This Day in Tech History

On This Day . . .

. . . generates the first Major Scientific Discovery of the Space Age


Jan 31, 1958:  Explorer 1 was the First Successful Launch of an American Salellite into Orbit

It was launched as part of its participation in the International Geophysical Year. The mission followed the first two Earth satellites the previous year, the Soviet Union’s Sputnik 1 and 2, beginning the Cold War Space Race between the two nations.

images explorer1_500px

Explorer 1 was launched on January 31, 1958 at 22:48 Eastern Time (equal to February 1, 03:48 UTC) atop the first Juno booster from LC-26 at the Cape Canaveral Missile Annex, Florida. It was the first spacecraft to detect the Van Allen radiation belt, returning data until its batteries were exhausted after nearly four months. It remained in orbit until 1970, and has been followed by more than 90 scientific spacecraft in the Explorer series.


Explorer 1 carried an instrument package developed by a team at the State University of Iowa under the direction of Professor James A. Van Allen. Data returned by Explorer 1 and Explorer 3 (launched in March 1958) provided evidence that the Earth is surrounded by intense bands of radiation, now called the Van Allen radiation belts. This was the first major scientific discovery of the space age.

Design Features (in comparison to Sputnik 1):

Exp1 Sputnik

  • More than twice the size of a basketball, Sputnik was larger and heavier than Explorer.   Only the striped section of Explorer contained the payload; the rear half was a solid-fuel rocket motor.
  • Sputnik’s sphere was polished to a high sheen to aid in tracking by telescope.  Explorer’s light and dark stripes helped      control its temperature.
  • Despite Sputnik’s streamlined appearance, it tumbled while in orbit.  Explorer spun about its long axis, which extended its four flexible antennas.
  • Sputnik contained two radio transmitters, which sent back the “beep-beep-beep” heard round the world.  Explorer contained a cosmic ray detector, radio transmitter, and temperature and micrometeoroid sensors.

Newsreel of Explorer 1 Launch:

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