any of a series of nine unmanned probes launched from 1961 to 1965 by the United States National Aeronautics and Space Administration (NASA). Project Ranger represented NASA's earliest attempt at lunar exploration. Ranger 4 (1962) became the first U.S. spacecraft to hit the moon, crash-landing on its surface as designed. The last three probes in the series, Ranger 7, 8, and 9 (1964–65), transmitted more than 17,000 high-resolution photographs of the Moon, including many from as close as 300 m (1,000 feet) above the lunar surface, before crashing.