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Posted by: dilo Oct 30 2007, 07:08 AM

In the last weeks, you can see again high dust levels on the sundial (perhaps comparable to pre-storm levels) and also lot of dirt/residuals on solar panels, clearly visible in Sol1355/58 self portraits!

Was the dust storm so violent to bring these smal pieces of rocks over Spirit?

Posted by: djellison Oct 30 2007, 11:58 AM

I can quite imagine stuff being airborne - or another option is dust pilling up around the complex shape of the PCMA and then falling off with motion or wind.

Doug

Posted by: slinted Oct 30 2007, 12:12 PM

Spirit's capture magnet is a mess too:

MI's from sol 1355: http://nasa.exploratorium.edu/mars/spirit/micro_imager/2007-10-26/2M246651970EFFAVQWP2956M2M1.JPG

Pre-storm comparison from sol 1230: http://marsrovers.jpl.nasa.gov/gallery/all/2/m/1230/2M235561703EFFAU00P2906M2M1.JPG

Posted by: fredk Oct 30 2007, 03:41 PM

Yeah, I noticed those marks on the panels http://www.unmannedspaceflight.com/index.php?s=&showtopic=4553&view=findpost&p=101266 but the last pre-storm views I could find had no marks. So it does look like an effect of the storm. It would be cool to see MIs of the marks, if the arm could reach.

Posted by: djellison Oct 30 2007, 04:04 PM

They can only MI the front few cells - it just doesn't reach further than that sadly

Doug

Posted by: ElkGroveDan Oct 30 2007, 05:00 PM

Hey you guys quit posting to this discussion unless it's really true. I got all excited when I saw the topic resurrected.

Posted by: Eric Hartwell Dec 12 2007, 02:12 PM

There's a nice color shot of all the dust: http://photojournal.jpl.nasa.gov/catalog/PIA10128 "The deck of NASA's Mars Exploration Rover Spirit is so dusty that the rover almost blends into the dusty background in this image assembled from frames taken by the panoramic camera (Pancam) during the period from Spirit's Sol 1,355 through Sol 1,358 (Oct. 26-29, 2007)."

I've combined this view with http://photojournal.jpl.nasa.gov/catalog/PIA03272 (Aug. 27, 2005) for comparison:
http://www.flickr.com/photos/ehartwell/2105760368/

Posted by: Oersted Dec 12 2007, 03:34 PM

Beautiful comparative view there, thanks!

Posted by: BrianL Dec 12 2007, 04:09 PM

To my eye, the "colourization" used on the new pictures seems very dull and washed out, and makes the dustiness look worse than it really is. Are there pre-storm pictures that use the same image parameters that could provide a better comparative view?

Brian

Posted by: ilbasso Dec 12 2007, 05:56 PM

To the red/green deficient pair of eyes that I'm equipped with, Spirit's panel's colors in the 2005 part of the shot were also very close in color to the surface - as close a match as in the recent JPL image.

Posted by: fredk Dec 13 2007, 12:46 AM

The colours in Eric's comparison do look a little funny. I've done a quick and dirty comparison myself, and only done a linear scaling of intensity on one mosaic to roughly match the overall brightnesses of the ground. The hues are pretty close, and the extra dust on the deck now is very clear:

Posted by: slinted Dec 13 2007, 01:30 AM

Great comparison, from both. Fredk, you've done an especially good job matching up the grounds, but I'm not sure that's a fully valid assumption (but great for a quick and dirty...no pun intended...matchup). I don't have anything firm to back this up yet, but I think the ground itself is going to be a bit lighter now as well from the copious dust that's come out the atmosphere. The whole of the Columbia Hills is inside the dark streaks left by wind and dust devils, although some of the newest MRO images suggest that is somewhat subdued now that the storm has passed.

Posted by: jamescanvin Dec 14 2007, 11:37 AM

Aggh! It happened again!

Maybe we need a "Spirit dirtier" thread?

Posted by: alan Dec 14 2007, 04:28 PM

Posts moved from Spirit cleaner thread to spare readers from unnecessary disappointment.

