The Lunar Orbiter project was initiated in 1963 as part of the U.S. Apollo program to land men on the Moon during the decade of the nineteen sixties.
Lunar Orbiter’s primary mission was to take and transmit both wide-angle and closeup images of the Moon. Lunar Orbiters photographed many areas of scientific interest and provided general photographic coverage of much of the moon’s surface. These pictures were then used to select the best landing sites for the first manned lunar landings. Orbiters also showed that the moon’s gravitational field permitted stable orbits.
Lunar Orbiter 1 was launched atop an Atlas-Agena D rocket on August 10, 1966. The last in the project, Lunar Orbiter 5, was launched on August 1, 1967. All five missions were successful.
The first three missions were similar. After each launch, the Agena stage’s booster engine was fired to send the spacecraft on a 90-hour coasting trajectory to the Moon, about 386,160 kilometers (240,000 miles) distant.
As the spacecraft neared the Moon, its on-board engine was fired as a retrorocket to slow the Orbiter and permit it to go into orbit around the Moon.