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Monday, June 1, 2009

Serious Squall

The data fusion avionics of the Dassault Rafale (Squall) represent a benchmark in advanced combat systems

Jean-Michel Guhl

The Dassault Aviation Rafale is the newest combat aircraft serving France’s Air Force and Navy. Over the past few years, the twin-engine fighter has replaced the Armée de l’Air’s older Jaguar fighter-bombers and the Aéronavale’s vintage F-8E (FN) Crusader ship-borne interceptors. It is presently in service with four squadrons.

In the near future, the Rafale is scheduled to supersede all remaining versions of the famous Mirage 2000 still in service with the French air force. By 2015-2020, it should become the linchpin of French military aviation, with an operational career lasting through 2050, especially as a lack of funds over the coming decades will prevent the development of any new French manned combat aircraft.

Conceived during the early 1980s and flown for the first time in prototype form in 1986, the Rafale could already be regarded as an "old" aircraft when compared to the Lockheed Martin F-35 Lightning II. But this is not the case, as the fly-by-wire (FBW), delta wing with canard-configured Rafale features one of the most advanced combat systems designed to date, both in terms of avionics and weapons.

The Rafale is a self-supported combat aircraft, 100 percent manufactured in France by Dassault Aviation for the airframe, with Thales, Sagem, Snecma and MBDA providing main subsystems. It has been produced in three standards: F1 (no longer operational), F2 (on the way out) and F3 (current). All models of the F2 standard are being upgraded to the F3 standard, which is the first true "omni role" variant of the fighter.

The present-day Rafale features some of the very latest avionics, including the Thales RBE2 multi-mode radar (the first in Europe with two-plane electronic scanning), advanced Sagem Gerfaut helmet-mounted display, Spectra defensive countermeasures system and OSF, a jam-resistant, advanced passive optronic surveillance and imaging system with laser rangefinder.

‘Omnirole’ Capability

Designed from the outset as a multi-role, low-observable combat aircraft with a diminutive radar cross section, and dubbed an "omnirole" fighter by Dassault Aviation, the Rafale is to replace all the existing combat aircraft in the French military aviation inventory, including the Mirage IV nuclear bomber.

It was reported in April that the Rafale had been eliminated from India’s $10 billion Medium-Range Multi-Role Combat Aircraft competition for 126 jets, leaving the Eurofighter Typhoon, Saab Gripen, MiG-35, Boeing F/A-18 and Lockheed Martin F-16 in contention. However, the Rafale remained in play in fighter competitions in Brazil, Switzerland, UAE and Kuwait.

The Rafale’s omnirole or "joint" capability was required by the French Ministry of Defense 20 years ago so that in the 21st century, the French air force could carry out the widest range of missions with the smallest number of aircraft.

The demand was the same on the part of the French Navy, which should receive 60 Rafales over the next decade to equip three ship-borne squadrons on board the aircraft carrier Charles de Gaulle. The French Air Force has requested 234 Rafales to fit out a minimum of 10 squadrons.

Current variants of the Rafale are the single-seat Rafale M for the Aéronavale, the single-seat Rafale C and the two-seat Rafale B for the Armée de l’Air. In French, M stands for "Marine" (Navy), C for Chasse (fighter) and B for Biplace (two seats). A two-seat strike attack model for the Navy, called Rafale N, was cancelled in 2005.

The types of missions assigned to the Rafale range from combat air-interdiction, including quick reaction alert and round-the-clock air defense, to ground attack and sea strikes, to deep nuclear strike missions with the MBDA nuclear-tipped ASMP-A cruise missile, expected next year. With its twin-engine architecture (two Snecma M88-3 turbofans) and a sophisticated self-protection concept that includes stealth characteristics, the Rafale enters the fight with a high level of survivability.

In addition to the AASM air-to-ground modular weapons, the fighter carries a comprehensive panel of strike weapons such as the MBDA SCALP EG cruise missile or Raytheon Paveway II/III laser-guided bombs.

Very soon, the Rafale F3 variant should be available for reconnaissance missions using the Thales Areos Reco NG airborne reconnaissance pod and for naval strike missions with the Exocet Block 2 anti-ship missile.

Data Fusion

The Rafale F3 not only integrates the largest and most modern range of sensors, it increases their efficiency through multi-sensor data fusion, allowing the aircraft to become a key element of a wider Network Centric Warfare system.

