On Jan. 31, 1958, the United States sent Explorer 1, its first satellite, into space. The spacecraft was small enough to be held triumphantly overhead. It orbited Earth from as far as 1,594 miles (2,565 km) above, and made the first U.S. scientific discovery in space.
The world had changed three months before Explorer 1’s launch, when the Soviet Union lofted Sputnik into orbit on Oct. 4, 1957. That satellite was followed a month later by a second Sputnik spacecraft. All of the missions were inspired when an international council of scientists called for satellites to be placed in Earth orbit in the pursuit of science. The Space Age was on.
When Explorer 1 launched, NASA didn’t yet exist. It was a project of the U.S. Army and was built by Caltech’s Jet Propulsion Laboratory in Southern California. After the Sputnik launch, the Army, Navy and Air Force were tasked by Pres. Eisenhower with getting a satellite into orbit within 90 days. The Navy’s Vanguard Rocket, the first choice, exploded on the launch pad Dec. 6, 1957.
University of Iowa physicist James Van Allen, whose proposal was chosen for the Vanguard satellite, had made sure his scientific instrument – a cosmic ray detector – would fit either launch vehicle. Wernher von Braun, working with the Army Ballistic Missile Agency in Alabama, directed the design of the Redstone Jupiter-C launch rocket, while JPL Director William Pickering oversaw the design of Explorer 1 and other upper stages of the rocket. JPL was also responsible for sending and receiving communications from the spacecraft.
Explorer 1’s last transmission was received May 21, 1958. The spacecraft re-entered Earth’s atmosphere and burned up on March 31, 1970, after 58,376 orbits. From 1958 on, more than 100 spacecraft would fall under the Explorer designation.
Read more in the NASA post here and the Explorer 1 website (with poster)