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Smarter radars for longer life

Over the past 20 years airborne fire-control radars have become smarter as the advent of micro-processing has improved the speed and capacity of the system to search for, track, and identify targets. At the same time, the physical size of the hardware has shrunk. Thus, it is possible for in-service fighter aircraft to be given a state-of-the-art radar system which, in turn, allows the use of new generations of air-to-air missiles.

Technology is now such that existing radars can be upgraded (for example, the Hughes AN/APG-63 still used in early-model F-15 Eagles of the US Air Force - USAF) or new radars can be fitted to older fighters (for example, Elta's EL/M-2032 on MiG-21MFs of the Romanian Air Force).

Although some radars can be upgraded on their own, such a modernization is usually accompanied by some sort of digital avionics upgrade. This would involve the installation of a 1553B databus, a new navigation system (such as a GPS/inertial hybrid system), central computer, multi-function cockpit displays, other "glass cockpit" instrumentation and, possibly, an improved or new electronic-warfare system (sometimes referred to as a defensive aids suite/subsystem - DAS/DASS).

The following analysis will concentrate on the radars themselves, covering those that are being upgraded or new radars that have been retrofitted (or have been added to new variants of aircraft that have previously not carried radar) together with those being offered to the market for this purpose.

Israel's radar house is the Elta Electronics division of Israel Aircraft Industries (IAI) and its current product is the EL/M-2032, derived from the EL/M-2035 of the now-defunct Lavi fighter aircraft. This pulse-Doppler, all-aspect, look-down/shoot-down, fire-control radar system has already scored three export successes in the fighter radar retrofit market: on Chile's F-5E upgrade and Romania's MiG-21 Lancer as well as an unnamed customer.

As is common to most, if not all, modern radars, the EL/M-2032 is modular and has multimode capabilities for use in the air-to-air and air-to-ground environments. It features a coherent traveling-wave tube (TWT) transmitter, an ultra-low sidelobe planar antenna (adaptable to aircraft nose limitations), two axes in monopulse and a guard channel, a programmable signal processor, full software control, and both adaptability and growth potential. Depending on antenna size, the EL/M-2032 weighs in at 78-100 kg, with a power requirement of 2-2.5 kVA.

The operational modes for air-to-air use include range-while-scan (RWS), single- target tracking (STT), track-while-scan (TWS), and a selection of air-combat modes (ACM) including vertical scan, slewable ACM, head-up display (HUD) ACM, and boresight. Detection range in look-up mode is 35-55 nm (65-102 km), dependent on the size of the aircraft platform/antenna.

For the air-to-ground mode the EL/M-2032 offers high-resolution mapping (in the synthetic aperture radar [SAR] mode); real beam-sharpening (RBS); Doppler beam-sharpening (DBS); air-to-ground ranging; sea search; and terrain-avoidance facilities. Typically, for the look-down mode, radar range is quoted as 30-45 nm (55-83 km).

The latest success for the EL/M-2032 is for Turkey's F-4E Phantom 2000 upgrade, where - after much haggling over cost - IAI persuaded Turkey to opt for this radar in place of the Norden (now part of Northrop Grumman's Electronic Sensors and Systems Division) AN/APG-76 used on the Israeli upgrade.

From Italy, the FIAR family of Grifo radars has achieved similar success. Four distinct versions of this radar have been adopted: the Grifo-M and Grifo-7 for the Mirage III and F7 (MiG-21), respectively, in service with the Pakistan Air Force; the Grifo-F for Singapore's F-5E upgrade (re-designated as F-5S); and the Grifo-L for the Czech Republic's Aero Vodochody L-159. Although previously a smaller part of Italian industry, FIAR is now the lead element of GF-Sistemi Avionici, a Finmeccanica company.

Development of the Grifo pulse-Doppler, multimode radar began in the late-1980s and, following a comprehensive series of flight testing on a company-owned T-39 Sabreliner testbed, is considered complete. The four versions share a common architecture and much common hardware and, according to the company, offer features normally associated with highly expensive and complex aircraft.

