Vanguard 3 is a scientific satellite to measure the Earth's magnetic field, solar X-ray radiation and its effects on the Earth's atmosphere and the near-Earth micrometeoroid environment. September 18, 1959 at 05:20 UTC · Launch Successful Vanguard — US Navy, to Medium Earth Orbit Launch Complex 18A, Cape Canaveral SFS, FL, USA The world's 49th orbital launch attempt, and 18th of 1959. Data: Launch Library 2, The Space Devs. Image by NASA (NASA Image and Media Guidelines) via The Space Devs.