The Ranger Spacecraft
The Ranger program consisted of nine spacecraft missions with the ultimate objective of obtaining high-resolution photographs of the lunar surface. The development of the basic Ranger spacecraft system was initiated in 1959. The spacecraft was conceived as a fully attitude-stabilized platform from which lunar or planetary observations could be made. The Ranger spacecraft had three different configurations.
Block I Missions
Block I, consisting of Ranger 1 and 2, were test missions. They were
launched in 1961 for nonlunar-oriented engineering development.
Block II Missions
These missions (Ranger 3, 4, and 5) were launched during 1962 to achieve
rough lunar landings, obtain science data, and test approach television
camera operations. These Ranger spacecraft experienced satisfactory vehicle
performance but either missed the Moon (Ranger 3) or failed before impacting
the lunar surface (Ranger 4 and 5).
Block III Missions
The experience of the earlier phases of the program led to the Block
III missions in 1964 and 1965: Ranger 6, 7, 8, and 9. These spacecraft were
designed to achieve lunar impact trajectories and to transmit high-resolution
photographs of the lunar surface during the final minutes of flight.
Ranger 6 performed satisfactorily, but the camera failed to operate before lunar impact. However, Ranger 7, 8, and 9 fulfilled the mission objective and provided more than 17,000 photographs at resolutions not previously obtained. The Ranger 7 and 8 missions provided coverage of the two types of mare terrain in which they impacted. The first type is modified by crater rays, and the second is crossed by a complex system of ridges. Ranger 9 provided coverage of the highland region, impacting in the large central highland crater Alphonsus.
The Ranger photographs provided valuable information for future landing site selection for Surveyor and Apollo missions, and feature designation of surface detail not heretofore visible to Earth-based observations. For more on the individual missions, select from the list below.
The Ranger 7 Mission
The Ranger 8 Mission
The Ranger 9 Mission
The Television Cameras
The Ranger television equipment had the same construction and operational capabilities for all missions. Included in the system were six cameras. The six cameras were fundamentally the same with differences in exposure times, fields of view, lenses, and scan rates. The camera fields of view were arranged to provide overlapping coverage so that a nested sequence of photographs was obtained.
The camera system was divided into two completely separate channels designated P (partial) and F (full). Each channel was self-contained with separate power supplies, timers, and transmitters. The F channel had two cameras. The A camera was wide angle, and the B camera was narrow angle. The P channel contained four cameras designated P1 and P2 (narrow angle) and P3 and P4 (wide angle).
The last F-channel picture was taken between 2.5 and 5 seconds before impact (from an altitude of about 5 kilometers); the last P-channel picture was taken between 0.2 and 0.4 seconds (from an altitude of about 600 meters) from which the highest resolutions were obtained. The resolution achieved by Ranger 9 (0.3 meters) was a factor of 1000 better than any Earth-based views of the Moon.
Final Photographs from Ranger 7