The Grifo incorporates a full range of air-to-air and air-to-ground modes. The performance demonstrated during the Sabreliner tests against fighter targets included detection and lock-on ranges, look-down capability, and air-to-ground ranging. The company told IDR that these tests "far exceeded the design objectives" of the radar but declined to be specific about the detection ranges. Company literature notes that the radar is able to detect and track multiple targets (up to eight) at all aspects and at all altitudes. The system weighs, depending on the aircraft platform, "less than 80 kg".

Integration of a modern radar into new avionics architecture is never as simple as it appears and it is understood that the Grifo-F for Singapore's F-5S experienced problems during integration, though their exact nature has not been revealed. That said, FIAR issued a statement during the 1996 Farnborough International air show noting that flight trials of the first Grifo-7 in a Pakistani F7 in April-May 1996, were declared "completely satisfactory" by the Pakistan Air Force and ministry of defense. Several sorties were flown ahead of the rainy season in order to test the full operability of the radar in the country's challenging hot weather conditions. Further trials are being conducted to verify other parameters.

At present, the Grifo's claimed lower cost and higher performance are its main selling points. FIAR states it has "signed orders for about 200 Grifo radars" with options on a further 100. Other candidate aircraft for the Grifo are seen as being the A-4 Skyhawk, MiG-21, Super F7, and the Yak-130.

The Blue Vixen multimode, pulse-Doppler, I-band radar from GEC-Marconi Avionics (GMAv) was designed specifically for the UK Royal Navy's (RN) Sea Harrier FA.2 upgrade, to be used in conjunction with the AIM-120 Advanced Medium Range Air-to-Air Missile (AMRAAM) beyond-visual-range (BVR) weapon. With miniature components, elements of the system are remotely sited (in the rear fuselage) and connected by a fiber-optic link.

Blue Vixen offers full all-weather capability across both land and sea in look-up/ look-down modes. The system automatically selects a high, medium, or low pulse-repetition frequency (PRF) for optimum detection, depending on the target density or background clutter. Tracks can be formed at ranges of between 75 nm and 80 nm (139-148 km). In look-down mode, a low PRF provides accurate range/velocity with all-aspect detection, while a high PRF offers detection of high-speed targets in a high-clutter environment. RN experience in the skies over Bosnia proved that the radar is capable of detecting slow-flying helicopters at low level. Intelligent automation reduces the pilot's workload in such areas as track-forming, mode selection, and threat prioritization.

According to Cdr Richard Hawkins, Commander Air Warfare at the Sea Harrier base of Yeovilton, in the air-to-air mode "the big winner is the BVR track-while-scan capability." He told IDR that "we don't require to single-target track: if you put out a lot of continuous-wave energy, this trips a radar warning receiver, but with our BVR capability the other guy has no idea you are engaging. We are flying a 1960s platform but knocking down 1980s platforms all the time." Hawkins maintains that the Blue Vixen/Sea Harrier combination is "the best air-defense aircraft in Europe - a view shared by all who have come up against it."

While GMAv is talking with India about Blue Vixen for its Sea Harrier FRS.51s, re-packaging the components so that the system can be installed without the airframe "stretch" given to the RN fleet, it is also alive to opportunities elsewhere. For example, it has signed an agreement with GEC-Marconi Systems in Australia to propose it for the Royal Australian Air Force F-18 Hornet upgrade.

Also on the market since 1992 but yet to secure a launch customer is GMAv's privately developed Blue Hawk radar. The Blue Hawk, which weighs 107 kg, was designed as a low-cost multimode radar for lightweight fighters. The retrofit market is crucial. Much use is made of standard components and conventional manufacturing technology, making it a near-COTS (commercial off-the-shelf) radar.

The elements of the system are a planar array antenna (sized to suit platform application); a high-power transmitter, using an air-cooled, ring bar TWT; a two-channel microwave receiver/exciter; and a digital processor for signal, data, and display application, with 50 per cent spare memory for growth and 50 per cent spare throughput. A continuous-wave illuminator is offered as an integrated option for medium-range air-to-air missile control.

