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|Title:||Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission||Authors:||CIARNIELLO, Mauro
DE SANCTIS, MARIA CRISTINA
CARROZZO, FILIPPO GIACOMO
Li, J. -Y.
Schröder, S. E.
Pieters, C. M.
Raymond, C. A.
Russell, C. T.
|Issue Date:||2017||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||598||First Page:||A130||Abstract:||Aims: We present a study of the spectrophotometric properties of dwarf planet Ceres in the visual-to-infrared (VIS-IR) spectral range by means of hyper-spectral images acquired by the VIR imaging spectrometer on board the NASA Dawn mission. Methods: Disk-resolved observations with a phase angle within the 7° <α < 132° interval were used to characterize Ceres' phase curve in the 0.465-4.05 μm spectral range. Hapke's model was applied to perform the photometric correction of the dataset to standard observation geometry at VIS-IR wavelength, allowing us to produce albedo and color maps of the surface. The V-band magnitude phase function of Ceres has been computed from disk-resolved images and fitted with both the classical linear model and H-G formalism. Results: The single-scattering albedo and the asymmetry parameter at 0.55 μm are w = 0.14 ± 0.02 and ξ = -0.11 ± 0.08, respectively (two-lobe Henyey-Greenstein phase function); at the same wavelength, Ceres' geometric albedo as derived from our modeling is 0.094 ± 0.007; the roughness parameter is θ=29° ± 6°. Albedo maps indicate small variability on a global scale with an average reflectance at standard geometry of 0.034 ± 0.003. Nonetheless, isolated areas such as the Occator bright spots, Haulani, and Oxo show an albedo much higher than average. We measure a significant spectral phase reddening, and the average spectral slope of Ceres' surface after photometric correction is 1.1% kÅ^-1 and 0.85% kÅ^-1 at VIS and IR wavelengths, respectively. Broadband color indices are V-R = 0.38 ± 0.01 and R-I = 0.33 ± 0.02. Color maps show that the brightest features typically exhibit smaller slopes. The H-G modeling of the V-band magnitude phase curve for α < 30° gives H = 3.14 ± 0.04 and G = 0.10 ± 0.04, while the classical linear model provides V(1,1,0°) = 3.48 ± 0.03 and β = 0.036 ± 0.002. The comparison of our results with spectrophotometric properties of other minor bodies indicates that Ceres has a less back-scattering phase function and a slightly higher albedo than comets and C-type objects. However, the latter represents the closest match in the usual asteroid taxonomy.||URI:||http://hdl.handle.net/20.500.12386/27182||URL:||https://www.aanda.org/articles/aa/full_html/2017/02/aa29490-16/aa29490-16.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201629490||Bibcode ADS:||2017A&A...598A.130C||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Sep 28, 2020
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