Signals from Microsatellite GPS/MET Give Access to Wealth of New Information
Highlight of December Conference Session
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The microsatellite for the National Science Foundation (NSF)-funded global sensing project known as GPS/MET has been in orbit since April, and is "allowing scientists unprecedented access to a wealth of information about Earth's atmosphere," says Robert Corell, National Science Foundation assistant director for geosciences.
A first look at this information will be presented in session G22B (Tuesday, December 12th at 1:30 PM in room 307) at the American Geophysical Union fall conference, to be held in San Francisco December 11-15.
Applications of GPS/MET data include better weather forecasts, especially over the oceans, where data are now scarce. The Air Transport Association attributes a loss of at least $4 billion annually to weather-related aircraft delays. Since commercial transoceanic flights are increasing at twice the rate of domestic flights, better short-term forecasts could result in huge savings. Improved forecasts could also save lives and billions of dollars in property damage caused by floods, tornadoes, drought, and other disasters.
The GPS/MET receiver, no larger than a shoebox, circles the earth every 100 minutes aboard the MicroLab-1 satellite. As it orbits, the receiver picks up signals transmitted from 24 GPS satellites. Approximately 500 times a day, the ray path between the receiver and one of the GPS satellites passes through the earth's atmosphere. These events -known as radio occultations -- provide a means to take soundings of the atmosphere. Scientists believed that these signals would provide a new way of obtaining vertical profiles of temperature, moisture, and other atmospheric parameters with improved resolution and frequency." Results to date are extremely promising," says Jay Fein, program director in NSF's atmospheric sciences division.
Scientists believe that this microsatellite will allow more detailed detection of long-term, global changes in the atmosphere. Says Fein, "For example, the atmosphere's temperatures between about seven and 30 km can be tracked with precision by GPS/MET, providing scientists with information about the earth that they have never before been able to obtain."
GPS/MET will serve as a much needed complement to a long used instrument: the radiosonde. An instrument package sent upward by balloon twice each day at approximately 1,000 locations worldwide, the radiosonde has endured for more than 50 years as the primary way to sense the atmosphere's vertical structure. GPS/MET can perform these vertical scans in only a minute or two, compared to around 100 minutes for a radiosonde. And GPS/MET is unhindered by oceans or other settings where balloon launches are hard to conduct. Although radiosondes have the advantage of making separate temperature and humidity measurements, the indirect readings derived from GPS/MET may work as well as radiosonde data for short-term weather prediction, studies show.
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