VIENNA, June 7 (UPI) -- The Earth's Global Positioning System can be a tool to detect illegal and clandestine nuclear tests, U.S. researchers said at a test-ban meeting in Europe.
At the Comprehensive Nuclear-Test-Ban Treaty Organization meeting this week in Vienna, researchers explained that even underground nuclear tests leave their mark on the part of the upper atmosphere known as the ionosphere, an effect known as ionospheric electron density that can be detected by GPS stations in nearby countries.
The phenomenon was discovered by researchers analyzing GPS data recorded the same day as a North Korean nuclear test in 2009.
"It's as if the shock wave from the underground explosion caused the earth to 'punch up' into the atmosphere, creating another shock wave that pushed the air away from ground zero," Ralph von Frese, professor of earth sciences at Ohio State University and senior author on the study, said.
Existing methods for detecting illegal nuclear tests, like seismic and acoustic detectors detecting shock waves in land and water and chemical sensors that can detect airborne radioactive gas and dust, can use GPS detection to confirm what they might otherwise miss, an Ohio State release reported Tuesday.
"GPS is a complement to these other methods, and can help confirm that a nuclear test has taken place -- especially when the test was underground, so that its effect in the air is very subtle, and otherwise nearly impossible to detect," Jihye Park, a doctoral student in geodetic science at Ohio State, said.
While GPS was designed for location purposes, the technology has always been especially sensitive to atmospheric disturbances, researchers say.
"GPS signals must pass from transmitters on satellites high above the planet down to ground-based receivers," Dorota Grejner-Brzezinska, a professor of geodetic science at Ohio State, explained.
"Air molecules -- more specifically, the electrons and other charged particles in the ionosphere -- interfere with the signal, generating position error. Part of our research concerns how to compensate for that vulnerability and make GPS work better.
"Jihye found a way to take that vulnerability and turn it into something useful," she said.
