View source for Infrared search and track

{{Short description|Method for detecting and tracking objects which give off infrared radiation}}
{{Redirect|IRST|the time zone in Iran|Iran Standard Time}}
[[File:Regiment100thAnniversary2018-08.jpg|thumb|300px|An IRST sensor on a [[Sukhoi Su-35]]]]

An '''Infrared Search and Track''' ('''IRST''') system (sometimes known as '''infrared sighting and tracking''') is a method for detecting and tracking objects which give off [[infrared]] [[radiation]], such as the [[infrared signature]]s of [[jet aircraft]] and [[helicopter]]s.<ref name=Mahulikar>Mahulikar, pp. 218-245</ref>

IRST is a generalized case of [[Forward Looking Infrared]] (FLIR), i.e. from forward-looking to all-round [[situation awareness]]. Such systems are passive ([[thermographic camera]]), meaning they do not give out any radiation of their own, unlike [[radar]]. This gives them the advantage that they are difficult to detect.

However, because the atmosphere attenuates infrared to some extent (although not as much as [[visible light]]) and because adverse weather can attenuate it also (again, not as badly as visible systems), their range compared to a radar is limited. Within range, an IRST's [[angular resolution]] is better than radar due to the shorter [[wavelength]].

== History ==
=== Early systems ===

[[File:F-8E VMFAW-235 DaNang Apr1966.jpg|thumb|An [[F-8 Crusader|F-8E Crusader]] of [[VMFA-235|VMF(AW)-235]] at [[Da Nang Air Base|Da Nang]], in April 1966 showing the IRST in front of the canopy.]]
The first uses of an IRST system appeared in the [[F-101 Voodoo]], [[F-102 Delta Dagger]] and [[F-106 Delta Dart]] [[interceptors]]. The F-106 had an early IRST mounting replaced in 1963 with a production retractable mount.<ref name="Kinzeyp12">Kinzey 1983, p. 12.</ref> The IRST was also incorporated into the [[F-8 Crusader]] (F-8E variant) allowing passive tracking of heat emissions and was similar to the later [[Texas Instruments]] '''AN/AAA-4''' installed on early [[F-4 Phantoms]].<ref name="Sweetmanp552">Sweetman 1987, p. 552.</ref>

[[File:The Phantom menace. March CA (8203458393).jpg|thumb|AN/AAA-4 IRST under nose of F-4 Phantom]]
The F-4 Phantom had a Texas Instruments AAA-4 infrared seeker<ref name="Sweetmanp526">Sweetman 1987, p. 526.</ref> under the nose of early production aircraft F-4Bs and F-4Cs. It was not not installed on later F-4Ds due to limited capabilities,<ref name="Sweetmanp532">Sweetman 1987, p. 532.</ref> but retained the bulge and indeed some F-4Ds had the IRST receiver retrofitted in a modified form.<ref name="Sweetmanp552"/>

The F-4E eliminated the AAA-4 IRST bulge and received an internal gun mount which took up the area under the nose.<ref name="Sweetmanp537">Sweetman 1987, p. 537.</ref> The F-4J which had a [[pulse-Doppler radar]] also eliminated the AAA-4 IRST receiver and bulge under the nose.<ref name="Edenp279">Eden 2004, p. 279.</ref>

The first use of IRST in a Eurasian country was the [[Mikoyan-Gurevich MiG-23]],<ref>{{Cite web |url= https://www.defencetalk.com/mig-23-flogger-16805/ |title=MiG-23 Flogger |website= DefenceTalk |date= April 12, 2009 |access-date= August 27, 2024}}</ref> which used the (TP-23ML) IRST; later versions used the (26SH1) IRST.<ref>{{cite web |url=https://fas.org/nuke/guide/russia/airdef/mig-23.htm |title = MiG-23 FLOGGER (MIKOYAN-GUREVICH) - Russia / Soviet Nuclear Forces}}</ref> The [[Mikoyan-Gurevich MiG-25]]PD was also equipped with a small IRST under the nose.<ref>Peter G. Dancey(2015)Soviet Aircraft Industry,Fonthill Media</ref>

The Swedish [[Saab 35 Draken#Variants|Saab J-35F2 Draken]] (1965) also used an IRST, a [[Hughes Aircraft Company]] N71.

