On Detecting Underground Nuclear Explosions with GNSS and Radio Astronomical Observations

This paper discusses a case study of detection of the underground nuclear explosion (UNE) using observations from the permanently tracking GPS stations and the Very Large Array (VLA) radio telescope located in New Mexico. These two methods independently recorded traveling ionospheric disturbances (TID) from the roughly 20 kiloton Hunters Trophy UNE, which was detonated at the Nevada Test site (NTS) on September 18, 1992 at 17: 00 UTC. GPS data from six stations of the International GNSS Service (IGS) were used to estimate the total electron content (TEC). The continuous slant TEC (STEC) data spans for all ray paths between the stations and the satellites they observed were processed for numerical third order horizontal 3-point derivatives. The STEC derivatives detailed the propagation of TIDs from the UNE as acoustic-gravity waves with velocities ranging over 562 -1088 m/s. In the VLA observations, the disturbance lasted until about 18: 30 UTC. Two-dimensional TEC fluctuation spectra were generated at time epochs with intervals of about 15 minutes. This spectral analysis detected the TID signature, revealing very little activity that increased slightly at 17:17.4 UTC. However, at 17: 27 UTC significant activity was detected with a notable peak in the power spectrum. The ionospheric disturbances were diminished by the end of the observing run at 18: 17.4 UTC. The arrival time of the TID implied a speed between 570 and 710 m/s, consistent with the GPS-based results. These results point to the possible utility of joint observations with GPS and radio telescopes like the VLA in monitoring for clandestine UNEs. In addition, this paper summarizes the GPS-based UNE detection results, by OSU-developed approach, using the 1992 US, 2006, 2009 and 2013 North Korean UNEs. As of March 2, 2013, the results of the 2013 UNE analysis were not fully completed, so only preliminary results are included here.