New York Times' How Do You Solve a Moon Mystery? Fire a Laser at It links to the new open access paper First two-way laser ranging to a lunar orbiter: infrared observations from the Grasse station to LRO’s retro-reflector array and I spotted the concept of "measurement proxy" in @DavidHammen's answer to How it's possible to measure temperature 2000 years ago?
While not conclusive, the strength of the "clean and fresh" retroreflectors on the LRO orbiting the Moon is as expected, suggesting that the reduced strength seen by the same laser ranging telescope from the ones on the Moon's surface is real and that there may be some substantial degradation in their performance. Returning light pulses from lasers bounced off of the retroreflector arrays on the Moon seem to be getting weaker and one obvious possible contribution could be the accumulation of a fine layer of dust on their optically flat faces.
Question: Are there any other possible ways to estimate the accumulation rate of dust on clean flat surfaces on the Moon? Have imagers from lunar orbiters been able to resolve apollo landers and estimate their albedos for example? Could geological data be used, looking accumulation of dust over millions or billions of years to as a way to estimate the rate per year? Anything else?