=== Later systems ===
IRST systems re-appeared on more modern designs starting in the 1980s with the introduction of 2-D sensors, which cued{{clarify|date=July 2021}} both horizontal and vertical angle. Sensitivities were also greatly improved, leading to better resolution and range. In more recent years, new systems have entered the market. In 2015, Northrop Grumman introduced its OpenPod IRST pod,<ref>{{Cite web|url=http://www.northropgrumman.com/Capabilities/openpod/Pages/default.aspx|title=OpenPod™ IRST and OpenPod™ Targeting|website=Northrop Grumman|language=en-US|access-date=2016-11-03|archiveurl=https://web.archive.org/web/20160317014751/http://www.northropgrumman.com/Capabilities/openpod/Pages/default.aspx|archivedate=2016-03-17|url-status=dead}}</ref> which uses a sensor by [[Leonardo S.p.A.|Leonardo]].<ref>{{cite web|last=Drew|first=Carey|title='Northrop unveils OpenPod as USAF seeks F-15 IRST|url=http://www.flightglobal.com/news/articles/northrop-unveils-openpod-as-usaf-seeks-f-15-irst-413022/|publisher=Flight Global|access-date=5 June 2015}}</ref> The United States Air Force is currently incorporating IRST systems for its fighter aircraft fleet, including the F-15, F-16, and F-22.<ref>{{Cite news|url=https://www.flightglobal.com/news/articles/usaf-taps-boeing-to-select-new-f-15-sensor-supplier-430208/|title=USAF taps Boeing to select new F-15 sensor supplier|date=2016-10-10|newspaper=Flightglobal.com|access-date=2016-11-03}}</ref><ref>[https://www.thedrive.com/the-war-zone/f-22-raptor-being-readied-for-aim-260-missile-by-green-bats-testers F-22 Raptor Being Readied For AIM-260 Missile By ‘Green Bats’ Testers]</ref>

[[File:Rafale B at Paris Air Show 2007.jpg|thumb|[[Optronique secteur frontal]] (IRST) of the [[Dassault Rafale]], below the cockpit and to the side of the refueling boom. On the left, the main IR sensor (100&nbsp;km range), on the right a TV/IR identification sensor with [[laser rangefinder]] (40 km range)]]
[[File:RAF Typhoon Prepares for Takeoff from Italy on Libyan Mission MOD 45152843.jpg|thumb|[[Eurofighter Typhoon]] with PIRATE IRST]]
[[File:VX-9 FA-18F with AIM-174 missiles.jpg|thumb|[[F/A-18F Super Hornet]] with AN/ASG-34(V)1 IRST21 sensor in a modified drop tank on its centerline ]]
While IRST systems are most common amongst aircraft, land-based, ship and submarine systems are available.<ref>{{cite web | url=https://www.rheinmetall-defence.com/en/rheinmetall_defence/systems_and_products/air_defence_systems/drohnenabwehr_toolbox/index.php | title=Rheinmetall Defence - Drone Defence Toolbox }}</ref><ref>{{cite web | url=https://www.thalesgroup.com/en/worldwide/defence/artemis-irst-360deg-naval-infrared-search-and-track-system | title=ARTEMIS IRST - 360° Naval InfraRed Search and Track system }}</ref><ref>{{cite web | url=https://www.militaryaerospace.com/defense-executive/article/16723967/photonics-mast-systems-for-eight-block-iii-virginiaclass-attack-submarines-provided-by-kollmorgen | title=StackPath | date=30 December 2010 }}</ref>

