Infra-red Search and Track - Later Systems

Later Systems

IRST systems re-appeared on more modern designs starting in the 1980s with the introduction of 2-D sensors, which cued both horizontal and vertical angle. Sensitivities were also greatly improved, leading to better resolution and range.

The best known users of modern IRST systems are:

• the Russian
  • Su-27 Flanker (OLS-27/30/35)
  • Mikoyan MiG-29 (OLS-29)
• the American
  • Grumman F-14 Tomcat (AN/AAS-42 IRST)
  • Lockheed Martin F-35 Lightning II AN/AAQ-37 electro-optical Distributed Aperture System (DAS) with a 360 degree IRST, missile detection/warning, and day/night vision capabilities, designed and produced by Northrop Grumman Electronic Systems.
  • Boeing F/A-18E/F Super Hornet
• the Swedish Gripen (SELEX Galileo IRST)
• the Pan-European Eurofighter Typhoon (PIRATE)
• the French Dassault Rafale (OSF)
• the Chinese Chengdu J-10 and JF-17 Thunder. Sichuan Changhong Electric Appliance Corporation,

These aircraft carry the IRST systems for use in lieu of their radars when the situation warrants it, such as when shadowing other aircraft or under the control of Airborne Early Warning and Control(AWACS) aircraft or Ground-controlled interception(GCI), where an external radar is being used to help vector them onto a target and the IRST is used to pick up and track the target once they are in range.

With infra-red homing or fire-and-forget missiles, the aircraft may be able to fire upon the targets without having to turn their radar sets on at all. Otherwise, they can turn the radar on and achieve a lock immediately before firing if desired. They could also close to within cannon range and engage that way.

Whether or not they use their radar, the IRST system can still allow them to launch a surprise attack.

An IRST system may also have a regular magnified optical sight slaved to it, to help the IRST-equipped aircraft identify the target at long range. As opposed to an ordinary forward looking infrared system, an IRST system will actually scan the space around the aircraft similarly to the way in which mechanically (or even electronically) steered radars work. The exception to the scanning technique is the F-35 JSF's DAS, which stares in all directions simultaneously, and automatically detects and declares aircraft and missiles in all directions, without a limit to the number of targets simultaneously tracked.

When they find one or more potential targets they will alert the pilot(s) and display the location of each target relative to the aircraft on a screen, much like a radar. Again similarly to the way a radar works, the operator can tell the IRST to track a particular target of interest, once it has been identified, or scan in a particular direction if a target is believed to be there (for example, because of an advisory from AWACS or another aircraft).

Note that, like infra-red homing seekers, an IRST is more likely to detect a target with its engine exhaust pointed towards the detector than away from it. This means that many jet aircraft will be detected at longer ranges if they are flying away from the IRST-equipped aircraft rather than towards it. However, most IRST systems are sensitive enough to detect the heat of a jet from head-on as well, either infra-red energy generated from the hot air coming out of the engines, from air friction heating the airframe, or both.

IRST systems can incorporate laser rangefinders in order to provide full fire-control solutions for cannon fire or launching missiles. The combination of an atmospheric propagation model, the apparent surface of the target, and target motion analysis (TMA) IRST can calculate the range.