The Far-IR Emissivity of Saturn's Rings Observed with Cassini CIRS

We study the effective emissivity derived from all far-IR spectra of Saturn's rings acquired by the Cassini Composite Infra-Red Spectrometer (CIRS) throughout the Cassini mission. To first order, the effective emissivity is determined by the optical filling factor of ring material within the field of view (FOV). Second order effects are due to variation in the emissivity of the ring ice and/or sub-FOV variations in temperature. We infer that emission from the A and C rings is qualitatively different from the B ring. The differences indicate that particle size should play a role in the effective emissivity, and tie this work to other research.