Scientists are examining the possibility of using global satellite networks to help detect clandestine underground nuclear explosions (UNE). The International Monitoring System (IMS), established by the Comprehensive Nuclear-Test-Ban Treaty (CTBT), currently employs seismic networks, hydroacoustic networks and radionuclide networks to detect clandestine nuclear weapons testing; however, these methods have the potential to miss clandestine explosions.
According to Andreas Persbo, executive director of the Verification Research, Training and Information Centre in London, proposals to use GPS in detonation detection have been present since 1979. Even when detonated underground, nuclear explosions emit electromagnetic pulses through the Earth’s ionosphere—an effect known as traveling ionospheric disturbance (TID) that should, in theory, be detectable with technologies that are sensitive to changes in the ionosphere. However, environmental occurrences, such as earthquakes, can also produce TIDs and disturb the data collected by the satellite system.
Now, researchers from Ohio State University have announced the development of methodology to improve positioning data from the global navigation satellite system and identify the desired signal within the noise. By analyzing signals from data collected by GPS stations during UNE testing near Las Vegas, Nev. in 1992, the team was able to develop an “identification profile” for the TIDs that included frequency, amplitude and speed of travel through the ionosphere. Once identified, these “profiles” can be used to pinpoint the location of the original signal.
The team acknowledges that several issues must be settled before the method can be made operational, including sensitivity limits and how well the method can distinguish between different point sources, but hopes that the method can be incorporated into formal CTBT monitoring in the near future.
