Van Allen Probes Mission Overview and Discoveries to Date

The morning of 30 August 2012 saw an Atlas V rocket launch NASA's second Living With a Star spacecraft mission, the twin Radiation Belt Storm Probes (RBSP), into orbit for an epic mission to understand Earth's space radiation environment. Renamed the Van Allen Probes soon after launch, the Probes are designed to determine how populations of high-energy charged particles within Earth's radiation belts, dangerous to astronauts and satellites, are created, respond to solar variations, and evolve in space environments. Operating in nearly identical geocentric 1.1 x 5.8 R sub(E)10[degrees] inclination) orbits, the two Probes have advanced the goals of NASA'sScience Plan (2014) by radically revising our understanding of Earth's radiation belts and inner magnetosphere. As a key new member of the Heliophysics System Observatory, the mission has led to the discovery of several new and unanticipated structures, the verification and quantification of previously suggested energization processes, and the discovery of new energization processes. It has revealed the critical importance of dynamic injections into the innermost magnetosphere and has coordinated with the high-altitude Antarctic balloon mission Balloon Array for RBSP Relativistic Electron Losses (BARREL) to determine the nature of particle precipitation. The uniquely capable instruments have revealed inner radiation belt features that were all but invisible to previous sensors, and the mission has profoundly advanced our understanding of the measurements critical for predictive modeling of space weather. This article describes the science objectives of the Van Allen Probes mission, highlights the discoveries made so far, and explains the objectives and observation plan for the extended mission.