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Originally posted by Chadwickus
Maybe, I'm sure the reflectors would have to be placed pretty precisely though, not just lobbed out of some unmanned craft.
Lunar Ranging Retro-Reflector (Apollo 11, 14, 15)
This passive experiment consisted of an array of 100 fused silica cubes on Apollo 11, arranged to reflect a beam of light back on a parallel path to its origin. The LRRR placed on the Moon was aligned precisely so that it faced the Earth. Scientists from around the world directed laser beams at the instrument which reflected them back to Earth; the elapsed time for the round trip allowed precise measurements of distances, down to an accuracy of 8 centimeters, between the Earth and the Moon. This instrument continued operating until June 1981.
Apart from accurately determining the Moon's distance from the Earth, results have shown there is considerable warping of the lunar surface as it journeys around the Earth.
These reflectors were also deployed on the Apollo 14 and 15 missions. The Apollo 15 reflector had 300 silica cubes.
The McDonald Observatory in Western Texas and a second observatory near the city of Grasse in southern France regularly send a laser beam through an optical telescope to hit one of the reflectors. The reflectors are too small to be seen from Earth, so even when the beam is correctly aligned in the telescope, actually hitting a lunar reflector is quite challenging. At the Moon's surface, the beam is a few kilometers or miles wide and scientists liken the task of properly aiming the beam to using a rifle to hit a moving dime 3.2 kilometers (two miles) away.
The unmanned Soviet Lunokhod 1 and Lunokhod 2 rovers carried smaller arrays. Reflected signals were initially received from Lunokhod 1, but no return signals have been detected since 1971, at least in part due to some uncertainty in its location on the Moon. Lunokhod 2's array continues to return signals to Earth