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Detection and estimation of spectral emissivity variations in the thermal infrared

When the thermal contrast between a target and the background is large it is usually sufficient to use a single spectral band for detection purposes and consequently spectral emissivity variations are ignored. We consider the problem of detection and estimation of spectral emissivity in the thermal infrared emphasizing the particular detection situation where the target thermal contrast is small. More generally, we show that temperature can be considered as random interference of low rank. This leads to a procedure of optimally estimating both the temperature and spectral emissivity components. of radiance measurements. In addition to temperature and spectral emissivity estimation we outline a phenomenology based optimal detector that is invariant to unknown levels of temperature variation and unknown levels of target thermal contrast.