Spacecraft try to avoid the Van Allen Radiation Belts, two doughnut-shaped regions around Earth filled with “killer electrons” and plasma waves. NASA launched two heavily-shielded spacecraft directly into the belts. The Radiation Belt Storm Probes are on a two-year mission to study the Van Allen Belts and to unravel the mystery of their unpredictability.
NASA’s Radiation Belt Storm Probes blasted off from Cape Canaveral on August 30th, 2012. Bristling with sensors, the heavily-shielded spacecraft are on a 2-year mission to discover what makes the radiation belts so dangerous and so devilishly unpredictable.
When the radiation belts were discovered in 1958, they upended orthodox ideas. Most people assumed the space around Earth was empty. America’s first satellite, Explorer 1, proved otherwise. The tiny spacecraft was equipped with a Geiger tube for counting energetic protons and electrons. Circling Earth, Explorer 1 found so many charged particles that the counter registered off-scale most of the time.
Back in the 1950s the radiation belts had little effect on ordinary people. Today they are crucial to our high-tech society. Hundreds of satellites used for everything from weather prediction to GPS to television routinely skim the belts, subjecting themselves to energetic particles that can damage solar panels and short-circuit sensitive electronics. During geomagnetic storms when the belts are swollen by solar activity, whole fleets of satellites can be engulfed, imperiling the technological underpinnings of daily life on the planet below.
One of the biggest mysteries of the radiation belts is the crazy way they react to solar storms. “Almost anything can happen.
When a storm cloud from the sun hits the radiation belts, they often respond in counterintuitive ways. One possible outcome is that the radiation belts fill with energetic particles such as the potent “killer electrons” that worry mission planners. However, just as often the opposite happens. A solar storm can cause the belts to lose their killer particles, temporarily making them a safer place. And sometimes nothing happens! The belts remain completely unchanged.