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Electro-optical and infrared (EO/IR) systems can fulfil several main roles aboard a warship.

by Doug Richardson

Optronic systems can provide surveillance, warn of incoming anti-ship missiles, acquire and track targets, handle the fire-control functions for individual weapons, and serve as navigation aids. They can be used either on their own, or as part of an integrated solution that combines them with radar and other sensors. In many cases, an EO/IR system may be used for a combination of roles, for example serving as part of the vessel’s fire-control system, but also providing surveillance coverage. While they lack the all-weather performance available from radar, EO/IR systems are passive, to give the target no warning that it is under surveillance. But it is important to note that the maritime environment can degrade their performance. Rain, fog, and haze can all have undesirable effects.

While this article describes but a representative range of the many EO/IR systems currently on offer, it shows the important role that these have as part of the equipment fit of a modern warship.

Performance Increases
Increases in performance along with reductions in weight, size, and power consumption allow modern EO/IR systems to provide all-weather situational awareness for vessels ranging from aircraft carriers to small surface craft.

Rafael’s TOPLITE EO turret can be fitted with up to four sensors.
Photo: Łukasz Golowanow

The simplest method of providing all-round EO/IR coverage is to rotate the sensor. This is the solution used for HGH Infrared Systems’ SPYNEL-C panoramic infrared surveillance system. Originally known as VIGISCAN, this was installed on five LA FAYETTE class frigates to meet an urgent operational requirement (UOR) to equip these vessels for the anti-piracy and maritime security roles. SPYNEL-C uses a cooled LWIR mercury cadmium telluride linear detector, which is rotated at 60 rpm to provide real-time 360 degree surveillance. Imagery is displayed in low-resolution, but areas of interest within the image can be displayed instantaneously in full resolution.
When a similar UOR was drawn up two years later to cover the D’ESTIENNE D’ORVES class light frigates and the DURANCE class underway replenishment tankers/command ships, the French Navy procured nine Chess Dynamics SEA COBRA EO/IR surveillance and tracking systems. Subsequently rebranded as the SEA EAGLE EOSS, this uses a sensor head that combines a Selex GALILEO HAWK 640×480 pixel 3 to 5 micron mid-wave infrared (MWIR) thermal imager with continuous zoom, a PIRANHA 36 colour CCD (Charge-Coupled Device) TV camera with an x36 zoom lens, a Cassidian Optronics LP17D eye-safe laser rangefinder and an HPLT V.7 laser designator.
At the 2018 Euronaval Exhibition in Paris Chess Dynamics promoted the most recent members of its SEA EAGLE family of fire-control systems. SEA EAGLE FCRO combines the company’s stabilised long-range EO tracking and ballistics system with a marinised Weibel doppler radar capable of tracking targets at ranges greater than 35 km in all weather conditions, day or night, while the SEA EAGLE FCEO-MK4 Electro-Optical Fire Control Director Stabilised System combines thermal and TV sensors with a laser rangefinder.

The VAMPIR NG infrared search and track (IRST) system onboard Australia’s ANZAC class frigates
Photo: Safran Electronics and Defense

