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Explorer 1 Satellite Launch

On January 31, 1958, the United States finally became a competitor in the Space Race.

Explorer 1 became America’s first successful satellite launch. It rode into Earth’s orbit aboard one of the Jupiter-C rockets Wernher von Braun developed, a precursor to the rockets that later launched the first Americans to the Moon.

Although the Russians had already put two Sputnik satellites into Earth orbit before the Explorer 1 launch, Explorer 1 still marked an important “first” for humankind: it carried the first scientific instruments to operate in space and produced the first scientific discovery made in space.

U.S. Nabs First Space Science Discovery

By far the largest instrument aboard Explorer 1 was a cosmic ray detector—a Geiger counter—designed by the University of Iowa’s Dr. James van Allen.

NASA’s Space Center Houston describes the significance of this instrument and its discoveries:

“To NASA’s surprise, it was registering radiation levels a thousand times greater than anyone expected. The radiation wasn’t of Earthly origin, and it occupied an area scientists had considered a void. It also far outpaced the levels of radiation that would be expected from cosmic rays alone.”

Future missions confirmed this momentous discovery: the presence of two powerful radiation areas trapped by Earth’s magnetic field, known today as the Van Allen radiation belts. Named for the scientist who discovered them, it was the intrepid little Explorer, weighing just around 31 pounds, with a high power transmitter that operated for only 31 days, that made their discovery possible.

Learn More with the Cosmosphere

See photographs of the Explorer 1 exhibit in our “Competition Begins” gallery.


Picture the satellite’s four whip-like antennae fully extended and flying around in a blur as the Explorer spun around its axis at 750 revolutions per minute!

You’ll see that the artifact description notes “This particular model is actually a Beacon 1 painted to look like an Explorer 1.”

Both Beacon 1 and Explorer 1 had those long antennae, but the Explorer 1’s distinctive paint job actually served an important design function!

NASA’s History Division notes:

“The external skin of the instrument section was painted in alternate strips of white and dark green to provide passive temperature control of the satellite. The proportions of the light and dark strips were determined by studies of shadow-sun-light intervals based on firing time, trajectory, orbit, and inclination.”

Visit the Cosmosphere and peer around back of the artifact to see the distinctive Explorer 1 striping.

In the artifact cut-away, you’ll find Beacon 1’s bulbous nitrogen bottle. This was attached to a valve built to fill a 12-foot inflatable satellite carried inside Beacon 1. Alas, Beacon 1’s space balloon never made it to orbit—the October, 1958 Beacon 1 mission failed when the payload separated prematurely from the upper stages.

The Explorer 1’s mission ten months earlier is still celebrated today as a complete success.

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