Pictured above is an animation of the Explorer orbiting Earth and a scale model of the
satellite being held up by (left to right) William Pickering, James Von Allen, and Wernher 
Von Braun. 

Explorer 1  was the first Earth satellite of the United States, launched as part of its participation in an international scientific project. The mission followed the first two
Earth satellites the previous year, the Soviet Union’s Sputnic l and 2, beginning the
Cold War Space Race between the two nations.

Explorer 1 was launched  atop the first Juno booster from at the Cape Canaveral, Florida. It returned data until its batteries were exhausted after nearly four months. It remained in orbit until 1970.