Investigations of the optical properties of Saturn's atmosphere carried out at the main astronomical observatory of the Ukrainian Academy of Sciences

Abstract

The results of polarimetric, photometric, and spectroscopic investigations of Saturn are given. Polarimetric and photometric investigations show that in the long wavelength spectral range ( λ > 0.5 μm) spherical particles play the dominant role in the reflected radiation. But for λ < 0.5 μm, oriented nonspherical particles are revealed in the equatorial region within planetocentric latitudes ±30°. It is suggested that Saturn's rings may be the source of these particles. According to photometric measurements, the brightness coefficient depends on the phase angle and marked temporal variations of the brightness coefficient were absent during the period from 1977 to 1981. A number of weak methane absorption bands were measured for the first time, and the ammonia absorption band at λ = 0.648 μm is present in our low-resolution photoelectric spectrophotometry. The reduction of high-resolution spectrograms has confirmed the presence of 20 ammonia lines belonging to the band at 0.648 μm. The observations can be fit to spherical aerosols with 1.35 ≤ n r ≤ 1.42, r 0 = 1 μm, σ 2 = 0.12; or n r = 1.93, r 0 ≅ 0.4 μm, σ 2 = 0.10; volume concentration 20 cm −3; and ammonia abundance (relative to methane) ≅ 0.01; and the optical thickness of the overlying gas layer is τ s = 0.2 to 0.4 for λ = 0.316 μm.