Unmanned Spacecraft
The Soviet Union sent the first spacecraft to the vicinity of the Moon, the unmanned vehicle Luna 1, on January 4, 1959. It passed within 6,000 kilometres (3,200 nmi; 3,700 mi) of the Moon's surface, but did not achieve lunar orbit. Luna 3, launched on October 4, 1959, was the first unmanned spacecraft to complete a circumlunar free return trajectory, still not a lunar orbit, but a figure-8 trajectory which swung around the far side of the Moon and returned to the Earth. This craft provided the first pictures of the far side of the Lunar surface.
The Soviet Luna 10 became the first spacecraft to actually orbit the Moon in April 1966. It studied micrometeoroid flux, and lunar environment until May 30, 1966.
The first United States spacecraft to orbit the Moon was Lunar Orbiter 1 on August 14, 1966. The first orbit was an elliptical orbit, with an apolune of 1,008 nautical miles (1,867 km; 1,160 mi) and a perilune of 102.1 nautical miles (189.1 km; 117.5 mi). Then the orbit was circularized at around 170 nautical miles (310 km; 200 mi) to obtain suitable imagery. Five such spacecraft were launched over a period of thirteen months, all of which successfully mapped the Moon, primarily for the purpose of finding suitable Apollo program landing sites.
The latest addition is the Lunar Reconnaissance Orbiter (LRO) since 2009.
Read more about this topic: Lunar Orbit