Nuclear threat detection with mobile distributed sensor networks

Abstract

The ability to track illicit radioactive source in an urban environment is critical in national security applications. To this end, two modes of operation are common: positioning individual portal monitors, and deploying a network of distributed sensors. We address here the use of multiple detectors, mounted on moving vehicles, for the purpose of detecting nuclear threats. An example scenario is that of multiple taxi cabs each carrying a detector. The detectors' positions are known in real-time as these are continuously reported from GPS data. The level of detected risk is then reported from each detector at each position. The problem is to delineate the presence of a potentially dangerous source and its approximate location by identifying a small area that has an elevated concentration of reported risk. This problem of using spatially deployed mobile detector networks to identify and locate risks is modeled and formulated here. The problem is shown to be solvable in polynomial time and with a combinatorial network flow algorithm. The efficiency of the algorithm enable its use in real time, and in areas containing a large number of deployed detectors. A simulation study, that takes into account false-positive and false-negatives reports from individual sensors, demonstrates the effectiveness of the algorithm in using the sensor network's detection capabilities.

Framework for Analyzing Environmental Indicators Measurements Acquired by Wireless Distributed Sensory Network – Air Pollution Showcase

“…Another, is to optimize a weighted combination of the goals. As was shown in (Hochbaum and Fishbain 2011) the latter problem is efficiently solvable in polynomial time.…”

“…One iteration of the CA problem finds one region with the highest concentration of sensors reporting highest levels of pollution, hence a binary decision, which is based on solving a minimum-cut problem on an associated graph (Hochbaum and Fishbain 2011). After each iteration the region that was tagged as risky with its corresponding sensors are removed and the process is repeated so equi-pollution contour lines are produced.…”

“…These have greatly enhanced monitoring of complex infrastructure and the natural environment, allowing the study of fundamental processes in the environment, as well as hazard warnings, such as flood (Hart and Martinez 2006;Martinez and Hart 2004;Zhou and Roure 2007) and pollution alerts (Hochbaum and Fishbain 2011), in a new way. In conjunction new hardware designs and algorithmic approaches to support these networks have emerged (Ramanathan et al 2006;Budde et al 2012;Denzer 2005;Kranz et al 2010;Bakken et al 2001).…”

Sensor Management Problems of Nuclear Detection

“…We are examining the viability of fleet-based sensing and addressing related statistical challenges in detection. Hochbaum [H09] and Hochbaum and Fishbain [HF09] have considered a similar fleet-based surveillance scenario, while Neidhardt et al [NLK08] have considered a two-level sensing system that includes a static network of sensors augmented with a mobile pool of opportunistic sensors, such as those on cell phones.…”

“…In contrast to our work to date, this work has a specific model of a region as a network with streets and assumes vehicles move along streets, the paper formulates the problem of finding an "optimal" area as a mathematical programming problem and presents a polynomial time algorithm for solving it. The study is extended in [HF09] with discussions of false alarms, simulations, and methods of aggregating results over time to improve the algorithm's performance.…”