Posted by: Stu Dec 16 2007, 09:10 AM

Not sure why, but this caught my eye this morning looking at the new rear Hazcams... look how caked with dust Spirit is down there.... between Dec 06 and now the holes have really been smothered by the dust, and the lettering at the top has been completely hidden.

Posted by: PhilCo126 Dec 16 2007, 02:08 PM

Waaw, this rover needs another dust clearing wind

Posted by: Doc Dec 16 2007, 07:30 PM

My, my..... I am begining towonder if Lady Luck is going to smile on Spirit this time

Posted by: Doc Dec 16 2007, 07:33 PM

We had better cross our fingers because with all this dust......u can never tell.

Posted by: Shaka Feb 24 2008, 08:24 PM

Oooohh! Feelthy peectures! http://qt.exploratorium.edu/mars/spirit/micro_imager/2008-02-24/2M257129521EFFAY00P2936M2M1.JPG
This looks positively yucky. At what point do we start to think about whether running the RAT brush across it would do more good than harm?
If the choice is scratched solar panels or the Big Sleep, do we dare? How hard is the panel surface?

Posted by: djellison Feb 24 2008, 08:41 PM

The RAT would be able to reach perhaps 3 cells out of the hundreds on the array, so it would achieve nothing if it were even a sensible thing to do. Which it really isn't. You could end up expending quite a few Whrs on the operation itself, with the very best result being perhaps a 2% power increase, and the worst result being a power decrease. Most likely, you would end up with three scratched cells, a damaged RAT brush, no more power, and an entirely wasted effort.

Doug

Posted by: dvandorn Feb 25 2008, 04:38 PM

Well... we're at a 30-degree angle. How difficult would it be to use the IDD to "tap" the rover deck a few times? Maybe get the larger clumps to fall off?

No brushing, just a few taps...

-the other Doug

Posted by: brellis Feb 25 2008, 05:00 PM

If not, next spring maybe they can "shake, rattle and roll".

Posted by: nprev Feb 25 2008, 05:29 PM

Has anyone determined whether the dust is just being loosely deposited on the MERs, or if it's adhering electrostatically as well? I suspect the former since the cleaning events to date would have had to have been extremely energetic to work, but this is a good-to-know thing for future missions.

Posted by: djellison Feb 25 2008, 06:00 PM

Well - bad analogy time. Go up to your coffee table. Now touch tap it, with a motion of about 5mm/sec in one corner. Does any of the dust come off?

Posted by: ddeerrff Feb 26 2008, 01:23 AM

Can the IDD make mechanical connection with the deck? How about bringing the IDD into mechanical contact with the deck then running the RAT a bit. I would think that would produce at least a bit of vibration.

Posted by: Shaka Feb 26 2008, 02:31 AM

Ooooh, derf, Like it, like it!
Worth trying. With the RAT ground down, it could well be out of balance.
Just rest the IDD arm on the panel edge and gun it!

Posted by: nprev Feb 26 2008, 03:53 AM

Thing is, though, even if this vibration is enough to shake the dust loose, where is it going to go? What we really need is a transverse force--wind--to sweep this stuff off of Spirit.

Posted by: dvandorn Feb 26 2008, 04:30 AM

Well -- if there was flour on it, not dust, and it was close to the flour's natural angle of repose, and if I kept my coffee table at a 30 degree angle, I could answer the question... *smile*...

I'm mostly thinking that, even with a relatively slow, soft impact, even a small vibration might shift rock/salt dust if it's near the dust's natural angle of repose. Of course, we've likely gotten more of a jolt from descending down this slope than we could generate with the IDD.

I will point out that you don't see a lot of dust collected on 30-degree slopes of exposed rocks in the area, and the only things around to clean them off are winds and seismic shocks. One might hope that a combination of this tilt and whatever natural vibrations plus winds might tend to clean Spirit off as time goes on, here.

Still, I think we need to generate some way to shake these things so the dust can shake off...

-the other Doug

Posted by: nprev Feb 26 2008, 05:10 AM

Many years ago, I recall someone asking why the MERs wouldn't carry compressed air (I'd favor compressed CO2) bottles & spray fixtures to blow off the solar panels. Didn't seem worth the mass penalty at the time considering the optimal 90-day mission duration, but given the MERs' longevity I'd definitely think about adding such a system for any future solar-powered rovers...