Control of Blue Hawk is optimized for hands-on-throttle-and-stick (HOTAS) use. For air-to-air work, GMAv quotes a look-up RWS range of 44 nm (81 km) and a look-down RWS range of 27 nm (50 km), and 34 nm (63 km) for velocity search. In air-to-ground mode, the radar can map up to 80 nm (148 km), while small-ship detection out to 42 nm (78 km) is claimed and, dependent on sea search mode, out to 54 nm (100 km).

The system is compatible with the 1553B databus and offers monopulse operation, coherent and non-coherent integration techniques, and electronic counter-countermeasure (ECCM) features. With extensive built-in test equipment (BITE), the company predicts a mean time between failures (MTBF) of 250 h.

GMAV is also offering another new low-cost, multimode radar designed as a direct replacement for the Skyranger system in the Chinese F7MG (MiG-21) fighter development. Known as the Super Skyranger, it is also proposed as retrofit for other "small-nosed" fighters.

The company claims that the Super Skyranger offers full look-down/shoot-down capability, using a planar-array antenna scanning +/-30, depending on the aircraft installation. It can provide target range, range rate, and line-of-sight data (such as head-steer data for a slewable short-range air-to-air missile) to the aircraft avionics system. It does this using an ARINC 429 serial link (with a 1553B option) and possesses what are described as "excellent" ECCM features.

As several of the radars described here are aimed at retrofits of Russian designs (notably the MiG-21), it is not surprising that Russia's own radar house, Phazotron, has some solutions of its own in its Kopyo family. A multimode search-and-track radar, it is offered in three versions (plus a pod-mounted option).

The basic Kopyo is a coherent, pulse-Doppler radar, weighing 165 kg, using digital signal processing and offering 13 operating modes. These include, for air-to-air: look-up/look-down, RWS, TWS of up to eight targets with simultaneous engagement of two, ACM vertical search, ACM HUD search, ACM wide-angle search, and ACM boresight. For air-to-ground use, facilities include: real-beam ground mapping, display enlargement or freeze, Doppler beam-sharpening, synthetic aperture, TWS of up to four targets, ground MTI/tracker, and air-to-surface ranging.

Super Kopyo is described as "a modernized Kopyo" that uses high-throughput signal and data processors. The weight has been reduced to 100 kg and the forward and rear hemisphere detection ranges have been increased from 57 km to 75 km and 35 km to 45 km respectively.

Super Kopyo-PH is an ultra-lightweight (weight not specified) radar for first-look, first-shot, first-kill use. It comprises a phased-array antenna, digital signal and data processors, and a 12-bit analog/digital converter unit. It is also reported to incorporate BITE down to printed circuit-board level. Air-to-air modes include look-up/look-down RWS, STT, and ACM; air-to-surface modes include real-beam ground mapping, Doppler beam-sharpening, and SAR target identification.

The basic Kopyo is included in the MiG-MAPO MiG-21-93 upgrade and the radar is understood to have been specified for India's MiG-21 upgrade. Another Phazotron radar competing in the retrofit market is the Mosquito targeted at the upgrade of India's maritime Jaguar force (of 6-12 aircraft), replacing the existing Agave. While the application is not strictly for a fighter, data published during the Farnborough air show does indicate an air combat mode, covering HUD search, slewable scan, vertical scan, and boresight. For air-to-surface use, it is designed to detect and provide co-ordinate measurements for the Sea Eagle anti-ship missile. Company literature claims a detection range of 100 km for a ship with a 300 m2 radar cross-section in Sea States 4-6.

In France, Thomson-CSF launched its RDC (Radar, Doppler, Compact) system for retrofit to Mirage III/5/50 and F1 fighters at Le Bourget in 1995 and is, reportedly, close to its first sale. This 100 kg modular system comprises a flat slotted antenna with guard horn and identification friend-or-foe dipoles, X-band coherent transmitter, dual-channel receiver, a digital programmable signal processor, and data processor. BITE ensures improved maintainability compared with the Cyrano radars it is intended to replace. The operational modes include all-aspect, look-up/look-down air-to-air capability with RWS, multi-target TWS, STT, and ACM; air-to-ground mapping, with Doppler beam-sharpening, range-finding, and MTI; air-to-sea BVR search and detection, and target designation, plus a weather mode.

