Breakthrough: Invisible surveillance of airspace

The passive TwInvis radar by Hensoldt in use
The passive TwInvis radar by Hensoldt in use
When the term radar is used, everyone immediately pictures the same thing: large radar dishes, a flashing round screen, a monotonous beeping. Since the 1930s, radar has been the most important technology for locating aircraft. Now the company Hensoldt from southern Germany sets out to revolutionize the technology.

Radar devices have been working in the same way for decades: The radar emits electromagnetic waves. Objects such as airplanes reflect these waves as echoes, which in turn are detected by the radar. This allows the position and direction of an aircraft, for example, to be precisely determined. At airports, during major events or at political summits requiring high security, radar technology is the central instrument for controlling traffic and monitoring airspace.

It's possible without radar waves

The passive radar newly developed by Hensoldt under the name TwInvis fundamentally changes the way radar works. Instead of emitting its own signals, it uses the signal echoes of existing third-party transmitters. These can be radio or television transmitters whose waves are also reflected by aircraft. TwInvis detects these reflected signals and locates the aircraft accordingly. In the process, the passive radar processes signal echoes that are billions of times weaker than the original signals. A single TwInvis unit can thus monitor up to 200 aircraft in 3D within a radius of 250 kilometers.

Many possibilities for use

The new passive radar is significantly smaller than previous radar systems and can be easily integrated into an off-road vehicle or a van. Since it does not emit its own signals, it can also be used in urban areas – unlike active radars. And it can also be used more quickly, because there is no need for coordination with the authorities. TwInvis is therefore perfect for monitoring major events such as football matches or critical infrastructures – even at short notice.

Passive radar can also be used at airports to supplement the sensors used in air traffic control, for example as a backup. TwInvis can be used as a new instrument for monitoring the airspace at small and medium-sized airports that are not yet equipped with primary radar. And it also provides support in areas with severe restrictions, such as areas where mountain slopes or other obstacles impede normal radar waves.

However, TwInvis also opens up new possibilities in the military sector. In areas with a low transmitter density, for example, several separately placed devices can work together. Since the lack of its own radar waves makes the radar practically invisible, it can neither be detected nor jammed by the enemy.

World-leading technology made in Germany

The technology underlying TwInvis has been researched worldwide for more than 15 years. Hensoldt has now achieved a breakthrough with TwInvis. A passive radar demonstrator was presented to the public for the first time at the ILA Berlin in April 2018 and shown in operation. The company has invested several million euros of its own funds in its development and carried out studies in cooperation with the Federal Ministry for Economic Affairs and Energy, among others. This innovation is further impressive proof of the global breakthroughs that aviation research in Germany can achieve.