Small but mighty.
The six COSMIC microsatellites already are revolutionizing weather forecasting.

Orbital Sciences Corporation

The Little Satellite Fleet That Could

SAN FRANCISCO, CALIFORNIA--Six microsatellites launched last April are proving that a tiny fleet of spacecraft is as good--if not better--than traditional satellites at forecasting Earth's weather.

The craft are part of a project known as the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC). Instead of large satellites bristling with instruments costing upwards of $300 million a pop, the 100-kilogram "microsats"--each shaped like a pair of sunglasses--carry little more than radio receivers to pick up GPS signals. A group of weather scientists from the University Corporation for Atmospheric Research in Boulder, Colorado, first proposed the $100 million project to NASA in 1997, but when the agency balked at the concept, the team secured funding from Formosat, the Taiwanese government's space enterprise.

The COSMIC team launched the microsats last April, and since then the craft have been trailing one another in a polar orbit some 800 kilometers high. They've already notched their first successes: Reporting here yesterday at the annual meeting of the American Geophysical Union, the team says meteorologists used data from the fleet earlier this year to predict the track of Tropical Storm Bilis, as well as capture the genesis of Ernesto and its transition from a tropical storm into a hurricane, with significantly greater precision than possible with traditional weather models. Data from the microsats, updated 1500 times each day, have been accessed by 360 subscribers so far worldwide, all of whom receive it free of charge. "We have already seen improvements of up to 10% in weather forecasting accuracy," says team leader Richard Anthes, who is president of UCAR.

The COSMIC concept is deceptively simple, Anthes explains. The satellites constantly interpret signals from NASA's global positioning satellite system as those signals pass through Earth's atmosphere. It turns out that changes in temperature, humidity, and air pressure can affect those signals in ways scientists can detect, and those changes are providing the basis for substantially more accurate weather forecasting. "It's all coming from these signals that are essentially being generated for free," Anthes says.

The science that COSMIC has generated so far has been "stunning," says Tom Yunck, a resident GPS specialist at NASA's Jet Propulsion Laboratory in Pasadena, California. Yunck, considered one of the pioneers in using GPS signals for Earth observation, calls the mission "the model of the future" and says its most important aspect is how it bucks the trend of "ever larger, more costly satellites that take years to develop."

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