“EMBEDDED SYSTEM DESIGN”(space )

 

INTRODUCTION

 The only way to provide safety to commercial passenger aircrafts from surface launched missiles is to incorporate a system within the aircraft which automatically detects the launch of the missile along with its direction and velocity and confuse the electronics of the missile. A leading technology is a directed laser device adapted from the military that blinds heat-seeking missiles.
                  Modern military aircrafts have for years had antimissile defenses largely relying on decoys such as flares fired from the aircrafts to distract or confuse attacking heat seeking missiles. The most recent incarnation is a Directional Infra-Red Countermeasures System, which consists of a double gimbaled turret that automatically detects the launch of a missile and then aims a laser beam at it to disrupt the missiles heat tracking sensor system, effectively blinding it.
                  The DIRCM concept has been under development for some time by the Department of Defense for protection of military and other government aircraft. Laser-based Directed Infra-red Countermeasure (DIRCM) jamming systems are at the leading edge of technology for the protection of aircraft against advanced air-to-air and surface-to-air infra-red weapon systems.
                    DIRCM will protect a wide variety of aircraft platforms, both rotary and fixed wing, against modern infra-red ground launched heat-seeking missiles. The system is readily upgradeable to meet the continually changing and emerging threats faced by modern aircrews and is a joint program for the UK Ministry of Defense and the US Special Operations Command. It operates completely autonomously using its own missile warning system. This alerts it to an impending attack and points a powerful lamp at the incoming missile to jam it and cause it to fly harmlessly away from the aircraft.
                       To develop DIRCM system the Department of Homeland Security issued a tender .One of the Prime Contractors the Northrop Grumman, won the bid and in turn subcontracted large parts of the system design and production to BAE SYSTEMS and the aircraft installation programs to a number of aircraft design companies. The system is being procured collaboratively with the US Special Operations Command under the terms of an MOU through a contract managed by the UK.  The problem of introducing the military DIRCM in to large passenger aircrafts is that the speed of passenger jets is much slower when compared to that of fighter aircrafts, so the infrared missile hits the aircraft before the latter detects the missile and diffuses it. So a system which could react faster than the military DIRCM should be developed, thus a LAIRCM (large aircraft infrared countermeasures) system evolved. In the LAIRCM system, a very powerful IR sensor unit and a MURLIN laser replaced their counterparts, while the other units remained unchanged as in the military DIRCM. There were several issues associated with the potential antimissile concepts that the Department of Homeland Security proposed to explore, before giving a green signal to the LAIRCM project they are:
System cost, including component, integration, and certification;
 Airframe & avionics integration and FAA certification issues;
 Performance against the current and emerging threat;
 Reliability and failure rate;
 Maintenance, including built-in testing, handling, and special ground support equipment needs; Operating and support costs;  Concept of operations, including air crew involvement, go/no-go doctrine, and airport operational procedures

THE NEMESIS DIRCM

  Defending against the IR-seeker weapon requires covering a number of bases, including recognition of a potential threat, identifying it, determining its range and lethal zone, how it's guided, and more. And as countermeasures evolve, we can optimistically look forward to more choices of defense than that related by one military retiree, who suggested from his own experience that, "Your best defense is to pop back into the hole you came out of.” The LAIRCM system is technically called the NEMESIS DIRCM. The AN/AAQ-24(V) NEMESIS Directional Infrared Countermeasure (DIRCM) system is the only DIRCM system in production today that will protect aircraft from today's infrared guided missiles. AAQ-24(V) NEMESIS is a modular system comprised of a family of proven components that can be mixed and matched (based on specific platform, mission and budget requirements) to protect a wide range of large and small aircraft, both rotary and fixed wing. The modular upgrades available will ensure protection against emerging threats.

