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Backup unit for the Explorer 4 satellite payload, built at the University of Iowa. The payload for Explorer 4 was designed to measure the nature of the newly discovered radiation belts that surround the Earth and to take measurements in conjunction with the planned Argus high altitude small-yield nuclear explosions.

The package was designed and built at the University of Iowa under the supervision of James Van Allen. The instrumentation included two Geiger tubes and two scintillation counters to measure cosmic ray intensities. Explorer 4 was authorized in spring 1958 and was fabricated in a matter of weeks. It was launched on July 26, 1958 on a Jupiter C and successfully achieved an elliptical orbit. The backup unit was donated to NASM by James Van Allen and the University of Iowa in April 1993.

 Display Status

This object is not on display at the National Air and Space Museum. It is either on loan or in storage.
Object Details
Country of Origin United States of America Type SPACECRAFT-Uncrewed-Instruments & Payloads Manufacturer University of Iowa
 Dimensions Overall: 6 in. wide x 23 1/2 in. deep (15.2 x 59.7cm)
 Materials Casing - steel
Payload cover - urea-formaldehyde foam
Rings - magnesium
 Inventory Number A19940235000 Credit Line Gift of James A. Van Allen and the University of Iowa Data Source National Air and Space Museum Restrictions & Rights Usage conditions apply
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