I see cleansing of optical surfaces as necessary for long-term work on Mars.
The best way to do this is by spraying carbon dioxide on the surfaces at high pressure. This would require a few pumps in stages to compress the Martian atmosphere from .01 bar to perhaps 10 bars. Then little arms with nozzles would blast the dust from the optical surfaces. The pumps would be small, and use little power, since this blasting would be done infrequently and only a little gas would be needed for each operation.