J/A+A/623/A6 VLT/SPHERE/ZIMPOL images of Vesta (Fetick+, 2019)
Closing the gap between Earth-based and interplanetary mission observations:
Vesta seen by VLT/SPHERE.
Fetick R.J., Jorda L., Vernazza P., Marsset M., Drouard A., Fusco T.,
Carry B., Marchis F., Hanus J., Viikinkoski M., Birlan M., Bartczak P.,
Berthier J., Castillo-Rogez J., Cipriani F., Colas F., DudziNski G.,
Dumas C., Ferrais M., Jehin E., Kaasalainen M., Kryszczynska A., Lamy P.,
Le Coroller H., Marciniak A., Michalowski T., Michel P., Mugnier L.M.,
Neichel B., Pajuelo M., Podlewska-Gaca E., Santana-Ros T., Tanga P.,
Vachier F., Vigan A., Witasse O., Yang B.
<Astron. Astrophys. 623, A6 (2019)>
=2019A&A...623A...6F 2019A&A...623A...6F (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets
Keywords: techniques: high angular resolution - techniques: image processing -
methods: observational - minor planets, asteroids: individual: Vesta
Abstract:
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 ∼20m/pixel scale.
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.
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.
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 ∼20-30km. Contour extraction shows an accuracy of
∼1-pixel (3.6mas). The present study provides the very first
quantitative estimate of the accuracy of ground-based adaptive-optics
imaging observations of asteroid surfaces.
In the case of Vesta, the upcoming generation of 30-40m 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.
Description:
Vesta observations with VLT/SPHERE/ZIMPOL as part of the ESO large
programme (ID 199.C-0074, PI: P.Vernazza) at six different epochs. The
provided data is a set of images in FITS format, whose names
correspond to the SPHERE observation times. Each image is of size
1024x1024 pixels. ESO header for each FITS provides information about
the observation.
Note that many observations are available for each of the six epochs.
object.dat :
--------------------------------------------------------------------
Planet Name H Diam i e a
mag km deg AU
--------------------------------------------------------------------
4 Vesta 3.20 468.3 7.141840 0.08874248 2.36126876
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 155 30 List of images
fits/* . 30 Individual images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 26 F7.5 arcsec/pix scale Scale of the image
28- 31 I4 --- Nx Number of pixels along X-axis
33- 36 I4 --- Ny Number of pixels along Y-axis
38- 60 A23 "datime" Obs.date Observation date
62- 65 I4 Kibyte size Size of FITS file
67- 90 A24 --- FileName Name of FITS file, in subdirectory fits
92-155 A64 --- Title Title of the FITS file
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Acknowledgements:
Romain Fetick, romain.fetick(at)lam.fr
(End) Romain Fetick [LAM, Marseille, France], Patricia Vannier [CDS] 01-Feb-2019