Satellite, Explorer 4, Payload

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.