HIGH-PHASE-ANGLE OBSERVATIONS OF URANUS AT 2650 ANGSTROM - HAZE STRUCTURE AND PARTICLE PROPERTIES

Spatially resolved photometric observations of Uranus at 2650 Angstrom obtained with the Voyager 2 Photopolarimeter Subsystem (PPS) are pres ented and analyzed with model atmospheres, A vertically homogenous atm ospheric model with Rayleigh scattering and absorption fits Uranus wel l at 2650 Angstrom at phase angles from 16 degrees to 157 degrees; no strong forward scattering typical of abundant large particles is obser ved, A microphysical model developed for Uranus to fit Voyager imaging system data CK, Rages, J, B, Pollack, M, G, Tomasko, and L, R, Doose, 1991, Icarus 89, 359-376) predicts the vertical distribution and prop erties of stratospheric haze aerosols at 22.5 degrees and 65 degrees S , This microphysical model also fits the 2650-Angstrom PPS data at low latitudes, Increasing the aerosol sizes in the Rages et al, size dist ribution by a factor of 1.2 creates an unobserved forward scattering p eak and can be excluded. The low-latitude upper stratospheric aerosols on Uranus are smaller (<0,1 mu m radius) and/or much less abundant th an the 0.2 to 0.25-mu m stratospheric aerosol population found by PPS on Neptune; however, to fit the Uranus 2650-Angstrom data at all latit udes requires darker and/or more abundant (1.5-3 times more) aerosols near the sunlit pole. (C) 1997 Academic Press.