=== Distributed Aperture Systems ===

The [[F-35]] is equipped with infrared search and track system [[AN/AAQ-37]] Distributed Aperture System (DAS), which consists of six IR sensors around the aircraft for full spherical coverage, providing day/night imaging and acting as an IRST and missile approach warning system.<ref>{{cite web|url=https://foxtrotalpha.jalopnik.com/infrared-search-and-track-systems-and-the-future-of-the-1691441747|title=Infrared Search And Track Systems And The Future Of The US Fighter Force|website=jalopnik|date=26 March 2015}}</ref>

[[Chengdu J-20]] and [[Shenyang FC-31]] is assumed to share the similar design concept with their system. IRST systems can also be used to detect stealth aircraft, in some cases, outperforming traditional radar.<ref>{{Cite web|url=https://jalopnik.com/infrared-search-and-track-systems-and-the-future-of-the-1691441747|title=Infrared Search And Track Systems And The Future Of The US Fighter Force|website=Jalopnik|date=26 March 2015 }}</ref>

== Technology ==
These were fairly simple systems consisting of an [[IR sensor|infra-red sensor]] with a horizontally rotating shutter in front of it. The shutter was slaved to a display under the main interception radar display in the cockpit. Any IR light falling on the sensor would generate a "pip" on the display, in a fashion similar to the [[B-scope]]s used on early radars.

The display was primarily intended to allow the radar operator to manually turn the radar to the approximate angle of the target, in an era when radar systems had to be "locked on" by hand. The system was considered to be of limited utility, and with the introduction of more automated radars they disappeared from fighter designs for some time.

== Performance ==
Detection range varies with external factors such as
* clouds
* altitude
* air temperature
* target's attitude
* target's speed

The higher the altitude, the less dense the atmosphere and the less infrared radiation it absorbs - especially at longer wavelengths. The effect of reduction in friction between air and aircraft does not compensate for the better transmission of infrared radiation. Therefore, infrared detection ranges are longer at high altitudes.

At high altitudes, temperatures range from −30 to −50&nbsp;°C - which provide better contrast between aircraft temperature and background temperature.

The Eurofighter Typhoon's PIRATE IRST can detect subsonic fighters from 50&nbsp;km from the front and 90&nbsp;km from the rear<ref>{{cite web |url= http://www.bmlv.gv.at/truppendienst/ausgaben/artikel.php?id=807 |access-date= 2014-02-05 |title= Der Eurofighter "Typhoon" (VII) - Radar und Selbstschutz |publisher= Österreicher Bundesheer |date= June 2008}}</ref> - the larger value being the consequence of directly observing the engine exhaust, with an even greater increase being possible if the target uses [[afterburners]].

The range at which a target can be identified with sufficient confidence to decide on weapon release is significantly inferior to the detection range - manufacturers have claimed it is about 65% of the detection range.

==Tactics==
[[File:German MIG-29 Nose.jpg|thumb|left|MiG-29 nose showing radome and S-31E2 KOLS IRST]]

With [[infrared homing]] or [[fire-and-forget]] missiles, the fighter may be able to fire upon the target without having to turn on its radar sets at all. Otherwise, the fighter can turn the radar on and achieve a lock immediately before firing if desired. The fighter could also close to within [[autocannon|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 [[FLIR|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'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).

IRST systems can incorporate [[laser rangefinder]]s in order to provide full [[fire-control system|fire-control]] solutions for cannon fire or launching missiles ([[Optronique secteur frontal|Optronique Secteur Frontal]]). The combination of an atmospheric propagation model, the apparent surface of the target, and target motion analysis (TMA) IRST can calculate the range.

