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Above-water warfare sensors for MPAs

The continuing importance of themaritime patrol aircraft (MPA) has again been highlighted during the recent Kosovo conflict. Originally devised as an open-ocean anti-submarine warfare (ASW) asset, the MPA has now convincingly proved that it possesses the inherent flexibility and versatility to act in surveillance, reconnaissance, attack and command and control roles throughout the violence spectrum at sea and over land. Its principal sensors for above-water warfare - radar, ESM and electro-optics - are the main enablers facilitating this mission shift.

The US Navy (USN) is the world's leading MPA operator. The service's MPA Vision 2010, which emphasizes the multi-role nature of MPAs, therefore is of significant interest. While the study points out that open-ocean ASW remains a vital core competency, other aspects have assumed greater importance since the end of the Cold War. In the field of joint strike operations, MPA are integral in establishing prestrike battlespace dominance via quick response from forward-operating sites. Effective high-search-rate surveillance, superior airborne endurance, stand-off identification and targeting, and [satellite communications] connectivity ensure a clear picture of the battlespace. In joint littoral warfare, the service adds, it is particularly important to focus on integration with all land- and sea-based assets. With multi-sensor search capability, rapid response, endurance and sustainability, the P-3 effectively sanitizes near-land areas before the arrival of sea-based ground forces or logistics missions.

MPA Vision 2010 emphasizes that maritime surveillance and reconnaissance has, and always will be, a fundamental MPA mission. P-3 endurance allows for broad-area search, indications and warning capability, and over-the-horizon targeting. Monitoring potential future threats will require increased surveillance.

Initial detection

From the time initial aircraft arrived in-theater during 'Desert Shield' until the conclusion of hostilities in 'Desert Storm', MPA provided initial detection, identification and monitoring of over 23,000 surface contacts. During the antisurface warfare (ASuW) campaign, most of the critical contacts of interest were initially identified by on-station P-3s that served as the priority targeting platform in the destruction of 56 Iraqi surface vessels.

Maritime patrol aircraft additionally play an important role in electronic warfare and intelligence. MPAs provides a quick-response covert surveillance capability through its forward-deployed assets, notes the USN. Utilizing emerging technologies, the P-3 can provide real-time surveillance and targeting via still and full-motion imagery transfer using digital cameras. OASIS [Over-the-horizon Airborne Sensor Information System] enables the transfer of real- time position data, and a specific emitter identification capability enables MPA to track surface vessels from port to port without requiring continuous visual surveillance.

In strategic sealift and protection, says the service, the multi- mission capabilities of MPA are most valuable at the onset of a crisis. Surveillance, reconnaissance and interdiction of potential adversaries at critical points of sea lines of communication remain essential to the protection of shipping. MPA helps to provide initial strategic mobility to a crisis area by building a maritime bridge for the sustainment of heavy joint forces.

The ASuW Improvement Program (AIP), which involves modifications to 146 P-3C Update III aircraft, is central to maintaining and enhancing the USN's MPA fleet until a replacement design becomes available at some unspecified date (see also IDR 2/1999). The first AIP variant entered service in April 1998, and all are due to have been converted by the end of Fiscal Year 2000. Lockheed Martin Tactical Defense Systems - prime contractor for AIP - is fitting much of the same equipment to four Royal Norwegian Air Force P-3Cs under that service's Upgrade Improvement Program.

The AIP made its combat debut during NATO's Operation 'Allied Force' against Yugoslavia earlier this year, when at least five of the P- 3Cs that the USN allocated to the Mediterranean maritime patrol force were to the upgraded standard. The Kosovo conflict saw the P-3C Orion detachment at Naval Air Station (NAS) Sigonella, Sicily, becoming engaged in "one of the most productive and demanding deployments in maritime patrol aviation history". From Sigonella, the detachment flew round the clock in support of the NATO and US operations in the former Yugoslavia, respectively 'Allied Force/Allied Harbour' and 'Noble Anvil'.

The core unit of the Sigonella detachment was VP-10 'Red Lancers', a patrol squadron forward-deployed from NAS Brunswick, Maine, with nine aircraft and twelve crews. For the Kosovo contingency, VP-10 was augmented by up to six USN aircraft and crews from other units (both active and reserve), while a Royal Netherlands Navy (RNLN) P-3C Update II.5 aircraft, aircrew and support personnel were fully integrated within VP-10 for the duration of the conflict.

