HR: 1340h
AN: P33B-0250    [Abstracts]
TI: CIRS Observations of a Thermal Enhancement Near Zero Phase in Saturn's Rings
AU: * Wallis, B D
EM: Bradford.D.Wallis@jpl.nasa.gov
AF: Jet Propulsion Lab/CALTECH, 4800 Oak Grove Dr, Pasadena, CA 91109 United States
AU: Spilker, L J
P33B-0250 AF: Jet Propulsion Lab/CALTECH, 4800 Oak Grove Dr, Pasadena, CA 91109 United States
AU: Pilorz, S H
EM: Stuart.H.Pilorz@jpl.nasa.gov
AF: Jet Propulsion Lab/CALTECH, 4800 Oak Grove Dr, Pasadena, CA 91109 United States
AU: Pearl, J C
EM: john.pearl@gsfc.nasa.gov
AF: Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 United States
AU: Altobelli, N
EM: nicolas.altobelli@jpl.nasa.gov
AF: Jet Propulsion Lab/CALTECH, 4800 Oak Grove Dr, Pasadena, CA 91109 United States
AU: Edgington, S G
EM: Scott.G.Edgington@jpl.nasa.gov
AF: Jet Propulsion Lab/CALTECH, 4800 Oak Grove Dr, Pasadena, CA 91109 United States
AU: Flasar, F M
EM: f.m.flasar@gsfc.nasa.gov
AF: Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 United States
AU: Team, C
EM: f.m.flasar@gsfc.nasa.gov
AF: Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 United States
AB: Cassini's Composite Infrared Spectrometer (CIRS) observations of Saturn's main rings during the first set of prime ring viewing geometry orbits have shown the main rings to be thermally complex. The thermal appearance of the rings changes significantly with viewing geometry, ring local time and phase angle. During one observation near the zero phase on the rings, the CIRS data showed an unexpected thermal enhancement in the A Ring at a phase angle of 0.3 degrees and a local time of gg. A similar radial scan taken one orbit later at a phase angle of 1.5 degrees showed a similar thermal enhancement. Since that finding, other CIRS ring scans have shown this effect to be present in all of Saturn's main rings We will presnt results from CIRS observations of the main ring shoing the thermal enhancement near zero degrees phase. While the effect is on the order of 5-6 K in the A and C Rings it drops to only 1-2 K throught much of the B Ring and is non existent at several small regions of the B Ring. The zero phase thermal enhancement is also present in the Cassini Division. The effect does not appear to have any prounced peak as is seen in a visible light oppostion effect and this thermal enhancement appears to be considerably broader and afftects thermal measurements out to 10 to 15 dgrees phase angle. Future observations are planned to help us to fully understand this thermal effect that has been observed near zero phase. At present we think that a sophisticated Radiative Transfer model of the rings may actually predict this effect. Such a model is being developed by S.Pilorz at JPL and has already yielded results predicting such an effect. At this point it would appear that this effect may allow a sophsticated radiative transfer ring model to yield considerable information about ring particle size and density distributions. This work was performed at JPL under contract with NASA.
DE: 5759 Rings and dust
DE: 6265 Planetary rings
SC: Planetary Sciences [P]
MN: Fall Meeting 2005