Explorer 1 became the United States’ first artificial satellite when it launched in January 1958.
The satellite was launched by a Juno I rocket from Cape Canaveral on 31 January 1958. Its successful flight followed the Soviet launches of Sputnik 1 and Sputnik 2, which had given the USSR an early lead in the Space Race.
Explorer 1 was built by the Jet Propulsion Laboratory and carried instruments designed by a team led by James Van Allen. Its most important discovery was the existence of radiation belts surrounding Earth, now known as the Van Allen belts.
Explorer 1 remained in orbit until March 1970. It is sometimes confused with Vanguard 1, which was the second U.S. satellite and remains one of the oldest objects still in orbit. Explorer 1 was the first American satellite, while its scientific results were also a major early success for the United States.