The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., will develop and operate twin NASA spacecraft to study how the sun interacts with Earth's radiation belts.

Part of NASA's Living With a Star Program, the Radiation Belt Storm Probes (RBSP) mission will determine how varying inputs of solar energy form or change populations of relativistic electrons and ions in the Earth's radiation belts -- the doughnut-shaped bands of charged particles trapped by Earth's magnetic field that extend some 20,000 miles around our planet. After launch, scheduled for 2012, the RBSP spacecraft will measure the distributions of charged particles as well as the electric and magnetic fields that energize, transport or remove the particles within these belts.

Detailed design of the probes will begin this summer, after NASA selects the spacecraft's science instruments. The mission's science results will provide the understanding needed to predict potentially hazardous space weather effects, much in the same way we forecast weather on Earth. Furthermore, observations from the spacecraft will be used to improve the characterization of planetary space environments. Increased knowledge of the space environment and effects of space weather will permit better design and operations of new technology on Earth and in space.

"For the first time, several spacecraft will simultaneously watch activity on the sun and the reaction to that activity within Earth's radiation belts," says Ken Potocki, APL's Living With a Star programs manager. "These probes will have to work in an incredibly difficult radiation environment where charging and discharging will occur, a lot like flying into an electrical storm. But our team looks forward to the engineering and design challenge. We know how important these data will be."

Radiation Belt Storm Probes is the first project assigned to APL under a 12-year contract, awarded in December 2000, to design, develop and operate missions in the Living With a Star and Solar Terrestrial Probes programs. The Lab's experience in developing spacecraft to study the sun-Earth relationship includes the TIMED satellite, currently examining solar effects on Earth's upper atmosphere, and the twin STEREO probes, which after launch this summer will begin taking the first 3-D images of solar events called coronal mass ejections, which can blast billions of tons of the sun's atmosphere into space and trigger severe magnetic storms when they collide with Earth.

APL spacecraft have flown into the charged-particle environment before: The Charge Composition Explorer, one of three spacecraft in the international Active Magnetospheric Particle Tracer Explorers (AMPTE) program of the 1980s, measured the composition of magnetospheric particles as well as the variations of these particles over space and time.

All told, APL has built 62 spacecraft and more than 150 space instruments.

The Living With a Star (LWS) Program Office at NASA Goddard Space Flight Center, Greenbelt, Md., has overall program responsibility for the Radiation Belt Storm Probes mission as well as the first LWS mission --the Solar Dynamics Observatory -- planned for launch in 2008. For more information on the program, visit http://lws.gsfc.nasa.gov.

The Applied Physics Laboratory (APL), a not-for-profit laboratory and division of The Johns Hopkins University, conducts research and development primarily for national security and for nondefense projects of national and global significance. For more information, visit www.jhuapl.edu.