Explorer 7 was designed to measure solar x-ray and Lyman-alpha flux, trapped energetic particles, and heavy primary cosmic rays. Secondary objectives included collecting data on micrometeoroid penetration, molecular sputtering and studying the Earth-atmosphere heat balance. October 13, 1959 at 15:30 UTC · Launch Successful Juno II — National Aeronautics and Space Administration, to Low Earth Orbit Launch Complex 5, Cape Canaveral SFS, FL, USA The world's 51st orbital launch attempt, and 20th of 1959. Data: Launch Library 2, The Space Devs. Image via The Space Devs.