JOURNAL OF BATTLEFIELD TECHNOLOGY VOL 11, NO 1, MARCH 2008 39

HIGH-FIDELITY INFRARED SIGNATURE MODELLING USING MATLAB VIRTUAL REALITY TOOLBOX

Shahid Baqar, Mark Richardson,1 and Robin Jenkin

Abstract. In light of the increasing terrorist surface-to-air missile (SAM) threat to civil and military aircraft, there is a continuing need for a high-fidelity, low-cost, PC-based, infrared (IR) signature scene modelling and simulation capability which could be used for development, testing, and evaluation of IR systems. An IR signature simulator has been developed utilizing the MATLAB Virtual Reality Toolbox software with the ability to adapt to rapidly changing tactical environments. It can model the IR signature of military targets in a 3D environment with special effects.

1 Department of Aerospace, Power & Sensors, Cranfield University at the Defence Academy of the United Kingdom, Shrivenham, SN6

8LA, United Kingdom.

INTRODUCTION

The advancements in the computational capabilities of personal computers (PCs) has been so rapid that a job which a few years ago, was difficult for the expensive high-end proprietary workstations to perform, can now be done easily by a low-cost PC [1]. The military simulation community has taken advantage of this trend and has developed low-cost, PC-based, high-fidelity simulators for military applications.

Fidelity of the Model

In the application of developing a computer model to simulate infrared (IR) scenes, the word “fidelity” has the twofold meaning: “accuracy” and “realism”. The accuracy relates to the mathematical modelling and means how close or truthful the results are to any measured readings. Whereas the realism relates to the appearance of correctness within the image presented. This essentially means how close to actuality or how realistic the scene looks, if compared with the actual scene and that any operator is convinced by what they see. The fidelity of the model depends upon the intended use. Low-fidelity models are simple and easy to use. On the other hand, the introduction of progressively more detail, leading to higher fidelity, has an obvious consequence on computational run time and operator expertise in running the simulation. High-fidelity models usually contain highly detailed terrains, man-made structures, atmospheric effects, detailed target geometry and thermal signature models. To make the model more realistic, the “special effects” such as the exhaust gas plume, dust, smoke, and clouds are added in these models.

High-Fidelity Simulators Developed

Many military simulator developers have provided an integrated IR/electro-optical (EO), three-dimensional (3D) modelling environment. The following are a few examples of such systems [source internet]:

• Real-time IR/EO Scene Simulator (RISS) of Amherst Systems Inc., Northrop Grumman, New York, USA.

• Tactical Engagement Simulation Software (TESS) developed by Tactical Technologies Inc. Ontario, Canada [2].

• IR Target Generator (IRTG) and Target IR Simulator (TIRS) of CI Institute CA, USA.

• IR Scene Projector (IRSP) of Dynetics Alabama, USA.

• Aerial Target IR Simulator and Naval Target and Countermeasures Simulator (NTCS) developed by W.R. Davis Engineering Ltd. Ottawa, Ontaria, Canada [3].

• Vega Prime IR Scene developed by MultiGen-Paradigm, CA, USA.

• IR Scene Generator of Raytheon Missile Systems USA.

• Multi-Service Electro-optics Signature Code (MuSES) and PRISM of ThermoAnalytics, Inc., USA.

• Cameo-Sim broad scene simulator developed under DSTL (UK) MoD.

• Sensor-Vision is terrain visualization tool developed by MultiGen-Paradigm CA, USA.

• SIMTERM is a PC based computer simulator of thermal imagers developed by Inframet Inc., USA.

• CounterSim is an aircraft decoy assessment model (ADAM) developed by Chemring Countermeasures, High Post, UK.

• NATO Infrared Air Target Model (NIRATAM) and NATO’s NPLUME [4].

• DSTL(UK) Fly-in 2000 simulates the engagement of an aircraft, equipped with IRCM, by a missile with an imaging IR seeker [5].

The aim of this work is therefore to develop an adaptable and versatile IR signature modelling system, to run on any low-cost PC (with preferably no modification), using the powerful functions and routines available in MATLAB, to render scenes of sufficient realism as to convince a military operator that the image is “fit for purpose” in as near to real-time as possible.

IR SIGNATURE MODELLING

All objects emit energy in the IR portion of the electromagnetic spectrum. The energy radiated from any object depends upon its property to absorb, reflect and transmit radiation. The temperature of the body and emissivity of the surface are the two dominant factors for IR signature modelling. The IR energy attenuates as it passes through the atmosphere. The IR energy received at the detector comprises of radiation from the target and background and reflected energy from other sources.

ISSN 1440-5113 © 2008 Argos Press