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Closing the gap between Earth-based and interplanetary mission observations: Vesta seen by VLT/SPHERE

Romain Jl. Fétick 1 Laurent Jorda 1 Pierre Vernazza 1 Michael Marsset 2 Alexis Drouard 3 Thierry Fusco 1, 4 Benoît Carry 5 Franck Marchis 6 Josef Hanuš 7 Matti Viikinkoski 8 Mirel Birlan 9 Przemyslław Bartczak 10 J. Berthier 11, 9 Julie Castillo-Rogez 12 Fabrice Cipriani 13 François Colas 9 Grzegorz Dudziński 10 Christophe Dumas 14 Marin Ferrais 15 Emmanuël Jehin 16 M. Kaasalainen 17 Agnieszka Kryszczynska 18 Philippe Lamy 1 Hervé Le Coroller 19 Anna Marciniak 20 Tadeusz Michalowski 10 Patrick Michel 5 Laurent M. Mugnier 4 Benoît Neichel 1, 21 Myriam Pajuelo 9, 22 Edyta Podlewska-Gaca 10, 23 Toni Santana-Ros 18 Paolo Tanga 5 Frédéric Vachier 9 Arthur Vigan 1 Oliver Witasse 13 Bin Yang 24
Abstract : Context. Over the past decades, several interplanetary missions have studied small bodies in situ, leading to major advances in our understanding of their geological and geophysical properties. These missions, however, have had a limited number of targets. Among them, the NASA Dawn mission has characterised in detail the topography and albedo variegation across the surface of asteroid (4) Vesta down to a spatial resolution of 20 m pixel-1 scale. Aims: Here our aim was to determine how much topographic and albedo information can be retrieved from the ground with VLT/SPHERE in the case of Vesta, having a former space mission (Dawn) providing us with the ground truth that can be used as a benchmark. Methods: We observed Vesta with VLT/SPHERE/ZIMPOL as part of our ESO large programme (ID 199.C-0074) at six different epochs, and deconvolved the collected images with a parametric point spread function (PSF). We then compared our images with synthetic views of Vesta generated from the 3D shape model of the Dawn mission, on which we projected Vesta's albedo information. Results: We show that the deconvolution of the VLT/SPHERE images with a parametric PSF allows the retrieval of the main topographic and albedo features present across the surface of Vesta down to a spatial resolution of 20-30 km. Contour extraction shows an accuracy of 1 pixel (3.6 mas). The present study provides the very first quantitative estimate of the accuracy of ground-based adaptive-optics imaging observations of asteroid surfaces. Conclusions: In the case of Vesta, the upcoming generation of 30-40 m telescopes (ELT, TMT, GMT) should in principle be able to resolve all of the main features present across its surface, including the troughs and the north-south crater dichotomy, provided that they operate at the diffraction limit. Reduced images of Table A.1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A6Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 199.C-0074 (PI: P. Vernazza).
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Romain Jl. Fétick, Laurent Jorda, Pierre Vernazza, Michael Marsset, Alexis Drouard, et al.. Closing the gap between Earth-based and interplanetary mission observations: Vesta seen by VLT/SPHERE. Astronomy and Astrophysics - A&A, EDP Sciences, 2019, 623, pp.A6. ⟨10.1051/0004-6361/201834749⟩. ⟨hal-02118093⟩

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