Explorer 1

  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

1. jpl.nasa.gov ↩

2. nasa.gov ↩

3. science.nasa.gov ↩

4. nasa.gov ↩

5. nasa.gov ↩

6. science.nasa.gov ↩