Ranger Photography of the Moon
The Ranger mission to the Moon marks a key milestone in the history of planetary exploration. Prior to 1964, the best lunar maps and images were all derived from Earth-based telescopes (without the benefit of orbiting telescopes or adaptive optics). With the call to land a Man on the Moon by John F Kennedy in 1961, the need to understand the surface of the Moon became paramount. Although dreams of lunar flight are centuries old, the new program brought unmanned Moon mission concepts to the front burner, and Project Ranger was given full funding.
Nothing came easy on the road to the Moon. Project Ranger became important not just for what it revealed about the Moon, but also for the critical roll it played in giving birth to American interplanetary capabilities. The initial plans for Ranger called for numerous scientific instruments to measure the Moon, including a "soft" lander with a seismometer. The first Ranger flights ended in disasters of one sort or another. Cries of anguish spread through the land (or at least JPL), and inquiries into JPL management were launched. Ranger was simplified, yet more launches meant only more defeats. However, in those defeats, JPL was learning how to run complex interplanetary missions over vast astronomical distances (vast in those days).
Finally, January, 1964, Ranger 6 was ready. Stripped down to little more than a flying TV station, everything had been checked and double checked. The machine was on course and all was go. The TV cameras were turned on. Nothing.
Another investigation, another program reevaluation. With Ranger 7 the following July, more than the Ranger program itself was at stake. That day, when the first high-resolution TV images from Ranger 7 came down, the audience at JPL went crazy. Those who were there recalled it as the most significant event of their careers.
The Ranger images showed one important thing: the Moon's surface was littered with impact craters down to the smallest size measurable. The success of Ranger had more profound implications. The successes of the last 3 Ranger missions (and the Mariner 2 mission to Venus earlier) gave the US space program the sound footing needed to move forward to the Moon and the planets beyond. The Soviet space program was undergoing a similar beginning. More lunar missions would follow, manned and unmanned, but Ranger stands apart for its pioneering role in getting us to the Moon and back.
Suggested Reading: Lunar Impact: A History of Project Ranger