Airborne IRST Prepares for Leap Into Uncharted Territory

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Date Posted: 08-Sep-2009 International Defence Review

On track: airborne IRST prepares for leap into uncharted territory Originally developed as a passive adjunct to radar, the airborne infrared search-andtrack (IRST) system is now seeing use in the secondary air-to-ground role. Michael J Gething surveys the state of the art The origins of airborne infrared detection and tracking of targets can be traced to the mid-1960s when F-101B Voodoo interceptors of the US Air Force (USAF) were equipped with an early form of infrared search and track (IRST), along with F-102 Delta Daggers. However, it was developments within the then-Soviet Union that produced what was referred to as "an optical radar" on the MiG-29 'Fulcrum' interceptor. The appearance of this aircraft in Finland in 1986, the UK in 1988 and Paris in 1989 provided the catalyst for renewed interest in the IRST. During the mid-1990s, the US Navy's F-14D Tomcat was equipped with the AN/AAS-42 IRST and, as Russia continued IRST development, across the MiG-29, Su-27 'Flanker' and Su-30, IRSTs were also being prepared for the Dassault Rafale and Eurofighter Typhoon. According to Lockheed Martin Missiles and Fire Control (LMMFC), the only US company with an active IRST production line, IRST is "a passive, long-wave infrared sensor system that enables long-range detection and weapons-quality track of airborne targets under normal and electronic attack environments and enhances survivability and lethality in both offensive and defensive counter-air roles". Put another way, it is a passive sensor for long-range identification of airborne targets and, as such, has a prime application in air defence, equipping fighter aircraft. The Lockheed Martin definition continues: "The system provides high-angular accuracy allowing dramatically improved raid cell resolution of multiple targets in formation much sooner than radar and has better track performance against moving targets accuracy." This information can stand alone or be fused with other sensor data to further enhance situational awareness, thus ensuring every fighter-pilot's dream scenario of 'first look, first shoot' capability - detecting, identifying and engaging enemy targets at extended ranges. An additional benefit of the IRST, the company claims, is that it is "also effective in air-to-ground modes, providing accurate ground moving target indications [GMTI] or large-area imagery updates". This is an application that is now emerging as a prime role for several NATO air forces. Meanwhile, in Russia, where the IRST renaissance began, the first examples of which were designated as "Opto-Electronic Pointing Stations" (OEPS) and fitted to MiG-29 'Fulcrum' and Su-27 fighters, the situation has moved forward. Developed by the Urals Optical and Mechanical Plant

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ihs.com (UOMZ), they are part of the aircraft's integrated weapon systems - an EO sighting system providing search, detection, tracking and ranging functions against airborne and ground targets. The installations, known as OEPS-29 for the 'Fulcrum' and OEPS-27 for the 'Flanker', are essentially the same equipment, only the OEPS-27 is larger and heavier (174 kg against 78 kg), offering greater detection range and field of regard (FoR). The OEPS-27 FoR scans ±60 degrees in azimuth and from -15 to +60 degrees in elevation, compared with ±30 degrees azimuth and -15 to +30 degrees elevation for OEPS-29. Few specific details are available as to the IR, TV and laser sensors involved. The OEPS-27 sensor has a range of up to 50 km, depending on the IR signature of the target. The collimated laser rangefinder (LRF) has a reported range of 8 km, functioning through common optics in a transparent housing forward of the windscreen. The OEPS-29 (with a smaller IRST sensor) has a reported range of approximately 15 km. The functionality of the system is similar for both variants, offering full integration with the earlier SHCH-3UM and, latterly, SURA helmet-mounted target-designation systems. Russian progress The development of enhanced/developed variants of the baseline OEPS-29 and OEPS-27 aircraft have proceeded in parallel with their parent aircraft, being enhanced to provide for greater range and discrimination of targets. These systems have now taken a new designator - OLS (OptikoLokatsionnaya-Stantsiya or Optical Locator Station). The OLS-30 is a development of OEPS-27, designed for installation in Su-30-series aircraft, with a greater detection range than the earlier system. A further variant, the OLS-36Sh-01, is an updated version of OLS-30, equipped with a vibration-isolated receiver and new cooling system and providing extended mean time between failures (MTBF) through the utilisation of more reliable imported components. The OLS-36Sh-01 incorporates a scanning detector, LRF and integrated system monitoring. The system performs passive search, detection and tracking of airborne targets at all aspects and against ground clutter, clouds and reflective water surfaces, by day and night and in the presence of IR countermeasures. The LRF provides accurate range measurement for the employment of short-range air-to-air missiles (AAMs) and against ground targets. The OLS-30 is installed on Su-30MKK and Su-30MK2 fighters supplied to China, while the OLS36Sh-01 station is installed on Su-30MKI fighters purchased by India, and the Su-30MKM for Malaysia. For the further-developed Su-35 fighter, UOMZ has taken the OLS-30 a step further, providing significantly increased detection and target recognition ranges. The OLS-35 version comprises a scanning IR detector array, a collocated daylight TV system, a multimode LRF/target designator (TD), a full field-of-view (FoV) stabilisation system and integrated monitor. The enhanced functionality of the OLS-35 includes all-aspect search and detection, together with acquisition, recognition and tracking of airborne targets. The LRF/TD enables accurate measurement of slant range and the output of angular co-ordinates and range values into the Su-35's EO sighting and navigation system to provide for target designation for medium-range AAMs and an asynchronous shooting mode for the integrated gun system. The OLS-35 was first displayed at the Paris Air Show in 2007.



