Van Allen Radiation Belts

Discovered by some of the earliest spacecraft in the late 1950s, knowledge of these belts of charged particles surrounding the Earth helped in the design of safe manned craft and satellites.

With the launch of Sputnik 1 in October 1957, there was a flurry of effort in the United States to send up some kind of answer to the Soviets’ first space flight achievement. Scrambling for a useful payload to send up with the first U.S. satellite—Explorer 1—the one set of instruments ready to go included a cosmic ray detector (essentially a Geiger counter) designed by scientist James Van Allen. His basic research concerning radiation in space at the University of Iowa, which led directly to Explorer 1’s payload, was funded by the Office of Naval Research.

Launched in January 1958, Explorer 1 was followed some weeks later by Explorer 3 with similar instruments on board. The combined data from the two satellites confirmed the first major scientific discovery of the Space Age: there was a series of “belts” of radiation encircling the Earth composed of charged particles trapped by the planet’s magnetic field. Any spacecraft leaving the Earth’s atmosphere would have to be designed to deal with these belts of radiation.

The discovery of these belts, named for Van Allen during a meeting of the National Academy of Sciences and the American Physical Society on May 1, 1958, alerted the space programs to new dangers both to electronics as well as to life and limb. In addition, entirely new areas of science were founded as a result of this discovery—such as plasma physics and magnetospheric physics—to investigate the complex relationship between the Earth and the Sun.

A depiction of the Van Allen radiation belts around the Earth, as well as the positions of several satellites and probes within the belts.A depiction of the Van Allen radiation belts around the Earth, as well as the positions of several satellites and probes within the belts.
(Image courtesy of NASA)

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