Explorer 1 Launches: America Enters the Space Race
Explorer 1 launched atop a Jupiter-C rocket from Cape Canaveral on January 31, 1958, just four months after Sputnik had humiliated the American space program. The satellite weighed only 30.8 pounds but carried a cosmic ray detector designed by James Van Allen of the University of Iowa. The instrument returned data that initially baffled scientists: the Geiger counter kept registering zero counts at high altitudes, the opposite of what was expected. Van Allen realized the detector was being overwhelmed by radiation so intense it was saturating the instrument. He had discovered two doughnut-shaped belts of charged particles trapped by Earth's magnetic field, now called the Van Allen radiation belts. This finding revealed that space was far more hostile than anyone had anticipated, forcing engineers to redesign spacecraft shielding for every subsequent mission. Explorer 1 orbited until 1970 before burning up on reentry.
January 31, 1958
68 years ago
Key Figures & Places
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