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Similarly, UOMZ development of the OEPS-29 has produced the OLS-13S and OLS-13SM (for the MiG-29SM and MiG-29SMT upgrade programmes). These units feature increased target detection and tracking range, increased reliability and reduced size and weight. They include a scanning thermal detector, LRF and built-in test system. The OLS-13SM sensor dome has a leuco-sapphire fairing, (increasing the reliability and safety margins), a new eyesafe LRF and a modernised photo receiver. According to UOMZ information, the company has "conducted work on the [OLS] for the MiG-29 fighters of the air forces of Malaysia, Poland, Slovakia, Kazakhstan, Ethiopia and others". With the latest generation of MiG-35 'Fulcrum' emerging, UOMZ revealed at the 2007 Paris Air Show a further development - the OLS-13SM-1, described as having "significantly increased" target detection and recognition ranges. Further reduced in weight (down to 60 kg), the OLS13SM-1 comprises a scanning thermal detector, a TV sensor for daylight target recognition, a multimode LRF/TD, an FoV stabilisation system and built-in test equipment. UOMZ says that OLS13SM-1 meets the challenges of air target detection "in their forward and backward semi-spheres" and can perform lock-on and auto-tracking of manoeuvring air targets "in the backward semisphere". With an FoR of ±60 degrees in azimuth and from -15 to +55 degrees in elevation, it can recognise and measure range to air target, passing the angular co-ordinates and range values to the sighting navigation complex for target designation and synchronisation for the aircraft's integral gun armament. The 2007 Paris Air Show also introduced a rival IRST for the MiG-35, in the form of the nosemounted OLS-UE/M from NII PP (Naucho-Issledovatelskiy Institut Pretsizionnogo Priborostroyeniya - Scientific Research Institute of Precision Instruments Engineering) which, paired with the OLS-K pod, covers the search for, detection of, and tracking and ranging of airborne and ground targets. Common optical path The same weight as the OEPS-29 fitted to earlier MiG-29 aircraft (78 kg), the OLS-UE/M incorporates a 320x256 pixel thermal detector and a 640x480 pixel TV camera. The scanning mirror and associated optical path is common to both sensors and protected by a semi-spherical transparent dome made of leuco-sapphire. The scanning mirror covers ±90 degrees in azimuth and -15/+60 degrees in elevation, with targets detected between 45 km (tail-on, with unobstructed view of the target aircraft's engines) and 15 km (head-on, with target aircraft engines obscured by the airframe). An LRF operates in the 1.57 µm (eye-safe) and 1.06 µm (operational) wavelengths, with a claimed range out to 20 km. The prototype OLS-UE/M was installed on the MiG-29M2 experimental aircraft in 2006 and was subsequently transferred into the MiG-35 prototype. A simplified version, the OLS-UE, is in production for the MiG-29K shipborne multirole fighters ordered by the Indian Navy. The OLS-K, also from NII PP, is used to detect and track surface targets and is claimed to be capable of detecting a tank-sized target from a distance of 20 km or a motor boat from 40 km. It is fitted with an IR detector and TV camera similar to the OLS-UE/M as well as an LRF/TD and laser spot tracker. For the MiG-29/-35, it is fitted in a conformal pod (some 1.98 m long and weighing 110 kg) under the starboard air intake.



