The Lunar Orbiter SpacecraftThe Lunar Orbiter program, initiated in early 1964, consisted of the investigation of the Moon by five identical unmanned spacecraft. The spacecraft weighed approximately 390 kilograms at launch, were 1.5 meters in diameter, and were 2 meters in length. Solar panels supplied the required power. The main purpose of the program was to locate smooth, level areas on the Moon’s nearside to confirm the areas as suitable for manned landing sites for the Apollo program. The specific objectives of the Lunar Orbiters were as follows:
- Photography. To obtain detailed lunar topographic and geologic information of various lunar-terrain types to assess their suitability for use as landing sites by Apollo and Surveyor spacecraft and to increase man’s scientific understanding of the Moon.
- Selenodesy. To provide precision trajectory information that would improve the definition of the lunar gravitational field.
- Analysis of the Moon’s environment. To provide measurements of the micrometeoroid and radiation flux in the lunar environment for spacecraft performance analysis.
During the first three missions, 20 potential lunar landing sites were photographed from low-inclination and comparatively low-altitude orbits. Analysis of the photography indicated that nearly all Lunar Orbiter program objectives had been met. Eight promising sites were selected for manned landings with additional photography required for confirmation of five of these sites.
The fourth and fifth missions were devoted to broader scientific objectives. The entire nearside of the Moon, and 95% of the farside, was photographed from high-altitude orbit. In addition, medium- and high-resolution photography of 36 preselected areas containing features of interest were acquired along with the additional photography required for confirmation of the Apollo landing sites.
With the completion of the five Lunar Orbiter missions, 99% of the Moon was photographed with resolution of 60 meters or better. This was 10 times better resolution than the best observations from Earth. For more information on the individual missions, select from the following list:
The Lunar Orbiter 1 Mission
The Lunar Orbiter 2 Mission
The Lunar Orbiter 3 Mission
The Lunar Orbiter 4 Mission
The Lunar Orbiter 5 Mission
The Lunar Orbiter Photographs
The five Lunar Orbiter spacecraft returned over 1654 high-quality photographs taken from lunar orbit. Each spacecraft was similarly equipped with two cameras that operated simultaneously and had the same line of sight but different fields of view and resolutions. The cameras utilized a common supply of 70-millimeter film, and the dual images they recorded are referred to as medium-resolution frames and high-resolution frames.
Of the 1654 Lunar Orbiter photographs, 840 depict areas photographed on the basis of Apollo program requirements and were obtained primarily during missions 1, 2, and 3. They were taken from low flight altitudes and provided detailed coverage of 22 areas along the equatorial region of the nearside of the Moon. The remaining 814 photographs were taken primarily during missions 4 and 5 and included 703 of the lunar nearside, 105 of the lunar farside, and 6 of Earth. These photographs were taken from flight altitudes ranging from approximately 44 kilometers over the nearside to approximately 6000 kilometers over the farside. They provide broad coverage of essentially the entire Moon and detailed coverage of 88 areas on the nearside.
The photographic system was housed in a pressurized, thermally controlled container, and included the cameras, film and film handling, film processor, and a readout device for transmission to Earth by the communications system. The two cameras simultaneously placed two discrete frame exposures on a common supply of 70-millimeter aerial film. Each camera operated at a fixed aperture of f/5.6 with controllable shutter speeds of 0.001, 0.02, or 0.04 seconds. One of the lenses had a 610-millimeter focal length, the other an 80-millimeter focal length. The film was developed onboard by passing the film into contact with a web that contained a single-solution processing chemical. After the film was dried, it was stored to be read out and transmitted to Earth.
Lunar Orbiter Imagery
Lunar Orbiter Atlas of the Moon