Discoverer 19 was an American optical reconnaissance satellite. It was part of the Missile Defence Alarm System. December 20, 1960 at 20:32 UTC · Launch Successful Thor DM-21 Agena-B — United States Air Force, to Low Earth Orbit Space Launch Complex 1E, Vandenberg SFB, CA, USA The world's 92nd orbital launch attempt, and 38th of 1960. Data: Launch Library 2, The Space Devs. Image by USAF via The Space Devs.