Characterization of OSIRIS NAC filters for the interpretation of multispectral data of comet 67P/Churyumov-Gerasimenko
Jorda, L.; Lamy, P. L.; Lara, L. M.; Bertaux, J. -L.; Sierks, H.; Fulle, M.; Kührt, E.; Güttler, C.; Keller, H. U.; Pajola, M.; Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip, W. -H.; Knollenberg, J.; Küppers, M.; Lazzarin, M.; Marzari, F.; Naletto, G.; Oklay, N.; Thomas, N.; Tubiana, C.; Vincent, J. -B.; Besse, S.; Kramm, J. -R.; Lopez-Moreno, J. J.; La Forgia, F.; Michalik, H.; Barucci, A. M.
Germany, Netherlands, Italy, Poland, Sweden, France, Spain, Switzerland, United States, Taiwan
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.