The Surveyor program was a NASA series of robotic lunar-landing missions that investigated the Moon's surface and tested soft-landing technology before crewed landings. Seven spacecraft were launched from 1966 to 1968, with five successful soft landings.[ref]
NASA Facts: Rangers and Surveyors to the Moon. Surveyor mission chronology and outcomes
Images and measurements from the landed vehicles provided local evidence about surface texture and bearing behaviour. Surveyor 1's pictures of its own footpad showed the actual interaction between landing hardware and lunar soil. This was information that distant imaging alone could not establish: a terrain's appearance and its response to an applied load are different observations.[ref]
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