== List of modern IRST systems ==
{{Unreferenced section|date=April 2023}}
The best known modern IRST systems are:
* {{flag|France}}
** [[Horizon-class frigate|Classe Orizzonte frigate]] ([[Safran]] Vampir MB)
** [[ROKS Dokdo|ROKS ''Dokdo'']] amphibious assault ship (Safran Vampir MB)
** [[Sejong the Great-class destroyer|''Sejong the Great''-class destroyer]] (Safran Vampir NG)
** [[Anzac-class frigate|''Anzac''-class frigate]] (Safran Vampir NG)
** [[Canberra-class landing helicopter dock|''Canberra''-class landing helicopter dock]] (Safran Vampir NG)
** [[Hobart-class destroyer|''Hobart''-class destroyer]] (Safran Vampir NG)
** [[Cassard-class frigate|''Cassard''-class frigate]] (Safran EOMS-NG)
** [[Floréal-class frigate|''Floréal-class'' frigate]] (Safran EOMS-NG)
** [[Horizon-class frigate]] (Safran EOMS-NG)
** [[Baynunah-class corvette|''Baynunah''-class corvette]] (Safran EOMS-NG)
** [[Gowind-class design|Gowind-class OPV for Argentina]] (Safran EOMS-NG)
** [[French aircraft carrier Charles de Gaulle|Aircraft carrier ''Charles de Gaulle'']] ([[Thales Group|Thales]] ARTEMIS)
** [[FREMM]] (Thales ARTEMIS)
** [[Rafale#Avionics and equipment|Dassault Rafale]] (Safran/Thales [[Optronique secteur frontal]] OSF)<ref name="articles.janes.com">{{Cite web|url=http://articles.janes.com/notice.html|title=Defense & Security Intelligence & Analysis: IHS Jane's &#124; IHS|website=articles.janes.com|access-date=2019-01-05|archive-date=2013-03-18|archive-url=https://web.archive.org/web/20130318075501/http://articles.janes.com/notice.html|url-status=dead}}</ref>
*{{flag|India}}
**[[Sukhoi Su-30MKI]] (OLS-30; to be replaced by indigenous dual-band IRST)<ref>{{cite web |title=Sky Searchers |url=https://www.janes.com/images/assets/018/45018/Sky_searchers.pdf |url-status=live |archive-url=https://web.archive.org/web/20190508031229/https://www.janes.com/images/assets/018/45018/Sky_searchers.pdf |archive-date=8 May 2019 |access-date=22 March 2020 |work=Jane's Defence Weekly |page=2}}</ref><ref>{{Cite web |date=2022-04-26 |title=HAL and BEL to co-develop IRST system for Su-30 MKI |url=https://www.business-standard.com/article/news-cm/hal-and-bel-to-co-develop-irst-system-for-su-30-mki-122042600747_1.html |url-status=live |archive-url=https://web.archive.org/web/20241207174317/https://www.business-standard.com/article/news-cm/hal-and-bel-to-co-develop-irst-system-for-su-30-mki-122042600747_1.html |archive-date=2024-12-07 |access-date=2024-12-07 |website=Business Standard}}</ref>
* {{flag|Italy}}
** [[Italian aircraft carrier Cavour|Aircraft carrier ''Cavour'']] ([[Leonardo S.p.A.|Leonardo]] SASS)
** [[FREMM]] (Leonardo SASS)
** [[Doha-class corvette]] (Leonardo SASS)
** [[Musherib-class offshore patrol vessel|''Musherib''-class offshore patrol vessel]] (Leonardo SASS)
** [[Saab JAS 39 Gripen#JAS 39E/F and other developments|Saab JAS 39 Gripen E/F]] (Leonardo Skyward-G)<ref>{{Cite web|url=https://australianaviation.com.au/2010/02/saab-selects-selex-galileo-irst-for-gripen-ng/|title=Saab selects SELEX Galileo IRST for Gripen NG|date=February 22, 2010}}</ref>
** [[Italian landing helicopter dock Trieste|LHD ''Trieste'']]  (Leonardo DSS-IRST)
* {{flag|Italy}} / {{flag|Spain}} / {{flag|United Kingdom}} 
**[[Eurofighter Typhoon#PIRATE|Eurofighter Typhoon]] ([[EuroFIRST PIRATE]]<ref>{{cite web |url=http://www.leonardocompany.com/-/pirate_irst |title = Home}}</ref>)<ref>{{cite web |url=http://typhoon.starstreak.net/Eurofighter/sensors.html#Pirate |title= Eurofighter Technology and Performance : Sensors|website=typhoon.starstreak.net |archive-url=https://web.archive.org/web/20150912193825/http://typhoon.starstreak.net/Eurofighter/sensors.html |archive-date=2015-09-12}}</ref><ref name="articles.janes.com"/>
* {{flag|Japan}}
