パイオニア計画
The United States attempted a series of seven lunar orbiter probes as part of its Pioneer program from August 1958 to December 1960; all (Pioneer 0, Pioneer 1, Pioneer 2, Pioneer P-1, Pioneer P-3, Pioneer P-30, and Pioneer P-31) were failures. Later, the US successfully flew five Lunar Orbiter spacecraft from August 1966 to August 1967, to map 99% of the lunar surface and help select landing sites for the Apollo crewed landing programme.