Aircraft
Counter-Stealth Technology Flourishes In Europe
Passive detection of aircraft has been developing for many decades and there is renewed interest in Eastern Europe.
The Ramona and follow-on Tamara passive detection systems were deployed by Warsaw Pact countries on 
mobile vehicles.
The Ramona and follow-on Tamara passive detection systems were deployed by Warsaw Pact countries on mobile vehicles.

European companies, especially in the East, are continuing to refine passive ground-based technologies with the potential to detect stealth aircraft. The best known of these is the detection and correlation of emissions from aircraft–such as from radars, radar altimeters and other navigation devices–using ESM/ELINT techniques, sometimes known as passive emitter tracking (PET).