Retroreflectors are devices which reflect light back to its source. Six were left at six sites on the Moon by three crews of the Apollo program, two by remote landers of the Lunokhod program, and one by the Chandrayaan program.[1] Lunar reflectors have enabled precise measurement of the Earth–Moon distance since 1969 using lunar laser ranging.[2]
Several unsuccessful attempts to land retroreflectors on the lunar surface have been made, and several future attempts are planned.
- ^ Lunar Retroreflectors
- ^ Slava G. Turyshev: From Quantum to Cosmos: Fundamental Physics Research in Space (2009), p. 300