Characterization of OSIRIS NAC filters for the interpretation of multispectral data of comet 67P/Churyumov-Gerasimenko^⋆

¹ Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
e-mail: oklay@mps.mpg.de
² Research and Scientific Support Department, European Space Agency, 2201 Noordwijk, The Netherlands
³ Center of Studies and Activities for Space, CISAS, “G. Colombo”, University of Padova, via Venezia 15, 35131 Padova, Italy
⁴ PAS Space Research Center, Bartycka 18A, 00-716 Warszawa, Poland
⁵ Department of Physics & Astronomy, Uppsala University, Box 516 75120, Uppsala, Sweden
⁶ Dipartimento di Fisica e Astronomia “Galileo Galilei”, University of Padova, vic. Osservatorio 3, 35122 Padova, Italy
⁷ LESIA, Observatoire de Paris, CNRS, UPMC Université Paris 06, Université Paris-Diderot, 5 place J. Janssen, 92195 Meudon Principal Cedex, France
⁸ Université Paris-Diderot, Sorbonne Paris Cité, 4 rue Elsa Morante, 75205 Paris Cedex 13, France
⁹ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astro-physique de Marseille) UMR 7326, 13388 Marseille, France
¹⁰ Centro de Astrobiologia (INTA-CSIC), European Space Agency (ESA), European Space Astronomy Centre (ESAC), PO Box 78, 28691 Villanueva de la Canada, Madrid, Spain
¹¹ International Space Science Institute, Hallerstrasse 6, 3012 Bern, Switzerland
¹² Department for Astronomy, University of Maryland, College Park, MD 20742-2421, USA
¹³ LATMOS, CNRS/UVSQ/IPSL, 11 boulevard d’Alembert, 78280 Guyancourt, France
¹⁴ INAF Osservatorio Astronomico di Padova, vic. dell’Osservatorio 5, 35122 Padova, Italy
¹⁵ CNR-IFN UOS Padova LUXOR, via Trasea 7, 35131 Padova, Italy
¹⁶ Department of Industrial Engineering, University of Padova, via Venezia 1, 35131 Padova, Italy
¹⁷ University of Trento, via Sommarive 9, 38123 Trento, Italy
¹⁸ INAF Osservatorio Astronomico di Trieste, via Tiepolo 11, 34014 Trieste, Italy
¹⁹ Instituto de Astrofisica de Andalucia-CSIC, Glorieta de la Astronomia, 18008 Granada, Spain
²⁰ Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Planetenforschung, Rutherfordstraße 2, 12489 Berlin, Germany
²¹ Graduate Institute of Astronomy, National Central University, 300 Chung-Da Rd, 32054 Chung-Li, Taiwan
²² Institut für Geophysik und extraterrestrische Physik, TU Braunschweig, 38106 Braunschweig, Germany
²³ Operations Department European Space Astronomy Centre ESA, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
²⁴ Institut für Datentechnik und Kommunikationsnetze der TU Braunschweig, Hans-Sommer-Str. 66, 38106 Braunschweig, Germany
²⁵ Department of Information Engineering, University of Padova, via Gradenigo 6/B, 35131 Padova, Italy
²⁶ Physikalisches Institut, Sidlerstrasse 5, University of Bern, 3012 Bern, Switzerland

Received: 28 February 2015
Accepted: 29 August 2015

Abstract

Context. We interpret multicolor data from OSIRISNAC for the remote-sensing exploration of comet 67P/Churyumov-Gerasimenko.

Aims. We determine the most meaningful definition of color maps for the characterization of surface variegation with filters available on OSIRIS NAC.

Methods. We analyzed laboratory spectra of selected minerals and olivine-pyroxene mixtures seen through OSIRIS NAC filters, with spectral methods existing in the literature: reflectance ratios, minimum band wavelength, spectral slopes, band tilt, band curvature, and visible tilt.

Results. We emphasize the importance of reflectance ratios and particularly the relation of visible tilt vs. band tilt. This technique provides a reliable diagnostic of the presence of silicates. Color maps constructed by red-green-blue colors defined with the green, orange, red, IR, and Fe₂O₃ filters let us define regions that may significantly differ in composition.