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In the United States, the withdrawal from service of the F-14D Tomcat in September 2006 saw the US Navy (USN) lose its IRST capability but it was not the end of the AN/AAS-42. It had been selected by the Boeing Airborne Laser (ABL) team to provide early missile launch detection and tracking for the ABL programme on the YAL-1A platform. Although this programme has been derated to a research project, the IRST continues to be used in this capacity. The YAL-1A is not the only platform equipped with the AN/AAS-42. In April 2002, it was revealed that the Boeing F-15K Eagles ordered by the Republic of Korea included the AN/AAS-42 IRST in the aircraft's electrooptic (EO) sensor suite. Subsequently, in April 2006, it was confirmed that the AN/AAS-42 was part of the EO suite of the F-15SG Eagle ordered by Singapore. These systems will be new-build units. US developments Work on the AN/AAS-42 IRST system, using Mid-Wave Infrared (MWIR) and Long-Wave Infrared (LWIR) detectors, originally started at GE Aerospace (now Lockheed Martin). At that time, it was funded by both the USAF and USN, the former planning to employ the IRST on modified F-15 aircraft. The USAF pulled out (although its Aeronautical Systems Division remains the contracting authority), citing the high cost of converting the aircraft. The USN continued with the IRST and, following extensive flight-test evaluation of both MWIR and LWIR detectors at the Pacific Missile Test Center, Point Mugu, California, the LWIR (8-12 µm) solution was selected for production, having demonstrated superior performance at operationally significant ranges. The sensor head, mounted in a chin pod under the nose of the F-14D, contains the optics and IR detector assembly with a long-wave scanned linear array. A three-axis, inertially stabilised gimbal allows the system to accurately search multiple scan volumes either automatically or under manual pilot control. Required signal and data processing is performed in the air-cooled controllerprocessor. The IRST functions in six separate modes similar in operation to the APG-71 tactical air intercept radar. Both azimuth and elevation scan volumes are selectable and separately controlled by the aircrew. The AN/AAS-42 allows multiple tracking of targets emitting heat at extremely long ranges to augment information supplied by conventional tactical radars. Using a series of sophisticated filter techniques and software algorithms, candidate detections are processed, background clutter is rejected and real targets are declared and displayed to the aircrew. For the installations on both the F-15K and F-15SG Eagles, the AN/AAS-42 is mounted on the leading edge of the port shoulder pylon. At the Singapore Air Show in February 2008, Lockheed Martin showed a mock-up of a pod-mounted AN/AAS-42 aimed at offering IRST capability to the F-16 community. The company reported regional interest, but would not be specific and, as IDR was going to press, still has not announced any orders for this variant. Having lost its only airborne IRST capability in 2006, the USN began looking for a replacement capability. By May 2007, it emerged it was talking with Boeing about equipping the F/A-18E/F Super Hornet with a New-Generation IRST and, in July 2007, Boeing selected LMMFC to supply up to 150 IRSTs for Block II Super Hornets. Pending a formal system design and development (SDD) contract, Boeing and LMMFC have together invested more than USD10 million to conduct a risk-reduction demonstration, with USN © Copyright IHS and its affiliated and subsidiary companies, all rights reserved. All trademarks belong to IHS and its affiliated and subsidiary companies, all rights reserved.


