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The newspaper of The Johns Hopkins University April 28, 2008 | Vol. 37 No. 32
Design Begins on Twin Probes That Will Study Radiation Belts

By Jennifer Huergo
Applied Physics Laboratory

NASA will launch two identical probes into the radiation belts to provide unprecedented insight into the physical dynamics of near-Earth space, where violent space weather can affect astronauts, satellites and even ground-based technologies.

Researchers and engineers at Johns Hopkins' Applied Physics Laboratory and a number of other institutions have begun detailed design of NASA's Radiation Belt Storm Probes Mission, or RBSP. APL will build and operate the twin probes, which are scheduled for a 2011 launch and a primary mission of two years.

"We're excited to move into the detailed planning," said Rick Fitzgerald, RBSP project manager at APL. "The Laboratory has a long-standing history in radiation science, so it's a natural fit for us to be building these two spacecraft to investigate how the radiation belts are created and change over time."

The radiation belts are two doughnut-shaped regions, encircling Earth, where high-energy particles are trapped by the planet's magnetic field. Most Earth-orbiting spacecraft pass through the belts, and when the energy and density of the particles increase, it becomes more likely that an astronaut or spacecraft will be affected.

High-energy particles striking human tissue can alter the chemical bonds within cells, damaging or destroying them. When a particle strikes a satellite, it can overwhelm sensors, damage solar cells and degrade wiring and other sensitive electronics. Large changes in the magnetic field near Earth's surface associated with space weather storms can induce currents that flow through — and affect the operation of — railroad systems, power transmission lines and pipelines.

The RBSP mission seeks to resolve decades-old scientific mysteries of how these particles become energized to such high levels, and how the radiation belts vary so dramatically with changing conditions on the sun.

"The radiation belts were a scientific curiosity when they were discovered 50 years ago by James Van Allen, who was one of the founding members of APL," said Barry Mauk, project scientist for RBSP. "But the belts are becoming very important because we have people and machines operating in them. That region of space is now part of our technology infrastructure. If we can understand the radiation belt environment and its variability, we can apply this knowledge to improve our spacecraft operation and system design, mission planning and astronaut safety."

The probes will measure the particles, waves and magnetic and electric fields that fill near- Earth space to improve our understanding of how the sun's changing energy flow affects them. These observations will help researchers understand not only how charged particles are energized at Earth but also the processes that create particle radiation throughout the universe in stars, interplanetary space and distant nebulae.

These observations also will help researchers develop various models for the radiation belts that will be used by engineers to design radiation-hardened spacecraft, and by forecasters to predict space weather phenomena and alert astronauts and spacecraft operators to potential hazards.

"We're now moving from figuring out what we're going to build to how we're going to build it," said APL's Doug Eng, RBSP's system engineer. "Our biggest technical challenge is to develop observatories that can survive the severe radiation belt environment for a two-year mission. RBSP operates in a place most spacecraft missions want to avoid."

The instruments will be provided by broad teams managed by Boston University, the universities of Iowa and Minnesota, New Jersey Institute of Technology and the National Reconnaissance Office.

The RBSP mission is part of NASA's Living With a Star Geospace program in the Heliophysics Division of the Science Mission Directorate. The program explores fundamental processes that operate throughout the solar system; in particular, those that generate hazardous space weather effects near Earth and phenomena that could affect solar system exploration. The Living With a Star program is managed by NASA Goddard Space Flight Center.


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