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

摘要

Stellar occultation data from Cassini's Ultraviolet Imaging Spectrograph (UVIS) have revealed diffraction spikes near sharp edges in Saturn's rings. The UVIS High Speed Photometer (HSP) observes these spikes as signals at ring edges that surpass measurements of the unocculted stellar signal. In Saturn's A ring, diffracted light can augment the direct stellar signal by up to 6% and can be detected tens of kilometers radially from the edge. The radial profile of the diffraction signal is dependent on the size distribution of the particle population near the ring edge. These diffraction signals are clearly observed at sharp edges throughout Saturn's ring system. In this paper we focus on the clearest detections at the outer edge of the A ring and at the edges of the Encke Gap.