Explorer I

Inaugurating the era of space exploration for the US, the First Explorer was launched into Earth orbit forty years ago (February 1, 1958) by the Army Ballistic Missle Agency . The Explorer I satellite weighed about 30 pounds, was 6 feet long, 6 inches in diameter and consisted of batteries, transmitters, and scientific instrumentation built into the fourth stage of a Jupiter-C rocket . Foreshadowing NASA and the adventurous and successful Explorer Program , Explorer I bolstered national prestige in the wake of Sputnik . The satellite also contributed to a spectacular scientific bonanza - the discovery of Earth-girdling belts of magnetically trapped charged particles now known as the Van Allen Radiation Belts .