ihs.com participation, prior to the formal start of the IRST development process. This saw a test-article IRST mounted in the front of a centreline fuel tank and test-flown on an F/A-18F Super Hornet of the USN's VX-23 test unit for six pre-SDD data collection sorties during late 2007. The modified fuel tank provides a cost effective, software-only integration approach, requiring no structural or wiring changes to the aircraft. This supports potential integration of the IRST on existing and future F/A-18E/F/G aircraft. In December 2008, Boeing was awarded a USD11.9 million contract for continuing research and development in support of the technology demonstration phase. A further series of pre-SDD riskreduction flights was successfully completed in March 2009. These tests demonstrated the compatibility and effectiveness of the IRST system on the Super Hornet strike fighter. According to Chris Wedewer, F/A-18E/F IRST programme manager for Boeing, the flight-tests will allow a low-risk entry into the SDD phase. He said that they "successfully demonstrated transfer alignment, long-range target detection, and the ability to operate in a fuel tank". Also demonstrated was the successful integration of the IRST into the F/A-18E/F's multisource integration algorithms, allowing for the fusion of IRST tracking data with data from other sensors, he said. Lockheed Martin announced receipt of a Boeing contract, valued at USD4 million, for the technology development phase on 18 May 2009. The F/A-18E/F IRST uses an LWIR mercury cadmium telluride (MCT) detector array, that searches for and detects heat sources within its large FoR. It is mounted in the forward section of a 480 US gal fuel tank, mounted on the aircraft's centreline, in order to maximise the detector FoR, while retaining a 330 US gal fuel capacity. Another operational advantage is that no weapons pylon is 'lost' to carriage of the IRST pod. The three subsystems that form the as-yet undesignated Hornet IRST comprise: the sensor head with a three-axis inertially stabilised gimbal that scans the optics and detector assembly; a COTS (commercial off-the-shelf) processor that hosts the algorithms and a high-density digital recorder; and an environmental control subsystem in the form of an air-to-liquid heat exchanger. Operating passively in a wide variety of flight regimes, the Hornet IRST will offer robust performance against a wide variety of targets, while ensuring immunity to electronic detection and RF (radio frequency) countermeasures. It provides the F/A-18E/F mission computer with track file data on all targets, at the same time providing IR imagery to cockpit displays. It can operate in either track-while-scan or single-target-track modes, with cockpit selectable HOTAS (hands-onthrottle-and-stick) controlled scan volumes in azimuth and elevation. The pilot interface is consistent with other F/A-18E/F sensors to reduce aircrew workload. At present, the USN plans an initial operating capability (IOC) date in 2013. While the Hornet IRST is, essentially, a retrofit or evolved capability, the Lockheed Martin F-35 Lightning II Joint Strike Fighter (JSF) will have an integral IRST capability from its entry into service. This comes in the form of the internally mounted electro-optical targeting system (EOTS) is now under development by LMMFC. It is intended to provide extended range detection and precision targeting against ground targets, plus long-range detection of air-to-air threats. IRST and more The F-35 EOTS features the latest sensor technology for long-range target recognition, using a compact single-aperture design with an advanced third-generation MWIR (3-5 µm) focal plane © Copyright IHS and its affiliated and subsidiary companies, all rights reserved. All trademarks belong to IHS and its affiliated and subsidiary companies, all rights reserved.


