The primary goal of the satellites was 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 assess.

The KH-1 payload included the C (for Corona) single, vertical-looking, panoramic camera that scanned back and forth, exposing its film at a right angle to the line of flight.

[4] The Discoverer program began with a series of three test flights whose satellites carried no cameras, all launched in the first half of 1959.

[8] Launched 15 Apr 1960 at 20:24:00 GMT from Vandenberg LC 75-3-5 by a Thor DM-21 Agena-A rocket,[7] Discoverer 11 was successfully placed into orbit.

However, the rockets designed to spin the Discoverer for stabilization apparently exploded on reentry, and the film capsule could not be recovered.

It was decided to follow up Discoverer 11 with a test satellite equipped with a comprehensive diagnostics (as well as a new spin motor and de-spin system) so that, in the event of failure, more lessons might be learned.