ARCHITECTURE OF NEMESIS DIRCM:

The NEMESIS DIRCM basically consists of four functional blocks, which have their unique job to work out, they are
           1: Missile warning system
           2: Processor unit
           3: Transmitter unit
           4: Control indicator unit

 MISSILE WARNING SYSTEM

MISSILE WARNING SYSTEM

AN/AAR-54(V) is a fourth-generation Missile Warning System (MWS), developed by the Northrop Grumman now in production and available for use on wide body aircraft. This compact, light weight system provides outstanding clutter rejection, long range and short shot missile detection, rapid automatic cuing to the countermeasures system, and increased situational awareness capabilities via heads-up display(HUD) or radar warning receiver (RWR) display .Designed for high performance protection, theAAR-54 passively detects ultraviolet (UV) energy from the missile’s exhaust plume, tracks multiple sources, rapidly and accurately classifies each source, and provides threat information to the countermeasures system for optimum response. The AAR-54 can be interfaced to a chaff/flare Countermeasures Dispenser System (CMDS) or integrated as part of a Directional Infrared Countermeasures (DIRCM) self-protection suite. System simplicity allows for internal installations or external mounting in a pod or pylon.                                             A system consists of from one to six high-resolution, enhanced-performance UV sensors and one Electronics Unit (EU). A unique, compact design approach results in a system with the lowest size, weight and power requirements. The system provides high mean time between failures (MTBF), even without external cooling, and low mean time to repair (MTTR). The AAR-54 is designed for an MTTR of 30 minutes. Comprehensive BIT/FIT, in conjunction with the high system reliability, allows for the implementation of a low life-cycle cost, two-level maintenance concept.

Demonstrated Benefits

• High sensitivity for extended detection range.
• Mature declaration software provides high probability of missile detection   while it minimizes false alarms.
• Full spec performance across entire 120º FOV.
• High resolution to separate threats in proximity to clutter.
• No mission programming required.
• Multiple interface options: RS-422, MIL-STD-1533, discretes.
• Supports chaff/flare and DIRCM countermeasures.
• Compact design offers lowest size, weight, power.
• No cooling required.
• Fine AOA as required for precise threat location.
• All weather operation from -54ºC to +71ºC.
•  Flexible installation options including internal or external in a pod or pylon.

PROCESSOR UNIT 

The DIRCM designed by the Northrop

Grumman is equipped with a processor, which ensures flexibility, availability and
Upgradability .a modular software architecture for ease of maintenance and
Enhancement is installed .the processor is
Also installed with a modern digital signal
Processing tracking algorithms for accurate
Pointing and tracking. The processor
Receives signals from missile warning system and evaluates it. The processor then decides whether there is a threat or not (i.e) whether a missile is approaching the flight .If it is so, the processor then sends a signal to the transmitter about the approaching threat.

TRANSMITTER UNIT

DIRCM is provided a transmitter high-resolution staring fine track sensor for accurate track in clutter environments. The transmitter contains a high reliable, high irradiant broadband lamp. The transmitter is compatible with four axis-systems so that it could be mounted on an aircraft
 In any orientation. An upgradeable laser Ready path and laser auto bore sight compatible with future IRCM laser sources has also been introduced in the transmitter. The Transmitter is equipped with MURLIN laser which is a very highly sophisticated laser that generates multiple, simultaneous laser spectral lines within the infra-red window in which a missile's heat-seeking sensors 'see' their target. The laser overwhelms these target sensors, causing the missile to go out of control. MURLIN uses optical parametric oscillators (OPOs) to produce a laser beam, which is tailored by control algorithms to match the IR sensors of potential threat missiles. The transmitter receives the threat information from the processor and slews to the location of threat and FTS acquires the signals the FTS locks on to the threat and tracks by slewing the transmitter. The transmitter sends a modulated beam of IR energy to the missile seeker and jams its guidance signal.

CONTROL INDICATOR UNIT

 This unit provides the operator control over the DIRCM system. The smart card in this unit enhances commonality so that the same DIRCM can be used for any other application and upgradeability in future.
The control indicator unit enhances the reprogramming of OFP and jamming techniques without removing the hardware, so that the system could be upgraded.
The control indicator unit maintains the interface between different units of the DIRCM system. This unit is also used to diagnose the faults in the system and to store the aircraft specific parameters.

