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On This Day in Space: January 31, 1958 Explore 1 Launched

Explorer 1 was the first successful American satellite, launched on January 31, 1958, as part of the United States’ response to the Soviet Union’s successful launch of Sputnik 1 in October 1957. The launch of Explorer 1 marked the beginning of the American space program and the Space Race between the two superpowers during the Cold War.

The Explorer 1 mission was initiated by the United States Army Ballistic Missile Agency and managed by the Jet Propulsion Laboratory (JPL). The satellite was was built around a 33.5-inch-long (85 cm) cylinder and weighed 31 pounds (14 kg). It was equipped with a scientific instrument package.

The launch of Explorer 1 took place from Cape Canaveral Air Force Station, Florida, using a Juno I rocket. The rocket was developed by the Army Ballistic Missile Agency and based on the Jupiter-C. Explorer 1 orbited the Earth every 115 minutes, reaching an altitude of over 580 miles (940 km). During its 98-day mission, the satellite sent back valuable data on the Earth’s magnetic field and cosmic rays, leading to the discovery of the Van Allen radiation belts, which are areas of high-energy particles trapped in the Earth’s magnetic field.

The launch of Explorer 1 was a major achievement for the United States and marked a turning point in the Space Race. It demonstrated the United States’ capability to launch a satellite into space and paved the way for future American space missions.