Explorer 5 was a United States satellite with a mass of 15.7 kg. It was the last of the original series of Explorers built, designed, and operated by the Jet Propulsion Laboratory. March 23, 1960 at 13:35 UTC · Launch Failure Juno II — National Aeronautics and Space Administration, to Medium Earth Orbit Launch Complex 26B, Cape Canaveral SFS, FL, USA The world's 59th orbital launch attempt, and 5th of 1960. Data: Launch Library 2, The Space Devs. Image via The Space Devs.