A semi-empirical IR signature model for tilted surfaces

In this document we present the further development that has been made of a previously presented semi-empirical model for calculation of thermal IR signatures from background elements. An improved modelling of non-horizontal surfaces has been included in the semi-empirical model. The model has been tested by curve-fitting the model to time histories of measured LWIR radiance from two flat, tilted panels. The two panels have different coatings with significantly different emissivities in the infrared. The correspondence between the curvefitted model and measurements is very good for both panels during the entire time period for which we have measurements. For the purpose of future evaluation we also present simple models for latent heat and precipitation which have been included in the semi-empirical model. It is concluded that the developed semi-empirical model could be a useful tool in several applications of IR-signature prediction and simulation. It is also noted that a continued development and, in particular, validation of the model would be of value.