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
Docking and berthing of spacecraft the Soyuz spacecraft to add an internal transfer tunnel and used it to transport cosmonauts during the Salyut space station program with the first successful space station visit beginning on 7 June 1971, when Soyuz 11 docked to Salyut 1. The United States followed suit, docking its Apollo spacecraft to the Skylab space station in May 1973. In July 1975, the two nations cooperated in the Apollo-Soyuz Test Project, docking an Apollo spacecraft with a Soyuz using a specially designed docking module to accommodate the different docking systems and spacecraft atmospheres. Beginning with Salyut 6 in 1978, the Soviet Union