There is a corner reflector mirror on the moon that you could bounce a laser beam off. Of course that doesn't prove that astronauts where on the moon but it at least proves that something visited the moon.
They are using this to monitor the Earth-Moon distance right? Could that kind of experiment interfere with this research? And for bouncing do you need to be precisely aligned, is the moon motion around the Earth sufficient compared to the speed of light to show up in the form of the beam not coming back exactly to the position of the sender?
Just out of curiosity, wouldn’t Synthetic Aperture Radar (SAR) be able to detect these? I assume we have those pointed at the Moon for lunar surveying...