Aircraft Engine's Lock-On Envelope due to Internal and External Sources of Infrared Signature

The lock-on envelope of target aircraft is important in determining its susceptibility against a heat-seeking missile and depends on the aircraft's infrared (IR) signature level (IRSL). In this investigation, the lock-on envelope is estimated in 3-5 μm and 8-12 μm bands, considering internal and external sources of IR signature from surfaces of aircraft engine layout. This is achieved by a synthesis of the following four major tasks: 1) analytical estimation of solid angles subtended by aircraft surfaces, 2) prediction of aircraft surface temperatures from convective and radiative heat transfer model, 3) computation of atmospheric transmission and background radiance, and 4) estimation of earthshine, skyshine, and sunshine irradiances. Polar plots in 2-D for lock-on range, for vertical and horizontal planes are analyzed, to study the role of internal and external sources for different aspects.