Comprehensive photometry of the rings and 16 satellites of Uranus with the Hubble Space Telescope

Photometric properties of 4 rings and 16 satellites of Uranus are presented, based on 41 Hubble Space Telescope images taken in 1997. Up to 25 filters per object covered the wavelength range 0.27-2 mum. The whole range of phase angles observable from Earth (0.03-3 degrees) was probed. Reflectivities were calibrated on an absolute scale to typically 4% accuracy. Below 1 mum, derived geometric albedos of major satellites are typically 30% higher than previously reported due to previously unobserved steep upturns of the phase curve shortward of 0.2 degrees phase angle, possibly caused by coherent backscatter. Portia is slightly oblong and Juliet and Belinda are very oblong based on their rotational lightcurves. Puck displays a weak spectral feature indicative of water ice absorption. Cordelia and Ophelia were recovered very close to the positions predicted from their gravitational influence on the E ring. They have not been observed since 1986. Subtle color variations within the satellite system were confirmed. Throughout the uranian system, the slope of phase curves below 1 degrees phase angle displays a strong correlation with the albedo and a strong anticorrelation with the slope at higher phase angles. Similar correlations were found for Hapke parameters. The brightness of 20 members of the uranian system is presented in functional form for a wide range of wavelengths, phase angles, and orbital longitudes. (C) 2001 Academic Press.