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NSF PR 95-80 - November 29, 1995
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Cheryl Dybas |
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Signals From Microsatellite GPS/MET Give Access to
Wealth of New Information Highlight of December Conference
Session
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. -end- Press releases
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