** [[Mitsubishi F-15J]]
* {{flag|Netherlands}}
** [[Halifax-class frigate|''Halifax''-class frigate]] ([[Thales Nederland]] Sirius)
** [[De Zeven Provinciën-class frigate|''De Zeven Provinciën''-class frigate]] (Thales Nederland Sirius)
** [[Sachsen-class frigate|''Sachsen''-class frigate]] (Thales Nederland Sirius)
**
* {{flag|Russia}}
** [[Sukhoi Su-27|Su-27/30/33/35/37 Flanker]] (OEPS-27/30; OLS-35)<ref name="ols">{{Cite web|url=https://www.janes.com/error/500|title=Internal Server Error|website=Janes.com}}</ref>
** [[Mikoyan MiG-31]](8TK)<ref>{{Cite web|url=https://www.vydavatelstvo-mps.sk/letectvi-kosmonautika/2617-mig-31-dale-rozvijen.html|title=MiG-31 dále rozvíjen - MagnetPress|website=www.vydavatelstvo-mps.sk|date=10 May 2018 }}</ref>
** [[Mikoyan MiG-29|MiG-29/35]] (OEPS-29/OLS-13SM-1)<ref name="ols"/>
** [[Sukhoi Su-57]] (101KS-V)
* {{flag|South Korea}}
** [[ROKS Marado|ROKS ''Marado'']] amphibious assault ship ([[Hanwha Systems|Hanwha]] SAQ-600K)
** [[Daegu-class frigate|''Daegu''-class frigate]] (Hanwha SAQ-600K)
** [[KAI KF-21 Boramae]]
* {{flag|Spain}}
** [[F110-class frigate]] ([[Indra Sistemas|Indra]]/[[Tecnobit]] IRST i110)
*{{flag|Sweden}}
**[[Saab JAS 39 Gripen|JAS-39E/F Gripen NG]] (Skyward-G)
* {{flag|Turkey}}
** [[Barbaros-class frigate|''Barbaros''-class frigate]] ([[Aselsan]] PIRI)
** [[TCG Anadolu|TCG ''Anadolu'']] (Aselsan PIRI)
** [[Istanbul-class frigate|''Istanbul''-class frigate]] (Aselsan PIRI)
** [[TAI TF Kaan]]
* {{flag|United States}}
** [[Vought F-8 Crusader]]
** [[Convair F-106 Delta Dart]]<ref>{{Cite book |last=Knaack |first=Marcelle Size |url=https://web.archive.org/web/20160303182633/http://www.afhso.af.mil/shared/media/document/AFD-100526-027.pdf |title=ENCYCLOPEDIA OF US AIR FORCE AIRCRAFT AND MISSILE SYSTEMS, Volume 1: Post-World War II Fighters, 1945-1973 |date=1978 |publisher=Washington, D.C.: Office of Air Force History |year=1978 |isbn=0-912799-59-5 |pages=214}}</ref>
** [[Grumman F-14 Tomcat|Grumman F-14D Tomcat]] (AN/AAS-42 IRST)<ref name="articles.janes.com" />
** [[McDonnell Douglas F-15 Eagle|McDonnell Douglas F-15C Eagle]] ([[Lockheed Martin]] AN/ASG-34 IRST21 in Legion Pod)<ref>{{cite web| url = https://www.defenseworld.net/news/30198/USAF_Conducts_First_Ever_Missile_Firing_from_F_15C_Using_IRST_System__Eliminating_RADAR_Tracking| title = USAF Conducts First Ever Missile Firing from F-15C Using IRST System, Eliminating RADAR Tracking| access-date = 2021-08-11| archive-date = 2021-08-11| archive-url = https://web.archive.org/web/20210811130442/https://www.defenseworld.net/news/30198/USAF_Conducts_First_Ever_Missile_Firing_from_F_15C_Using_IRST_System__Eliminating_RADAR_Tracking| url-status = dead}}</ref>
** [[McDonnell Douglas F-15E Strike Eagle#F-15K|Boeing F-15K]]/[[McDonnell Douglas F-15E Strike Eagle#F-15SG|SG]]/[[Boeing F-15EX Eagle II#F-15SA|SA]]/[[Boeing F-15EX Eagle II#F-15QA|QA]]/[[Boeing F-15EX Eagle II#F-15IA|IA]] Strike/Advanced Eagle (AN/AAS-42 “Tiger Eyes”)
** [[Boeing F-15EX Eagle II]] (AN/ASG-34 in Legion Pod)
** [[General Dynamics F-16 Fighting Falcon variants#F-16C/D| Lockheed Martin F-16C/D/V]] (AN/ASG-34 in Legion Pod)
** [[General Dynamics F-16 Fighting Falcon#Variants|Lockheed Martin F-16E/F Block 60/62]] (AN/AAQ-32 IFTS)
** [[Boeing F/A-18E/F Super Hornet#Upgrades|Boeing F/A-18E/F Super Hornet Block III]] (AN/ASG-34)
** [[Lockheed Martin F-22 Raptor]] (AIRST)
** [[Lockheed Martin F-35 Lightning II#Sensors and avionics|Lockheed Martin F-35 Lightning II]] (AN/AAQ-40 Electro-Optical Targeting System, [[AN/AAQ-37 Electro-optical Distributed Aperture System]])
** [[Arleigh Burke-class guided missile destroyer|''Arleigh Burke''-class guided missile destroyer]] (Mark 46 Mod 1 on Flight I/II/IIA, Mark 20 Mod 1 on Flight III)
** [[Phalanx CIWS|Phalanx CIWS Block 1B]]

