SIZE ESTIMATES OF TITAN'S AEROSOLS BASED ON VOYAGER HIGH-PHASE-ANGLE IMAGES.

Limits on the physical properties of the scattering haze near the top of Titan's atmosphere are derived from data obtained from seven high-phase-angle images from Voyager 1 and 2. From the ratio of the intensities observed at two different high phase angles, an estimate can be made of the forward scattering lobe of the single-scattering phase function. By comparing the forward scattering estimate with diffraction lobes from particles of different radii, it is concluded that the average radius of the particles found in the upper few tenths of an optical depth exceeds 0. 19 mu m. Judging from data observed at four different phase angles, the haze particles probably have a refractive index near 1. 6 and a mean size of approximately 0. 5 mu m, if the widths of their diffraction peaks are close to those for equal volume spheres.