Radar is the most recognized and most widely used means of tracking the location of aircraft, but certain situations require a means of tracking aircraft without alerting them to the fact that they are being tracked. Instead of sending out a radar pulse that can be detected, we can intercept an aircraft’s own radio frequency (RF) transmissions to passively determine its location and characteristics.

Targets themselves are not merely singular RADAR tracks in space; an airborne entity is a platform emitting a variety of signals which can be tracked, providing a more accurate picture of potential capability and probable threat. For example, certain signals will only emanate from specific types of aircraft, such as fighter or ISR platforms. Identifying these signal sources within a 3-Dimensional space, latitude longitude and altitude, can give us an even greater indication of what the target actually is.

How does it work?

Using a network of four or more receivers (RFeye Nodes) distributed across a geographical area, it is possible to measure the different times that a signal is received. The difference in these times gives information about the distance to the source, and having four receivers provides sufficient information to pinpoint the source location in three dimensions. And for airborne targets, information on the third dimension, altitude, is essential. This technique is called Time Difference Of Arrival (TDOA).

Read more on 3D TDOA

What kinds of RF transmissions can be used for tracking?

RFeye can detect all the signal types commonly associated with aircraft, including:

  • IFF
  • ADS-B
  • Link16
  • TACAN/DME
  • Radar
  • ATC channels

Geolocation can be performed using any or all of these detected signal types.

What can it be used for?

Complement to fire-control radar

Incoming aircraft can be passively tracked using 3D TDOA as they approach an air defense missile battery, meaning they are not aware of its location and are not deploying counter measures . As the aircraft reach the optimal range for use of anti-aircraft missiles, the fire-control radar systems can be engaged at the last possible moment, allowing for precise missile targeting.

ADS-B spoofing detection

ADS-B transmissions can be spoofed, giving a false location for aircraft. RFeye can be used to determine the true location of RF signals, which can then be checked against the transmitted ADS-B information to detect when spoofing is taking place.

Passive tracking of enemy aircraft RF emissions by friendly forces

Passive tracking and surveillance of adversary aircraft can be performed by the RFeye sensor network providing essential covert intelligence on enemy activity, capabilities and equipment.

Additional benefits

The RFeye network can be used for all spectrum management and monitoring needs, not just passive aircraft tracking. For example, many airports and secure locations are vulnerable to intrusions by drones/UAS. The RFeye network can be used to detect and locate such drones as well as their operators. It can also be used to detect and locate sources of interference, such as radar jammers, that could affect radio communications and/or disrupt scheduled flights.

Further reading

RFeye AirDefense

3D geolocation and tracking of aircraft and UAS

3D TDOA Whitepaper

Operating principles of 3D TDOA