Apollo 15 15 separated from the booster, the S-IVB maneuvered away, and would impact the Moon about an hour after the crewed spacecraft entered lunar orbit, though due to an error the impact was away from the intended target. The booster's impact was detected by the seismometers left on the Moon by Apollo 12 and Apollo 14, providing useful scientific data. There was a malfunctioning light on the craft's service propulsion system (SPS); after considerable troubleshooting, the astronauts did a test burn of the system that also served as a midcourse correction. This occurred about 028:40:00 into the mission. Fearing that the
Third-party evidence for Apollo Moon landings 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. Both the United States and the USSR had the capability to soft-land objects on the surface of the Moon for several years before that. The USSR successfully landed its first unmanned probe (Luna 9) on the Moon in February 1966, and the United States followed with Surveyor 1 in June 1966, but no unmanned landers carried retroreflectors before Lunokhod 1 in November 1970. Post-Apollo lunar exploration missions have located and imaged artifacts of