HR: 09:15h
AN: P31D-06 [Abstracts]
TI: Physical Properties of the Saturnian Ring System Inferred from Cassini VIMS Opposition
Observations
AU: * Hapke, B
EM: hapke@pitt.edu
AF: U. of Pittsburgh, 321 OEH, Pittsburgh, PA 15260
United States
AU: Nelson, R M
EM: robert.m.nelson@jpl.nasa.gov
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Brown, R H
EM: rhb@lpl.arizona.edu
AF: U. of Arizona, a, Tucson, AZ 90555
United States
AU: Spilker, L J
EM: linda.j.spilker@jpl.nasa.gov
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Smythe, W D
EM: w.d.smythe@jpl.nasa.gov
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Kamp, L
EM: l.kamp@jpl.nasa.gov
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Boryta, M
EM: mboryta@instinet.com
AF: Mt. SAC, Walnut, Walnut, CA 91111
United States
AU: Leader, F
EM: f.leader@jpl.nasa.gov
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Matson, D L
EM: dennis.l.matson@jpl.nasa.gov
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Edgington, S
EM: s.edgington@jpl.nasa.gov
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Nicholson, P D
EM: nicholson@astro.cornell.edu
AF: Cornell, c, Ithaca, NY 14853
AU: Filacchione, G
EM: gianrico.filacchione@rm.iasf.cnr.it
AF: Ins Astf. Spaz, Rome, Rome, 94444
Italy
AU: Clark, R N
EM: rclark@usgs.gov
AF: USGS, D, Denver, CO 22345
United States
AU: Bibring, J
EM: bibring@ias.fr
AF: U. Paris, Sud Orsay, Paris, 34567
France
AU: Baines, K H
EM: blueskies4321@yahoo.com
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Buratti, B J
EM: bonnie.j.buratti@jpl.nasa.gov
AF: JPL, 4800 Oak Grove Drive, Pasadena, CA 91109
United States
AU: Bellucci, G
EM: giancarlo.bellucci@ifsi.rm.cnr.it
AF: Ins Astf. Spaz, Rome, Rome, 94444
Italy
AU: Capaccioni, F
EM: capaccio@rm.iasf.cnr.it
AF: Ins Astf. Spaz, Rome, Rome, 94444
Italy
AU: Cerroni, P
EM: priscio@rm.iasf.cnr.it
AF: Ins Astf. Spaz, Rome, Rome, 94444
Italy
AU: Combes, M
EM: michel.combes@obspm.fr
AF: Obs Paris, P, Paris, 23345
France
AU: Coradini, A
EM: coradini@rm.iasf.cnr.it
AF: Ins Astf. Spaz, Rome, Rome, 94444
Italy
AU: Cruikshank, D P
EM: dcruikshank@mail.arc.nasa.gov
AF: NASA AMES, N, Mountain View, CA 34467
United States
AU: Drossart, P
EM: Pierre.Drossart@obspm.fr
AF: Obs Paris, P, Muedon, 12345
France
AU: Formisano, V
EM: formisan@nike.ifsi.rm.cnr.it
AF: Ins Astf. Spaz, Rome, Rome, 94444
Italy
AU: Jaumann, R
EM: ralf.jaumann@dlr.de
AF: Ins Plant Exp, DLR, Berlin, 45678
Germany
AU: Langevin, Y
EM: langevin@ias.fr
AF: U. Paris, Sud Orsay, Paris, 34567
France
AU: McCord, T
EM: mccordtb@aol.com
AF: U. Washington, Seattle, Seattle, WA 34567
United States
AU: Menella, V
EM: mennella@na.astro.it
AF: Obs Ast Capitomonde, Napoli, Naples, 34567
Italy
AU: Sicardy, B
EM: bruno.sicardy@obspm.fr
AF: U. Paris, Sud Orsay, Paris, 34567
France
AB:
Much can be learned about the nature of Saturn's ring particles and their regoliths by studying the wavelength dependence of
their reflectance as a function of phase angle. At small phase angles the reflectance of the rings exhibits the opposition
effect (OE) a significant increase in reflectance as phase angle approaches zero degrees. The wavelength dependence of the
width and the peak of the OE are indicators of important physical properties of the regoliths of the ring particles such as
particle size, particle shape, packing density and albedo. The Cassini VIMS multi spectral imaging spectrometer obtained low
phase observations of the Saturnian ring system from 0.4-5.2 microns during 2005. These data clearly show a pronounced (OE).
Cassini VIMS opposition surge data indicate a wavelength dependence of the OE that relates to the size and separation of the
scattering centers on the surface of the ring particles. Laboratory studies and theoretical models of the OE relate the size
and shape of the reflectance increase to physical properties of the medium (Nelson et al, 2002; Spilker et al. 1995; Hapke et
al., 1993)). The OE arises from two processes, shadow hiding (SH) and coherent backscattering (CB). The SHOE is observed
because shadows cast by the particulate grains on one another are eliminated as phase angle approaches zero degrees. The CBOE
is due to constructive interference between light rays traveling in opposite paths through the medium as the path length
decreases with decreasing phase angle. The VIMS data at 1.9 microns, where the rings are highly reflective, indicate a strong
CBOE effect, however, at 2.1 microns, where the rings are very absorbing, the shape of the phase curve is consistent with
SHOE. Hapke et al. 1993,Science, 260, 509-511 Nelson, R. M. et al., 2002. Planetary and Space Science, 50, 849-856 Spilker
aka Horn, L.J et al., 1995. IAU Colloquium #150 This work done at JPL under contract with NASA
DE: 6099 General or miscellaneous
DE: 6213 Dust
DE: 6265 Planetary rings
DE: 6275 Saturn
DE: 6280 Saturnian satellites
SC: Planetary Sciences [P]
MN: Fall Meeting 2005