The Wide Area Tracking System (WATS) is a prototype wireless sensor network for detecting a ground-based nuclear device http://www.llnl.gov/str/Imbro.html such as a nuclear "briefcase bomb." WATS is presently being developed at the Lawrence Livermore National Laboratory (LLNL).
WATS would be made up of wireless gamma and neutron sensors connected through a communications network. Data picked up by the sensors undergoes "data fusion", which converts the information into easily interpreted forms; this data fusion is the most important aspect of the system http://www.fas.org/spp/starwars/congress/1997_h/has274010_1.htm#79.
The data fusion process occurs within the sensor network rather than at a centralized computer and is performed by a specially developed algorithm based on Bayesian statisticshttp://www.llnl.gov/str/JulAug01/Hills.html. WATS would not use a centralized computer for analysis because researchers found that factors such as latency and available bandwidth tended to create significant bottlenecks. Data processed in the field by the network itself (by transferring small amounts of data between neighboring sensors) is faster and makes the network more scalable http://www.llnl.gov/str/JulAug01/Hills.html.
An important factor in WATS development is ease of deployment, since more sensors both improves the detection rate and reduces false alarms http://www.llnl.gov/str/JulAug01/Hills.html. WATS sensors could be deployed in permanent positions or mounted in vehicles for mobile protection of specific locations.
One barrier to the implementation of WATS is the size, weight, energy requirements and cost of currently available wireless sensors http://www.llnl.gov/str/JulAug01/Hills.html. The development of improved sensors is a major component of current research at the Nonproliferation, Arms Control, and International Security (NAI) Directorate at LLNL.
WATS was profiled to the U.S. House of Representative's Military Research and Development Subcommittee on October 1, 1997 during a hearing on nuclear terrorism and countermeasures http://www.fas.org/spp/starwars/congress/1997_h/has274010_1.htm#79. On August 4, 1998 in a subsequent meeting of that subcommittee, Chairman Curt Weldon stated that research funding for WATS had been cut by the Clinton administration to a subsistence level and that the program had been poorly re-organized http://commdocs.house.gov/committees/security/has216010.000/has216010_1.HTM#12.