"Launching the first artificial satellites began the space age and started the Soviet-American space race."

Display Status:

This object is on display in the Boeing Milestones of Flight Hall exhibition at the National Air and Space Museum in Washington, DC.

Collection Item Summary:

This artifact is one of several replicas and flight spare Explorer 1 spacecraft in the collection. It was identified as a fully instrumented flight spare of the Explorer-1 satellite attached to an empty fourth stage Sergeant rocket when it was transferred in 1961 to the collection by the NASA Jet Propulsion Laboratory, the builder of the object. It was initially displayed in the Arts and Industries Building. It was on loan to the Museum of Medical Progress in Madison, WI, (4/70-6/70) and briefly to WETA in Arlington, VA, (6/75-7/75). It was inspected in late 2005 and found to be empty of instrumentation save for the micrometeoroid sensor. But markings in the interior frame indicate it to be "Payload II" which was indeed the flight backup that was sent to James Van Allen's laboratory in Iowa for inspection and testing and then returned to JPL in 1958. That payload was donated to NASM by George Ludwig in 2006 (A20060086). The satellite is displayed in the Milestones of Flight Gallery at NASM.

Explorer-1 was the United States' first successful orbiting satellite. Following the failure of Vanguard in December 1957, the JPL- ABMA group was permitted to adapt the Jupiter-C reentry test vehicle to carry an instrumented satellite into earth orbit. The resulting Explorer-1 satellite was successfully launched and placed into Earth orbit on January 31, 1958. Explorer-1, also known unofficially as Satellite 1958 alpha, 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.

Collection Item Long Description:

  • Why is Explorer striped?

    The striped front section of Explorer contained the payload; the rear section was a solid-fuel rocket motor. Explorer’s light and dark stripes helped control its temperature. As Explorer spun about its long axis, four flexible antennas extended.

Inventory Number


Credit Line

Transferred from the National Aeronautics and Space Administration's Jet Propulsion Laboratory

Country of Origin

United States of America


Steel, copper alloy, aluminum, rubber, paint, electrical wires


Other: 205.7 × 15.2cm, 12.9kg (81 × 6 in., 28 1/2lb.)

Data Source

National Air and Space Museum

Restrictions & Rights

Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum



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