Recently, a geneticist was mysteriously abducted in Washington DC, leading to the US government deploying a small army of detectives to foil a dirty bomb plot. At least, that was the fictional scenario of a DARPA field test that saw a thousand volunteers equipped with smartphone-sized radiation detectors fan out over the National Mall in a radioactive scavenger hunt to test the progress of the agency's SIGMA project, which is tasked with developing technology to combat nuclear terrorism.

Nuclear terrorism is one of the top nightmares of security services. Not only is the prospect of a dirty bomb involving radioactive materials dispersed by conventional explosives alarming, but tracking down illegal nuclear materials in an urban setting requires covering far too large an area for fixed sensors. Since 2014, DARPA has been working on how to produce a portable sensor array based on low-cost, high-efficiency, radiation sensors networked by smartphone networks to detect gamma and neutron radiation and evaluate the information in real time

According to DARPA, the SIGMA array was first tested in New York and New Jersey using 100 sensors. For the Washington test, 1,000 sensors were carried in backpacks by hundreds of ROTC cadets from the universities in the National Capital Region, midshipmen from the US Naval Academy, and DARPA personnel coordinated by the University of Maryland's National Consortium for the Study of Terrorism and Responses to Terrorism (START). The volunteers were provided with the plot of a scientist kidnapped by masked men and sent on a scavenger hunt to gather clues to save the scientist and foil the terrorists using the detectors.

According to the agency, the purpose of the test was to help the SIGMA team to determine how effective the sensors were as mobile network nodes over an area of five square miles (13 km2). The information from the test will be used to refine algorithms for the version of the system expected to be operational by 2018.

"The SIGMA system performed very well, and we collected and analyzed a huge amount of streaming data as we watched in real-time as participants covered a large portion of DC," says Vincent Tang, DARPA program manager. "The data collected is already proving invaluable for further development of the system, and we're excited that SIGMA is on track to provide US cities an enhanced layer of defense against radiological and nuclear threats."

DARPA plans citywide and region-wide continuous area tests sometime next year.

The video below outlines the Washington DC test.

Source: DARPA