 PRINCIPLE AND WORKING

           Plume emissions, emissions of the hot engine parts, control system parts and emissions from warm avionics bay make the atmosphere near the aircraft hot while the cool clouds and wind keep the surrounds of the aircraft cooler, which can be seen in the figure. Thus there is a variation between the temperature which is made use of by the heat-seeking missiles. Infra-red guided missiles utilize passive sensors to lock on to the heat from an aircraft's engine. Unlike radar-guided missiles, they do not radiate energy in order to illuminate their target.A DIRCM system confuses the IR seeker in the nose cone of an incoming missile, prompting it to plow into the ground well short or well wide of its intended target. An on-board DIRCM system first warns of an incoming IR missile up to 10 miles away and then hands off the information to a jammer. This jammer uses an IR tracker to follow the missile and guide a laser beam onto its nose, which houses the IR seeker. The system then transmits jamming signals that send the missile off target.
                  Here's where things get really complicated. For each IR missile type, there is an optimum set of jamming algorithms. Since a DIRCM system can't identify specific missiles, it uses generic jamming algorithms or else sequences through a catalog of specific jamming codes. The IR tracker measures the effectiveness of the jamming as it tracks the incoming missile. Through trial and error it determines which algorithms work—all in as little as 3 seconds.
                  Researchers have achieved remarkable success with a novel laser designed to disable heat-seeking missiles. The multi-band IR (infra-red) device is designed to be superior, in terms of cost, size and effectiveness, to both current and next generation missile countermeasure lasers.The novel multi-band solid-state laser can quickly and effectively disable the sensors of an infra-red seeking missile, jamming them and causing the missile to 'porpoise' out of control.
The heat of the laser fools the missile into thinking the plane is somewhere else. The missile will thus fly off somewhere into the ground.

     When a missile is fired at an aeroplane the NEMESIS DIRCM system which has been incorporated in the aeroplane reacts to the situation in the following manner, which can be divided in to four phases. In the first phase the sensor in the Missile Warning System (MWS) passively detects the UV energy from the exhaust plume of the missile and then the Missile Warning System sends the signal to the processor, the second phase of diffusing the missile starts here.
                    The processor receives the signal sent by the Missile Warning System , evaluates the signal and then decides whether there is a threat to the aircraft or not .
In case of a threat the processor sends a signal to the transmitter to track, slew and then jam the electronics of the missile by sending a modulated beam of IR energy to the missile seeker in the last phase of diffusing the missile.

UPGRADE OF “NEMESIS DIRCM“SYSTEM

 NEMESIS has undergone several recent upgrades. The MIMS Two-Color Infrared Missile Warning Sensor has been added, which improves dealing with threats detected against a highly cluttered background. The two-color IR concept permits spectral discrimination between target and clutter IR signatures. A prototype MIMS sensor has undergone three generations of upgrades and has participated in live fire tests involving a variety of threat missiles at Pendine, Wales; Meppen, Germany; and WSMR.Northrop Grumman and Fibertek Inc. have collaborated to develop a modular, compact, air-cooled, all-band laser for IRCM applications, known as the Viper, a modular upgrade to the existing NEMESIS system.
                 Viper fits in a truncated, pancake-like chassis of 13-inch diameter and 2-inch height. The entire laser chassis mounts directly to NEMESIS transmitters. The current, flight-qualified prototype version of this laser weighs less than 10 pounds, uses 320 Watts of electrical power, and delivers jamming energy in Bands I, II, and IV at significant levels above that of a lamp-based system. As another part of the NEMESIS product improvement program, a new transmitter called WANDA is being developed. WANDA is a miniature, all-laser based transmitter which takes advantage of the lack of large arc lamps to provide higher performance in a smaller, lightweight, low drag package. WANDA has a four-axis gimbaled system, which can effectively jam at nadir allowing for mounting in any position on the aircraft.

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