摘要：The Global Positioning System (GPS) has revolutionized the process of getting from point A to point B—and so much more. A large fraction of the world's population relies on GPS (and its counterparts from other nations) for precision timing, location, and navigation. Most GPS users are unaware that the spacecraft providing the signals they rely on are operating in a very harsh space environment—the radiation belts—where energetic particles trapped in Earth's magnetic field dash about at nearly the speed of light. These subatomic particles relentlessly pummel GPS satellites. So by design, every GPS satellite and its sensors are radiation “hardened.” Each spacecraft carries particle detectors that provide health and status data to system operators. Although these data reveal much about the state of the space radiation environment, heretofore they have been available only to system operators and supporting scientists. Research scientists have long sought a policy shift to allow more general access.
