LOR meaning in Space Science ?

Lunar orbit rendezvous (LOR) is a key concept for efficiently landing humans on the Moon and returning them to Earth. It was utilized for the Apollo program missions in the 1960s and 1970s. In a LOR mission, a main spacecraft and a smaller lunar lander travel to 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.

Lunar orbit rendezvous was first known to be proposed in 1919 by Ukrainian engineer Yuri Kondratyuk, as the most economical way of sending a human on a round-trip journey to the Moon.

The most famous example involved Project Apollo's command and service module (CSM) and lunar excursion module (LEM), where they were both sent to a translunar flight in a single rocket stack. However, variants where the landers and main spacecraft travel separately, such as the lunar landing plan proposed for Shuttle-Derived Heavy Lift Launch Vehicle and Golden Spike, are also considered as Lunar Orbit rendezvous.