which requires directional reflectance or emittancc of the earth surface as the boundary condition of the radiative transfer problem. But the actual reflectance or eminence characteristics of the earth surface are what the quantitative remote sensing aims at. This presents as a deadlock. In order to solve the problem
Hu et al. suggested a BRDF-based correction loop. However the convergence of such an iteration loop is to be studied. Hu et al. used simulations to show the loop converging. But it’s not easy to exhaust all the possible cases by simulations. This paper is to analyse theoretically the loop’s convergence and its conditions.