Discoverer 18 was an American optical reconnaissance satellite. This was the first successful mission employing the KH-2 camera system December 7, 1960 at 20:20 UTC · Launch Successful Thor DM-21 Agena-B — United States Air Force, to Low Earth Orbit Space Launch Complex 1W, Vandenberg SFB, CA, USA The world's 90th orbital launch attempt, and 36th of 1960. Data: Launch Library 2, The Space Devs. Image by USAF via The Space Devs.