Technical note CARABAS: A programmable radiometer for the characterization of backgrounds in the thermal infrared

Abstract

The detectability of an object in the infrared spectral region is, next to its own thermal characteristics, determined by the thermal behaviour of the background (the thermodynamics of various elements, like grass, trees, soil, etc.). In this sense; the temperature and emissivity variation of these background elements as a function of position, viewing angle and time is of major importance. To enhance the understanding of the thermodynamics and directional emittance properties of backgrounds, measurements of background and meteorological parameters over long periods of time, covering a representative set of wealher data, are needed. For this purpose a dual-channel (3-5 and 8-12μm) radiometer was developed. To be able to perform measurements over long periods of time, the system was designed to operate in an automatic and autonomous way. Once the system has been programmed with the coordinates of the desired background elements, it automatically measures these every pre-set time interval. The system was fielded in April 1990 with a wealher station and has been operating undisturbed over a full year. System design and performance are discussed in this paper.