any of a series of seven unmanned U.S. space probes sent to the Moon between 1966 and 1968 to photograph and study the lunar surface. Surveyor 1 (launched May 30, 1966), carrying a scanning television camera and special sensors, landed on the Moon on June 2, 1966, and transmitted 11,150 photographs as well as information about environmental conditions on the Moon. Surveyor 2 crashed on the Moon (Sept. 23, 1966). Surveyor 3 (April 17, 1967) included additional equipment such as a surface-sampling device and two small mirrors to expand the camera vision; it returned 6,315 photographs. Surveyor 4 crashed or soft-landed on the Moon (July 16, 1967). Surveyor 5 (Sept. 8, 1967) measured the proportions of chemical elements in lunar soil and studied other surface properties; it returned 18,000 photographs.