On March 26, 1958, the United States launched its third satellite into space. Explorer 3 was almost identical to Explorer 1, the first satellite the U.S. ever launched.
Explorer 3 launched on a Juno I rocket from Cape Canaveral and entered an eccentric orbit. This means it was following a long elliptical path around the Earth. Its payload included a cosmic ray counter and a micrometeorite detector.
The data from Explorer 3 and Explorer 1 led to the discovery of the Van Allen radiation belt. This is a region around the Earth where charged particles from the sun get trapped by Earth's magnetic field. Explorer 3 spent 93 days orbiting the Earth before its orbit decayed.
Relive the Launch of Explorer 1, America's 1st Satellite (Videos)
Explorer 1: How the First American Satellite Worked (Infographic)
Explorer 1: America's First Satellite in Pictures
Catch up on our entire "On This Day In Space" series on YouTube with this playlist.
Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us @Spacedotcom and on Facebook.
