sentences:  Uncrewed missions are known to have placed such objects on the Moon, albeit not before 1970.Smaller retroreflectors were carried by the uncrewed landers Lunokhod 1 and Lunokhod 2 in 1970 and 1973, respectively.The location of Lunokhod 1 was unknown for nearly 40 years but it was rediscovered in 2010 in photographs by the Lunar Reconnaissance Orbiter (LRO) and its retroreflector is now in use.