  42. Lunar Orbiter.
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. The closest approach to the Moon in each orbit was about 45 kilometers (28 miles), and the spacecraft swung out to about 1850 kilometers (1150 miles) from the Moon. Photography was conducted while the Orbiter was near the lunar surface. Lunar photography for the Apollo Program landing-site selection was completed by the first three Lunar Orbiters. Each was then intentionally crashed into the Moon to prevent it from interfering with later missions. The last two Lunar Orbiters were used for scientific photography of the Moon. Both were placed into polar orbits so that they could photograph all of the sunlit areas of the Moon. Each Lunar Orbiter carried a camera with both a telephoto and a wide-angle lens. The telephoto lens was capable of resolving objects on the lunar surface as small as 91.4 centimeters (three feet) in diameter. The wide-angle lens could resolve objects as small as 7.6 meters (25 feet) in diameter. The photographic images were converted to electrical signals for transmission to Earth. The Lunar Orbiter project was a complete success. All spacecraft operated properly, photographing a total of more than 36-million square kilometers (14-million square miles) of the moon’s surface. Prime contractor for the Lunar Orbiter program was the Boeing Company. Principal subcontractors were Eastman Kodak Company and RCA. The Lunar Orbiter in the National Air and Space Museum’s collection was used for thermal testing of spacecraft systems. Lunar Orbiter is from the National Aeronautics and Space Administration.
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