Uncover the world of passive radar – an intriguing technology capable of potentially detecting stealth aircraft, currently being tested by the German Air Force. A notable achievement was recorded when Hensoldt's passive radar Twinvis detected two F-35A stealth fighter-bombers at Berlin's ILA aerospace show in 2018.
Passive Radar: An Overview
Passive radar utilises a broad spectrum of signals such as those from radio, television, mobile phones, active radar, telecommunications and geolocation satellites to detect and track objects. This is done by capturing the signals that are reflected off obstacles like moving aircraft by the passive radar receiver. The most incredible part of this technology is that it doesn't emit any signals, rendering it nearly impossible to detect or jam.
Further giving it an edge, passive radar makes use of low-frequency bands, thereby providing additional air coverage, especially at low altitudes. This is of significant concern for the fifth-generation combat aircraft as their absorbing coatings are less effective against these low-frequency waves, thus making them more susceptible to passive radar.
Notable Developments in Passive Radar
The French Directorate General of Armaments (DGA) expressed an interest in passive radar technology. A landmark test of an airborne passive radar was conducted in 2015 by ONERA, CReA and SONDRA. Moreover, the 2021 Defense Innovation Orientation Reference Document (DROID) mentioned the development of a passive radar demonstrator for aerial surveillance.
Companies are also making strides in this field. Thales has developed the MSPR (Muti-static Silent Primary Radar), while Hensoldt's Twinvis system is currently being examined by the German Air Force. The objective of these developments is to determine whether passive radar technology can provide an early signal of incoming threats. Hensoldt has also reported that three undisclosed countries have signed contracts for a few units.
The Challenges of Passive Radar
Despite its many assets, passive radar comes with some potential setbacks. One of these includes a need for advancements in computational power. Additionally, the characteristics and precise location of transmitters used are required, necessitating systems dedicated to retrieving this information.
Even with these challenges, the passive radar sphere continues to evolve. The fact that it has caught the attention of militaries around the world highlights its potential in transforming air defence systems.