(The following appears in "NASA, The First 25 Years," NASA, U.S. Government Printing Office, Washington, D.C., 1983, p. 97.)
Final unmanned lunar program. The Orbiters worked in conjunction with Surveyor to acquire photographic and scientific data in preparation for the Apollo landings. All five Lunar Orbiters were successful. They made more than 6,000 orbits of the Moon and photographed more than 99 percent of the lunar surface. The first three provided sufficient coverage for selection of eight candidate sites for Apollo, the fourth supplied detailed coverage of the front side of the Moon, and the fifth supplemented data provided by the others. At the end of their lifetimes, all were commanded to impact the Moon so as not to interfere with manned spacecraft.
Lunar Orbiter 1
August 10, 1966
First U.S. spacecraft to orbit another planetary body; returned medium and high resolution photos of nine primary and seven potential Apollo landing sites; and crashed on Moon, October 29, 1966.
Lunar Orbiter 2
November 6, 1966
Returned 211 frames (422 medium and high resolution pictures); crashed on Moon, October 11, 1967.
Lunar Orbiter 3
February 5, 1967
Returned 211 frames including photographs of Surveyor 1; crashed on Moon, October 9, 1967.
Lunar Orbiter 4
May 4, 1967
Returned 163 frames; crashed on Moon, October 6, 1967.
Lunar Orbiter 5
August 1, 1967
Returned 212 frames including five Apollo sites, and provided near-lunar micrometeoroid data; crashed on Moon, January 31, 1968.