In this regard, Rafale crews, along with French Army Sperwer tactical UAV crews, this past winter developed a series of new procedures for launching the AASM rocket-bomb. The bomb is programmed in flight at the last moment from real-time reconnaissance coordinates of ground targets spotted by the Sperwer UAV flying at low altitude forward of a Rafale strike party.

The data fusion process between all onboard sensors is the essential difference of the Rafale. The core of the enhanced capabilities lies in the Thales Modular Data Processing Unit (MDPU). According to Dassault Aviation, it has a processing power 50 times higher than that of the 2084 XRI-type computer fitted on the early versions of Mirage 2000-5. The MDPU is the cornerstone of the avionics/weapon upgradeability of the Rafale.

AESA Radar

While the first 100 or so Rafales were fitted with the early Thales RBE2 radar, the most important sensor of the next generation Rafale will be the new Thales RBE2 AA active electronically scanned array (AESA) radar, which will replace the passive array of the RBE2.

Thales completed its first active phased array, comprising 1,000 gallium-arsenide Transmit/Receive modules, in 2006. In late April this year, the company said the RBE2 AA had successfully completed a new series of tests on Rafale, carried out jointly with the French DGA defense procurement agency, at the Cazaux flight-test center.

"This milestone marks the latest step toward qualifying the RBE2 AESA radars this year in readiness for delivery of the first two units to Dassault Aviation during the first quarter of 2010," Thales stated. "The radars will be installed on the aircraft in 2011 for delivery to the French Air Force early in 2012."

In operational terms, the RBE2 AA radar can track many targets in the radar field of view irrespective of the relative location between targets and/or the host aircraft. In addition, the radar provides a significant increase in detection range on enemy aircraft and a significant increase in reliability with respect to previous-generation radars.

Since the AESA radar antenna comprises a very large number of active modules, the failure of some of these modules has no noticeable effect on the overall performance and reliability of the system. Consequently, the active front end only requires maintenance every 10 years or more, thereby contributing to increased aircraft availability and reducing replacement part costs.

The RBE2 is a track while scan, monopulse-doppler X-band multimode fire-control radar system built around a modular concept. Air-to-air tracking and air-to-ground mapping functions can be interleaved due to the radar’s agile beam sweeping capabilities.

Fitted in the aircraft’s pointed nose, the RBE2 provides +/- 60 degree azimuth and elevation coverage and includes the SB-25A MkXII compatible IFF interrogator/transponder with Mode S capability. The IFF system uses phased array antennas just like the Spectra active electronic countermeasures (ECM) antennas.

The present radar air-to-air modes include long-range search; multi target track and engagement; air combat modes; Non-Cooperative Target Recognition (NCTR); and look down/shoot down functions. In air-to-air mode, the RBE2 gives a tracking range beyond 60 nautical miles against a 30-square-foot target, with detection ranges up to 75 nautical miles. The radar can track and prioritize up to 40 targets simultaneously and engage up to eight with Mica, and soon Meteor, air-to-air missiles.

The RBE2 air-to-ground modes include: Doppler Beam Sharpening (DBS) mapping; SAR mapping; Fixed Target Track (FTT); Sea Surface Search and Track While Scan; Ground Moving Target Identification and Track (GMTI/T); target acquisition and air-to-ground ranging. Terrain following and avoidance modes can be combined to generate 3-D radar maps, thus enabling full automatic terrain following flights using the radar only.

The Rafale also can rely on several other sensors:

  • Front-Sector Optronics (or OSF for optronique secteur frontal) system, developed by Thales (for TV) and Sagem (IR). Integrated over the aircraft’s nose in the form of a double ball, it can operate in the optronic wavelengths and provide long-distance tracking in the full passive mode. It is immune to radar jamming and provides covert long-range detection and identification, high resolution angular tracking and laser range-finding for air, sea and ground targets.

  • Spectra EW system, developed by Thales and MBDA, provides a multi-spectral threat warning capability against hostile radars, missiles and lasers. According to test pilots who have flown the Rafale, the EW system provides the aircraft with the highest survivability assets against airborne and ground threats to date. It also provides passive, 360-degree tactical situation awareness.

Considered a fully automatic self-protection system, Spectra provides passive, all-weather reliable, long-range detection, identification and geographical location of threats in the infrared, electromagnectic and electro-optical ranges. It uses short response times and cutting-edge defensive measures based on a combination of jamming, decoying and evasive maneuvers and technologies, such as Digital Radio Frequency Memory (DRFM) for signal processing.

