update:

Current events makes this question even more poignant

  1. sols 5183 to 5189, Aug. 23, 2018 - Aug. 29, 2018: Team Continues to Listen for Opportunity

  2. Curiosity selfie has been released just a few days ago, showing better the collection of sand on top of the rover:

After snagging a new rock sample on August 9, 2018 (Sol 2137), NASA's Curiosity rover surveyed its surroundings on Mars, producing a 360-degree panorama of its current location on Vera Rubin Ridge. The scene is presented with a color adjustment that approximates white balancing, to resemble how the rocks and sand would appear under daytime lighting conditions on Earth. Two versions are included here: one with scale bars, and one without.

The panorama includes umber skies, darkened by a fading global dust storm. It also includes a rare view by the Mast Camera of the rover itself, revealing a thin layer of dust on Curiosity's deck. In the foreground is the rover's most recent drill target, named "Stoer" after a town in Scotland near where important discoveries about early life on Earth were made in lakebed sediments.

enter image description here

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Edit: In light (or lack of light in this case) of the current dust storm on Mars discussed in the recent NASA news article Opportunity Hunkers Down During Dust Storm and since almost two years have passed, I've un-accepted @Phiteros' answer to see if there is an update on ExoMARS' dust-on-solar-panels strategy.

Since it does not have an RTG, ExoMARS relies on efficient collection of solar radiation for its mission to succeed.

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above: "This global map of Mars shows a growing dust storm as of June 6, 2018. The map was produced by the Mars Color Imager (MARCI) camera on NASA's Mars Reconnaissance Orbiter spacecraft. The blue dot indicates the approximate location of Opportunity." From here. Credits: NASA/JPL-Caltech/MSSS



I remember reading stories about the Spirit and Opportunity Mars rovers related to solar power and dust - about problems with dust storms, and parking on an incline for the winter in order to collect enough power to 'stay alive'.

The Curiosity rover carries a large, powerful RTG for both thermal heat (circulating fluids) and of course electrical power.

Now it seems the ExoMARS rover will use solar panels again. The do seem a bit larger compared to the size (or volume) of the craft compared to Spirit and Opportunity, but I am wondering, what management techniques are begin considered for the ExoMARS rover to handle covering of the horizontal panels by dust, or low solar elevation in 'winter'?

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above: "A 1:4 model of the ExoMars rover at the ESA pavilion, 2007 International Paris Air Show at the Le Bourget airport." From here.

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above: "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)... Dust on the solar panels reduces the amount of electrical power the rover can generate from sunlight each sol." From here.

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    Maybe they too will trust the Devil to take care of it ;-/ – LocalFluff Sep 18 '16 at 10:53
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    @LocalFluff you mean this one? – uhoh Sep 18 '16 at 10:58
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    It took a lot of looking and special software to detect changes in images in order to catch those dust devils. It was not luck. – Mark Adler Sep 18 '16 at 15:11
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    During an astronomy class I took in college, the professor said that the dust devils would often clean the solar panels off and that would help keep the rovers operating for far longer than expected. I don't have a citation for this, however. – Cody Sep 19 '16 at 18:12
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    @uhoh: And risk another case of unplanned mission time extension by 5700%? Scientists may be happy, but managers are secretly praying for Opportunity to finally break down and free up the funds. – SF. Jun 11 at 23:57

They will likely be relying on two things:

  1. Since the rate at which dust will accumulate on the solar panels is pretty well known, they can estimate a lifespan of the rover. All space probes have some form of estimated lifespan, and the primary science mission is generally planned to fit within that low timeframe. However, as we've seen from Spirit and (especially) Opportunity, the actual lifespan of the rover can be much longer because of:
  2. Cleaning events. Basically, Mars has just enough of an atmosphere to have wind that blows the dust around. This cleans off the solar panels every once in a while, allowing the rovers to keep operating. Here's a picture of Opportunity before and after one such cleaning event:

Opportunity Cleaning Event

Spirit and Opportunity were only expected to last 90 days, but when it was discovered that the dust occasionally gets cleared off, the missions became much longer. Spirit only stopped when it became stuck in soft sand and could no longer angle its solar panels correctly. Opportunity, on the other hand, is still going, 12 years later.

Here is a news article about one of the more recent cleaning events for Opportunity.

As far as hibernation during the winter, they will likely follow the same techniques used by Spirit and Opportunity. Unfortunately, I do not know this for sure, but since it worked for MER, they will likely use the same legacy technique. Some of the instruments will also have their own independent batteries, such as the DREAMS experiment, which will operate during the dust storm season.

Here you can see the difference in dust before and after a cleaning event

In all likelihood, ExoMars will not have any method to remove the dust. There are several reasons for this. A mechanical device would probably have trouble because of the dust's static charge. Tilting and shaking the rover could work, but it would be complicated and possibly damaging to sensitive instruments. Other methods involve washing them (which requires liquid), using an electrostatic charge (still requires tilting the panels, and could also damage sensitive electronics), and blowing them off (requires moving a high-powered fan across the panels).

  • Thanks - this sounds like an opinion and it's fairly consistent with my best guess as well, but I'm asking here in SX SE because I'd like to read information about the ExoMARS rover supported by links. Can you add a link that shows that "the rate at which dust will accumulate on the solar panels is pretty well known" Is that rate steady? The same everywhere? Since both collection and removal of dust is related to wind and therefore weather, I don't see how either one can be reliable. Also, are you 100% sure there will not be any dust mitigating technology? Has that been stated? – uhoh Sep 22 '16 at 5:03
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    @uhoh Bam, gotcha covered. As far as whether or not its well known over the whole planet, I think they have a fairly consistent model. In addition to the instrument on Sojourner, they can characterize how quickly the dust settles by using these selfies to determine how much dust is on the rover in a before and after picture. As far as whether or not there will be any dust removal methods, I will add a section on that. – Phiteros Sep 22 '16 at 5:11
  • Excellent! However if there is future answer with information directly about the ExoMARS solar panels that tops this, I'll have to go with that. But you've convinced me this is probably what's going to happen. Thanks for all the links! – uhoh Sep 22 '16 at 5:19
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    @uhoh And that is completely understandable. But, as I am sure you found, information on specific design elements for the rover appears to be scarce. Such information may be limited in release to the public. Hopefully we'll get to know more about it after it begins its mission. – Phiteros Sep 22 '16 at 5:22
  • I enjoyed the Emily Lakdawalla blog post - especially the before/after sliders! – uhoh Sep 23 '16 at 1:35

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