Happy Anniversary, Explorer I

Laika mockup60 years ago today, on January 31, 1958, Americans made our first venture into space with the unmanned satellite Explorer I.   Explorer I was a welcome accomplishment during the tense days of the Cold War.  The Soviets had gotten off to an early lead in the space race, launching the first-ever artificial satellite, Sputnik I, in October of 1957, and following that up in November with Sputnik 2, which carried the first living being to orbit, a dog named Laika.


Vanguard rocket explodesAmericans had hoped to catch up with the Navy’s Vanguard TV3 rocket, which was slated for launch on December 6, 1957.  Unfortunately, the rocket failed to develop sufficient thrust and rose only a few feet before crashing back onto the launchpad in a fiery explosion.  This increased the pressure for a successful American launch.


In an amazing 84 days from the launch of Sputnik I, the Jet Propulsion Laboratory (JPL) built Explorer I and the Army Ballistic Missile Agency modified the Jupiter-C rocket, part of an earlier program which had been cancelled, to carry it into space.  Famed rocket pioneer Wernher von Braun directed this repurposing of the Jupiter-C.  (NASA did not even exist until 6 months after Explorer I lifted off.)  Below, left to right, JPL director William Pickering, Explorer I chief investigator James Van Allen, and von Braun hold up a model of the satellite.

Explorer I model Pickering Van Allen von Braun


Explorer I diagramExplorer I carried limited instrumentation by today’s standards.  It had a cosmic ray detection package, several internal and external temperature sensors, a micrometeorite impact microphone, and micrometeorite erosion gauges.  Data was sent back to Earth by 2 transmitters, a high-powered one that operated for 31 days and a low-powered one that operated for 105 days.   After its batteries died on May 23, 1958, Explorer I remained in space, completing over 58,000 orbits before falling back to Earth and burning up in the atmosphere on March 31, 1970.



While it was a tremendous boost for American national pride,  Explorer I was also a scientifically significant venture.  Its instruments relayed a much lower cosmic ray count than was expected.   Designer James Van Allen speculated that the equipment might have been overwhelmed by charged particles trapped in the Earth’s magnetic field.  The Explorer 3 spacecraft, launched in March of 1958, confirmed this theory and the bands of radiation are now known as the Van Allen Belt.

Click HERE for NASA’s more detailed description of Explorer I.

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