Directional reflectance of optically dense planetary atmosphere illuminated by solar light: An approximate solution and its verification

A new combined approach to calculate the spectral directional reflectance of optically thick cloudy atmosphere illuminated by solar light is suggested. First of all, the approximate method based on the idea of previously developed two-step procedure and a set of 1-D solutions is employed to calculate the local bi-directional reflectance of the cloud layer. After that, the Monte Carlo ray-tracing procedure is used to determine the reflectance of the planet as a whole in the case of a remote sensing from a space vehicle at large distances from the planet. This combined approach appeared to be applicable for planets with opaque cloudy atmosphere. A comparison with the reference Monte Carlo simulation of the complete problem in a wide range of volumetric optical parameters typical of Venus atmosphere in the visible and infrared spectral ranges confirmed very good accuracy of suggested approach. It is recommended to consider the solution obtained as an alternative multi-wavelength method in navigation systems of space vehicles.