ihs.com array (derived from the company's AN/AAQ-33 Sniper advanced targeting pod). The system also includes a tactical and eyesafe diode-pumped LRF/designator and a laser spot tracker. EOTS is integrated into the lower forward nose of the F-35 in a rugged, low-profile sapphirefaceted window. It is linked to the aircraft's integrated central computer through a high-speed fibre-optic interface and features automatic boresighting and aircraft alignment. It is intended that EOTS will act as an air-to-air IRST and an air-to-ground forward-looking infrared (FLIR) tracker. The lightweight system (expected to be under 200 lb) features passive and active ranging, plus the ability to generate highly accurate geo co-ordinates to meet strike requirements. The modular design of EOTS allows for two-level maintenance to reduce life-cycle costs. It shares a common integrated detector assembly with the F-35's AN/AAQ-37 Electro-Optic Distributed Aperture System (EO-DAS) being developed by Northrop Grumman Electronic Systems, plus COTS-based electronic modules. The first EOTS production unit was delivered to Lockheed Martin Aeronautics in Fort Worth, Texas, on 30 July 2009 for integration onto the F-35, successfully marking its entry into low-rate initial production (LRIP). According to Rich Hinkle, EOTS programme director LMMFC, this is "the first of over 3,000 units we will build to equip all variants of the US and international F-35 Lightning II aircraft." Production is now ramping up to produce up to 200 units a year, with the next delivery scheduled for November 2009. In the UK, work on an IRST was in hand in the early 1990s, with Marconi Avionics (now Selex Galileo) completing development of an IRST technology demonstrator for the UK Ministry of Defence (MoD) in March 1995. The demonstration unit comprised a pointing and stabilisation mechanism, a new high-performance telescope, IRST algorithm suite, target detection and tracking algorithms together with a high-performance thermal imager. Installed in a (then) Defence Evaluation and Research Agency (DERA) trials Tornado GR.1, the system demonstrated three principal modes of operation: autonomous search mode - the capability to locate and track multiple targets over a wide field of search; slaved acquisition mode - accepting position demands from the mission computer, which may be sourced from the pilot's hands-on-throttle-and-stick (HOTAS) controls, the pilot's helmet-mounted sight or from external sensors such as radar; and, once positioned, targets within the single FoV were tracked; and single-target track mode - provided the capability to track a single designated target within the FoR. The sensor FoV is centred on the target position, located during the autonomous search or slaved acquisition modes and uses image tracking techniques. PIRATE emerges The technology demonstrator provided the functionality and performance required of an in-service IRST equipment. It worked in parallel to the development of the PIRATE (Passive InfraRed Airborne Tracking Equipment) - a dual-role IRST/FLIR system - for the Eurofighter Typhoon. PIRATE is a development from the EuroFirst consortium, led by Selex Galileo of Italy, with Thales UK (part of Thales Land & Joint Systems) and Grupo Tecnobit of Spain as major partners. The development contract was awarded in 1992 and flight trials, using pre-production hardware, began in 1999, followed by full system testing and development during 2000-01. The consortium signed the production contract to supply Typhoon Tranche 1 aircraft in December 2003. The first production aircraft to be delivered with PIRATE installed was the first of Italy's Block 5 aircraft, © Copyright IHS and its affiliated and subsidiary companies, all rights reserved. All trademarks belong to IHS and its affiliated and subsidiary companies, all rights reserved.


ihs.com which was received in early August 2007. This was one of five aircraft making up the last of the Tranche 1 aircraft and early examples of Tranche 2 will also be to Block 5 configuration. Some Tranche 1 aircraft are being brought up to Block 5 configuration, which includes PIRATE. The system is now also in service with the Spanish Air Force and the UK's RAF. The PIRATE sensor head is mounted above the Typhoon's radome (the optimum positioning for IRST air-to-air operations) and slightly to the left of the aircraft centreline (allowing for limited 'look-down' in FLIR mode). As a result, air-to-ground applications (particularly at low level) will inevitably be compromised by this configuration. However, it is understood that much work has been undertaken to minimise interference with 'look-down' modes due to energy absorption by, and re-radiation from, the radome. Working in both MWIR and LWIR spectrums, PIRATE automatically detects the IR signature of aircraft at long ranges (beyond-visual-range - in excess of 50 km), over the entire FoR. As part of Typhoon's integrated avionics suite, PIRATE performs automatic detection and track-while-scan operation in its IRST mode and, in FLIR mode, IR imagery for cockpit multifunction head-down displays (HDDs) and helmet-mounted displays (HMDs). In IRST air-to-air mode, PIRATE's capabilities (operating in cluttered scenarios) include: multiple target tracking (MTT), where engagement (detection, tracking and Tyoprioritisation) of multiple targets in air-to-air, look up/down operation over the whole FoR or over a selectable volume are possible, plus a passive ranging capability; single target tracking (STT), where angle tracking of a single acquired target can be selected. Automatic target re-acquisition is available; and slaved acquisition, where line-of-sight is slaved to externally defined (such as an HMD) pointing angles and automatic acquisition of a single target activated. In its limited air-to-ground FLIR mode, PIRATE provides IR imagery for the following applications: navigation - where the fixed forward IR picture is presented on the HUD, overlaid on the pilot's view of the outside world; thermal cueing - highlighting the position of hot spots (according to size) and thermal contrast of ground targets, relative to the flight path or HMD sightline; steerable IR picture on helmet, where the IR picture is presented on the HMD with the sensor pointing angle slaved to the helmet by means of a head tracker; and identification - when in STT mode, the IR image can be presented to the pilot on the HDD and frozen to allow visual identification. Avoiding detection The signals-processing technology used in PIRATE demonstrates a very high suppression rate of false alarms and is derived from proven algorithms derived from the Thales Air Defence Alerting Device. As a totally passive sensor, it enables the aircraft to gather early intelligence of threats and to manoeuvre into a tactically advantageous position without being detected by hostile ECM (electronic countermeasures) systems, assisting the stealthiness of an interception and enhancing situation awareness in both air-to-air and air-to-ground missions. While the UK Royal Air Force's (RAF's) Typhoon FGR.4 aircraft (and PIRATE) await their combat debut, F2-standard Dassault Rafale B (two-seat) fighters from the French Air Force have already been in action over Afghanistan. The significance of the F2-standard, which entered service from mid-2006, is that the avionics suite on the aircraft incorporates the Optronique Secteur Frontal (OSF) IRST system.



