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Observations with the Visual and Infrared Mapping Spectrometer (VIMS) during Cassini's flyby of Jupiter |
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| Authors: | R.H. Brown K.H. Baines J.-P. Bibring F. Capaccioni R.N. Clark D.P. Cruikshank V. Formisano Y. Langevin T.B. McCord V. Mennella P.D. Nicholson C. Sotin M.A. Chamberlain G. Hansen M. Showalter |
| Affiliation: | a Lunar and Planetary Lab and Steward Observatory, University of Arizona, Tucson, AR 85721, USA b Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA c Instituto di Fisica dello Spazio Interplanetario, CNR, Rome, Italy d Institut d'Astrophysique Spatiale, Université de Paris, Orsay, France e Instituto di Astrofisica Spatiale, CNR, Rome, Italy f U.S. Geological Survey, Denver, CO 80255, USA g NASA Ames Research Center, Moffett Field, CA 94035, USA h Observatoire de Paris, Meudon, France i Institute for Planetary Exploration, DLR, Berlin, Germany j University of Hawaii, HIGP/SOEST, Honolulu, HI 98195, USA k INAF, Osservatorio Astronomico di Capodimonte, Rome, Italy l Cornell University, Astronomy Department, Ithaca, NY 14853, USA m Laboratoire de Planetologie et Geodynamique, Université de Nantes, Nantes, France n Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA |
| Abstract: | The Cassini Visual and Infrared Mapping Spectrometer (VIMS) is an imaging spectrometer covering the wavelength range 0.3-5.2 μm in 352 spectral channels, with a nominal instantaneous field of view of 0.5 mrad. The Cassini flyby of Jupiter represented a unique opportunity to accomplish two important goals: scientific observations of the jovian system and functional tests of the VIMS instrument under conditions similar to those expected to obtain during Cassini's 4-year tour of the saturnian system. Results acquired over a complete range of visual to near-infrared wavelengths from 0.3 to 5.2 μm are presented. First detections include methane fluorescence on Jupiter, a surprisingly high opposition surge on Europa, the first visual-near-IR spectra of Himalia and Jupiter's optically-thin ring system, and the first near-infrared observations of the rings over an extensive range of phase angles (0-120°). Similarities in the center-to-limb profiles of H+3 and CH4 emissions indicate that the H+3 ionospheric density is solar-controlled outside of the auroral regions. The existence of jovian NH3 absorption at 0.93 μm is confirmed. Himalia has a slightly reddish spectrum, an apparent absorption near 3 μm, and a geometric albedo of 0.06±0.01 at 2.2 μm (assuming an 85-km radius). If the 3-μm feature in Himalia's spectrum is eventually confirmed, it would be suggestive of the presence of water in some form, either free, bound, or incorporated in layer-lattice silicates. Finally, a mean ring-particle radius of 10 μm is found to be consistent with Mie-scattering models fit to VIMS near-infrared observations acquired over 0-120° phase angle. |
| Keywords: | Jupiter Jovian satellites Jupiter's ring Spectroscopy Planetary atmospheres Planetary surfaces Cassini mission |
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