In November 1998, the USN began flying daily surveillance missions over Kosovo with Sigonella-based P-3C Orions for Operation 'Eagle Eye'. The sorties, supporting the OSCE verification mission in the troubled province, took advantage of the P-3's multi-sensor surveillance payload and its long unrefueled endurance of 10-12h. Synthetic-aperture radar and electro-optical cameras provided high- resolution imagery in real time to ground-based commanders in all weathers, day or night, from stand-off ranges.

To take part in 'Eagle Eye', the RNLN at the end of last year had three of its P-3Cs upgraded at NAS Patuxent River, Maryland, with a self-protection suite taken from the USN's AIP program (AN/AAR-47 missile warning system integrated with six AN/ALE-47 chaff/flare dispensers). The Dutch also had a new US-built turret-mounted electro-optic sensor installed in these three aircraft: the FLIR Systems Inc (FSI) Star SAFIRE system including third-generation FLIR, daylight TV and spotter-scope TV.

Some US aircraft at Sigonella were equipped with the Canadian WESCAM AN/ASX-4 Advanced Imaging Multi-spectral System (AIMS), which uses a turret-mounted WESCAM Model 20 infrared/electro-optical sensor installation. Other P-3Cs carried the earlier AN/AVX-1 Cluster Ranger electro-optic surveillance system, including video cameras and a 35mm still camera operated via a gimbaled mirror and mounted on the window at the tactical co-ordinators station on the port side of the forward fuselage.

Around-the-clock

On 22 March, two days before the start of hostilities, AIP aircraft began around-the-clock armed force-protection surveillance flights over the Adriatic in direct support of ships armed with Tomahawk land-attack missiles. For the next 94 days, MPAs conducted all of the surface combat air patrol (SUCAP) operations for the USS Theodore Roosevelt carrier battle group and other allied ships operating in the area. This marked the first time that SUCAP during combat had been performed exclusively by non carrier-based aircraft.

AIP-equipped P-3s, as well as the modified Dutch aircraft, were able to directly observe commercial ships carrying contraband, as well as mobile coastal missile batteries that could pose a threat to NATO shipping in the Adriatic; and individual Former Republic of Yugoslavia naval ships and submarines that were continuously moved around inside the Bay of Kotor and the port of Bar. They downlinked imagery to the battle group commander, giving him an unprecedented view of the tactical situation in real- and near-real time.

Cdr Fred Noom, commanding officer of the RNLN's operational MPA unit - 320 Squadron based at NAS Valkenburg near The Hague - said that two continuously manned P-3 patrol orbits were positioned well forward of the USN's Aegis cruiser/destroyer air-defense screen that was to protect the NATO naval forces operating further out at sea. IDR understands that for this round-the-clock observation mission, the P-3s were traveling just outside Montenegrin territorial waters (around 15nm offshore) at Flight Level 150 (15,000ft).

Cdr Noom said: "This operation was very much a stand-alone, dedicated mission under US auspices. Other NATO MPAs also flew over the Adriatic, but they operated in a more traditional role maintaining the recognized maritime picture."

A real asset proved to be the capability to downlink video imagery in real time. "Using a make-shift solution, engineered by the US detachment at Sigonella itself, we were able to establish a real time video downlink to portable ground stations with Commander Task Force Six Seven (CTF-67) at sea and with deployed forces ashore," Cdr Noom said. "This is a capability MPAs have not had before and which was extremely useful during the operations over Montenegro."

On board the RNLN aircraft, the real time video downlink solution made use of an off-the-shelf transmitter antenna unit that was installed from inside the cabin in the free-fall chute after take- off (installation before take-off was not possible because the antenna protrudes about 1m from the underside of the fuselage aft). The chute was then sealed so that pressurized flight was still possible. A standard-issue cable, laid out inside the cabin forward to the Star SAFIRE's Panasonic AG 6400 multi-recorder (both PAL and NTSC), completed the set-up, which will now be re-engineered and subsequently procured by the RNLN (and presumably also the USN) in greater numbers to sustain the real time video downlink capability during the next few years.

