ROSETTA/OSIRIS observations of the 67P nucleus during the April 2016 flyby: high-resolution spectrophotometry. (arXiv:1812.09415v1 [astro-ph.EP])

ROSETTA/OSIRIS observations of the 67P nucleus during the April 2016 flyby: high-resolution spectrophotometry. (arXiv:1812.09415v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Feller_C/0/1/0/all/0/1">C. Feller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fornasier_S/0/1/0/all/0/1">S. Fornasier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ferrari_S/0/1/0/all/0/1">S. Ferrari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hasselmann_P/0/1/0/all/0/1">P.H. Hasselmann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barucci_A/0/1/0/all/0/1">A. Barucci</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Massironi_M/0/1/0/all/0/1">M. Massironi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deshapriya_J/0/1/0/all/0/1">J.D.P Deshapriya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sierks_H/0/1/0/all/0/1">H. Sierks</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Naletto_G/0/1/0/all/0/1">G. Naletto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lamy_P/0/1/0/all/0/1">P. L. Lamy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodrigo_R/0/1/0/all/0/1">R. Rodrigo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koschny_D/0/1/0/all/0/1">D. Koschny</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Davidsson_B/0/1/0/all/0/1">B.J.R. Davidsson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bertaux_J/0/1/0/all/0/1">J.-L. Bertaux</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bertini_I/0/1/0/all/0/1">I. Bertini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bodewits_D/0/1/0/all/0/1">D. Bodewits</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cremonese_G/0/1/0/all/0/1">G. Cremonese</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Deppo_V/0/1/0/all/0/1">V. Da Deppo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Debei_S/0/1/0/all/0/1">S. Debei</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cecco_M/0/1/0/all/0/1">M. De Cecco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fulle_M/0/1/0/all/0/1">M. Fulle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gutierrez_P/0/1/0/all/0/1">P. J. Gutiérrez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guttler_C/0/1/0/all/0/1">C. Güttler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ip_W/0/1/0/all/0/1">W.-H. Ip</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Keller_H/0/1/0/all/0/1">H. U. Keller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lara_L/0/1/0/all/0/1">L. M. Lara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lazzarin_M/0/1/0/all/0/1">M. Lazzarin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_Moreno_J/0/1/0/all/0/1">J. J. López-Moreno</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marzari_F/0/1/0/all/0/1">F. Marzari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shi_X/0/1/0/all/0/1">X. Shi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tubiana_C/0/1/0/all/0/1">C. Tubiana</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gaskell_B/0/1/0/all/0/1">B. Gaskell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Forgia_F/0/1/0/all/0/1">F. La Forgia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lucchetti_A/0/1/0/all/0/1">A. Lucchetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mottola_S/0/1/0/all/0/1">S. Mottola</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pajola_M/0/1/0/all/0/1">M. Pajola</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Preusker_F/0/1/0/all/0/1">F. Preusker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scholten_F/0/1/0/all/0/1">F. Scholten</a>

In April 2016, the Rosetta spacecraft performed a low-altitude
low-phase-angle flyby over the Imhotep-Khepry transition of
67P/Churyumov-Gerasimenko’s nucleus. The OSIRIS/Narrow-Angle-Camera (NAC)
acquired 112 images with mainly 3 broadband filters in the visible at a
resolution of up to 0.53 m/px and for phase angles between 0.095{deg} and
62{deg}. Using those images, we have investigated the morphological and
spectrophotometrical properties of this area. We assembled the images into
coregistered color cubes. Using a 3D shape model, we produced the illumination
conditions and georeference for each image. We projected the observations on a
map to investigate its geomorphology. Observations were photometrically
corrected using the Lommel-Seeliger disk law. Spectrophotometric analyses were
performed on the coregistered color cubes. These data were used to estimate the
local phase reddening. This region of the nucleus hosts numerous and varied
types of terrains and features. We observe an association between a feature’s
nature, its reflectance, and its spectral slope. Fine material deposits exhibit
an average reflectance and spectral slope, while terrains with diamictons,
consolidated material, degraded outcrops, or features such as somber boulders,
present a lower-than-average reflectance and higher-than-average spectral
slope. Bright surfaces present here a spectral behavior consistent with
terrains enriched in water-ice. We find a phase-reddening slope of
0.064{pm}0.001{%}/100nm/{deg} at 2.7 au outbound, similarly to the one
obtained at 2.3 au inbound during the February 2015 flyby. Identified as the
source region of multiple jets and a host of water-ice material, the
Imhotep-Khepry transition appeared in April 2016, close to the frost line, to
further harbor several potential locations with exposed water-ice material
among its numerous different morphological terrain units.

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