Origins and Context
The United States launched Explorer 1 on January 31, 1958, in response to the Soviet Union's Sputnik launches.1 The Army Ballistic Missile Agency and Jet Propulsion Laboratory developed the satellite in less than 90 days after President Eisenhower's directive.2
Program Structure
JPL designed and built the 30.8-pound satellite while von Braun's team modified a Jupiter-C rocket (designated Juno I) for the launch.3 The spacecraft carried instruments including a cosmic ray detector, micrometeorite sensors, and temperature probes.4
Legacy
Explorer 1's cosmic ray detector, designed by James Van Allen, led to the discovery of radiation belts around Earth trapped by the planet's magnetic field.5 The satellite transmitted data until May 23, 1958, and remained in orbit until March 31, 1970, completing over 58,000 orbits.6
References
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"Explorer 1 became the first successfully launched satellite by the United States when it was sent to space on January 31, 1958." - NASA JPL ↩
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"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." ↩
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"The satellite weighed 14 kilograms (30.66 pounds) and was launched atop a modified Jupiter-C rocket designated Juno I." ↩
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"The primary science instrument on Explorer 1 was a cosmic ray detector designed to measure the radiation environment in Earth orbit." ↩
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"Van Allen theorized that the instrument may have been saturated by very strong radiation from a belt of charged particles trapped in space by Earth's magnetic field." ↩
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"Explorer 1 made its final transmission on May 23, 1958. It entered Earth's atmosphere and burned up on March 31, 1970, after more than 58,000 orbits." ↩