QUOTE (Alex Chapman @ May 23 2008, 11:51 AM)
The real answer is just to make the solar panels large enough so that they produce enough power throughout the mission even with dust accumulation. For long duration missions go nuke and have it powered by an RTG, they really are the way to go.
RTGs are unfortunately expensive, and fuel is getting scarce. The US has stopped production of Pu-238, and AFAIK the Russians are shutting theirs down as well. From what I understand, we have enough available for the currently planned missions but little beyond that.
Thinking about panel cleaning, it seems to me you don't need to run it very frequently. From the MER experience, averaging once every 3 months would probably be plenty. If you only need a few tens of cycles total, simple filters may be sufficient to make Hendrics suggestion workable from a dust POV. You'd need to be able to isolate it (lock the valves closed and cover the filters), but that should fairly straightforward. OTOH, at that level of use an expendable source might be competitive. If you use something that is liquid or solid at modest pressures, you can get a large volume without wasting too much mass on pressure vessels. CO2 seems like the obvious choice, although you may have to expend some effort keeping it in the desired state.
Larger panels are clearly the simpler (= lower technical risk) way, but being able to clean off after a major dust storm has a certain attraction.