Phoebe: Albedo Map and Photometric Properties

摘要: Using clear-filter images from Voyager 2 (effective wavelength 0.48 μm), we have constructed the first-ever digital albedo map of Saturn's moon Phoebe. Most normal reflectances in this new are between 0.07 and 0.11; histogram is largely bimodal, suggesting that satellite covered predominantly by two different types surface materials. The highest albedos confined to isolated, quasi-circular spots 40 100 km across, including three varying a band immediately south equator one especially bright spot at latitude 60°N (normal reflectance as high 0.13, ≈50% brighter than average surface). northern brightest southern occur approximately same longitude, an alignment gives Phoebe its significant rotational lightcurve. low resolution does not permit interpretation spots' origin. Phoebe's global-average photometric function was determined combining satellite's telescopic near-opposition phase curve (S. Kruseet al.1986,Icarus68, 168–175) with absolute disk-resolved measured (triaxial-ellipsoid shape assumed radii 115, 110, 105 km). Modeling observations supports presence opposition surge, although scatter data allow unambiguous determination surge's exact strength. derived consistent idea C-type object—probably primitive, captured body related Chiron, Pholus, inhabitants Kuiper Belt. information will aid planning high-resolution Cassini Phoebe, which represent our first close look class primitive outer Solar-System object.