Structure of Saturn's rings from Voyager radio occultation measurements
ABSTRACTRadio occultation observations of Saturn's rings with Voyager 1 provided measurements of the collective microwave opacity and the near-forward scattering characteristics of the ring particles at 3.6 and 13 cm wavelengths. These measurements were obtained at a ring opening of 6.1°. Experimentally, the three classical rings and the Cassini division comprise four distinct structural regimes whose characteristics are as follows: Ring C exhibits a background of gently undulating (~ 1000 km radial scale) structure of normal opacity τ(3.6cm) ≲0.25, [τ = sin(6.1 °)1 n(I/Io)], imbedded in which are several narrow ringlets of less than few hundred km in width and of microwave opacity in the range 0.5 to 1.0. The opacity ratio ρ = τ(3.6cm)/τ(13cm) falls in the range 1.4 to 1.6 for most of ring C, indicating that a substantial fraction of the crosssectional area is due to particles in the 1 to 4 cm diameter range. Three gaps are clearly evident in ring C, two of them encompass imbedded ringlets of extremely sharp edges. The dual-wavelength opacity of several imbedded ringlets is consistent with models in which particles smaller than a few centimeters pile-up near the edges. In the Cassini division, several gaps of extremely sharp edges separate regions of opacity in the range 0.08 to 0.25; the opacity is nearly independent of the wavelength, precluding the existance of a substantial fraction of particles less than about 4 cm in size.