DARPA, or the Defense Advanced Research Projects Agency, published a request for proposals from tech firms capable of developing an “Aerial Dragnet” program to conduct “persistent, wide-area surveillance of small unmanned aerial systems (UASs) in urban terrain on a city-wide scale.”

In other words, DARPA wants to equip the military with a system which would allow it to track every drone in an urban area, especially in combat zones.

Currently, drones tracking is mostly done visually, which has obvious limitations. The “Aerial Dragnet” program would likely use its own drones to track others. 

naked-science.ru