engineer about this once in person.

He said they considered it. But then you have to remember that each of these things has moving parts, which are prone to getting dust in them and clogging, or breaking, or whatever. If you wanted, you could also have multiple layers of solar panels and when one got too dusty, it could "molt" and then the fresh panel would be exposed. They've thought of each of these things.

The problem is that they all add complexity and weight. When you're trying to hurtle something at a planet and have it touch down for landing, making the damn thing bulkier doesn't exactly add to reliability.

If your robot vibrates, then that could loosen screws and the whole thing could rattle itself into a pile of scrap metal.

If your robot blows itself off with an air hose, then you need to have a filter system so you know you're not blowing dusty air on it. But filters get clogged, so eventually the hose system would stop working, and the panels would get dusty.

If your robot molts panels, you then need to add extra motors to lift off a given layer. But these are heavy, and could break. Heavier = more power draw to move around. So if the motors malfunctioned, it wouldn't have gone as far as it would've if it only had a single layer of panels -- meaning you'd get less exploring done.

Wiper motors ... same problem.

Nothing political about it.

Re:hmmm...

[cot]

What about several layers of thin clear plastic that's tensioned?

You have each layer held down with tabs,and release them one by one as the cells accumulate dust. The released plastic curls up at one end of the cells when released.

You could probably do this at least several times.

Re:hmmm...

[Anonymous Coward]

Sounds a lot like what they use in motorcross.They have multiple layers on the goggles that can be pulled off. Also the cameras they put on race cars use this, but its a continuous roll.

Re:hmmm...

[cot]

Well, I was actually thinking of something that didn't come completely off, but sat off to the side, either crinkled or rolled up. So it'd have to be stretched to cover the cells(hence the "tensioned" part of the original post)

the continues film on rollers idea another person posted is nice too. As long as the thing in front of the cells is clear, how bad can failure be? If it doesn't come off, it's no worse than if it weren't there.

you'd just have to be damn sure it didn't come off completely and jam in some other system, but i think that's true for just about every part of the rover.

Re: Water clearly visible on Mars?

[Anonymous Coward]

http://qt.exploratorium.edu/mars/jpl-images/web/op portunity/pancam/2004-12-19/1P155450047EFF38EVP255 7L4M1.JPG [exploratorium.edu]

Look in the bottom right corner. Looks like a pool of water to me. And this is supposedly a picture from Mars. Just a thought...

Ultrasonic cleaning

[EvilMidnightBomber]

I had almost exactly the same problem when prototyping my robot lawn mower. (crappy pic in profile) The first rev. used optical interrupters to sense a cut grass edge, and these would rapidly become unusable due to dust. I ran through the feasibility of using such an onboard(liqufied) gas tank, but the ratio of functionality to weight is king in any mobile (and especially spaceborne) app and this falls short on that mark (beside being non-renewable). Wipers (and worse yet the geared motor to drive them) are similarly bulky, and unless you're using diamond coated optics,(no water here to lubricate things) wiping the dust eventually produces hazing due to microscratches. The solution I found was to incorporate the equivalent of an ultrasonic parts cleaner. A cheap high-powered motorola peizo tweeter from rat-shack acoustically coupled to the optics support bar and driven at 40khz does an incredible job of knocking off ALL the loose dust, and it's very light weight. The rover could do the same thing by tilting it's panels vertically and then letting rip with the u-sound. About one x-ducer per square meter is all it would take.

Re:Nitrogen

[shiftless]

What could possibly happen to cause a failure of the bottle that wouldn't also annihilate the probe?

Keeps going and going and going...

[Nalez]

I have been folowing the MER stuff a bit, and when they put these suckers on mars, I would have never expected them to last this long. Remember that Pathfinder lasted about 90 days. If everything went as it should, I would have expected one of the two MER rovers to last 200 days.

Both rovers are still up and running, and pushing 340 days of operation. At this rate, one of them is sure to last 365 days.

I think we do not give enough credit to this program. the MER team took a robot, threw it on a rocket, sent it to mars, had it land on mars, and both rovers have been running for over 300 days. I think this is just simply amazing.

Re:hmmm...

[Lumpy]

then why do they not take a cue from NASCAR and Motocross and have thin mylar tear offs on the panels? that technology has existed cince 1980.

one on each would ass less than 1/2 gram of weight and using one of the motors that already exists for folding the panels out to perform the tear off would solve the motor problem.

There really is no excuse except maybe that the materials available for the thin tear offs may reduce the output way too much or might react badly with the higher UV index there and yellow really quickly.