Fighter aircraft carry the IRST systems for use instead of radar when the situation warrants it, such as when shadowing other aircraft, under the control of [[Airborne Early Warning and Control|airborne early warning and control]] (AWACS) aircraft, or executing a [[ground-controlled interception]] (GCI), where an external radar is used to help vector the fighter to a target and the IRST is used to pick up and track the target once the fighter is in range.

== See also ==
* [[Electro-optical targeting system]]
* [[AN/AAQ-37 Electro-optical Distributed Aperture System]]

== References ==

=== Citations ===
{{Reflist|30em}}

=== Bibliography ===
* {{Citation |last1= Mahulikar |first1= S.P. |last2= Sonawane |first2= H.R. |last3= Rao |first3= G.A. |date= 2007 |title= Infrared signature studies of aerospace vehicles |journal= Progress in Aerospace Sciences |volume= 43(7-8) |pages= 218-245}}
* {{Citation |editor= Eden, Paul |title= The Encyclopedia of Modern Military Aircraft |location= London |publisher= Amber Books Ltd |date= 2004 |ISBN= 1-904687-84-9}}
* {{Citation |last= Kinzey |first= Bert |title= F-106 Delta Dart, in Detail & Scale |location= Fallbrook, CA |publisher= Aero Publishers |date= 1983 |ISBN= 0-8168-5027-5}}.
* {{Citation |last1= Sweetman |first1= Bill |last2= Bonds |first2= Ray |title= The Great Book of Modern Warplanes |location= New York, New York |publisher= Crown Publishers |date= 1987 |ISBN= 0-517-63367-1}}

== External links ==
{{Commons category|Infra-red search and track}}
* [https://web.archive.org/web/20090731042619/http://www.iaf.fraunhofer.de/pdf/jahresbericht-2006/sensor.pdf Fraunhofer Institut IAF annual report 2006] German and English.

[[Category:Targeting (warfare)]]
[[Category:Military aviation]]
[[Category:Military electronics]]
[[Category:Infrared imaging]]