摘要：Late in the evening on 31 January 1958, a Juno (Jupiter-C) rocket blasted into space, lofting the first U.S. artificial Earth satellite into orbit. This spacecraft, dubbed Explorer 1, joined in space one other satellite, Sputnik 2, which had been launched on 3 November 1957 by the Soviet Union. The Explorer 1 mission was groundbreaking, for it carried a small scientific payload prepared at the University of Iowa by a team of researchers led by James A. Van Allen. The instrumentation on Explorer 1 (and on the subsequently successful Explorer 3) would make the first truly revolutionary discovery of the space age, namely, that Earth is enshrouded in toroids, or belts, of extraordinarily high energy, high-intensity radiation.