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Designed to meet the operational requirements for both the French Air Force and the navy, OSF is the result of a collaboration between Thales Optronique - responsible for the EO sensors - and Sagem Défense Sécurité (part of the Safran group) - responsible for the IR detectors. The initial OSF contract from France's Délégation Générale pour l'Armement (DGA) procurement agency, worth EUR110 million (USD155 million), was placed in late 2000. Along with the SPECTRA countermeasures system and RBE2 radar, the OSF is the third element of the Rafale's navigation and attack system (SNA - Système de Navigation et d'Attaque). The Rafale's weapon system uses this variety of sensors to perform air-to-air and air-to-ground ranging, tracking and targeting functions, including IR, TV and laser rangefinding. Having multispectral capability allows the OSF to perform several of these functions in parallel. The French Ministry of Defence noted in May 2007, that these aircraft undertook operational missions in support of the International Security Assistance Force (ISAF) using US-supplied GBU12 Paveway II laser-guided bombs. Subsequently, Marc Brousse, head of the Rafale programme within Thales Optronique, told Jane's that the OSF systems on these aircraft "were doing quite a good job" in the air-to-ground role. He compared the use of OSF with that of US aircraft equipped with the Sniper advanced targeting pod for the armed reconnaissance role. Brousse also noted that the French Navy Rafale M aircraft also deployed over Afghanistan were not F2 standard, although the French Navy received some F2-standard aircraft and that a planned retrofit of OSF to all Rafale M aircraft had not (as of July 2009) been formalised. Unlike the majority of other IRST, OSF has dual sensor heads: the long-range IR passive detector (with very low false-alarm rates) and a high-definition charge-coupled device (CCD) TV sensor; plus an eyesafe LRF. Fusing the imagery from the IR detector (with a very large FoR) and CCD TV sensor (with a narrow FoV), which can be supplemented by employing the seeker heads of MICA missiles fitted to the Rafale's wingtip launchers, enhances target detection. Together they can facilitate multiple, simultaneous search/identification/telemetry operation. While declining to be specific on the details of the sensors in OSF, Brousse confirmed to Jane's that "the dual-channel IR/CCD TV, linked with the LRF, allows 3-D targeting co-ordinates to be fed into the system" thus making "silent" (ie 'passive') visual identification of targets possible. Other sources have suggested that the IR element of OSF has a maximum operational range of 150 km. OSF evolves The feedback from training and operations, Brousse indicated, is enabling the OSF (and the whole Rafale weapons system) to be fine tuned. Future improvements to the OSF include enhancing the system's video system and investigating the retrofit of improved detectors. The enhanced variant is referred to as OSF-IT (Improved Technologies). In Sweden, the late 1990s saw Saab Dynamics (now Saab Bofors Dynamics) design and develop a prototype multifunctional IRST system, known as IR-OTIS, intended to provide passive situation awareness for the JAS 39 Gripen at long range, during day and night operations, against air and ground targets. Using a LWIR detector, the system could operate both as an IRST and a FLIR with a large scanning field. However, this project was put "into limbo" in the early 2000s and, although the Gripen NG model is evolving, there has been no sign of IR-OTIS being revived.



