The development and optimisation of modern infrared systems necessitates the use of simulation systems to create
radiometrically realistic representations (e.g. images) of infrared scenes. Such simulation systems are used in
signature prediction, the development of surveillance and missile sensors, signal/image processing algorithm
development and aircraft self-protection countermeasure system development and evaluation.
Even the most cursory investigation reveals a multitude of factors affecting the infrared signatures of realworld
objects. Factors such as spectral emissivity, spatial/volumetric radiance distribution, specular reflection,
reflected direct sunlight, reflected ambient light, atmospheric degradation and more, all affect the presentation of
an object's instantaneous signature. The signature is furthermore dynamically varying as a result of internal and
external influences on the object, resulting from the heat balance comprising insolation, internal heat sources,
aerodynamic heating (airborne objects), conduction, convection and radiation. In order to accurately render the
object's signature in a computer simulation, the rendering equations must therefore account for all the elements
of the signature.
In this overview paper, the signature models, rendering equations and application frameworks of three infrared
simulation systems are reviewed and compared. The paper first considers the problem of infrared scene simulation
in a framework for simulation validation. This approach provides concise definitions and a convenient context for
considering signature models and subsequent computer implementation. The primary radiometric requirements
for an infrared scene simulator are presented next.
The signature models and rendering equations implemented in OSMOSIS (Belgian Royal Military Academy),
DIRSIG (Rochester Institute of Technology) and OSSIM (CSIR & Denel Dynamics) are reviewed. In spite
of these three simulation systems' different application focus areas, their underlying physics-based approach is
similar. The commonalities and differences between the different systems are investigated, in the context of their
somewhat different application areas.
The application of an infrared scene simulation system towards the development of imaging missiles and
missile countermeasures are briefly described.
Flowing from the review of the available models and equations, recommendations are made to further enhance
and improve the signature models and rendering equations in infrared scene simulators.