SURFACE-TEMPERATURE CORRECTION FOR ACTIVE INFRARED REFLECTANCE MEASUREMENTS OF NATURAL MATERIALS

Land surface temperature algorithms for the moderate resolution imagin g spectroradiometer satellite instrument will require the spectral bid irectional reflectance distribution function (BRDF) of natural surface s in the thermal infrared. We designed the spectral infrared bidirecti onal reflectance and emissivity instrument to provide such measurement s by the use of a Fourier transform infrared spectrometer. A problem w e encountered is the unavoidable surface heating caused by the source irradiance. For our system, the effects of the heating can cause a 30% error in the measured BRDF. The error caused by heating is corrected by temporally curve fitting the radiance signal. This curve-fitting te chnique isolates the radiance caused by reflected irradiance. With thi s correction, other factors dominate the BRDF error. It is now similar to 5% and can be improved further. The method is illustrated with mea surements of soil BRDF. (C) 1996 Optical Society of America