CCD PHOTOMETRY OF THE URANIAN SATELLITES

Broadband V and R CCD observations of the Uranian satellite system have been obtained over the full range of solar phase angles observable from Earth. These first visual observations of the phase curves of Miranda, A-riel, and Umbriel show that Ariel and Miranda exhibit the large opposition surges previously seen on the two outer Uranian satellites. Umbriel, however, lacks an appreciable opposition surge; its surface is either extremely compact or consists of small particles which lack a backscattered component. The tenuous structure of the other satellites is most likely due to the effects of eons of meteoritic gardening.