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Mars Science Lab Cameras
djellison
post Nov 11 2008, 03:03 PM
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You still have to render the entire box air tight. That means seals of every access panel, seals for every cable in, every cable out. That pressure is going to go up and down with thermal cycles. It might change the thermal properties of the box itself. Then you've got to have valves, flexible pipe work out the box, up the past and to the front of the lenses. Pipework that's going to bend with every camera movement. With all due respect, a $1.X billion dollar rover is just a tiny bit more complex than an R/C sub.

AND - at the end of all that - if you've got a CRT monitor or an old TV - go and blow on it. The dust doesn't move very much, if at all. I know - wind has cleared arrays etc before, but we don't know the mechanism by which that occurs, nor do we know the mechanism by which it sticks.

If we really really want to have dust-removal - the best way is with the thin-film technique I blogged about at Valencia '06. Tiny power, low mass, low complexity. Turn them on for a few seconds - dust gone. Gas tanks, wipers, rolls of film - they're all very heavy, complicated, and have their own failure modes.

DOug
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AndyG
post Nov 11 2008, 03:40 PM
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QUOTE (djellison @ Nov 11 2008, 03:03 PM) *
...if you've got a CRT monitor or an old TV - go and blow on it.


Unfair! smile.gif Any CRT being bombarded by electrons (and thereby charged) in a dry, dusty atmosphere is not quite in the same league as a glass lens sat in front of a passive CCD.

Personally I like the thin film concept (much better than abrasive wipers - though even one of those would be helping Spirit's solar panels right now), but I also like the home-engineering "what if...?" kind of discussions here. Hmmm...Blame it on a childhood filled with Meccano.

Andy
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Jeff7
post Nov 12 2008, 08:24 AM
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I wonder about maybe some kind of electrostatic "wiper" - maybe something to move across the lens while holding a charge. Might the dust adhere to something like that, or perhaps be repelled by it? Either way, it could get rid of dust. Possibly maybe. I'm afraid I've not got much experience with electrostatics.

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tedstryk
post Nov 12 2008, 08:45 PM
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There is also the issue of having to make sure that whatever pressurized gas you used didn't cause a residue to build up on the lens. The cure could be worse than the disease.


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mcaplinger
post Nov 12 2008, 09:05 PM
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QUOTE (djellison @ Nov 11 2008, 07:03 AM) *
If we really really want to have dust-removal - the best way is with the thin-film technique I blogged about at Valencia '06.

I don't recall this reference, could you point me at it again?

This is all getting pretty off-topic for MSL; the hardware is built and doesn't include any kind of active dust removal.


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Del Palmer
post Nov 12 2008, 10:47 PM
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The thin-film technique is described here:

http://science.nasa.gov/headlines/y2006/19apr_dustbuster.htm
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djellison
post Nov 12 2008, 10:56 PM
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Bingo. That's it. The wires are so fine, I bet for a future design, one could put something like that over the front of a Mastcam like Hood. The wires would be totally out of focus and not noticeable ( like the heating element in a heated front windscreen).

It certainly beats wipers, rollers, blowers etc.

Doug
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mcaplinger
post Nov 12 2008, 10:59 PM
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QUOTE (Del Palmer @ Nov 12 2008, 02:47 PM) *
The thin-film technique is described here...

Cool, thanks! But I don't think this would work for a camera without a good bit of technology development, because it'd be very difficult to make the transparent material optically flat.


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djellison
post Dec 4 2008, 11:55 AM
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Just noticed

http://mars.jpl.nasa.gov/msl/spotlight/ima.../20081119_1.gif

It has four rear hazcams - two each side of the RTG. I wonder if it's the same at the front.
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Doc
post Dec 4 2008, 02:54 PM
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Perhaps, but isn't the reason because the RTG would block the view of 1 set of hazcams if mounted in the middle? Or maybe because the rover is just so big; hazards increase with size?


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djellison
post Dec 4 2008, 03:01 PM
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I think it's just that you can't put them where you would want to - because the RTG is there. Can't
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Guest_Oersted_*
post Jan 4 2009, 12:30 AM
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What about a stationary brush placed somewhere reachable by the mastcam? The brush could be wiped by the back (or whatever) of the camera housing to brush off dust, and then the brush itself could be used to clean the lenses. We might be on Mars for 10 years (oh joy!), so some sort of cleaning mechanism would seem necessary...

On another subject, I was thinking to myself whether there is some sort of mastcam lens protection during landing. Caps or just turning the lenses towards an enclosed space? A lot of dust will swirl up.

Also, wouldn't it be great if the navcams were turned on during landing, taking a movie? Not just great, but helpful for analysing EDL. If they have caps on them during landing, maybe the caps could be made of transparent material, so some filming would still be possible despite the dust.
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djellison
post Jan 4 2009, 12:56 AM
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QUOTE (Oersted @ Jan 4 2009, 12:30 AM) *
What about a stationary brush placed somewhere reachable by the mastcam?


No hardware changes from the current design before launch.

We have MARDI doing a movie during descent, we don't need Navcams doing it - and they'll be pointing into the rover deck at that time anyway - along with MastCam I presume.

Doug
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mcaplinger
post Jan 4 2009, 01:12 AM
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QUOTE (Oersted @ Jan 3 2009, 04:30 PM) *
What about a stationary brush placed somewhere reachable by the mastcam?

As I said earlier in this thread, the Mastcam lens is many inches inside its sunshade and could not be reached by any plausible brush.

As to the navcams imaging during EDL: of course Doug is right, the navcams and Mastcam are pointed down towards the deck when the RSM is stowed. I guess the hazcams are looking at the ground during descent but the hazcam frame rate is quite slow (remember DIMES from MER) so only a few images could be taken, whereas MARDI will be running at about 4 FPS.


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ElkGroveDan
post Jan 4 2009, 02:11 AM
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Does this MARDI have a microphone, Mike?


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