A New Technique for Separation of Temperature and Emissivity
DEFENCE RESEARCH AND DEVELOPMENT CANADA VALCARTIER (QUEBEC)
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We describe in this report a new technique for the separation of temperature and emissivity in the thermal infrared part of the electromagnetic spectrum. The measurement taken with by a passive remote sensing instrument is radiance. This radiance is a combination of components originating from the atmosphere and from the ground. Once the atmospheric contribution is removed, the result is radiance from the ground that depends on its fundamental parameters i.e. temperature and emissivity. These parameters are useful to determine the nature and use of the material under observation. The new technique presented here is based on an iterative scheme for the selection of temperature and of its corresponding emissivity. At each temperature it evaluates a criterion, the total square error. The selected temperature is the one showing the smallest error. To evaluate the error we first compute the equivalent emissivity at a given temperature, we smooth the emissivity using a linear procedure then we compute a new radiance for the smoothed emissivity. The error is computed by the summation of the squared difference between the ground radiance and the new radiance. This technique is robust to noise and atmospheric parameters errors. The currently airborne imaging FTIR sensor AIRIS built by DRDC Valcartier is targeted as an application of interest for this algorithm. However, it can be applied to imaging sensor with at least six bands.
- Numerical Mathematics