Characterizing the particle size distribution of Saturn's A ring with Cassini UVIS occultation data

We present a forward model in which we reconstruct the spacecraft's observations for each stellar occultation by ring edges. The model produces a synthetic diffraction signal for a given truncated power-law particle size distribution, which we compare with the observed signal. We find an overall steepening of the power-law size distribution and a decrease in the minimum particle size at the outer edge of the A ring when compared with the Encke Gap edges. This suggests that interparticle collisions caused by satellite perturbations in the region result in more shedding of regolith or fragmentation of particles in the outermost parts of the A ring. We rule out any significant population of sub-millimeter-sized particles in Saturn's A ring, placing a lower limitation of 1-mm on the minimum particle size in the ring.