THERMAL INFRARED (3-14 MU-M) 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 th e relative optical properties of natural materials in the thermal infr ared. We constructed a goniometer and measured the spectral, angular e missivity, and bidirectional reflectance of sands and soils in the 3-1 4 mu m range. In this paper, we present the results for five diverse s urfaces and examine the validity of the LST assumptions. We conclude t hat the change in emissivity with angle was small across the entire ra nge for all of the materials except sand. In addition, for all of the materials, the measured variation in bidirectional reflectance anisotr opy with wavelength was small enough to neglect. (C) Elsevier Science Inc., 1997.