The first successful U.S. satellite, Explorer I, was launched into Earth orbit by the Army on Jan. 31, 1958, at Cape Canaveral, Florida, four months after Russia orbited Sputnik. The 18-pound satellite had a cylindrical shape and was 80 inches long and six inches in diameter.
Explorer I’s small package of instruments produced the first major discovery of the Space Age—The Van Allen radiation belts surrounding the Earth. Explorer I burned up in the atmosphere on March 30, 1970.