Thermal Infrared (3–14 μm) bidirectional reflectance measurements of sands and soils

Recent day/night land surface temperature (LST) algorithms can recover both emissivity and temperature but require some assumptions about the relative optical properties of natural materials in the thermal infrared. We constructed a goniometer and measured the spectral, angular emissivity, and bidirectional reflectance of sands and soils in the 3–14 μm range. In this paper, we present the results for five diverse surfaces and examine the validity of the LST assumptions. We conclude that the change in emissivity with angle was small across the entire range for all of the materials except sand. In addition, for all of the materials, the measured variation in bidirectional reflectance anisotropy with wavelength was small enough to neglect.