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A. R. Hendrix (LASP/CU), D. L. Domingue (APL/JHU)
Results from an analysis of Europa’s ultraviolet photometric parameters based on data from Galileo, Hubble Space Telescope Faint Object Spectrograph (HST/FOS) and International Ultraviolet Explorer (IUE) are presented. Rotational phase curves for wavelengths between 250 and 320 nm based on the disk-integrated data set display a brightness variation with longitude similar to that seen in the visible. Hapke modeling of the disk-integrated solar phase curve for the global data set, as well as the individual leading, trailing, jovian and anti-jovian hemispheres provides an understanding of large-scale variations in photometric properties. The disk-resolved data set, consisting entirely of data from the Galileo Ultraviolet Spectrometer, is used to uniquely constrain the disk-integrated modeling results. Variations in photometric properties, such as single-scattering albedo, single particle scattering function, surface roughness and grain size vs. porosity are presented. The disk-resolved data set is also used to determine the photometric properties of terrain types such as bright plains and dark mottled terrain. These results are interpreted based on knowledge of Europa’s charged particle environment and variations in composition and geologic features across the surface, to provide a greater understanding of the effects on surface structure. These are the first UV Hapke photometric parameters to be derived for any solar system object. The results are compared with visible photometric parameters derived using Voyager and ground-based observations to gain insight into the effects of surface scattering vs. volume scattering on an icy object.