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

R. Jl. Fétick 1 L. Jorda 1 P. Vernazza 1 M. Marsset 2 A. Drouard 3 T. Fusco 4, 1 B. Carry 5 F. Marchis 6 J. Hanuš M. Viikinkoski 7 M. Birlan 8 P. Bartczak J. Berthier 9 J. Castillo-Rogez 10 F. Cipriani 11 F. Colas G. Dudziński C. Dumas 12 M. Ferrais E. Jehin 13 M. Kaasalainen 14 A. Kryszczynska 15 P. Lamy 1 H. Le Coroller 16 A. Marciniak 17 T. Michalowski 18 P. Michel 5 L. M. Mugnier 4 B. Neichel 19 M. Pajuelo 20 E. Podlewska-Gaca T. Santana-Ros 15 P. Tanga 5 F. Vachier 8 Arthur Vigan 1 O. Witasse 11 B. Yang
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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R. Jl. Fétick, L. Jorda, P. Vernazza, M. Marsset, A. 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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