The Structure of Saturn's B Ring from CIRS High-Resolution Thermal Scans
Abstract
Cassini's 126th flyby of Titan on 29 November 2016, sent the spacecraft on a trajectory carrying it within 10,000 kilometers of Saturn's F ring before the encounter on 22 April 2017 dropped the spacecraft's periapse location between Saturn's cloud tops and the planet's D ring. This geometry has proven beneficial for high-resolution rings studies because of Cassini's proximity to the rings and the spacecraft's high elevation angle above the rings, which reduces the foreshortening that tends to degrade resolution in the ring plane. We will report on high spatial resolution observations made by Cassini's Composite Infrared Spectrometer of Saturn's main rings, particularly the B ring, during the F-ring and proximal orbits. CIRS' three infrared detectors cover a combined spectral range of 10 to 1400 cm-1 (1 mm down to 7 μm). We use data from Focal Plane 1, which covers the 10 to 600 cm-1 range (1 mm to 16 μm) (Flasar et al. 2004). FP1's wavelength range makes it well-suited to sensing thermal emission from objects at temperatures typical of Saturn's rings. Correlating temperatures retrieved from scans of the lit and unlit rings with ring optical depth suggests differences in ring structure or particle transport between the lit and unlit rings in different regions of the B ring. The lit/unlit side temperature differential varies from 2-3 K in the most optically thin sections of the B ring's B1 region up to 20 K in the optically thick portions of the B2 region of the B ring. Moreover, temperatures on the unlit side of the B ring's B3 region vary by 5-6 K and are correlated with slight optical depth variations. No such correlated temperature variations are observed on the lit side of the B3 region. Hedman et al. (2013) report unusual photometric properties in this region of the B ring. Ferrari et al. (2013) and Pilorz et al. (2015) published thorough analyses of the thermal throughput across this optically thick ring. We will discuss these CIRS observations and their implications in the context of such work. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2018 California Institute of Technology. Government sponsorship acknowledged.
- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #50
- Pub Date:
- October 2018
- Bibcode:
- 2018DPS....5011702B