As demonstrated in the previous chapter, prevailing weather conditions largely drive the thermodynamic behavior of objects. For targets, internal heat sources also may affect the exterior thermal signature. To understand the thermal behavior of objects and quantify the IR radiation exchange, a number of weather parameters have to be measured in the target area together with target signature data. Chapter 4 showed that sophisticated models need a large array of meteorological input parameters, and special measurement facilities are required to collect these. However, this array is too big to be practical, and the challenge is to choose a minimum set of parameters that give sufficient (complete) information to quantify thermal signatures. From a practical point of view, it would be beneficial to relate calculated as well as measured thermal signatures to a limited set of weather data that are readily available or easy to obtain.
For the characterization of IR signatures, this indeed is a difficult choice. It must be weighed against costs, time, and sensor availability. Unfortunately, the result often is a bad compromise, resulting in a poor and/or inadequate recording of the weather conditions.
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