<P> Explorer 1 was launched on January 31, 1958 at 22: 48 Eastern Time (equal to February 1, 03: 48 UTC) atop the first Juno booster from LC - 26 at the Cape Canaveral Missile Annex, Florida . It was the first spacecraft to detect the Van Allen radiation belt, returning data until its batteries were exhausted after nearly four months . It remained in orbit until 1970, and has been followed by more than 90 scientific spacecraft in the Explorer series . </P> <P> Explorer 1 was given Satellite Catalog Number 4, and the Harvard designation 1958 Alpha 1, the forerunner to the modern International Designator . </P> <P> The U.S. Earth satellite program began in 1954 as a joint U.S. Army and U.S. Navy proposal, called Project Orbiter, to put a scientific satellite into orbit during the International Geophysical Year . The proposal, using a military Redstone missile, was rejected in 1955 by the Eisenhower administration in favor of the Navy's Project Vanguard, using a booster advertised as more civilian in nature . Following the launch of the Soviet satellite Sputnik 1 on October 4, 1957, the initial Project Orbiter program was revived as the Explorer program to catch up with the Soviet Union . </P> <P> Explorer 1 was designed and built by the Jet Propulsion Laboratory (JPL), while a Jupiter - C rocket was modified by the Army Ballistic Missile Agency (ABMA) to accommodate a satellite payload; the resulting rocket known as the Juno I . The Jupiter - C design used for the launch had already been flight - tested in nose cone reentry tests for the Jupiter IRBM, and was modified into Juno I. Working closely together, ABMA and JPL completed the job of modifying the Jupiter - C and building Explorer 1 in 84 days . However, before work was completed, the Soviet Union launched a second satellite, Sputnik 2, on November 3, 1957 . The U.S. Navy's attempt to put the first U.S. satellite into orbit failed with the launch of the Vanguard TV3 on December 6, 1957 . </P>

When was the first satellite put in space