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.