The research arm of the Defense Department, is working on a variety of projects to improve national security, such as using genetic engineering to protect food supplies or constructing smart materials for buildings in order to withstand external damage.

One project the agency is working on is called SIGMA, which will entail implementing a cost-effective network of sensors built into existing infrastructure to provide immediate real-time radiation detection throughout large urban areas. It could theoretically give state and federal official’s awareness of radiological threats in the vicinity prompting a response.

DARPA ran a second field test in October in Washington, D.C., deploying 1,000 sensors throughout the city marking the largest number of detectors tested at the same time. A previous test held at the Port Authority of New York and New Jersey only involved more than 100 sensors.

The purpose of this experiment was to have hundreds of volunteers with backpacks containing smartphone-sized radiation detectors walk around the National Mall. It was part of a scavenger where the participants had to search for a geneticist who had been mysteriously abducted.

DARPA and partners like Lawrence Livermore National Laboratory worked together to refine the SIGMA software’s algorithms and analyzing data emitted by the detectors in order to strengthen the network’s performance.

You can watch a video of the scavenger hunt below.