Experimental satellite equipped with a nuclear power system and a cesium ion engine. April 3, 1965 at 21:25 UTC · Launch Successful Atlas SLV-3 Agena D — United States Air Force, to Polar Orbit Space Launch Complex 4E, Vandenberg SFB, CA, USA The world's 424th orbital launch attempt, and 31st of 1965. Data: Launch Library 2, The Space Devs. Image by USAF via The Space Devs.