According to electro-optic sensor operator Sgt Mick Bouwman of the RNLN, FSI's Star SAFIRE is capable of +30 through -120 of tilt in elevation and offers a full 360 coverage in azimuth. Targets of interests were highlighted by the aircraft's tactical co-ordinator (TACCO) and/or navigator/communications officer (NAVCOM) and then manually tracked by the sensor operator. The system as installed on board the RNLN aircraft has no automatic target lock-on feature. "Because we use a 360 rotatable turret, we can instantly react to any visual observations from the flight deck, an advantage over fixed side-looking sensor configurations such as the Cluster Ranger set-up," Sgt Bouwman said.

The Star SAFIRE produces high-quality imagery, as was shown to IDR while flying by the Spanish airport of Vitoria near Bilbao. Even from a distance of 40nm and an altitude of 27,000ft the individual aircraft parked on the ramp were clearly identifiable. Cdr Noom claimed that at closer ranges, the system could make out a "bicycle standing against a wall".

In addition to the electro-optic sensors, the P-3s off the Montenegrin coast also employed other sensors including ESM and passive sonobuoys.

Throughout the conflict, the aircraft of CTF-67 detected and reported more than 3,500 surface contacts. In another first, AIP- equipped P-3s fired a total of 14 Standoff Land Attack Missiles (SLAMs) at Serb targets. Because of the P-3's ability to stay on- station for hours at a time, battle group commanders had the flexibility to hit mobile targets on short notice. According to the USN, this in-flight planning/retargeting ability for SLAM attacks validated the importance of the P-3's strike role.

Industry is already in full swing to provide the improved above- water warfare sensor technology that is required by the MPA community. IDR has surveyed market developments in the three key sensor fields.

Israel Aircraft Industries (IAI)'s Elta division has scored success with its EL/M-2022A multi-mode maritime surveillance radar family, sold to equip both fixed-wing (MPAs, UAVs) and rotary- wing airborne platforms against strong competition from key US, UK and French suppliers. The radar is derived from the EL/M-2032 fire-control radar used in fighter aircraft, and is designed to perform maritime target surveillance, and economic exclusion zone protection and sea-traffic control.

There are three baseline versions: EL/M-2022A(V)1 lightweight/remote controlled for use on board UAVs; EL/M-2022A(V)2 and EL/M-2022A (V) 3. The last two are typically for use on board MPAs and the most capable one, the (V)3, at a weight of up to 103kg and a power consumption of 2.3kW, can detect a 1m[2] target in Sea State 3 out to 30nm (54km) and a small ship out to 80nm (144km), according to Elta data.

Modernization program

The main customer for the EL/M-2022A(V)3 is the Royal Australian Air Force (RAAF), which has incorporated this radar for its Project Air 5276 AP-3C modernization program. It is understood that besides low cost, a major factor in the selection of the Elta product over the AN/APS-137 and Searchwater 2 competitors has been the willingness by Elta to provide all radar source codes for future upgrade work performed by Australia's Defence Science & Technology Organisation (DSTO).

Operational modes include long-range surveillance, maritime airborne MTI, wide-area Doppler beam-sharpening, navigtaion and weather, while the radar is claimed to be capable of 100-target track-while- scan. Integrated radar and electro-optical sensor video display is optional.

Dasa's Defense and Civil Systems unit and Thomson-CSF Detexis have teamed to develop the Ocean Master airborne maritime patrol radar, designed to meet the requirements of both fixed- and rotary-wing aircraft. The two companies claim the following major features for the Ocean Master radar: outstanding radar performance in all situations; ultra-light design and simple installation in fixed- and rotary-wing aircraft; proven state-of-the-art technology.

Ocean Master is designed to fulfil both civil and military maritime missions including economic exclusion zone (EEZ) surveillance; search and rescue (SAR); anti-surface vessel warfare (ASVW) and anti-submarine warfare (ASW); air-to-air detection. Two basic versions of the radar are offered: the Ocean Master 100 and the Ocean Master 400. These designations relate to the use of either a 100W fully coherent traveling wave tube (TWT) amplifier, or a 400W fully coherent TWT amplifier. Options and growth potential are available to meet specific user requirements, including inverse synthetic aperture radar (ISAR) processing to provide ship classification capability.

