The Missing History of the Explorer 1 Satellite

Three principal players stayed in close touch and remained ready to act: physicist James Van Allen of Iowa State University, who would provide the primary scientific instrument for the payload; JPL director William H. Pickering, who would provide the satellite itself; and Wernher von Braun of the ABMA, who would provide the launch system. The bullet-shaped satellite payload, about 6.5 inches in diameter and 3 feet long, carried three micrometeorite detectors (a microphone, a wire grid, and metallic film), temperature sensors, and a special cosmic-ray chamber developed by Van Allen’s graduate students at Iowa State University to determine the intensity of high-energy charged particles surrounding the Earth. Only after the successful launch of Explorer 3 on March 26 and its insertion into a highly elliptical orbit, and after several weeks of data collection, did Van Allen’s team figure out why the Geiger counter was silent only at certain altitudes above 600 miles: counter saturation.

Source: airandspace.si.edu