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Abstract: In this paper, we characterize the morphology of the disk-integrated phasefunctions of satellites and rings around the giant planets of our Solar System.We find that the shape of the phase function is accurately represented by alogarithmic model Bobrov, 1970, in Surfaces and Interiors of Planets andSatellites, Academic, edited by A. Dollfus. For practical purposes, we alsoparametrize the phase curves by a linear-exponential model Kaasalainen et al.,2001, Journal of Quantitative Spectroscopy and Radiative Transfer, 70, 529-543and a simple linear-by-parts model Lumme and Irvine, 1976, AstronomicalJournal, 81, 865-893, which provides three morphological parameters : theamplitude A and the Half-Width at Half-Maximum HWHM of the opposition surge,and the slope S of the linear part of the phase function at larger phaseangles. Our analysis demonstrates that all of these morphological parametersare correlated with the single scattering albedos of the surfaces. By takingmore accurately into consideration the finite angular size of the Sun, we findthat the Galilean, Saturnian, Uranian and Neptunian satellites have similarHWHMs 0.5 degrees, whereas they have a wide range of amplitudes A. The Moonhas the largest HWHM 2 degrees. We interpret that as a consequence of thesolar size bias, via the finite size of the Sun which varies dramatically fromthe Earth to Neptune. By applying a new method that attempts to morphologicallydeconvolve the phase function to the solar angular size, we find that icy andyoung surfaces, with active resurfacing, have the smallest values of A andHWHM, whereas dark objects and perhaps older surfaces such as the Moon,Nereid and Saturn C ring have the largest A and HWHM.



Author: Estelle Deau, Luke Dones, Sebastien Rodriguez, Sebastien Charnoz, Andre Brahic

Source: https://arxiv.org/







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