The Van Allen belts, one of the many regions within the
magnetosphere, were the first major scientific discovery of the Space Age.
In 1958, Geiger counters aboard the U.S. satellites Explorers 1 and 3,
detected energetic charged particles trapped in magnetic field regions
fairly close to Earth.
In this photo, Dr. William H. Pickering, Dr. James A. Van Allen and Dr. Wernher
von Braun (left to right) hoist a model of Explorer I and the final
stage after the launching Jan. 31, 1958.
Photo courtesy NASA.