Following Discoverer 38, the Discoverer program was terminated, and a veil of secrecy was placed on all photographic surveillance missions and related test missions. The number following the KH- designation indicates what type camera system was used on the satellite. In 1995, President Clinton signed an Executive Order directing the declassification of intelligence imagery acquired by the Corona, Argon, and Lanyard missions. The order provides for the declassification of more than 860,000 images of the Earth's surface, collected between 1960 and 1972. These images are now publically available.
Little information is available about the various satellite designs.
However, some details about the various camera systems have been made available. The KH-6 camera was programmed to tilt between fore and aft to cover the same land area twice during a photographic pass and thus provide stereo coverage. Additionally, the fore and aft camera's film were packaged separately for missions that carried twin panoramic cameras. Occasionally one of the pair of cameras malfunctioned or was programmed to halt, while its mate continued to operate.