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VIRTIS observations of the nucleus of 67P/Churyumov-Gerasimenko at low phase angle

Ciarniello, M. and Filacchione, G. and Capaccioni, F. and Raponi, A. and Desanctis, M.C. and Tosi, F. and Piccioni, G. and Migliorini, A. and Cerroni, P. and Capria, M. T. and Erard, S. and Bockelee-Morvan, D. and Leyrat, C. and Arnold, Gabriele and Barucci, M. A. and Schmitt, B. and Quirico, E. and Taylor, F.W. and Kappel, David and Longobardo, A (2016) VIRTIS observations of the nucleus of 67P/Churyumov-Gerasimenko at low phase angle. In: Comets Symposium: A new vision after Rosetta and Philae, p. 31. Comets Symposium: A new vision after Rosetta and Philae, Toulouse 14-18 November 2016, 14-18 November 2016, Toulouse.

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Official URL: http://www.comets2016toulouse.com

Abstract

On 9-10 of April 2016, the Rosetta orbiter completed a close flyby around the nucleus of 67P/Churyumov-Gerasimenko, when the comet was at heliocentric distance of 2.76 AU, along the outbound leg of its orbit around the Sun. This allowed the VIRTIS-M imaging spectrometer to observe the surface of 67P at visible wavelengths (0.2-1 μm) in the 0.93°-89.7° phase angle range with a spatial resolution ranging from 7 to 46 m/pix, resulting in a total of 105 hyperspectral images. Previous observations of the comet at low phase angle were acquired by VIRTIS-M during the approach phase on July 2014 (3.7 AU), with pixel resolution varying from 450 to 3200 m/pix, preventing disk-resolved imaging. The April 2016 observations fill this gap, allowing us to constrain the spectrophotometric properties of the surface at higher spatial resolution in the opposition surge geometry, therefore investigating both the 'shadow hiding' and 'coherent backscattering' opposition effect. Extrapolation to 0° phase angle of the reflectance measured during the flyby at latitude between -10° and 30° indicates a surface normal albedo of 0.06 at 0.55 μm. This result is close to the previous average value derived by Ciarniello et al. (2015) from a full-disk analysis giving 0.062+/-0.002 (3.7 AU, inbound orbit). Subsequent measurements by Filacchione et al. (2016) and Ciarniello et al. (submitted), derived from pre-perihelion observations at lower heliocentric distances, revealed a progressive enrichment of water ice abundance on the nucleus, in northern hemisphere regions, with a consequent brightening of the surface. The measured normal albedo derived from the 9-10 April 2016 dataset seems to indicate that during the post-perihelion phase the northern hemisphere has returned to albedo values compatible to the ones measured during the inbound part of the orbit, when the comet was at 3.7 AU from the Sun. This could be an indication that the northern hemisphere has been either covered by dust emitted by the southern hemisphere during the very active perihelion phase, or that dehydration of the upper surface layers has taken place.

Item URL in elib:https://elib.dlr.de/115308/
Document Type:Conference or Workshop Item (Poster)
Title:VIRTIS observations of the nucleus of 67P/Churyumov-Gerasimenko at low phase angle
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Ciarniello, M.inaf-iasf, italyUNSPECIFIED
Filacchione, G.inaf-iasf, rome, italyUNSPECIFIED
Capaccioni, F.inaf-iasf, italyUNSPECIFIED
Raponi, A.inaf-iasf, italyUNSPECIFIED
Desanctis, M.C.inaf, istituto di astrofisica spaziale e fisica cosmica, roma, italyUNSPECIFIED
Tosi, F.inaf-iasf istituto di astrofisica spaziale e fisica cosmica, roma italyUNSPECIFIED
Piccioni, G.inaf-iasfUNSPECIFIED
Migliorini, A.inaf-iasfUNSPECIFIED
Cerroni, P.inaf-iasf, rome, italyUNSPECIFIED
Capria, M. T.instituto di astrofisica spaziale e fisica cosmica, roma, italyUNSPECIFIED
Erard, S.lesiaUNSPECIFIED
Bockelee-Morvan, D.observatoire de paris, meudonUNSPECIFIED
Leyrat, C.lesiaUNSPECIFIED
Arnold, Gabrielegabriele.arnold (at) dlr.deUNSPECIFIED
Barucci, M. A.observatoire de paris, meudon, franceUNSPECIFIED
Schmitt, B.grenoble planetology laboratoryUNSPECIFIED
Quirico, E.laboratory of planetology, cnrs joseph fourier universityUNSPECIFIED
Taylor, F.W.university of oxfordUNSPECIFIED
Kappel, Daviddavid.kappel (at) dlr.deUNSPECIFIED
Longobardo, Ainaf-laps, via del fosso del cavaliere 100, i-00133 rome, italyUNSPECIFIED
Date:November 2016
Journal or Publication Title:Comets Symposium: A new vision after Rosetta and Philae
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Page Range:p. 31
Status:Published
Keywords:VIRTIS, comets, spectrophotometry, Rosetta, 67P
Event Title:Comets Symposium: A new vision after Rosetta and Philae, Toulouse 14-18 November 2016
Event Location:Toulouse
Event Type:international Conference
Event Dates:14-18 November 2016
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Projekt ROSETTA Instrumente
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Asteroids and Comets
Institute of Planetary Research > Leitungsbereich PF
Deposited By: Kappel, David
Deposited On:20 Nov 2017 14:59
Last Modified:20 Nov 2017 14:59

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