Discoverer 15 was an American optical reconnaissance satellite. The orbital mission was successful but when the capsule was returned it failed to be captured and sank into the ocean. September 13, 1960 at 22:13 UTC · Launch Successful Thor Agena A — United States Air Force, to Low Earth Orbit Space Launch Complex 1E, Vandenberg SFB, CA, USA The world's 76th orbital launch attempt, and 22nd of 1960. Data: Launch Library 2, The Space Devs.