Key Aspects for the Definition of On-site Inspection Challenging Environments

On-site inspection (OSI) is an element of the verification regime of the Comprehensive Nuclear Test Ban Treaty (CTBT), with the sole purpose to clarify whether a nuclear weapon test explosion or any other nuclear explosion has been carried out in violation of the Treaty. An OSI could be launched in any environment where a triggering event occurred. A challenging environment may affect not only the signatures and observables of a nuclear explosion, but also the possibility to conduct the OSI. Harsh environmental conditions, such as extreme climate conditions, high vegetation coverage and complicated topographic characteristics, among others, could slow down the deployment of field missions, and affect the state-of-health of OSI equipment and even the performance of inspectors, thereby compromising the whole inspection. Thus, the operationalization of OSI in different environments is an important aspect in the development of OSI capability. In this respect, well defined OSI environment is an important step towards the development of comprehensive OSI capabilities. Based on the analysis of historical underground nuclear explosions data and knowledge on the environmental impact on observables, equipment and inspectors, a definition of OSI environment was developed. Climatic conditions were grouped into the main five groups of the Köppen-Geiger classification scheme. Vegetation coverage was re-grouped in four of the 16 classes of land coverage (not including water bodies) following the International Geosphere-Biosphere Programme. Complicated landforms grouped in topographic classification using a digital elevation model based on slope gradient, surface texture and local convexity within neighboring cells was used to classify topographic relief of four types of landforms for OSI. In this presentation, it is shown how these key environmental aspects will impact the conduct of an OSI.