BRDF modeling and analysis of the pseudo-invariant calibration site in northwest China

As an important parameter characterizing the bi-directional reflectance of objects, the Bidirectional Reflectance Distribution Function (BRDF) is one of the key parameters in the on-orbit substitute calibration of satellite remote sensors based on stable ground targets. It is a crucial factor affecting the calibration accuracy. With the development of quantitative remote sensing, hyperspectral BRDF measurement for calibration and spectral analysis of land surface features has become increasingly important. Efficient and high-quality methods for collecting multi-angle reflectance data of land surfaces are currently a research focus. This study uses co-observation of two spectrometer to measure the BRDF characteristics of the pseudo-invariant calibration site in wild environment. Based on the selected results of the pseudo-invariant calibration site in Northwest China by previous research, BRDF for three different types of land surfaces were measured including desert, Gobi, and saline-alkali land. Based on the Ross-li kernel-driven model, a hyperspectral BRDF characteristic data set of the three different surface types is fitted, and the spatial distribution characteristics and hotspot effects of the BRDF directional reflection of the ground targets are analyzed. The results show that different surface types have different directional reflectance values and different hot spot effects. Therefore, a stable target radiation reference library with different radiation brightness levels can be constructed to provide a benchmark model for long-term consistent radiometric calibration of Chinese remote sensing satellites.