The substitution of Thomson's RDY radar (in place of the RDI and RDM radars) in the Mirage 2000-5 upgrade for 37 French aircraft brings this within our scope. This multifunction radar offers long-range detection of very low and very high penetrating targets. It features a new flat-plate, low-inertia aperture antenna, a compact dual-peak power transmitter and a programmable signal processor with a 1 Gflop capacity. In air-to-air mode the TWS function enables multi-target tracking and engagement, while for air-to-ground use mapping with Doppler beam-sharpening, terrain-avoidance, and ranging can be done. In the air-to-sea mode a range of 296 km is claimed, even in high sea states.

In the US, Hughes Aircraft - which developed the AN/APG-63 radar to equip early-model F-15s - has since evolved the design to form the AN/APG-70 that is installed in USAF F-15Es and some of its later F-15C/Ds. The APG-70 is also fitted to the F-15I and F-15S models for the Israeli and Saudi air forces respectively. Hughes is developing the APG-63(V)1 variant for retrofitting to those F-15C/Ds that at present carry the basic radar.

The USAF launched this upgrade program primarily to address problems resulting from parts obsolescence, and to improve reliability and maintainability. Many of the microelectronic parts in the original APG-63 are now obsolete, and this number is increasing rapidly. The (V)1 variant also draws on Hughes' experience with the APG-70 and, also, with the APG-73 for the F/A-18 family. This has led to improvements in both the hardware - in areas including the signal and data processors, power supply, transmitter, and receiver/ exciter - and in the software. The latter is written in the JOVIAL high-order language that has already been adopted for the APG-70 and APG-73.

As a result, the APG-63(V)1 will detect smaller targets than can the original equipment, and has better tracking performance against all targets. It incorporates greater resistance to electronic countermeasures, provides additional combat-identification facilities, and offers improved pilot-directed modes and displays. The (V)1 is also pre-wired to accept further improvements in processing and in image resolution, when operating in SAR mode.

The AN/APG-65 that Hughes originally developed to equip early F/A-18s is also being fitted to AV-8B Harrier II Plus aircraft of the US Marine Corps, together with the Italian and Spanish navies. In addition, the Luftwaffe has adopted the APG-65 to upgrade more than 100 of its F-4Fs. This program will be completed during 1997.

Hughes is producing the AN/APG-73, which the US Navy is fitting to its F/A-18C/Ds and which forms the baseline fit for the F/A-18E/F. The F-18s ordered by recent export customers - Finland, Malaysia, Switzerland, and Thailand - also carry the APG-73. The US Navy adopted a phased approach to the program.

Phase I involved developing the basic radar, and proceeding through operational test and evaluation into production. Phase II, for which Hughes was awarded a contract in March 1995 and delivered the first production hardware in mid-1996, implements improvements that were designed into the system from the outset. These include a stretch waveform generator, the addition of a motion-sensing system (MSS) to support reconnaissance and precision-strike missions, and a special test equipment instrumentation and reconnaissance (SIR) module.

The stretch waveform generator module, installed in the radar receiver, expands the waveform by means of a linear frequency modulator. This results in higher-resolution imagery, and extends the mapping range. The MSS is attached to the bulkhead of the radar rack directly aft of the antenna. It provides accurate antenna position and vibration information. This enables the radar to supply higher-resolution ground maps and improved designation accuracy for air-to-surface weapons. The SIR module, located in the data processor, is an interface buffer that allows the APG-73 to record raw radar data aboard the aircraft or transfer it by datalink to the ground.

