Evolution of the statistical fluctuations in the measured temperature differences between painted metal plates of a CUBI infrared calibration target

To validate thermal infrared signature models, we need data from well-characterized targets, typically of simple geometric shape measured under known atmospheric and environmental conditions. An important parameter of the target's signature is the variability in surface temperature due to an orientation with regard to the dominant heat source: The sun. In this paper, we report on the fluctuations in the temperature differences between surfaces of a CUBI geometrical test target mounted at roof level in an urban environment. Specifically, we investigate those surfaces orientated in a step-like manner. Measurements are recorded at regular intervals by digital temperature sensors operating in a network and remotely accessed via intranet. Our results assess the statistical variation in relative temperature contrast between surfaces for the entire dataset, where queries to a database highlight patterns in the data. We show not only a pronounced difference in probability density functions due to the influence of the sun by day and radiative cooling by night, but also the statistical variability of the temperature differences with local time. In summary, we show statistical limits on the probable temperature differences between plates as a function of time of day over a number of months, which provide a useful insight to the IR signature.