The lunar orbiter used a film scanning process taken from a classified program and returned high-resolution images of the surface back to Earth. These images were vital to planning of the subsequent Surveyor and Apollo lunar landings.
Gross mass: 388 kg (855 lb).
First Launch: 1966.08.10.
Last Launch: 1967.08.01.
Number: 5 .
The document called for five flight and three test articles. The Lunar Orbiter spacecraft would be capable of photographing the moon from a distance of 22 miles above the surface. Overall cost of the program was estimated at between $150 and $200 million.
During the spacecraft's stay in the final close-in orbit, the gravitational fields of the earth and the moon were expected to influence the orbital elements. The influence was verified by spacecraft tracking data, which showed that the perilune altitude varied with time. From an initial perilune altitude of 58 kilometers, the perilune decreased to 49 kilometers. At this time an orbit adjustment maneuver began an increase in the altitude, which was expected to reach a maximum after three months and then begin to decrease again. The spacecraft was expected to impact on the lunar surface about six months after the orbit adjustment.
During the photo-acquisition phase of the flight, August 18 to 29, Lunar Orbiter I photographed the 9 selected primary potential Apollo landing sites, including the one in which Surveyor I landed; 7 other potential Apollo landing sites; the east limb of the moon; and 11 areas on the far side of the moon. Lunar Orbiter I also took photos of the earth, giving man the first view of the earth from the vicinity of the moon (this particular view has been widely publicized). A total of 207 frames (sets of medium- and high-resolution pictures) were taken, 38 while the spacecraft was in initial orbit, the remainder while it was in the final close-in orbit. Lunar Orbiter I achieved its mission objectives, and, with the exception of the high-resolution camera, the performance of the photo subsystem and other spacecraft subsystems was outstanding. At the completion of the photo readouts, the spacecraft had responded to about 5,000 discrete commands from the earth and had made about 700 maneuvers.
Photographs obtained during the mission were assessed and screened by representatives of the Lunar Orbiter Project Office, U.S. Geological Survey, DOD mapping agencies, MSC, and Jet Propulsion Laboratory. The spacecraft was deliberately crashed into moon after the mission was completed.
"Screening teams . . . are studying the photographs as they become available at the Lunar Orbiter Project Office, Langley Research Center. Several promising areas for Apollo landing sites have been studied here in Houston by the screening teams and will be studied in more detail later. This preliminary study has already influenced the selection of sites to be photographed on the next Orbiter mission. . . ."
The spacecraft executed a deboost maneuver at 3:26 p.m., November 10, while 352,370 kilometers from the earth and 1,260 kilometers from the moon and traveling at a speed of 5,028 kilometers per hour. The maneuver permitted the lunar gravitational field to pull the spacecraft into the planned initial orbit around the moon. On November 15, a micrometeoroid hit was detected by one of the 20 thin-walled pressurized sensors.
The spacecraft was transferred into its final close-in orbit around the moon at 5:58 p.m. November 15 and the photo-acquisition phase of Lunar Orbiter II's mission began November 18. Thirteen selected primary potential landing sites and a number of secondary sites were to be photographed. By the morning of November 25, the spacecraft had taken 208 of the 211 photographs planned and pictures of all 13 selected potential landing sites. It also made 205 attitude change maneuvers and responded to 2,421 commands.
The status report of the Lunar Orbiter II mission as of November 28 indicated that the first phase of the photographic mission was completed when the final photo was taken on the afternoon of November 25. On November 26, the developing web was cut with a hot wire in response to a command from the earth. Failure to achieve the cut would have prevented the final readout of all 211 photos. Readout began immediately after the cut was made. One day early, December 6, the readout terminated when a transmitter failed, and three medium-resolution and two high-resolution photos of primary site 1 were lost. Full low-resolution coverage of the site had been provided, however, and other data continued to be transmitted. Three meteoroid hits had been detected.