The efficiency of Spectra notably was demonstrated in 2008 at the Red Flag exercise at Nellis Air Force Base, Nevada, where during all sorties the Rafale escaped SAM missile threats. This followed a successful demonstration at the NATO MACE electronic warfare campaign in Europe.

The angular localization performance of Spectra makes it possible to precisely discover ground threats and to target them for immediate destruction with precision-guided munitions. In this totally passive mode, Spectra is also used as a general awareness and intelligence reporting system.

Instrumental in the Spectra’s performance is a threat library that can be defined, integrated and updated on short notice by users in their own country, allowing agile and continuous enhancement of the aircraft’s protection as operations unfold. Being of modular design, the system is controlled by a dedicated computer with three processors.

  • Real-time NATO Link 16 tactical data link, allowing encrypted communication with other aircraft as well as with fixed and mobile command and control centers, while providing a source for tactical data onboard.

  • Thales IFF system yields information on any platform in the battlespace.

Additional Sensors

For conventional strike and reconnaissance, the Rafale F3 can be fitted with the Thales Damocles optronic multifunction pod or the Areos stand-off optronic reconnaissance system.

Damocles is a multi-function optronic pod comparable to American or Israeli-designed podded systems. Its laser designation function enables full day and night laser-guided weapons capability. The IR sensor of the Damocles operates in the mid-wave infrared band, allowing it to retain its effectiveness in warm and/or humid conditions. It is interoperable with all existing laser-guided weapons and provides outstanding performance for long-distance recognition.

Equipped with an embedded digital recorder, the Damocles pod provides a tactical reconnaissance capacity with post-flight images analysis. A FLIR navigation module is part of the pod. It provides an infrared image superimposed on the pilot’s display combined with the data supplied by the navigation and weapon system.

Areos, or Reco NG in French parlance, is a full imagery intelligence (IMINT) system composed of an airborne pod and a ground station.

The Rafale already is combat proven. Today, French Air Force Rafales daily fly from Kandahar, Afghanistan, in support of ISAF and Afghan National Army operations against Taliban rebels. The aircraft is being used to deliver AASM and Paveway II bombs, or to perform 30mm gun passes during missions in support of the Afghan army, French troops and NATO allies.


Rafale F3 Avionics Suite

Today’s Rafale F3 features a fully integrated digital avionics suite with a modular core architecture. The modular data processing unit (MDPU), a mission computer comprising 18 processor modules, hosts software for most of the aircraft’s systems and forms the heart of the avionics suite.

Avionics integration is assured by linking the various systems via four to six Mil-Std-1553B databuses and one optical STANAG 3910 databus. Communication between the aircraft’s onboard systems and its weapons is enabled by a pair of Mil-Std-1760 databuses.

The Rafale’s navigation suite includes two Sagem SIGMA 95 laser gyro inertial navigation system (LINS) platforms with embedded hybrid NSS-100 GPS units. The LINS allows flight plans with up to 600 waypoints to be programmed and stored.

Additional navigation equipment includes the NC-12E TACAN radio navigation system, the TLS-2020 multimode receiver, which includes VOR and ILS/MLS functions, a digital map generator (DMG), a digital terrain reference navigation system, and the digital AHV 2930 radar altimeter, operational to 10,000 feet and optimized for discretion and high performance at very low altitudes.

Communications equipment comprises EAS TRA 2020 V/UHF radios for civil communication and secured TRA 6032 radios for tactical military communications. The aircraft additionally features the MIDS-LVT/Link 16 bi-directional data link terminal for secure and jam resistant near real-time communication and data exchange. The high-rate data link provides tactical data in combined air operations with other friendly assets, such as other aircraft in the formation, airborne and surface command and control centers and forward air controllers. NATO Link 16 as well as non-NATO solutions can be provided at the customer’s option.

In support of its mission systems, the Rafale relies for all sorties on the Sagem SLPRM, or Système Local de Préparation et de Restitution de Mission, a portable computer system enabling the preparation of an operational mission on a standard flash card that is later inserted in the Rafale’s main navigation computer.

Rafale recording systems include a Thales ESPAS digital solid state flight data recorder and an OTA 1320 CCD TV camera plus recorder for VTH/HUD video footage. The recording systems record maintenance data as well. An integrated health and usage monitoring system features fully integrated and automated built-in test equipment along with sensors and digital recorders for airframe structure and engine components life monitoring. — Jean-Michel Guhl

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