Posted by: edstrick Feb 26 2008, 08:20 AM

grumble...
What Spirit needs to do is find a nice low hanging bush and sidle up under the branches and bear-rub the dust off.
<dream on>

Posted by: djellison Feb 26 2008, 08:38 AM

RAT+Array=Bad idea. There are so many ways it could go dreadfully wrong. If there WAS anything that could be done in that way, they would have done it 1200 sols ago when they were at the 300 Whrs level before Larrys Lookout. There is nothing MER could do to dislodge the dust. I can understand the desperation - but it's just a case of holding tight. That's it.

Doug

Posted by: jasedm Feb 26 2008, 02:32 PM

I think nprev has a good point here - the Apollo astronauts complained that lunar dust got into everything during the moon walks; The moon's regolith is quite different to Mars', but Martian soil probably has a component that is mere microns in size, and there must be an electrostatic charge on the rovers relative to their surroundings.

Probably the arrays have a mix of small rock chips, sand, dust, and electrostatically-adhering fine dust covering them, and the cleaning events only remove one or two of these components.

Unfortunately I don't think the rover can do anything in this regard to help itself, and it will probably be the pulverulent panels that will eventually cause Spirit's slow demise before lack of funding, or other mishap.

Posted by: Doc Feb 26 2008, 03:13 PM

I agree.....

The best thing the MER team can do is to improvise, be faithful to Spirit and the martian environment.

Posted by: BrianL Feb 26 2008, 06:01 PM

Better yet, find a traffic light. There should be a down on his luck Martian there with a squeegee looking to make a buck. Well, more likely a brush, squeegees don't work too well without water. I mean, we have to be realistic here.

Brian

Posted by: Astro0 Feb 26 2008, 11:36 PM

Have no fear....I have dispatched a fleet of special craft to save the day!

Ha, ha!
Astro0

Posted by: nprev Feb 27 2008, 12:15 AM

Once again, the enormous resourcefullness of UMSF members astonishes me...go get 'em, Astro0!!!

Posted by: PaulM Feb 28 2008, 06:07 PM

The Planetary Society MER update from 31/12/2007 includes the following statement:

The other affected instrument is the miniature thermal emission spectrometer, better known as the Mini-TES. “It sits in the belly of the rover, but looks up the Pancam mast assembly, almost like a periscope and there is a series of mirrors, folded optics [it uses],” Callas explained. “Our only meaningful theory is that there is a thick layer of dust on one or more of the optical surfaces.”

The plan to “vibrate” some of the dust off those mirrors, discussed in the November MER Update, is still on. “There's actually a mode we discovered during integration and test of the rovers more than four years ago, where you get a slight instability in the motion control -- the positive feedback hits a resonance. We've actually been able to reproduce that successfully and it doesn't propose a threat to the actuator mechanism, so we're going to try that.”

This made me wonder whether these movements would be sufficient to cause the whole of Spirit's solar panel array to vibrate. Spirit is currently tilted at 30 degrees and in my dreams these vibrations could be used to shake much of the dust from Spirit's solar panels.

Posted by: climber Feb 28 2008, 10:00 PM

Got another (very) mad idea, kinda extreme tough.
Put the IDD on the soil as close as possible from the deck. Then if you order Spirit to extand the arm, this will result in actualy lifting the deck. Then release the arm and Spirit will fall back.
The risk is to break the arm and I'm not sure there's enough power to lift the whole Spirit, but I guess the shock would be enough to release some dust.
Don't blame me for thinking at "creative" solutions

Posted by: nprev Feb 28 2008, 10:16 PM

Your creativity is noted & appreciated, Climber!

Thing is, I'm still not sure how much of the dust is being held electrostatically, and a jolt wouldn't do much good for dislodging that crap. The winds do a good job, but that also might involve some friction-induced charge transfer as well as sheer kinetics; the place is so damn dry.

Posted by: jamescanvin Feb 29 2008, 09:05 AM

No. They are just going to vibrate the mirror used to point the Mini-TES to try and shake off some dust. I don't know the mass of this mirror, but I think it's fair to say it's negligible compared to the rest of the rover. Hence there will be essentially no vibration of Spirit as a whole.

