Lunar Orbiter 4 . Courtesy of NASA's National Space Science Data Center . ... The Lunar Orbiter 4 spacecraft was designed primarily to photograph smooth areas of the lunar surface for selection and verification of safe landing sites for the Surveyor and Apollo missions. ... This experiment consisted of a dual-lens camera system designed to satisfy the primary mission objective of providing photogaphic information for mapping and for the evaluation of Apollo and Surveyor landing sites. ...