In January 1958 the U.S. Army Ballistic Missile Agency successfully launched a satellite using a Jupiter C rocket developed by Dr. Wernher von Braun.
The satellite carried a cosmic ray detector designed to measure the radiation environment in Earth’s orbit. The radiation belts discovered by Explorer 1 subsequently were known as the Van Allen Belts.
Making one orbit every 114.8 minutes, Explorer 1 revolved around Earth in a looping orbit from 354 kilometers (220 miles) to Earth to 2,515 kilometers (1,563 miles).
Explorer 1 made its final transmission in May 1958.
Explorer1 entered Earth’s atmosphere and burned up on March 31, 1970, after more than 58,000 orbits.
Source: NASA