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*'''Explorer 1''' was the first satellite launched by the United States when it was sent into space on January 31, 1958. Following the launch of the Soviet Union's Sputnik 1 on October 4, 1957, the U.S. Army Ballistic Missile Agency was directed to launch a satellite using its Jupiter C rocket developed under the direction of Dr. Wernher von Braun. The Jet Propulsion Laboratory received the assignment to design, build and operate the artificial satellite that would serve as the rocket's payload. JPL completed this job in less than three months.  

*'''Explorer 1''' was the first satellite launched by the United States when it was sent into space on January 31, 1958. Following the launch of the Soviet Union's Sputnik 1 on October 4, 1957, the U.S. Army Ballistic Missile Agency was directed to launch a satellite using its Jupiter C rocket developed under the direction of Dr. Wernher von Braun. The Jet Propulsion Laboratory received the assignment to design, build and operate the artificial satellite that would serve as the rocket's payload. JPL completed this job in less than three months.  

:The primary science instrument on Explorer 1 was a cosmic ray detector designed to measure the radiation environment in Earth orbit. Once in space this experiment, provided by Dr. James Van Allen of the University of Iowa, revealed a much lower cosmic ray count than expected.  The existence of these radiation belts was confirmed by another U.S. satellite launched two months later, and they became known as the Van Allen Belts in honor of their discoverer.<ref>http://www.nasa.gov/mission_pages/explorer/explorer-overview.html</ref>

:The primary science instrument on Explorer 1 was a [[cosmic ray]] detector designed to measure the radiation environment in Earth orbit. Once in space this experiment, provided by Dr. James Van Allen of the University of Iowa, revealed a much lower cosmic ray count than expected.  The existence of these radiation belts was confirmed by another U.S. satellite launched two months later, and they became known as the Van Allen Belts in honor of their discoverer.<ref>http://www.nasa.gov/mission_pages/explorer/explorer-overview.html</ref>