Ocean Master would perform the following other modes: multitarget track-while-scan operation; ground mapping; target classification; weather detection and beacon mode. Ocean Master in the basic version comprises only three units: antenna unit (360 rotation and/or sector scan); transmitter unit; exciter/ receiver/processor. In addition, the man- machine interface includes display and controls. The system is in production; first deliveries were made at the end of 1994. More than 30 systems have been ordered by France, Indonesia, Japan, and Pakistan including for use on Falcon 50, C-212 and Atlantique MPAs.

The Searchwater 2000MR I/J-band (X-band) surveillance radar that Racal Defence Electronics is supplying to equip the 21 BAe- modernized UK Royal Air Force Nimrod MRA.4 aircraft will include advanced SAR and ISAR modes for high-resolution target profiling and classification, as well as adaptive threshold control for maximum sensitivity and minimum false alarms. To facilitate this, it will incorporate the TriSAR processor and associated software provided by Canadian company Array Systems Computing. Searchwater 2000MR will additionally feature secondary air-to-air and ground surveillance modes. The multi-mode (ASW, ASuW, Littoral Waters/Open Sea, Swath SAR, and pulse Doppler air-to-air) high mean power TWT coherent surveillance radar system is being equipped with a range of display options (see below).

Searchwater 2000MR flight trials will start in 2000 on board Racal's own DC-3 trials aircraft and subsequently continue onboard the BAe MRA.4 prototype aircraft. The radar uses a conventional horn-fed reflector antenna with selectable polarization and cosec[2] (elliptical) beam shape. The company intends to offer the 2000MR radar to the New Zealand P-3K upgrade project and for other large MPA upgrade and newbuild programs. For the German-Italian MPA program, Racal plans to team with a German partner, possibly Dasa with whom it has worked closely in the past on German Navy EW programs.

Searchwater 2000MR is one of three variants to suit specific airborne surveillance needs, the others being Searchwater 2000AEW (in production for the UK RN Sea King AEW Mk7 program, featuring a different transmitter and antenna combination optimised for Pulse Doppler MTD modes to achieve long range detection of stealthy aircraft against a high sea clutter background) and Searchwater 2000MS, according to the joint DERA/Racal presentation at the DSEi exhibition in September. The last is a lighter weight (100kg) variant of Searchwater 2000MR with many of the same features. It is intended for lightweight MPA and ASW/ASuW helicopters and benefits from experience with lightweight technology from the Supersearcher radar family.

According to DERA and Racal, Searchwater 2000MR is designed to provide the "highest quality airborne maritime surveillance for MPAs", able to detect, classify and track surface targets in a wide range of sea conditions. The radar was designed from the outset to offer the best possible detection of submarine masts, including detection during short exposures. The manufacturer claims a proven ability of the signal processing and detection algorithms to control false alarms in difficult clutter conditions often found in Atlantic areas of operation.

Recreating Atlantic swell

These are based on extensive research by Racal and DERA which has resulted in the definition of the 'compound K-distribution clutter model', which is said to accurately represent the spatial and temporal characteristics of the 'spiky' and long swell characteristics of the Atlantic, together with improved detection techniques based on this model and equivalent studies of target characteristics.

A littoral-waters processing mode is provided which is specifically aimed at the detection of targets close to land.

Additional display modes assist the operator in setting up the radar for the prevailing conditions to optimise the probability of successfully detecting, classifying and tracking targets, including:

- high resolution B-Scope (with the cursor placed on a target the B- Scope will expand the area immediately around the radar response to indicate if it comprises a single or multiple targets; a single target may then be selected for further investigation or tracking);

- range profiling A-Scope (selected from the B-Scope display, an amplitude profile against range is displayed in the immediate vicinity of the target. The bow and stern of a vessel may be marked, and if the target is being tracked by the radar, the true length will be automatically calculated from the aspect angle);

- detection range display for ASW and ASuW operation (as the radar scans, it is continuously adapting to local conditions in order to control the false alarm rate whilst maximising the probability of target detection. It is possible to infer the local clutter conditions from the adaptive settings of the radar and from these to predict the detection performance in small sections of the area under surveillance);

- SAR/ISAR Imaging Displays.

