Thermal contrast detected with a thermal detector

We show that the thermal contrast detected in a wavelength interval with a thermal detector consists of two terms. The first term agrees with the prev iously published results. The second term represents the contribution of th e temperature-dependent emissivity. Neglecting this term results in approxi mately 20% error for traditional room temperature applications. For the cas e of remote crop-monitoring, the contribution of the emissivity changes to the detected thermal contrast is even more important: the infection of the vegetation results in the modification of its emissivity, its temperature a nd its change of emissivity with temperature. (C) 1999 Elsevier Science B.V . All rights reserved.