Detected 40 years ago, the doughnut-shaped particles belts extending more than 20,000 miles around the planet were thought to be very stable, waxing and waning over a period of months. Under those conditions, the charged particles can pierce a sheet of aluminum a half-inch thick, possibly resulting in a catastrophic accumulation of particles in the sensitive electronics of hundreds of orbiting satellites. Shielding people and hardware in space is expensive and heavy, and the discovery may compel space engineers to design orbiting systems differently. In early May, sensors on at least 10 science satellites started picking up indications that electrons were accelerating. On May 19, a heavily used telecommunications satellite, Galaxy 4, failed suddenly and 45 million customers lost pager service.
Scientists think the electron flow contributed to the outage.
Such fluxes also may have contributed to the failure of a Canadian telecommunications satellite, Anik E1, in 1996. The risk to NASA's manned space program is less certain. Satellites orbit 22,000 miles above the planet in the midst of the most energetic fields of the Van Allen Belts. The space shuttle and the space station orbit within about 250 miles of Earth. Scientists said that during intense periods the charged particles pulse down into the atmosphere.