The incorporation of these Phase II enhancements allows the F/A-18 to collect strip-map and spot-map data with resolutions that are comparable to those achieved by the F-15E and U-2. Software modifications would support the generation of onboard imagery. The Phase II hardware can also accommodate a future software upgrade that would give the F/A-18 a precision-strike capability, using advanced image-correlation algorithms. Phase III, which is not yet funded, would add an active antenna array.

Northrop Grumman's Electronic Sensors and Systems Division (ESSD) - formerly Westinghouse Electronic Systems - has produced about 4,000 AN/APG-66 and 2,500 AN/APG-68 radars since 1976, primarily to equip the F-16A/B and F-16C/D, respectively. The APG-66 equips a total of 16 platform types, however, and is the baseline equipment for the British Aerospace Hawk 200. The radar will remain in production until at least the year 2000 and ESSD has committed itself to providing support for a further 20 years beyond that date.

The Belgian, Danish, Dutch, and Norwegian air forces are upgrading the APG-66s aboard their 301 F-16s to AN/APG-66(V)2 standard as part of the Mid-Life Update (MLU) program being conducted by the European Participating Governments (EPG). ESSD completed developmental test and evaluation (DTE) of the (V)2 aboard an F-16 at Leeuwarden Air Base, the Netherlands, in August 1996. EPG pilots flew 17 radar sorties, totaling 37 h.

The (V)2 incorporates a newly developed signal data processor with a faster throughput and other improvements. Among other benefits, this results in a range increase of about 25 per cent. Other changes include minor enhancements to the low-power radio-frequency (RF) section, and reduced antenna switching times. Together, these alterations confer a substantial increase in MTBF, to about 240 h.

DTE involved trials in both air-to-air and air-to-ground modes, with emphasis on the former. This focused on the radar's low- altitude look-up and medium-altitude look-down performance over terrain with varying clutter conditions. Detection ranges, false-alarm rates, and automatic acquisition and track performance were all significantly better than the specified levels. Jim Pitts, vice-president of Avionic Systems within ESSD, says that the DTE results confirmed those obtained during earlier trials of the (V)2 aboard the company's BAC One-Eleven testbed in the summer of 1994. He says that ESSD "learned good lessons" during these trials, which were carried out over representative clutter backgrounds in the Netherlands and Norway.

A variant of the EPG radar, optimized to match its operation with the AIM-7 Sparrow air-to-air missile, will equip Taiwan's newly built F-16A/Bs. ESSD is also talking to other actual and potential F-16A/B operators in Europe, including Portugal and several Central European countries, and in South America and the Far East. The company is developing a complete rework of the low-power RF section. This will combine the (V)2 signal data processor and the existing low-power improvements into a single box, thereby improving reliability and maintainability and reducing costs.

ESSD says that the APG-68 is the most reliable fighter fire-control radar in the world, achieving a MTBF of 200-300 h aboard Block 50 F-16C/Ds. Potential new customers include Saudi Arabia, countries in Central Europe, and Norway. The latter is considering a variant of the APG-68 incorporating an affordable electronically scanned array that Northrop Grumman is developing with company funds, and which will be available in two to three years. Israel and other Middle Eastern countries are further possible customers for this enhancement. ESSD believes that an international order could lead to the USAF expressing interest in upgrading its own radars.

Northrop Grumman is also considering an APG-68 upgrade that would incorporate improvements in the signal data processor and low-power RF section similar to those being implemented in the APG-66(V)2. The company also aims to transfer technology from the AN/APG-77, under development for the F-22, into other systems. In addition, it plans to draw on low-cost technologies implemented in the AN/APN-241 that equips C-130H/Js as the basis of further improvements to the APG-66 and -68.

Lockheed Martin maintains the AN/APG-67 in its product range, aimed at the F-5 market, but IDR has been unable to ascertain its current status. Company literature released at Farnborough indicates that the APG-67 comprises four LRUs: antenna, transmitter, radar data computer, and target data processor. This 104 kg radar offers a full range of air-to-air and air-to-surface modes, including look-up/look-down RWS, TWS, STT, and ACM for the former; and real-beam ground mapping with Doppler beam-sharpening, MTI, and ranging for the latter.