VAMPIR-MB (Modular Bispectral) from Sagem (now Safran Electronics & Defence) was adopted for the French Navy’s aircraft carrier CHARLES DE GAULLE, and for some of its air-defence and anti-submarine frigates, while Italy uses it on its HORIZON class destroyers, and South Korea has it on its KDX-III AEGIS destroyers and LPX class amphibious assault ships (LHD). Australia selected the follow-on VAMPIR-NG (Veille Air-Mer Panoramique InfraRouge – Nouvelle Generation) infrared search and track (IRST) system for its ANZAC class frigates, LHDs, and HOBART class destroyers. Designed to meet the needs of ocean and littoral operations, VAMPIR-NG uses third-generation MWIR thermal imaging technology to provide high-definition long-range and panoramic coverage. It is designed to automatically detect and track threats such as incoming anti-ship missiles.
Coastal Surveillance
EO systems can also play a role in role in coastal surveillance. For example, the Controp Precision Technologies TORNADO-ER panoramic infrared scanning system uses two cooled MWIR thermal imaging channels fitted with 100 mm and 400 mm focal length lenses respectively to automatically detect targets ranging from large vessels to small floating objects or even swimmers at ranges of 400 m to 12 km.
In the same way that advanced naval radars are using fixed-array antennas rather than the more traditional rotating array, EO/IR systems are starting to use multiple fixed arrays. Thales’ GATEKEEPER EO/IR surveillance and alerter system uses an array of four fixed sensor heads – each houses uncooled long-wave infrared (LWIR) thermal imagers operating in the 8-12 micron region of the spectrum, and high-definition (HD) colour TV cameras. The latter can be used in daylight to help identify and classify targets detected by the LWIR sensors. Since each sensor head covers 120 degrees in azimuth, they provide a useful degree of overlap. The system’s video processing unit uses advanced algorithms to provide automatic detection and tracking of targets. GATEKEEPER is teamed with the SEASTAR active phased-array radar in the integrated mast, which first entered service on the upgraded Dutch KAREL DOORMAN class frigate, VAN SPEIJK.
As part of its recently-completed refit programme, the French aircraft carrier CHARLES DE GAULLE has been equipped with the Thales Optronique ARTEMIS (Advanced Reliable Third-generation Electro-optical Multiplexing Infrared Search-and-track) system. Already operational on board FREMM multi-mission frigates in service with the French, Moroccan and Egyptian navies, this uses an array of three fixed MWIR sensors to perform surface surveillance out to the horizon during the day and night. These sensors incorporate electronic image stabilisation, and provide 360 degree panoramic surveillance of the surface and any nearby coast line. Being fixed, they have data refresh rates 10 times higher than those of a scanning IRST system, so can detect and classify a broad array of airborne, maritime and land-based threats faster than was possible with earlier-generation sensors.
Thales is currently working with DRT Technologies to develop an ARTEMIS derivative known as OMNISTARE. It is being proposed for use on the planned class of fifteen new BAE Systems Type 26 frigates that is expected to replace Canada’s current IROQUOIS and HALIFAX class warships beginning in the early 2020s. ARTEMIS is designed to automatically detect, track and classify both air and surface targets simultaneously, detecting and tracking manoeuvring and stealthy threats as well as surface asymmetric threats.
EO Fire Control
One of the most basic tasks assigned to naval EO systems is to act as part of the fire-control system for gun and missile systems. Subsystems such as thermal imager, image intensifying camera, or a laser range-finder can be used singly or in combination to point the weapon system towards its target.

Work on Ball Aerospace & Technologies Corporation’s STALKER Long-Range Electro-Optic/infrared/laser Sensor System (SLREOSS) started in 2008 to meet an urgent USN requirement for a system to combat fast attack craft/fast inshore attack craft. Three prototype systems deployed and cross-decked across a variety of US Navy warships were followed by eight developmental models, and in 2014 the company received a US$23.9M contract from the NATO SEASPARROW Project Office covering the manufacture, test, and deployment of production hardware. SLREOSS combines long-range visible-band and IR sensors with a laser rangefinder. Intended to be a form/fit replacement for the Mk 16 low-light-level TV camera mounted on the Mk 9 Tracking Illuminator System of the Mk 57 NATO SEASPARROW Surface Missile System (NSSMS), it was designed to provide multispectral target imagery and accurate range data.

Two Electro-Optic/Infrared sensors placed forward and aft of the USS DWIGHT D. EISENHOWER’s island provide 360 degree surveillance capability
Photo: US Navy

