Discoverer 12 was an American optical reconnaissance satellite. The fourth of five test flights of the Corona KH-1 spy satellite series. It was lost when the second stage failed during launch. June 29, 1960 at 22:00 UTC · Launch Failure Thor Agena A — United States Air Force, to Low Earth Orbit Space Launch Complex 1W, Vandenberg SFB, CA, USA The world's 69th orbital launch attempt, and 15th of 1960. Data: Launch Library 2, The Space Devs.