This is a full-scale replica of Explorer 1, the United States' first artificial satellite. It was one of several transferred to the Smithsonian Institution by the Army Ballistic Missile Agency in September 1958. It is a machined metal shell representing the payload section and is devoid of instrumentation. It is attached to a Sergeant fourth stage solid-fuel rocket motor. The Explorer-1 satellite was successfully placed into Earth orbit on January 31, 1958. The satellite transmitted data on micrometeorites and cosmic radiation for 105 days. Data from this and two subsequent Explorer satellites led to the discovery by James Van Allen of a belt of intense radiation surrounding the earth.
Transferred from the U.S. Army Ballistic Missile Agency