Naval Group has selected Safran Electronics & Defense’s PASEO XLR (eXtra Long Range) optronic fire control system for integration on the French Navy’s new medium-size Frégates de Taille Intermédiaire (FTI). Each vessel will be fitted with a pair of two-axis stabilised turrets. Derived from the DALAS (Dispositif díaide à I’Appontage au Laser) NG deck approach and landing laser system developed for the aircraft carrier CHARLES DE GAULLE, these will house a high-definition television (HDTV) camera, a SATIS XLR infrared imager, and an eye-safe laser rangefinder. An optional short-wave infrared (SWIR) channel operating in the 0.9-1.7 micron region of the spectrum could be provided to enhance performance under foggy conditions.
Safran Electronics & Defense Australasia is to supply the latest version of its VIGY ENGAGE electro-optical surveillance and fire control multisensor system for installation on the 12 new offshore patrol vessels (OPVs) due to enter service with the Royal Australian Navy. VIGY ENGAGE is a full panoramic stabilised long-range sighting system that can act as the primary optronic system aboard small naval craft such as fast patrol boats, or can supplement the other sensors on larger vessels. The stabilised head weighs less than 20 kg, but houses a 1,024×768 pixel colour video camera with 40, 12 and 2.4 degree fields of view, a cooled thermal imager based on a MWIR focal plane array, and an eye-safe laser rangefinder.
The functionality of the VIGY 105 EOD and VAMPIR MB are combined in the company’s EOMS and EOMS NG systems. These use a panoramic sensor head housing a SWIR or MWIR thermal imager, TV camera, and laser rangefinder. The main user is the French Navy, which has installed the EOMS NG on its FORBIN class destroyers, FLORÉAL class and CASSARD class frigates, and MISTRAL class amphibious ships. The UAE’s BAYNUNA class FAC also have the EOMS NG, while Finland and Bulgarian have the older EOMS.
Rheinmetall Defence Electronics’ MSP 600 is on service on German Navy frigates, including the F124 SACHSEN class and new F125 BADEN-WÜRTTEMBERG class, and is also used by the Malaysian and Finnish Navies. A development of the earlier MSP 500, it combines a high-resolution LWIR thermal imager, a daylight TV camera with a zoom lens, and a laser rangefinder.
The BADEN-WÜRTTEMBERG class frigates are also fitted with a Diehl Defence Ship’s Infrared Monitoring Observation and Navigation Equipment (SIMONE) IRST system. This relies on a combination of single-sensor and multi-sensor modules based on LWIR sensors whose output is electronically combined to provide 360 degree coverage of the sea surface out to ranges of up to several kilometres. It is intended to automatically detect asymmetric threats approaching the ship by air or on the surface.
Rafael’s TOPLITE EO turret is based on technology from the same company’s aircraft-mounted LITENING EO pod. Designed for use on land, naval and air platforms, TOPLITE can be fitted with up to four sensors. The system typically weighs 60-65 kg, and has four-axis stabilisation. As TOPLITE evolved, later models introduced higher-performance sensors. For example, while TOPLITE III featured a third-generation 640×480 pixel MWIR sensor, TOPLITE MHD was fitted with a third-generation 1,289×1,024 MWIR sensor, while the colour TV camera gave way to an HDTV version with visual and IR (VIR) and near-IR (NIR) capability. Both versions included a laser rangefinder and a laser marker.

Leonardo’s MEDUSA Mk4 is the latest in a series of EO fire-control systems.
Photo: Leonardo

