The Surveyor spacecraft series was conceived in 1959 to soft-land scientific experiments on the Moon and carry out initial surface investigations. It was an ambitious undertaking at the time, of it relied on developing the new technology of closed-lop, radar-controlled landings, and, in addition, required the successful development of the world's first hydrogen-oxygen rocket stage, the Centaur. Of seven spacecraft, five were completely successful; two experienced in-flight failures prior to landing. The Surveyor not only studied four potential Apollo landing areas, but on its last mission visited the scientifically interesting crater Tycho. In addition to relaying thousands of surface photographs of Earth, Surveyor measured surface properties by manipulating the lunar soil with mechanical arm and conducted chemical analysis of the lunar material.
