Today, on the Mars Rover site the NASA geeks put up a pitiful cry for help.
“If Mars had an on-line Web site for ads, one of them might say something like this: “Wanted: Gentle space-age dust removal system to clean solar cells without leaving grit behind. Please direct inquiries to NASA.
NASA’s Spirit rover has accumulated a lot of dust during four years of exploring Mars, especially following last year’s dust storms. Only about one-third of incoming sunlight is able to penetrate dust on the rover’s solar panels to be converted to electricity. As a result, Spirit is experiencing the lowest energy levels to date and accumulating a backlog of data waiting to be transmitted to Earth. The only available cleaning agent would be a timely gust of Martian wind! “
This photo was taken when the sun driven solar-electric cells were clean.
That was then but this is now and here below is what they look like now.
Obviously this is a terrible situation, because if the solar cells don’t get any sunlight then the rovers will be useless in the short run, and will soon die because they can’t store up any energy to maintain their critical minimal functions. Clearly they need help. NASA shouldn’t be faulted, because these machines were designed to be as light as possible, and when you add even the tiniest component it adds weight, and that compromises the other components. There are extreme limitations on weight. These things were only expected to work for 90 days or so, and as of today it has been 1530 for Spirit and 1507 for Opportunity. In 90 days of operation dust accumulation probably wouldn’t have been a problem, but with such a very long life it has become a death warrant. Imagine for perspective a man living to be 90 years old. You would expect that with a little luck his son might live to be 90 years old. But, instead he has two sons and both are now 1,530 years old and they are not dead yet, only a little weakened, because they are covered in dust.
Here is a simulated portrait of Spirit or Opportunity on Mars. It was made cute — an apparent necessity for NASA’s public relations — by having its eyes forward, and its hand on a rock which it is inspecting with its nose. It is a good picture for showing the arm extended which is what I want to write about. It turns out that this arm was designed to be highly flexible, and if told to do so could bring the instrument package on its arm’s tip up and above the flat panel of solar cells (seen edge on). The two photos shown above were taken with the camera in the tip from above the solar cells.
What I propose as a dusting device on the next rovers would require a tiny amount of weight, but is quite simple to install, and safe to operate when dusting because it would never touch the solar cells as a brush system would. Here’s how. Take the forward tube of the arm and pressurize it with a pump using Martian atmospheric gas. The tube and gas would add no weight whatsoever to the rover, because the tube is already robust enough from its other uses, and the gas is from the Martian atmosphere. Out on the arm’s head, probably mounted on the grinder portion or on the camera, install a very small electric-powered gas-pump. This pump is used to pressurize the tube; you might even use the grinder’s motor for this operation, although it is probably easier to have its own dedicated motor. This motor could be very small because it only needs to pressurize the arm tube once a day or even less. Now all that is needed is a hole or tube from which to release puffs of wind, and a valve to be opened on command. Bring the arm up into position where it is pointing at a dusty place, and blow for a few seconds with a sweeping motion, and there you will now have have a clean spot. Repeat occasionally, as needed
Well, I suppose they have considered de-dusting the solar panels in this way. But if they would have thought of it in the past, one would think they would have put it into operation on these current rovers. The whole thing I am talking about is smaller than a thimble perhaps than an aspirin tablet. And it shouldn’t cost much or weigh much. One advantage of this system is that it will add only a couple of grams weight to the rover and it could also be used for cleaning the camera lens, wheels treads, wheels axles, joints, surface objects, photo color charts and anything else within reach.
Another obvious thing for a new Rover would be to install the solar panels at about a 45° angle so most of the dust would slip off and when it didn’t park the Rover on a hill so the angel becomes much steeper. The path taken by the Rover could be planed to be mostly down-sun to maintain a higher charging rate.