Once in orbit, the cosmic ray equipment of Explorer I indicated a much lower cosmic ray count than had been anticipated. Dr. Van Allen theorized that the equipment may have been saturated by very strong caused by the existence of a belt of charged particles trapped in space by the earth's magnetic field. The existence of these Van Allen Belts, discovered by Explorer I, was confirmed by Explorer III, which was launched by a Jupiter C on 26 March 1958.
The discovery of the Van Allen Belts by the Explorer satellites was considered to be one of the outstanding discoveries of the International Geophysical Year.
Characteristics - Explorer I Satellite
Explorer I was placed in an orbit with a perigee of 224 miles and an apogee of 1,575 miles having a period of 114.9 minutes. Its total weight was 30.66 pounds, of which 18.35 pounds were instrumentation. The instrument section at the front end of the satellite and the empty scaled down Sergeant fourth stage rocket casing orbited as a single unit, spinning around its long axis at 750 revolutions per minute.
