Concentric rings of highly charged radiation encircle our planet, and we know surprisingly little about them. But once NASA completes a $US686 million mission to launch a twin pair of space probes into the eye of this solar storm, the Van Allen belts should be much less of a mystery.
The Van Allen belts were discovered in 1958 by University of Iowa professor James A. Van Allen. The belts are two layers of the same doughnut of charged plasma — the inner belt stretches from the edge of the atmosphere to a radius of 6400kg, and the outer belt stretches from 12,800km to roughly 39,000km. Thy're held in place by our planet's magnetic field. Nearly all of humanity's communications satellites orbit at the outer edge of the 6400km gap that separates the two belts.
These belts shrink and swell in accordance to the larger solar weather patterns in our galactic neighbourhood. Increased solar activity can bend these bands closer to the Earth and into the orbital range of our communication satellites. Much like solar flares, these bands of intensely charged particles can wreak havoc with modern electronics, GPS, power grids and satellites. The belts tend to knock satellites offline, but NASA has developed a specialised pair of satellites to send in there to figure out why.
The Radiation Belt Storm Probes (RBSP) have been developed by NASA as part of its Living With a Star program. Their sole purpose is to collect data about the inner workings of this volatile radiation shroud, and learn how its constituent electrons and ions react to solar winds. The RBSPs themselves are a duo of spin-stabilized spacecraft fortified against a constant assault from high-energy particles and designed to continue collecting data in conditions that would render conventional satellites floating scrap metal.
After launching from Cape Canaveral aboard an Atlas V 401 rocket (after four delays, hopefully on August 30th, 2012), the probes will spend two years in the belts, collecting an unprecedented data set on the composition and activity of the region. Each probe will fly a nearly identical 9-hour orbit but the spacecrafts' speeds will differ slightly so that every 75 days or so, the two will cross paths. This will allow scientists to record the structure of the belt and measure any fluctuation since the previous flyby.
To collect this data, the RBSPs are each packed with instrumentation needed to identify and quantify the makeup of these ion clouds — not just the particles themselves but also their associated plasma waves and electromagnetic fields. The sport everything from Energetic Particle, Composition, and Thermal Plasma Instrument suites to Relativistic Particle Spectrometers.
At the end of the probes' mission, NASA researchers hope to apply the gleaned data towards better understanding how to defend spacecraft against these belts and operate them most effectively near them. They may also be able to shed light on how these belts, which are found throughout the universe, are formed.