BRDF models to predict spectral reflectance and emissivity in the thermal infrared

This paper presents modifications to the linear kernel bidirectional reflectance distribution function (BRDF) models from Roujean et al. and from Wanner et al. that extend the spectral range into the thermal infrared (TIR). Our application is to synthesize the TIR optical properties of a scene pixel from laboratory component measurements. The angular reflectance and emissivity are needed to convert the radiance of a pixel as measured from space to land-surface temperature. The kernel models will be applied to develop a look-up table for the MODIS land-surface temperature algorithm to estimate the spectral, angular scene emissivity from land cover classification. A shrub scene and a dense canopy scene illustrate qualitative differences in angular emissivity that would not be evident without the kernel model modifications. We conclude that the modified models provide a simple and efficient way to estimate scene optical properties over a wide spectral range.