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As might be expected, Israeli companies are also developing airborne IRST systems. However, no specific products have yet emerged. A spokeswoman from Elbit Systems Electro-Optic (Elop) told Jane's: "Not only that we are still in the business of IRST, but we are in the process of developing new IRST systems for different types of aircraft." These systems, she suggested, "are based on major Elop technologies like thermal imaging, lasers, signal processing and more, to ensure the best possible results". The other major Israeli player in this field - Rafael Advanced Defense Systems - has already launched a naval IRST, known as Sea Spotter, using a staring focal plane array. A spokeswoman for Rafael told Jane's: "We are presently using the naval algorithms from the Sea Spotter and developing an airborne application but, as yet, we are not marketing a specific airborne IRST product." Thus, it seems that, quietly, all the major manufacturers have developed, or are developing, airborne IRST technology. The initial concept for air-to-air application, giving fighter pilots a passive target detection capability, has - in the light of operational requirements - seen the secondary air-to-ground function assume a higher priority.

The component parts of the Typhoon’s PIRATE system. (EuroFirst) 0106260



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This diagram shows the search-and-track zones of the OEPS-29 system, equipping early-model MiG-29 fighters. (UOMZ) 0106280

A head-on view of the nose of an F-35 Lightning II showing the low-observable nature of the EOTS sapphire crystal window fairing. (Lockheed Martin) 0568460



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A Sukhoi Su-30MKK ‘Flanker’ launches a laser-guided Kh-29L (AS-13 ‘Kingbolt’) missile at 10-km range; its ground target having been illuminated by the OLS-30 electro-optical search-and-track unit. (Sukhoi) 1039086

The sensor ball of the OLS-30 system is clearly visible offset to starboard, ahead of the canopy of this Su-27SKM, displayed at the 2005 Paris Air Show. (IHS Jane’s/Patrick Allen) 1144950



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This artist’s concept shows the AN/AAS-42 IRST installation (circled) in the leading edge of the port shoulder pylon of an F-15K Eagle. (Lockheed Martin) 1166898

A test-article IRST mounted in the front of a centreline external fuel tank of an F/A-18F Super Hornet, which still retains a 330 US gal fuel capacity. (Lockheed Martin) 1166899



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A pair of RAF Typhoon FGR.4 multirole fighters equipped with the PIRATE IRST, located on the upper port nose above the radome. (Eurofighter/Geoff Lee) 1330696

A further development of the OEPS-29 used on the early models of MiG-29 – the OLS-13SM-1, bid for the MiG-35 – is described as having “significantly increased” target detection and recognition ranges. (UOMZ) 1347209



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An improved version of the OLS-30 is known as the OLS-36Sh-01 and features a new cooling system and extended MTBF. Users include India and Malaysia (UOMZ) 1347211



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An upgraded MIG-29AS ‘Fulcrum-A’ of the Slovak Air Force, showing the sensor ball mounted ahead of the cockpit on the starboard side of the aircraft. Seen at the 2008 Farnborough Air Show, it is probable that this is the OLS-13S or -13SM version upgraded from the OEPS-29. (IHS Jane’s/Patrick Allen) 1367829



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A Rafale C of the French Air Force fitted with the OSF system prepares for a ground attack mission from Kandahar Air Base in Afghanistan in February 2009, armed with Sagem AASM laserguided bombs. (IHS Jane’s/Patrick Allen) 1377103

The two elements of the Optronique Secteur Frontal (OSF) installation on the nose of a Rafale fighter, with the IRST ball on the left of the picture and the CCD sensor to the right. Both sensors are shielded for flight mode. (IHS Jane’s/Patrick Allen) © Copyright IHS and its affiliated and subsidiary companies, all rights reserved. All trademarks belong to IHS and its affiliated and subsidiary companies, all rights reserved.


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Airborne IRST Prepares for Leap Into Uncharted Territory

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