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Saturn's icy satellites investigated by Cassini-VIMS: I. Full-disk properties: 350-5100 nm reflectance spectra and phase curves |
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| Authors: | G. Filacchione F. Capaccioni A. Coradini P. Cerroni F. Tosi V. Formisano K.H. Baines B.J. Buratti M. Combes P. Drossart Y. Langevin V. Mennella P.D. Nicholson C. Sotin K. Hibbitts S. Newman |
| Affiliation: | a INAF-IASF Istituto di Astrofisica Spaziale e Fisica Cosmica, Via del Fosso del Cavaliere, 100, 00133 Roma, Italy b Bear Fight Center, Space Science Institute, 22 Fiddlers Rd., Winthrop, WA 98862, USA c Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, USA d INAF-IFSI Istituto di Fisica dello Spazio Interplanetario, Via del Fosso del Cavaliere, 100, 00133 Roma, Italy e University of Arizona, Department of Planetary Sciences, Lunar & Planetary Laboratory, 1629 E. University Blvd., Tucson, AZ 85721-0092, USA f Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099, USA g Université de Paris Sud-Orsay, Institut d'Astrophysique Spatiale, Batiment 120, 91405 Orsay Cedex, France h United States Geological Survey, Denver Federal Center, Denver, CO 80225, USA i NASA Ames Research Center, Astrophysics Branch, Moffett Field, CA 94035-1000, USA j Observatoire de Paris-Meudon, Département de Recherche Spatial, 5 Place Jules Jannsen, 92195 Meudon Cedex, France k German Aerospace Center (DLR), Institute of Space Sensor Technology and Planetary Exploration, Rutherfordstrasse 2, D-12489 Berlin, Germany l INAF-OAC, Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, 80131 Napoli, Italy m Cornell University, Astronomy Department, 418 Space Sciences Building, Ithaca, NY 14853, USA n Laboratoire de Planétologie et Géodynamique, Faculté des Sciences, B.P. 92208, 2 Rue de la Houssinière, 44072 Nantes Cedex 3, France o Stanford University, Department of Electrical Engineering, 161 Packard Building, 350 Serra Mall, Stanford, CA 94305-9505, USA |
| Abstract: | Saturn's icy satellites are among the main scientific objectives of the Cassini-VIMS (Visual and Infrared Mapping Spectrometer) experiment. This paper contains a first systematic and comparative analysis of the full-disk spectral properties of Dione, Enceladus, Epimetheus, Hyperion, Iapetus, Mimas, Phoebe, Rhea and Tethys as observed by VIMS from July 2004 to June 2005. The disk integrated properties (350-5100 nm reflectance spectra and phase curves at 550-2232 nm) and images of satellites are reported and discussed in detail together with the observed geometry. In general, the spectra in the visible spectral range are almost featureless and can be classified according to the spectral slopes: from the bluish Enceladus and Phoebe to the redder Iapetus, Hyperion and Epimetheus. In the 1000-1300 nm range the spectra of Enceladus, Tethys, Mimas and Rhea are characterized by a negative slope, consistent with a surface largely dominated by water ice, while the spectra of Iapetus, Hyperion and Phoebe show a considerable reddening pointing out the relevant role played by darkening materials present on the surface. In between these two classes are Dione and Epimetheus, which have a flat spectrum in this range. The main absorption bands identified in the infrared are the 1520, 2020, 3000 nm H2O/OH bands (for all satellites), although Iapetus dark terrains show mostly a deep 3000 nm band while the 1520 and 2020 nm bands are very faint. In this spectral range, the Iapetus spectrum is characterized by a strong reddening. The CO2 band at 4260 nm and the Fresnel ice peak around 3100 nm are evident only on Hyperion, Phoebe and Iapetus. The phase curves at 550 and at 2232 nm are reported for all the available observations in the 0°-144° range; Rhea shows an opposition surge at visible wavelengths in the 0.5°-1.17° interval. The improvement on the retrieval of the full-disk reflectance spectra can be appreciated by a direct comparison with ground-based telescopic data available from literature. Finally, data processing strategies and recent upgrades introduced in the VIMS-V calibration pipeline (flat-field and destriping-despiking algorithm) are discussed in appendices. |
| Keywords: | Saturn, satellites Spectroscopy Infrared observations Image processing |
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