Satellites measure the health of planet Earth by bouncing signals off a patch of ocean, ice sheet, or rainforest and discerning digital vital signs upon their return. But a new cluster of satellites will harness the global positioning system to help predict weather patterns, long-term climate change, and even crippling interference from solar flares.
The same GPS signals you rely on to navigate through rush-hour traffic, find a restaurant, or track your kids can also be used to forecast when hurricanes form in tropical waters. At least that’s the hope of researchers who developed a fleet of six small satellites scheduled to blast off on a SpaceX Falcon Heavy rocket next Monday from Cape Canaveral. The mission is also the latest round in an ongoing contest of sorts between government-sponsored and privately operated weather data collection systems, a competition that many observers hope will result in better forecasts that cost less money.
Known as the Constellation Observing System for Meteorology, Ionosphere and Climate (or COSMIC-2), the mission takes advantage of a weird property of GPS radio signals: They actually bend and slow down slightly as they travel through the atmosphere. This bending doesn't affect the accuracy of navigation on the ground; it's only visible from the side by something else in orbit. It's a bit like what when you dip a pencil in a half-full glass of water and the image refracts slightly through the denser liquid (physics folks know it as Snell's Law).
The denser the atmosphere, the more the GPS radio wave bends. Once scientists get this information about density, they can figure out atmospheric moisture, pressure, and temperature at one-kilometer intervals. Getting this kind of granular information about what's happening up and down the atmosphere is key to making weather prediction models more accurate.
“It’s a very elegant technique,” says Bill Schreiner, director of the COSMIC program at the University Corporation for Atmospheric Research in Boulder, Colorado, one of the sponsors of the mission along with the National Oceanic and Atmospheric Administration, the Air Force, and Taiwan’s National Space Organization. “It’s a precise way to measure the atmosphere, and it’s also repeatable.”
Schreiner likens radio occultation, as it's known, to launching 5,000 additional weather balloons every day—that's how many more measurements the six COSMIC-2 satellites will be able to gather. The radio occultation system will also collect more information about the equatorial oceans, the spawning ground of the hurricanes and typhoons that batter the world's coastlines. The other advantage is it can collect information about atmospheric conditions in remote parts of the globe that ships and weather stations can’t reach. The COSMIC-2 satellite also carries a sensor that measures how fast solar particles are traveling, information that will help space weather scientists know when a big solar flare or eruption might be on the way.