CORONA started under the name "Discoverer" as part of the WS-117L satellite reconnaissance and protection program of the U.S. Air Force in 1956. The WS-117L was based on recommendations and designs from the RAND Corporation. The primary goal of the program was to develop a film-return photographic satellite to replace the U-2 spyplane in surveilling the Sino-Soviet Bloc, determining the disposition and speed of production of Soviet missiles and long-range bombers assets. The CORONA program was also used to produce maps and charts for the Department of Defense and other U.S. government mapping programs.