Satellite Payload, Explorer I Instrument Package Display Mock-Up

This full-scale mock-up of the instrument package carried on the Explorer 1 satellite illustrates the appearance of instruments used in the original to measure and transmit data on micrometeorites, cosmic radiation and temperatures. It was transferred by the Jet Propulsion Laboratory to the Smithsonian Institution in August 1961.

Explorer 1, also known unofficially as Satellite 1958 alpha, was the first American satellite to successfully orbit the earth. Since the mid-1950's Caltech's Jet Propulsion Laboratory (JPL) had underway a development program for missile reentry vehicles in conjunction with the Army Ballistic Missile Agency (ABMA). Soon after the failure of the first Vanguard launch attempt in December 1957, the JPL- ABMA-Iowa team was authorized by DoD to prepare an Army vehicle to launch an instrumented Earth satellite. The resulting 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.