The operational implications of these imaging modes are that the radar offers a powerful capability to detect and classify maritime targets close to the shore, as well as the ability to image ground terrain with detection and classification of land based targets. This considerably enhances the potency of the MPA as a military asset, giving it a much greater deployability and flexibility in a wide range of scenarios.

The P-3C Update III aircraft that the USN is upgrading under its AIP effort carry the (V)5 variant of Raytheon's AN/APS-137B surveillance and targeting radar. Also used by others including Norway, this operates in multiple modes to provide capabilities that include long-range surface search, detection of periscopes and small targets, navigation, weather avoidance, and imaging in the form of both synthetic-aperture radar (SAR) and inverse SAR (ISAR) modes.

The US Naval Research Laboratory (NRL), with funding from the Office of Naval Research, has been conducting the Automatic Radar Periscope Detection and Discrimination (ARPDD) advanced development program since 1993. According to the NRL, "because the APS-137 requires human operators to distinguish sea clutter and other objects from periscopes, it is completely overwhelmed in high sea states and dense-target littoral seas".

Objectives of the ARPDD program include demonstrating technologies that confer a detection probability of greater than 50% against "briefly exposed" periscopes, with less than one false declaration per day. The challenge is to maintain detection sensitivity while automatically eliminating the huge number of radar reflections from sea clutter and objects near the shore, such as small boats, buoys and floating trash.

The ARPDD team includes radar developer Raytheon; the Applied Physics Laboratory at Johns Hopkins University, a center of excellence for ASW; and the Naval Air Warfare Center's Weapons Division at China Lake, contributing its expertise in automatic pattern recognition. The basic radar retains the high power, fast antenna scan rate and 30cm range resolution of the APS-137. Augmentations include: a novel design of constant-false-alarm-rate processor, which maintains system sensitivity; a "retrospective" processor, which eliminates noise and uncorrelated sea clutter; a direct discriminator, which applies automatic target recognition to a 5sec history of features with 30cm range resolution, to eliminate correlated sea clutter and objects other than periscopes; and an indirect discriminator, which combines the results of the direct discriminator with context information developed by a track-while- scan processor, to provide final periscope declarations.

Following several proof-of-concept trials, the USN tested a brassboard version of the radar aboard the destroyer USS Stump in April 1998. The equipment participated in exercises that summer, with what the NRL describes as "outstanding" results, eliciting comments such as "ARPDD has proven itself to be an invaluable sensor in the conduct of undersea warfare." Trials are continuing aboard NRL's P-3 flying testbed.

The USN plans to award one or more contracts to develop algorithms that permit real-time ISAR imaging of maneuvering aircraft, small ships at sea, and moving ground vehicles. The ability to extract reliable features from this imagery would support automated nonco- operative classification covering up to about 30 types of target. The USN hopes to incorporate such a facility into programs such as Small Craft Automatic Target Recognition (SCATR) and All Aspect Complex Target ID Variable Engagements (ACTIVE).

In response to an urgent requirement from the Chief of Naval Operations, the USN has implemented a Counter Drug Update program to modify 18 active-duty and 14 reserve P-3C Update IIIs so that they can accept roll-on/roll-off sensor packages as required. This effort includes the procurement of 10 Northrop Grumman AN/APG-66 radars, to be fitted in place of the APS-137s, which provide higher performance against airborne targets.

Raytheon Systems Company has supplied earlier variants of the APS- 134 and APS-137 for a wide variety of MPA applications, including P-3Cs for USN and export customers, USN S-3B Vikings, German Navy Atlantics and Singapore's Fokker Maritime Mk 2s. For applications where these designs are too heavy and/or expensive, the company is promoting its Sea Vue (SV) family of lightweight modular radars.

Lockheed Martin Canada of Kanata, Ontario, has a C$25-million development contract for an advanced development model Spotlight Synthetic Aperture Radar (SpotSAR). The SpotSAR adaptation of the APS-506 multi-mode radar is to be included in the upgrade of Canada's CP-140 Aurora fleet of maritime patrol aircraft. The SpotSAR is key to expanding the role of the Aurora to surveillance over land.

The SpotSAR will operate in three modes: spotlight, strip map, and range Doppler profiling/inverse SAR. It will allow for detection and classification of objects such as submarine periscopes from a long stand-off distance.

