Whole-disk polarization measurements of Uranus at visible wavelengths.

The whole-disk polarization of Uranus was measured over two apparitons in blue and red light. The blue polarization becomes negative near the 0.5-deg phase, indicating non-Rayleigh scattering. The red polarization phase curve shows positive polarization smaller than suggested by Rayleigh scattering models. An explanation of these data is that the blue and red radiation is scattered by the CH4 haze layer that has been suggested to reside high in the atmosphere of Uranus. As expected, there is no whole-disk circular polarization, an observation which confirms other observations and theoretical predictions.