Russia advances IRST tech as US revisits infrared sensors
How can you detect an aircraft that is too far away to see? Radar is not the only solution—an aircraft can also be located using an IRST sensor. Although the Americans invented this technology, contemporary American aircraft mostly lack it. The Russians, however, effectively utilise IRST.
Many modern aircraft feature a distinct detail on the front section of the fuselage: a small dome, usually positioned slightly below the pilot's cabin. Inside this dome is an important sensor—IRST (Infra-Red Search and Track). What is its function?
IRST (thermal sensor, thermolocator) is an infrared sensor that allows the detection of objects varying in temperature from the background. This capability applies to stealth aircraft to some extent as well. Unlike radar, IRST operates completely passively—it does not reveal the presence and position of the aircraft utilising it, and the target remains unaware it is being tracked.
The IRST sensor is standard in Russia
The first IRST sensors were used by Americans in their F-101, F-102, and F-106 aircraft around the 1950s and 1960s. These early sensors were far from perfect, serving more as a supplement to radar than as independent sensors.
Connected to a radar screen, the IRST indicated the detection of an object, but determining its exact location required activating the radar. Nonetheless, such sensors were installed in subsequent American aircraft, such as the F-8 Crusader, F-4 Phantom, and F-14 Tomcat.
As technology advanced in the USA, IRST sensors were abandoned in favour of increasingly sophisticated radars, leaving the F-15, F-16, F-18, and F-22 aircraft without basic versions of thermal sensors.
This technology was further developed and implemented in Russian aircraft. The identifiable dome housing the sensor can be seen in front of the cockpits of MiG-29 and Su-27 family aircraft. IRST has also been installed in Dassault Rafale and Eurofighter Typhoon aircraft.
How does IRST work?
Modern thermolocators offer very high capabilities, allowing the detection of an aircraft from tens of miles away. Detection distance increases when the target uses afterburner. Their role is not limited to detecting aerial targets; thermal signatures can also be used to detect and identify sea and ground targets.
Americans have once again recognised IRST's advantages. An advanced, space-scanning sensor of this type is featured in the F-35 (Electro-Optical Targeting System—EOTS).
Older machines—originally lacking the sensor—are also being equipped with it through hanging pods, significantly increasing passive target detection capabilities.
IRST for American aircraft
In recent years, the IRST sensor (IRST21/AN/ASG-34) has been integrated into various aircraft, including the F-16 and F-15, which can use it thanks to Legion Pod pods. The thermolocator is also part of the modernisation package for F/A-18F Super Hornet aircraft.
Infrared sensors are also to be fitted in F-22 Raptor aircraft, with reports on this emerging in March 2024. Additionally, early 2024 saw successful IRST sensor testing on the Gripen E aircraft.