Lockheed, which received the development contract in 1995, was scheduled to install the ADM on a CP-140 in late 1996. Development problems, however, have delayed the program, which is now running approximately three years behind schedule.

Meanwhile, working separately, the Defence Research Board (DRB) has developed new capabilities for the SpotSAR. These are: an off-track strip mapping mode for unconstrained high resolution ground imaging; an extreme aperture spotlight mode for super-high resolution ship imaging; and, a Doppler beam-sharpening mode to provide low resolution inverse SAR images of ships without having to leave the normal search mode.

Polish radar house PIT has developed the ASR-400 surface search radar which is in service onboard Polish Navy An-28RM Bryza-1R sea surveillance aircraft.

And in Russia, the Leninets radar company of St Petersburg has developed the Sea Dragon mission suite for MPAs, including a powerful, slotted waveguide antenna radar that is planned to be fitted into several types of MPAs, including the Tu-142MZ 'Bear-F' (55 of which are in Russian service and eight in India); the Il-38 'May' (35 in service) and the new Tu-204 MPA now under development.

Australian AP-3C fleet

In addition to the radar, Elta has also provided the ESM equipment for the Australian AP-3C fleet, acquired under a separate program called Project Air 5140. Designated ALR-2001 in Australian service, the technology has been further developed and has been successfully sold to the UK's Nimrod MRA.4 program under the Elta nomenclature of EL/L-8300, an ESM/ELINT system for MPAs. The system is also in service on board Fokker 50 Enforcer Mk.2, CN-235, Do-228 and C-130 aircraft in various countries around the world. Main system elements include an ESM/ELINT operator console and display; four antenna arrays installed on the wingtips, forward and aft fuselage; rotating antenna for spinning DF; equipment rack and an optional radar warning receiver display in the cockpit. The system covers the bandwidth between 0.5-18GHz and offers an instantaneous bandwidth of 4GHz. Spatial coverage is 360 in azimuth and +/- 35 in elevation.

The Nimrod MRA.4s will carry the EL/L-8300UK system, together with a separate AN/ALR-56M radar warning receiver (RWR) in order not to compromize its performance. The RWR forms part of a defensive-aids subsystem (DASS), being provided by Lockheed Martin, that uses its own databus. In addition to the radar warner, the DASS includes a missile-approach warner, the Raytheon AN/ALE-50 towed radar decoy (with a Racal techniques generator), and expendable countermeasures. Growth options include a laser warner, directional infrared countermeasures (DIRCM) and jammers.

The Litton Applied Technologies AN/ALR-66C(V)3 ESM set that forms part of the USN's P-3C Update III AIP provides the same features as the earlier ALR-66B(V)3, with the addition of an AS-105 spinning direction-finding antenna installed in a belly-mounted radome (together with associated changes to the operational flight program). In response to requests from operators, the USN has developed a new method of processing ESM contacts. Software changes have reduced the 11 keystroke entries required previously to a single button- press. The ALR-66C(V)3 also provides inputs to the EP-2060 pulse analyzer, an upgraded version of the earlier AN/ULQ-16. The EP-2060 provides electronic intelligence about emitters on land, sea and air platforms.

Other ESM systems being marketed for MPA applications include Indra's AMES-C, the Condor Systems ALR-801 maritime patrol ESM system, the CS-5060 ELINT system and the CS-5550 ESM system; Thomson-CSF RCM which offers a range of ESM and ELINT solutions; and Mitsubishi which has supplied the HLR-109 ESM to the Japanese P-3 fleet. Racal of the UK supports the current Nimrod MR.2 ESM fit.

Israel's Elisra company is marketing the AES-210E ESM system for MPAs, which features automatic detection, measurement and identification of all radar emissions within 0.5-18GHz over long ranges and with precision DF capability. The system is incorporated in a full-up Maritime Patrol Suite that also includes multi-mode SAR/ISAR radar (probably Elta 2022A); FLIR and TV electro-optical sensors, ASW subsystem with magnetic anomaly detector, sonobuoys, acoustic receiver and processor; navigation, communications and a central mission management system (CMMS) all interfaced via MIL-STD- 1553B databus - a solution that will likely be offered to Turkey's nine-aircraft CN-235 MPA program.

