The verification system of the Comprehensive Nuclear-Test-Ban Treaty

Abstract

The Comprehensive Nuclear-Test-Ban Treaty was opened for signature in September 1996. To date, the treaty has been signed by 165 countries and ratified by 93; among the latter, 31 out of the 44 whose ratification is needed for the treaty to enter into force. The treaty calls for the installation and operation of a verification system to ensure compliance. The verification system is composed of the International Monitoring System (IMS), the International Data Centre (IDC), and the On Site Inspection Division (OSI). The IMS is a global network of 321 stations hosted by 90 countries. The primary network is composed of 50 seismic stations, 31 of which are seismic arrays and 19 three-component, broad-band stations, 11 hydroacoustic stations, 60 infrasound arrays, and 80 radionuclide monitoring stations measuring radioactive particulates and noble gases in the atmosphere. The radionuclide network is supported by 16 laboratories. The auxiliary network of 120 seismic stations is interrogated on request by the IDC to improve the accuracy of the locations. The data from the 321 stations and from the laboratories is transmitted to the IDC in Vienna via a dedicated Global Communication Infrastructure (GCI) based on VSAT antennas. The IDC collects and processes the data collected from the four technologies and produces bulletins of events. The raw data and bulletins are distributed to state signatories. Upon entry into force, an on-site inspection may be carried out if it is suspected that a nuclear explosion has taken place. Since mid-1997, when the Provisional Technical Secretariat responsible for the implementation of the verification system began its work in Vienna, over 86% of the sites have been surveyed and the final location of the stations selected. By the end of 2002 this number will reach about 90%, essentially completing this phase. To date, 131 stations have been built or upgraded, and 80 are now sending data to the IDC; 112 others are under construction or under negotiation. Over 392 authorized users from 53 state signatories are now receiving data and products from the IDC. In addition, under the auspices of the signatories of the treaty, several projects are being funded to improve the calibration of seismic stations, the software used routinely at the NDC, and the analysis of radionuclides, among others.