Leonardo Land & Naval Defence Electronics offers the MEDUSA Mk4, the latest in a series of EO fire-control systems that included the NA-18, PEGASO, and earlier members of the MEDUSA series. Its sensors are the classic combination of thermal imager, daylight TV, and laser rangefinder, and the company promotes is as suitable for use as a surveillance system, as one component of a more complex naval fire-control system, or as a stand-alone fire-control system.
EO or EO/IR sensors can also be mounted on a weapon such as a gun or missile launcher. The Type B version of the OTO Melara FORTY LIGHT 40mm naval gun system incorporates a high-resolution daylight TV camera that gives the weapon a reversionary autonomous mode to supplement the normal remote-control operation via the ship’s combat management system. The Type C has a stand-alone fire control system based three EO sensors – daylight TV, a cooled thermal camera, and an eye-safe laser rangefinder. Even a light weapon such as FN Herstal’s SEA DEFNDER remote weapon station armed with a machine gun of 12.7mm or even 5.56mm calibre can incorporate a sight module that can be fitted with a CCD camera and cooled or uncooled IR sensor as required by the customer.
Submarine Periscopes
During 1970s the evolution of EO technology such as lowlight TV image intensifiers and thermal cameras reached the point where these could be integrated into the traditional submarine periscope. However their imagery was still displayed in the instrument’s eyepiece. The traditional periscope requires a deep penetration into the pressure hull, a deep well into which its tube can be retracted, and heavy hoist mechanism located within the structure of the fin or sail. Elimination of the direct-view optics and total reliance on the electronic imagery allowed the creation of the optronic mast – a multi-sensor system whose output is passed to the control room or other locations within the pressure hull via an electronic cable.
EO Masts
Work on the Kollmorgen (later L-3 KEO, and now L3 Technologies) AN/BVS-1 Photonics Mast Programme (PMP) began in 1995, and the resulting system had an EO IR suite made up of an MWIR staring-array thermal imager, a low light level TV camera, a colour HDTV camera; and an eye-safe laser rangefinder. It also incorporated an extensive radio-frequency (RF) suite that included ESM, radar, GPS, and communications antennas. As a result, its sensor head was 18 inches (c.46 cm) in diameter, so had a distinctive appearance which – if sighted by an opponent – betrayed the presence of a US submarine. It also had a significant radar cross-section that increased the probability of detection by enemy surface ships and aircraft.
In 2012 contracts were awarded for the development of a Low-Profile Photonics Mast (LPPM) that was intended to provide as much of the PMP capability as could be installed in a sensor head whose diameter of approximately 7.5 inches (19 cm) was similar to that of a traditional periscope. Developed by what was then L-3 KEO, the LPPM entered service in 2015 on Virginia-class submarines.
Like a traditional periscope, the PMP and LPPM had to be rotated in order to provide full 360 degree coverage. A follow-on concept called the Task-Oriented Technical Insertion Mast (TOTIM) is intended to produce a mast incorporating staring sensors covering a full 360 degrees, and able to house interchangeable subsystem modules that would allow the mast to be reconfigured as required to suit changed conditions or even individual missions, or even modernised by the installation of improved subsystems. The maximum diameter of 8.5 inches (21.6 cm) is expected to including any treatments required to meet RCS reduction requirements, but when seeking potential contractors in 2016 the USN accepted that this target may not be achievable, so asked responders to indicate how the outside diameter could be minimised while still meeting the performance requirements.
In the early 1990s what was then Barr & Stroud (now Thales UK) began development of what would become the CM010 family of optronic masts. Following a successful test and evaluation installation on board the TRAFALGAR class submarine TRENCHANT, masts from the CM010 family were selected for service on the UK’s new ASTUTE class SSNs. The CM010 has a three-axis stabilisation system which operates at sub-pixel accuracy, countering the effects of submarine movement in rough sea conditions. A range of thermal imaging, image intensification, and colour HDTV sensors can be selected by a customer, and the mast can also house antennas for ESM, communications, and GPS. The CM010 has also been adopted by Japan, where it is manufactured by Mitsubishi Electric Corporation (MELCO) for installation on SORYU class submarines. The Japanese Navy was not prepared to rely totally on an optronics mast, but fitted the SORYU class with both a conventional periscope and a CM010 mast.
In France, Safran Electronics & Defense (formerly Sagem) developed the Series 30 search optronics mast system (SOM). This is dual-axis stabilised, and can accommodate a high-definition MWIR thermal imager, colour HDTV camera, a low-light camera, and an eye-safe laser rangefinder, as well as EW and GPS antennas. Adopted for the French Navy’s SUFFREN class SSNs, the Series 30 SOM has attracted export orders from Brazil, Chile, India, South Korea, Malaysia, and Sweden. It also formed the basis for Safran Electronics & Defense’s low-signature Series 30 Attack Optronic Mast (AOM).
While still Sagem, the company was also responsible for the Optoradar Mast System (OMS) fitted to the French Navy’s LE TRIOMPHANT class ballistic-missile submarines. This carries a dual-field of-view infrared charge-coupled device [IRCCD] thermal imaging system, an HDTV system with two magnifications, and antennas for an X-band navigation radar, ESM, and GPS.
Series production of the Hensoldt Optronics OMS 100 optronic mast system started in 1999, and the system has been adopted by Germany, Greece, India, Indonesia, Italy, South Korea, Portugal, and Turkey. It can be installed alongside the same company’s SERO 400 direct-view periscope. 2012 saw the introduction of the OMS 110 optronic mast, which features a dual-axis stabilised sensor package that includes a high-resolution TV camera and MWIR thermal camera (both fitted with zoom lenses), and an eye-safe laser rangefinder. The follow-on OMS 200 teams a high-resolution TV camera with an SWIR thermal camera, but an additional MWIR thermal camera can also be housed in order to provide imagery under conditions that the SWIR camera would find difficult.