Instrumentation radar

Passive radar systems (also referred to as passive coherent location, passive surveillance systems, and passive covert radar) encompass a class of radar systems that detect and track objects by processing reflections from non-cooperative sources of illumination in the environment, such as commercial broadcast and …

An active radar actively sends out a radar pulse, in which it listens for the return signal. A passive radar, on the other hand, does not do anything but listens for the return pulse from other radars.

Passive radar detects radiation signals emitted by other sources — be they radio broadcasts or mobile phone networks — and analyses distortions to figure out where objects are located.

The most well-known Passive Bistatic Radar systems are Silent Sentry 3 developed by Lockheed Martin , and the Home Alerter 100 developed by Thales. Passive Bistatic Radar systems offer covert air surveillance at a potentially low cost.