We have many long-term satellite observatories and probes in outer space way above the Earth's magnetosphere, and some of them progressively cruising out of our Solar system. Off the top of my head, some of such satellites, probes and observatories are the Chandra X-ray Observatory, Hubble Space Telescope (HST), the Solar and Heliospheric Observatory (SOHO), the two Voyager probes, Cassini–Huygens of the Cassini Solstice Mission, e.t.c.
I guess it could be easily misconceived that these man-made objects are passing through the emptiness of space, devoid of any mass particles hitting their outer hull or other equipment, but that simply cannot be true. Depending on their position in our Solar system, they would be sailing through variously dense clouds of cosmic dust (granted, still at environmental pressure near zero), whichever their origins (remains of comets' tails and comas, remains of the circumstellar disk not cleared by larger mass bodies orbiting the Sun from the accretion period when the Solar system was forming, ejected materials from Mass Coronal Ejections and asteroid impacts on atmosphereless celestial bodies, even constant grinding of the colliding rocks in asteroid belts, and so on). So there would be some dust, and depending on its origins / formation, its electrostatic charge due to it being exposed to solar radiation (or other causes), and its relative velocity to our man-made objects cruising through these clouds possibly low enough in some circumstances to not simply bounce off, some of this cosmic dust could easily stick on their surface and gather in time, either on their outer hull, or even sensitive equipment (e.g. lenses) they carry aboard.
My question is, do we have any data on individual probes, satellites and space observatories on how much of this dust do they gather in long years of service, has it ever been a problem and caused equipment failure or degradation, and do any of our man-made objects in outer space employ dust mitigation techniques, perhaps in a similar fashion to professional grade photographic lenses using various dust reduction systems like piezo crystal ultrasonic vibration, coupled with electrostatic discharge systems and/or degaussing?
Just to be clear, I'm not asking about implications of micrometeorites, but dust particles that individually don't pose a threat to our man-made objects in outer space, but could gather in longer periods of time and either degrade or cause a failure of onboard experiments and scientific equipment.