Mars Science Lab Cameras |
Mars Science Lab Cameras |
Nov 8 2008, 09:31 PM
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#16
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Founder Group: Chairman Posts: 14431 Joined: 8-February 04 Member No.: 1 |
I had thought the dust buildup was mostly on the hazcams, which are much closer to the ground. Spirit's cameras all remain in great health Opportunity got a smattering in both Navcams and Pancam's. If you notice a lot of Pancam imaging with Opportunity is done with only one half, or 3/4s of the CCD, as one side got quite a smattering. http://marsrovers.jpl.nasa.gov/gallery/all...nity_p1671.html is an example of the technique. http://marsrovers.jpl.nasa.gov/gallery/all...CSP2629L4M1.JPG is a typical example of the obstruction Doug |
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Nov 8 2008, 09:46 PM
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#17
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Senior Member Group: Moderator Posts: 3431 Joined: 11-August 04 From: USA Member No.: 98 |
Opportunity got a smattering in both Navcams and Pancam's. The contamination happened during the dust storm, didn't it? So it's not exactly 'buildup' so much as a 'smattering' as you put it. Regardless, the contamination of Opportunity's optics remains distressing - I'm sure to the science team as well as the sightseers. |
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Nov 8 2008, 11:34 PM
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#18
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Senior Member Group: Members Posts: 2502 Joined: 13-September 05 Member No.: 497 |
Regardless, the contamination of Opportunity's optics remains distressing... http://www.planetary.org/news/2007/0930_Ma...ate_Spirit.html It looks like the effects of this contamination could easily be taken out with a proper flat field, and I'm a little surprised that they haven't done this. That said, owing to the configuration of the Mastcam I think it will be far more resilient to this sort of problem. There was never any serious consideration given to adding a cover mechanism to the Mastcam, and nothing I see in the Pancam data would justify the added cost, complexity, and risk. I wouldn't even know how to begin to implement a "wiper" that would work reliably under martian conditions, and some kind of roll of clear material that could be driven past the lens would be problematic for all kinds of reasons. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Nov 9 2008, 09:40 PM
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#19
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
http://www.planetary.org/news/2007/0930_Ma...ate_Spirit.html It looks like the effects of this contamination could easily be taken out with a proper flat field, and I'm a little surprised that they haven't done this. If you look closely at the comparison mosaic on that page, notice that while the corner darkening was removed with a new flatfield, the frames suffer from lowered contrast there. The dust particles are no longer just a nuisance in the way, they diffuse/diffract the light. The effect can be likened to Titan's haze but on a much different scale. A flatfield simply cannot remove that. Had the dust been deposited on the actual CCD the situation would probably have been different. -------------------- |
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Nov 9 2008, 10:20 PM
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#20
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
The cameras are normally stowed pointing down. Was there some period on MER when they were left pointing up? This is a question I've been wondering about too. Were the cameras left unstowed at some point, or did Oppy just happen to get smacked in the face with an unusually large pile of dust during the brief period when it was trying to do imaging one day? --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Nov 10 2008, 01:05 AM
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#21
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Senior Member Group: Members Posts: 2502 Joined: 13-September 05 Member No.: 497 |
A flatfield simply cannot remove that. If by "flat field" you mean something that merely multiplies each pixel by a single number, I agree. But these sorts of stray/scattered light problems can be addressed with more sophisticated techniques, for example the way the NEAR images were recovered after the front elements were covered with monoprop burn products. See "Inflight Calibration of the NEAR Multispectral Imager II. Results from Eros Approach and Orbit" by Murchie et al in Icarus 155, 1. I'm not sure the MER images are bad enough to require that level of processing though. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Nov 10 2008, 01:53 AM
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#22
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Martian Photographer Group: Members Posts: 352 Joined: 3-March 05 Member No.: 183 |
This is a question I've been wondering about too. Were the cameras left unstowed at some point... First, a 'stowed' camera is still at risk on MER. There are no in-flight dust shields for Navcam, Pancam. Looking down avoids sedimentation of dust, but not turbulence. I think turbulence maybe was involved. Second, I don't think the camera bar has been left stowed at nadir in quite some time. Stowing the cameras now places them looking sorta down, sorta out, I think. The actuators were not designed for a 5 year mission, let alone one with Opportunity's current ambition. If they fail, they should fail where Navcam is still useful rather than contemplating the rover's navel, umm, deck. |
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Nov 10 2008, 09:07 PM
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#23
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Member Group: Members Posts: 194 Joined: 8-February 04 Member No.: 10 |
I wouldn't even know how to begin to implement a "wiper" that would work reliably under martian conditions...
I recall reading that Viking had two methods to avoid dusty optics, a physical barrier which covered the 'slit' when the camera was in its 'rest' position as well as compressed air which could be used to blow off the optics. I would think the latter could be adapted to a wide variety of camera designs. Don |
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Nov 10 2008, 10:41 PM
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#24
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Solar System Cartographer Group: Members Posts: 10122 Joined: 5-April 05 From: Canada Member No.: 227 |
"I would think the latter could be adapted to a wide variety of camera designs."
I think we need it for Spirit's solar panels now... Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Nov 10 2008, 10:59 PM
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#25
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Senior Member Group: Members Posts: 2502 Joined: 13-September 05 Member No.: 497 |
I would think the latter could be adapted to a wide variety of camera designs. I'd be willing to bet that the tank to contain the gas would weigh more than an entire Mastcam camera head. Not really practical given the mass constraints. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Nov 11 2008, 12:18 AM
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#26
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Member Group: Members Posts: 194 Joined: 8-February 04 Member No.: 10 |
the tank to contain the gas would weigh more than...
Perhaps, but I wonder what the Viking unit weighed? How much more compact cound a similar modern system be built? I imagine something like a soda charger cylinder filled with very clean compressed gas, perhaps giving puff(s) of gas upon demand. A magnetic 'ring' around the lens could also help. However this is dealt with, cameras for long term Mars surface missions will require more attention to the dust hazard as part of the design. Don |
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Nov 11 2008, 12:28 AM
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#27
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Founder Group: Chairman Posts: 14431 Joined: 8-February 04 Member No.: 1 |
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Nov 11 2008, 12:34 AM
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#28
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Member Group: Members Posts: 293 Joined: 22-September 08 From: Spain Member No.: 4350 |
What about holding the air in the bodywork itself?
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Nov 11 2008, 08:27 AM
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#29
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Founder Group: Chairman Posts: 14431 Joined: 8-February 04 Member No.: 1 |
Making the entire electronics box a pressurised body? Given that it has to travel thru a vaccum? How do you engineer in the insruments and their openings to the sample collection mechanisms. That's an epic engineering challenge right there.
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Nov 11 2008, 10:33 AM
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#30
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Member Group: Members Posts: 593 Joined: 20-April 05 Member No.: 279 |
For Mars the body wouldn't have to be at insane levels of pressure - just "enough" over the external ~1 kPa to provide a squirt of gas where and when you need it. I don't think the high pressure 20 MPa sort of structure you see on air tanks is at all necessary here.
Just to put this into perspective: the r/c model sub community regularly work with pressures up to ~50kPa and manage with commercial linkages/prop shafts, etc., penetrating the core electronics box without too many problems. That said, this Giotto air puffer would seem to be a more practical solution. And it's even rocket-shaped! Andy |
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