50 Years Later: First U.S. Satellite's Souvenirs Still Circle the Earth

Fifty years ago today, the 70-foot (21-meter) tall Juno 1 rocket, a modified Redstone missile, launched the Explorer I satellite, marking the first U.S. built payload to enter Earth orbit. Three of the booster's four stages fell into the ocean while the fourth, which was used to boost Explorer I's velocity, entered orbit behind the satellite.

Explorer I - a 30-pound (13-kg), 7-foot (2-meter) satellite - was the third man-made moon to circle Earth, following the Soviet Union's Sputnik I and II spacecraft. It was the second satellite with a payload, a small science package that was built to measure cosmic rays, which led to the detection of a radiation belt (the Van Allen belt, named after Dr. James van Allen, who designed and built the instrumentation).

collectSPACE.com Editor