Elta has also delivered a compact Airborne Surveillance System to a customer in South America. This system combined a 1.5-1,000MHz COMINT/DF sensor and an electro-optical payload, installed on a Beechcraft 200 King-Air aircraft.

The new Nimrod MRA.4s will carry the Northrop Grumman Nighthunter electro-optical surveillance and detection system (EOSDS). The company is supplying 21 installations to Boeing under a contract worth more than US$50 million. Nighthunter is a variant of the Nightgiant system that equips some US Air Force special-mission C-130s. It consists of a turret containing various sensors mounted on a gyro-stabilized gimbal 61cm in diameter. IDR understands that Nighthunter accommodates both long-wave (8-12m) and mid-wave (3-5m) thermal imagers, together with a low-light television (LLTV) camera.

Greater sensitivity

The system has greater sensitivity, stability, resolution and range even than Nightgiant, which itself boasts impressive performance, according to British Aerospace. Nightgiant carries a long-wave thermal imager based on a 480 x 4-element scanning detector array with time delay and integration, together with an LLTV camera, both having magnifications of up to x 40. The associated electronics provide facilities including image fusion from the various sensors, together with multiple trackers (large-area, centroid, and target- motion compensation). Nightgiant's line of sight is stabilized to 25rad.

The USN's (and Norway's) AIP program for P-3C Update IIIs includes installing an enhanced version of the AN/AAS-36A Infrared Detection Set (IRDS), mainly involving the adoption of an improved afocal lens.

Raytheon Systems Company has delivered more than 500 examples of the AAS-36 family to equip P-3Cs operated by the USN and overseas customers. The company also supplies the OR-263/AA imager for S-3s, and the OR-5008/AA for the Canadian Forces' CP-140s, while the RAYFLIR-49 Day Night Airborne Thermal Sensor (DNATS) is on offer as a low-weight, multi-purpose thermal imaging sensor.

AIP additionally involves installation of the AN/AVX-1 Cluster Ranger Electro-Optical Sensor System (EOSS) for stand-off surveillance. The stabilized AVX-1 sensor head, which is mounted against an optically flat window at the TACCO station, provides video for surveillance and reconnaissance missions. It can detect and monitor objects during the day in conditions up to medium haze, extending into dawn and dusk, and during the night from a full moon to starlight illumination.

The USN will also buy AVX-1 kits for 10 active-duty and five reserve P-3C Update IIIs under its Counter Drug Update program.

However, Canada's WESCAM Inc of Flamborough, Ontario, has obtained a strong position in the USN recently by winning orders for a new AIP sensor. WESCAM's Paul Jennison says his company's newest model, the WESCAM 20, has "a unique combination of sensors" that has allowed it to take "a bit of a lead in the marketplace".

It has a high-magnification thermal imager as well as a high magnification TV (FOV down to 1/8 with 3200mm focal length), allowing for high stand-off distance and day-night capability. The WESCAM 20 turret-mounted EO/IR sensor, as AN/ASX-4 Advanced Imaging Multi-spectral System (AIMS), was selected for the USN's P-3 AIP program by Lockheed Martin Tactical Defense Systems which last July exercised a third set of options worth C$18.3 million of a total potential procurement of up to 160 systems (worth up to C$180 million) through 2005. The latest set of WESCAM 20 units is to be delivered between the third quarter of 2000 and the first quarter of 2001. The US Coast Guard has also ordered the WESCAM 20 for use of Hercules aircraft and Jennison expects the system would also be a "natural sensor" for the Canadian Aurora upgrade project. WESCAM also offers the smaller Model 16DS-M.

WESCAM's main competitor in North America is US company FLIR Systems Inc, which offers the AN/AAQ-22 SAFIRE and the more capable Star SAFIRE (see above).

The Canadian DRB has produced a laboratory model of the next generation FLIR (known as IR Eye). The model has demonstrated the fusion of high resolution imagery over a lower resolution display.

The DRB expects that this wide area surveillance and detection system (60 vs. 20 FOV) will reduce the workload on search missions. Funding problems, however, have delayed the development of an airborne version of the IR Eye.

In Europe, the leading FLIR product for MPA applications is the Thomson-CSF Chlio, which is used on the French Navy's new Falcon 50 SurMar surveillance aircraft and on Alize carrier-based MPAs.