Thermal image measurements of infrared signatures

Abstract

Thermal images of an instrumented ship target against a sea background have been recorded under varying environmental conditions, using an AGA Thermovision 780 radiometric imaging system with digital data recording. Data were obtained in the 8 -14 um spectral band at an angle of incidence of approximately 89 degrees against the sea background. These pictures have been analyzed together with measured target emissivity and meteorological parameters to give the temperature and radiance distributions of the target. The influences of reflected sky radiation on the background radiance was observed under varying sea surface conditions. A predictive model of effective radiance temperature difference of the target versus sea background in terms of the environmental parameters using the LOWTRAN 6 Radiance Transmittance computer-code was developed. This effective temperature difference has been shown to vary both positively and negatively compared with the thermometric temperature difference depending on the wind speed and the air and sea surface temperatures.