Radio telescopes could spot nuclear tests

In the effort to uncover clandestine underground nuclear tests, U.S. researchers say they've discovered an unlikely tool: astronomical radio telescopes. Ohio State University researchers say the instruments can spot rogue nuclear testing because underground nuclear explosions leave their mark on the outer reaches of Earth's atmosphere. Working with astronomers at the U.S. Naval Research Laboratory, they have analyzed historical data from the Very Large Array, a constellation of 27 radio telescopes near Socorro, New Mexico, and found the equipment recorded a distinctive pattern of atmospheric disturbances during the last two American underground nuclear tests in Nevada in 1992. The Ohio State researchers had previously demonstrated another unlikely tool, when they showed that South Korean global positioning system stations detected telltale disturbances of charged particles in the ionosphere, the outermost layer of the atmosphere, from North Korea's 2009 nuclear test. The two technologies can complement each other, with telescopes offering higher-resolution measurements over a smaller area, researchers said. "The observations we make as radio astronomers are not so different from GPS," geodetic and geoinformation engineering Professor Dorota Grejner-Brzezinska said. "We may be looking up at a distant galaxy instead of down to the Earth, but either way, we're all looking at radio waves traveling through the ionosphere."