GPS Satellites Could Detect Nuclear Tests

[bananas]

http://news.sciencemag.org/sciencenow/2012/12/satellites-could-detect-nuclear-.html

Satellites Could Detect Nuclear Tests
by Carolyn Gramling on 4 December 2012, 8:25 PM | 0 Comments

SAN FRANCISCO, CALIFORNIA—Even when they're underground, nuclear tests can be detected in the skies—and as a result, global satellite networks could become a powerful new tool in the arsenal of weapons to help detect clandestine underground nuclear explosions, a team of scientists reported here today at the fall meeting of the American Geophysical Union.

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Park and her colleagues previously demonstrated that it was possible to identify a UNE by its ionospheric fingerprint, in a study published in Geophysical Research Letters in 2011. The target in that case was North Korea's 25 May 2009 UNE: Park and her team found a unique TID that also pinpointed the location of the explosion to within about 4 kilometers of its seismically determined epicenter. They saw this TID pattern in data from 11 different Global Navigation Satellite System stations—astronomically unlikely for a random event.

In the current study, the team analyzed signals that GPS stations received after two 20-kiloton UNE tests the United States conducted in 1992. The two tests were part of a series of eight UNEs conducted from 1991 to 1992 at a dusty Department of Energy reservation 100 kilometers northwest of Las Vegas, Nevada. Researchers had begun testing nuclear devices at the Nevada Test Site in 1951; this latest series of blasts was codenamed Operation Julin, and the final two tests of the series—dubbed Hunters Trophy and Divider—took place on 18 September and 23 September, respectively. Those two also became the last nuclear tests the United States conducted before President George H. W. Bush signed a law imposing a moratorium on all nuclear weapons testing, on 2 October 1992. (The 1963 Limited Test Ban Treaty had already banned all but underground tests.) In 1996, the United States, Russia, the United Kingdom, France, and China signed the Comprehensive Nuclear-Test-Ban Treaty—but the United States has yet to ratify it.

The team came up with a relatively simple algorithm to find the signal within the noise. They first removed the effect of distortions from changes to the diurnal cycle and from the changing geometry of the satellites themselves. Then they converted the ionospheric delay between satellites and stations into a "total electron content" in the TIDs. From all of these data, they came up with a profile for the TIDs: their amplitude, their frequency, and how quickly they traveled through the ionosphere. That same profile appeared in multiple stations—and as a result, based on where the stations were and how long it took that fingerprinted signal to arrive, the team was also able to pinpoint the location of the original signal—the Hunters Trophy blast. They devised a similar algorithm to identify and characterize the Divider blast using GPS data.

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[krispos42]

1. TID = traveling ionospheric disturbance

Comes from the massive EM burst of the detonation.