Between 1966 and 1968, the Jet Propulsion Laboratory in California managed the Surveyor Program, a series of robotic landers designed to make soft landings on the Moon to study lunar surface properties and to act as precursors for future human landings. They provided ground-level information at potential Apollo landing sites that, combined with orbital imagery from Lunar Orbiters, increased our knowledge of the Moon in preparation for human missions. Surveyor 7, the seventh and last in the series, launched January 7, 1968, from Cape Canaveral on an Atlas-Centaur rocket and landed successfully on the Moon three days later near the outer rim of the crater Tycho in the Moon’s southern hemisphere. Because previous Surveyors had provided adequate coverage of possible landing sites for early Apollo missions and had proven the technical feasibility of soft landings, it was possible for Surveyor 7 to explore a different region of the Moon, away from the lunar maria and into the lunar highlands, primarily for scientific purposes. It began sending back images of its landing site and analyzing the lunar soil’s composition. The spacecraft survived one 14-day lunar night, but damage to its battery limited operations during the second lunar day. By the time its mission ended on February 21, 1968, Surveyor 7 had returned approximately 21,000 pictures of itself and its surroundings and studied the chemical composition of the lunar surface, finding lower concentrations of iron than at other landing sites. The spacecraft’s camera observed two laser beams pointed at it from two observatories on the night side of the crescent Earth. This was a test for a future Apollo laser retro-reflector experiment to precisely measure the Earth-Moon distance with an accurately pointed laser beam. For a time there were thoughts to send one of the later Apollo missions to visit Surveyor 7 at Tycho, but budget cuts ended those plans.
Surveyor 7 ended a very successful program that brought NASA closer to achieving the goal of safely landing men on the Moon. Five of the seven missions achieved a soft landing on the lunar surface and explored areas that looked promising for Apollo astronauts to visit. Cumulatively, the five spacecraft operated for about 17 months, returned 87,000 photographs from the lunar surface and performed chemical analyses of the soil at three of the landing sites. In February 1968, the NASA Apollo Site Selection Board chose five potential landing zones for the first manned mission, meeting suitability criteria such as smooth flat terrain and a clear approach path, based on the information collected by Surveyors on the Moon’s surface and Lunar Orbiters in orbit around the Moon.
For more on the Surveyor program, please visit https://nssdc.gsfc.nasa.gov/planetary/lunar/surveyor.html