What did the Explorer 1 discover in October 1 1958?

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.