55 Years Ago: Lunar Orbiter 1 Launches to Survey the Moon

The Lunar Orbiter 1 spacecraft lifted off on Aug. 10, 1966, to begin its journey to photograph the Moon. To identify suitable landing sites for the Apollo missions, NASA established the Lunar Orbiter program, a series of spacecraft placed in lunar orbit to take medium- and high-resolution photographs of the surface. The Boeing Missile Production Center in Seattle built the spacecraft, and NASA’s Langley Research Center in Hampton, Virginia, managed the program. Lunar Orbiter 1 accomplished its goals of imaging potential Apollo landing sites. Five Lunar Orbiters flew in 1966 and 1967, achieving all their objectives to map 99% of the Moon’s surface with a resolution of 200 feet or better. The spacecraft also studied the Moon’s gravity field and its radiation and micrometeoroid environment.

Left: Launch of Lunar Orbiter 1 on an Atlas-Agena D rocket. Middle: A Lunar Orbiter spacecraft, with the two cameras of its imaging system visible at center. Right: The Lunar Orbiter imaging system, including two cameras and the film developing, scanning, and transmission systems. Credits: NASA

Lunar Orbiter 1 lifted on Aug. 10, 1966, atop an Atlas-Agena D rocket from the Cape Kennedy Air Force Station in Florida, now the Cape Canaveral Space Force Station. On Aug. 14, after a 92-hour cruise, Lunar Orbiter 1 entered an elliptical 117-by-1,160-mile orbit around the Moon, becoming the first American spacecraft to do so (following the Soviet Union’s Luna 10 achieving that first on April 3). Lunar Orbiter 1’s goals included imaging nine primary and seven secondary potential Apollo landing sites on the Moon’s near side, and 11 areas at lower resolution on the far side. On Aug. 15, Lunar Orbiter 1 activated its camera system, a 145-pound package built by Eastman-Kodak in Rochester, New York, and based on a system designed for a classified military satellite. The apparatus consisted of both a narrow-angle and a wide-angle camera to achieve a best resolution of three and 25 feet, respectively. The system developed the exposed film onboard the spacecraft and scanned it for transmission back to Earth, where the signals were converted into photographs. The first days’ activities involved testing the scanning and transmission of several pre-exposed frames of film.

Left: The first medium-resolution photograph returned by Lunar Orbiter 1, showing the Mare Smythii region of the Moon. Middle: Medium-resolution image of the lunar far side, including the crater Tsiolkovsky at top right. Right: The first image of Earth taken from lunar orbit, as Lunar Orbiter 1 emerged from the lunar far side. Credits: NASA

On Aug. 18, the spacecraft took its first photographs, exposing 16 high-resolution and four medium-resolution frames. The medium-resolution photos were of good quality, but the failure of the spacecraft’s motion compensation system caused blurring of the high-resolution images. An issue with the film-developing system required the film to be advanced more frequently than planned, resulting in the need to take additional, unplanned photographs. A positive outcome of this problem resulted in mission managers deciding that additional photographs could be acquired by temporarily reorienting the spacecraft from its cameras facing downward and pointing them in the direction of flight.

On Aug. 23, as Lunar Orbiter 1 emerged from the Moon’s far side, it imaged the Earth as it appeared to rise over the lunar horizon — the first time the home planet was imaged from lunar orbit. The black-and-white Earthrise image was well-received by scientists and the public alike, and the spacecraft repeated the photograph two days later. Two years later, the Apollo 8 astronauts would take the more famous Earthrise photograph, but in color. The oblique, or out-of-vertical, views of the lunar surface added a new and useful perspective, more fully developed on the later Lunar Orbiter missions.

Left: The first image of Earth taken from lunar orbit, acquired by Lunar Orbiter 1 on Aug. 23, 1966. Right: The same image digitally reprocessed by the Lunar Orbiter Image Recovery Project. Credits: NASA

Lunar Orbiter 1 took its last photograph of the Moon on Aug. 28, and transmission of the 205 images continued until Sept. 16. The spacecraft photographed all the planned potential Apollo landing sites, returning the highest-resolution images of the Moon’s near and far sides to that time. Its photography mission completed, it continued to return radiation, micrometeoroid, and engineering data, and tracking of its orbit enabled a preliminary understanding of mass concentrations, or mascons, on the Moon that, over time, perturbed the spacecraft’s trajectory. On Oct. 29, with the spacecraft’s systems deteriorating and its fuel tanks nearly empty, ground controllers commanded Lunar Orbiter 1 to fire its engine to crash it onto the Moon on its 577th orbit, with the impact occurring on the lunar far side. Deorbiting it prevented interference with future Lunar Orbiter spacecraft.

In all, the five Lunar Orbiter spacecraft returned 3,062 images of the Moon. Based on these photographs, scientists and mission planners identified several sites that met the criteria for the first lunar landing: such as near the equator, in relatively flat terrain, and with an unobstructed approach path. The NASA Apollo Site Selection Board named five candidate landing sites in February 1968, one of which, in the Sea of Tranquility, became the location where Apollo 11 touched down on July 20, 1969. 

For more on the Lunar Orbiter program, see: https://nssdc.gsfc.nasa.gov/planetary/lunar/lunarorb.html

Lunar Orbiter imagery is available online at: http://www.lpi.usra.edu/resources/lunar_orbiter/

Between 2008 and 2014, the Lunar Orbiter Image Recovery Project digitized most of the original photographs to enhance their quality. They are accessible at NASA’s Planetary Data System.