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Aircraft Detection Systems


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Hey all,


I wanted to open a thread to start a discussion about the many different detection systems used to detect aircraft. I am interested in learning more about how these systems work and the advantages and disadvantages of each. I am especially interested in learning more about FLIR, IRST, and Electro-Optical systems. Maybe I am not looking hard enough, but I do not understand the differences associated with these systems.


I guess I can start by expressing my knowledge on the subject and what I know about these various different systems. If I have something incorrect or mixed up, please politely correct me.


First, there are mainly two different types of Detection Systems. There are Passive systems that do not produce any emissions and active systems in which do produce emissions. Because of this, with passive systems you will not be able to pick up on any incoming emissions from the detection system itself where as active systems it is possible to pick up on the detection system's emissions.


Ex. of Passive Systems include:

- Infrared Search & Track (IRST)

- Electro-Optical

- Foreward Looking Infrared (FLIR)

- Radar Warning Receiver (RWR)


Ex. of Active Systems include:

- Radio Detection and Ranging (RADAR)

(I heard the F-35 has passive Radar, how might that work?)


The most common and effective way to detect and track an aircraft is by Radar.



- Radio waves are sent out and reflected back to the radar when encountering an object allowing the Radar to calculate the objects location, aspect, speed and altitude

- As soon as a radar is turned on, a target equipped with an RWR can pickup on incoming radar emissions



- Picks up on an aircraft's heat signature

(How? not entirely sure)



Electro Optical

-detects objects by powerful optics and a computer system differentiating the pixels

( I think)



(Do not know how this differs from IRST)



-Picks up on incoming radio waves from RADARs

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Yes, detection of anything is broken down to both active and passive. There's a few more detection systems onboard some military aircraft that detect other things that may not necessarily be other aircraft.... but just to highlight on the things you mentioned.


IRST is mainly meant for detection of aircraft, mostly. Some systems will detect an aircraft or otherwise something IR significant and point out limited information to the pilot. Modes can include both manual and automatic scanning, while not actually showing the image of the target. Others can provide some or all of this capability AND provide a visual image to the pilot. Most, if not all systems can provide location data to slew a missile seeker (before launch) to the target location.


Electro optical is any type of sensor, AFAIK, that will provide a display representation of the visible spectrum. I dont know if this includes the IR spectrum, but it may include some fusing, such as low light TV.

FLIR is both a term and a brand name. It was a more common term in the past for sensors that we generally regard as targeting pods. Though the term is still used today and applies to sensors both including and, more commonly, not including targeting pods.....such as police helicopters, transport helicopters which aid in night flying.


RWR is exactly what you said. Several different generations can vary from rudimentary versions that did not of themselves identify the type of the threat, to highly advanced systems. Older versions, circa Vietnam, would require an Electronic Warfare Officer (EWO) to recognize the type of threat based on the emissions received. Modern ones can be coupled with Digital Radio Frequency Memory (DRFM) to record a database of threats, even against newer systems for analysis. Some may transmit and mimic a host radar to deceive them.

Other things are used, RF wise for passive detection, such as transponder signals, radio communications and being able to locate sources of emissions, such as on a HTS pod (F-16CJ/CM)


Missile Warning Systems (MWS) typically use one or a number of IR sensors located around the skin of the aircraft, and look for specific IR significant events that match a certain set of parameters most corresponding with a missile launch.


Laser detection systems and laser countermeasures work the same way as MWS. Aircraft are not the only vehicles to use MWS and laser detection. Some modern ground vehicles and armor equip them as well. Directional IR Countermeasures (DIRCM) can detect missiles and employ various infrared signals in an attempt to confuse or saturate IR seekers.


RADAR; an RF transmitter and receiver. Most ones in use today are broken down into three types: Mechanically scanned/pulse doppler, Passive Electronic Scanned Array (PESA) and Active Electronic Scanned Array (AESA). Note that passive in PESA doesn't mean "no emissions". All scanned array radars use a large number of antennae to direct and focus radar beams. How they accomplish this is what separates the two. There's a great page on them somewhere and if I find it I will link it.


Modern -ESA radars often have the ability to rapidly change frequencies. This can serve two purposes: First, this helps combat jamming; as jamming requires knowledge of the host radar's frequencies. Broadband jamming is possible but it requires an exponential amount of power to acheive the same effect vs against known frequencies. Think of a laser vs a flashlight. A one watt flashlight will likely not cause eye damage, where a 1 watt laser will almost instantly result in eye damage, due to the fact that it's coherent.


The second purpose is to reduce detection by opposing RWRs. A frequency agile radar can often detect an aircraft whilst the target aircraft has no idea someone is targeting them, due to the fact that the pulses are so short and minute that it may appear as background RF energy.


Note that many of the passive systems we mentioned reference the IR spectrum....which is very broad, especially in military terms.



The term "IR" is very vague in this sense. If you have an IR strobe emitting, a laser designator pulsing on a target and a short wave IR beacon emitting......And say three detectors; a FLIR pod, a targeting pod with a laser spot tracker and night vision goggles.....then it's possible if not likely that any one of the detectors will only be able to detect one of the three emitters.

Edited by Mike5560
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