James

Posted by: James Sorenson Feb 29 2008, 09:21 AM

I'm no expert or anything, but since the mini-TES mirrors are located in PMA, when they attempt to vibrate the dust off, isn't there a risk of dust that was on the mirrors just falling onto the mini-TES telescope at the bottom of the PMA?.

Posted by: tasp Feb 29 2008, 04:00 PM

Just brainstorming an idea or two;

* We probably haven't noticed a 'node' or something where dustdevil tracks consistently cross, and we would be able to park the rover(s) for an enhanced shot at a convenient cleaning, but in the unlikely event this hasn't been looked into before . . . .

* Any convenient nearby large appropriately spaced boulders we can park between for an enhanced venturi effect to keep the prevailing winds at a higher speed to reduce dust rate accumulation ?

* or parking 'downwind' of a suitable large boulder or cliff and being in a leeward spot of dead air where deposition rate is low?

* How 'supple' is the suspension system for the undercarrriage at this point? Has the dust 'froze up' the shocks yet? Giving the rover(s) a bumpy ride might knock some dust off, but if the suspension system is still isolating the deck from bumps, then this probably won't work.

* any dust free spots nearby that seem to have (as yet) mysterious dust repeling properties? Go park there and figure out what is doing it.

Posted by: centsworth_II Feb 29 2008, 04:25 PM

Of course Spirit is not going to go anywhere
until winter is over. So any plans involving
driving -- or much movement at all -- will have
to wait until then. A 30 degree slope in the
hand beats two dust devils in the bush.

Posted by: hendric Feb 29 2008, 05:25 PM

How fast does the RAT on the IDD run? In the videos it looks like it's pretty fast. I'm just wondering if maybe we don't need to actually touch the solar cells with the RAT, but instead blow on them from a short distance. It would be an interesting experiment to place the RAT a sucessively decreasing distances to a dust-covered rock, some unbroken duricrust, and to the tracks, to see what kind of results we could potentially get. It might not be something we can try this winter, except maybe on Opportunity.

It would be a nice feature to add to future IDD/RATs to design the cutting blades/brush to generate a little bit of wind that could be useful for the solar cells.

Posted by: nprev Feb 29 2008, 05:45 PM

I'd actually prefer a compressed gas blow-off ability, but that's problematic in a lot of ways (weight & gas composition for starters). Dry CO2 would be best, but it'd have to be really dry, or you'd get nozzle freezing in short order; plus, it's heavy.

Posted by: djellison Feb 29 2008, 06:14 PM

You just need the pizoelectric techniques I blogged about at Valencia some time ago. A very thin film, very low mass, very low power. Turn it on and the dust just goes away - it's amazing.

http://marstech.jpl.nasa.gov/content/image.cfm?Sect=PU&Cat=base&subCat=LCMT&subSubCat=&TaskID=2300


Doug

Posted by: nprev Feb 29 2008, 06:27 PM

Oh, yeah; that'd work great!!! Do that biweekly or so, never a prob.

Posted by: climber Feb 29 2008, 07:19 PM

I believe that venturi effect was involved on the very first cleaning event that caught everybody by surprise. At this time, Spirit was sitting on the "north col" of Husband hill.
Nevertheless as centworth point out, we'll not move for a while and if we rove again after winter, I guess that "north col" of Von Braun would be the right place to get some Venturi effect...unless you can point out the 2 right boulders !!!

Posted by: slinted Mar 1 2008, 12:10 AM

The sol 420 event? Maybe there was some local enhancement to those winds, but functionally I think being anywhere within the center of Gusev would have been enough. See http://www.planetary.org/blog/article/00000924/

Posted by: stewjack Mar 1 2008, 07:38 PM

I don't have a professional interest in unmanned space flight. That may be why, although I remember viewing the beginning of that linked page almost a year ago, I never read any further than the first paragraph. I totally missed the point of the article! I thought it was about the fact that Mar's had lots of seasonal dust devil tracks, and I already knew that.

I am glad that I got a chance to re-read the full article. If the last two sentences are still accurate, I may not be the only person to skip over the article.

... there hasn't been a publication (or at least a conference abstract) on this event. Maybe it's not that surprising to the professionals?


Jack