The Van Allen Probes (formerly known as the Radiation Belt Storm Probes (RBSP)) will study two extreme and dynamic regions of space known as the Van Allen Radiation Belts that surround Earth. Named for their discoverer, James Van Allen, these two concentric, donut-shaped rings are filled with high-energy particles that gyrate, bounce, and drift through the region, sometimes shooting down to Earth's atmosphere, sometimes escaping out into space. The radiation belts swell and shrink over time as part of a much larger space weather system driven by energy and material that erupt off the sun's surface and fill the entire solar system.
The identical Van Allen Probes will follow similar orbits that will take them through both the inner and outer radiation belts. Credit: JHU/APL, NASA
Space weather is the source of aurora that shimmer in the night sky, but it also can disrupt satellites, cause power grid failures and disrupt GPS communications. The Van Allen Probes will help scientists to understand this region and to better design spacecraft that can survive the rigors of space. As the second mission in NASA's Living With a Star program, the Van Allen Probes will take its place as part of a fleet of spacecraft that may someday help predict space weather before it even impacts Earth's environs.
While earlier missions have sent back some information about the radiation belts, the Van Allen Probes are the first to use two spacecraft in tandem. As they speed through the belts at some 2000 mph, the spacecraft will naturally pass through changing conditions. But a single moving spacecraft cannot discern whether any changes it observes are due to traveling disturbances, or if the spacecraft simply flew through two static, but differing, regions. Two spacecraft with identical instruments, however, can distinguish between these possibilities.
Launch on August 30, 2012, the two Van Allen Probes spacecraft operate in the harsh conditions they are studying. While other satellites have the luxury of turning off or protecting themselves in the middle of intense space weather, the Van Allen Probes must continue to collect data, and therefore, been built to withstand the constant bombardment of particles and radiation they will experience in this intense area of space.
The mission's general scientific objectives are to
Discover which processes -- singly or in combination -- accelerate and transport the particles in the radiation belt, and under what conditions.
Understand and quantify the loss of electrons from the radiation belts.
Determine the balance between the processes that cause electron acceleration and those that cause losses.
Understand how the radiation belts change in the context of geomagnetic storms.