lunar orbit rendezvous

Lunar orbit rendezvous (LOR) is a key concept for landing humans on the Moon and returning them to Earth and was first utilized for the Project Apollo missions in the 1960s and 1970s. In a LOR mission, a main spacecraft (such as the Apollo CSM) and a smaller lunar lander (such as the Apollo LM) travel together into lunar orbit. The lunar lander then independently descends to the surface of the Moon, while the main spacecraft remains in lunar orbit. After completion of the mission there, the lander returns to lunar orbit to rendezvous and re-dock with the main spacecraft, then is discarded after transfer of crew and payload. Only the main spacecraft returns to Earth.