The Optical Properties of Venus and the Jovian Planets. II. Methods and Results of Calculations of the Intensity of Radiation Diffusely Reflected from Semi-infinite Homogeneous Atmospheres

An efficient method is proposed for computation of the intensity of radiation diffusely reflected from a semi-infinite homogeneous atmosphere with arbitrary phase function. We present the results of calculations of the brightness distribution over the disk of a planet when the phase angle α = 0, as well as spherical and geometrical albedos and other auxiliary functions. The calculations are carried out for the Rayleigh and the Henyey-Greenstein phase functions with g = 0, 0.5, 0.75, 0.8, 0.85, 0.9 and single scattering albedo λ = 1, 0.999, 0.995, 0.99, 0.98, 0.95, 0.9, 0.8, and 0.7. The curves of dependence of center-of-disk reflection coefficient and geometrical albedo of a planet upon spherical albedo were found to differ slightly for different phase functions. Using these dependences and results of spectrophotometric observations of the reflection coefficient for the center of disk of Saturn and geometrical albedo of Uranus, the integral (radiometric) albedo of these planets is estimated (0.50 ± 0.03 and 0.37 ± 0.05, respectively). The corresponding effective temperature is T_e = 76 ± 1° for Saturn and T_e = 57° ± 1° for Uranus.