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1. Exposed bright features on the comet 67P/Churyumov-Gerasimenko : distribution and evolution

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Hasselmann, P. H., Feller, C., Sierks, H., Lucchetti, A., Pajola, M., Oklay, N., Mottola, S., Masoumzadeh, N., Tubiana, C., Guettler, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Bertaux, J. -L, Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Hoang, H. V., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kuppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Preusker, F., Shi, X., Thomas, N., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Hasselmann, P. H., Feller, C., Sierks, H., Lucchetti, A., Pajola, M., Oklay, N., Mottola, S., Masoumzadeh, N., Tubiana, C., Guettler, C., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Bertaux, J. -L, Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Hoang, H. V., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kuppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Preusker, F., Shi, X., Thomas, N., and Vincent, J. -B
Abstract: Context. Since its arrival at the comet 67P/Churyumov-Gerasimenko in August 2014, the Rosetta spacecraft followed the comet as it went past the perihelion and beyond until September 2016. During this time there were many scientific instruments operating on board Rosetta to study the comet and its evolution in unprecedented detail. In this context, our study focusses on the distribution and evolution of exposed bright features that have been observed by OSIRIS, which is the scientific imaging instrument aboard Rosetta. Aims. We envisage investigating various morphologies of exposed bright features and the mechanisms that triggered their appearance. Methods. We co-registered multi-filter observations of OSIRIS images that are available in reflectance. The Lommel-Seeliger disk function was used to correct for the illumination conditions and the resulting colour cubes were used to perform spectrophotometric analyses on regions of interest. Results. We present a catalogue of 57 exposed bright features observed on the nucleus of the comet, all of which are attributed to the presence of H2O ice on the comet. Furthermore, we categorise these patches under four different morphologies and present geometric albedos for each category. Conclusions. Although the nucleus of 67P/Churyumov-Gerasimenko appears to be dark in general, there are localised H2O ice sources on the comet. Cometary activity escalates towards the perihelion passage and reveals such volatile ices. We propose that isolated H2O ice patches found in smooth terrains in regions, such as Imhotep, Bes, and Hapi, result from frost as an aftermath of the cessation of the diurnal water cycle on the comet as it recedes from perihelion. Upon the comet's return to perihelion, such patches are revealed when sublimation-driven erosion removes the thin dust layers that got deposited earlier. More powerful activity sources such as cometary outbursts are capable of revealing much fresher, less contaminated H2O ice that is prese
Published: 2018
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2. Exposed bright features on the comet 67P/Churyumov-Gerasimenko: Distribution and evolution

Author: German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Ministerio de Educación y Ciencia (España), European Space Agency, Swedish National Space Board, Deshapriya, J.D.P., Barucci, M.A., Fornasier, S., Hasselmann, P.H., Feller, C., Sierks, H., Lucchetti, A., Pajola, M., Oklay, N., Mottola, S., Masoumzadeh, N., Tubiana, C., Güttler, C., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, Björn J. R., Debei, S., Cecco, M.D., Deller, J., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Hoang, H. V., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Preusker, F., Shi, X., Thomas, N., Vincent, J.B., German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Ministerio de Educación y Ciencia (España), European Space Agency, Swedish National Space Board, Deshapriya, J.D.P., Barucci, M.A., Fornasier, S., Hasselmann, P.H., Feller, C., Sierks, H., Lucchetti, A., Pajola, M., Oklay, N., Mottola, S., Masoumzadeh, N., Tubiana, C., Güttler, C., Barbieri, C., Lamy, P.L., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, Björn J. R., Debei, S., Cecco, M.D., Deller, J., Fulle, M., Groussin, O., Gutiérrez, Pedro J., Hoang, H. V., Hviid, S.F., Ip, W. H., Jorda, L., Keller, H.U., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Marzari, F., Naletto, G., Preusker, F., Shi, X., Thomas, N., and Vincent, J.B.
Abstract: Context. Since its arrival at the comet 67P/Churyumov-Gerasimenko in August 2014, the Rosetta spacecraft followed the comet as it went past the perihelion and beyond until September 2016. During this time there were many scientific instruments operating on board Rosetta to study the comet and its evolution in unprecedented detail. In this context, our study focusses on the distribution and evolution of exposed bright features that have been observed by OSIRIS, which is the scientific imaging instrument aboard Rosetta. Aims. We envisage investigating various morphologies of exposed bright features and the mechanisms that triggered their appearance. Methods. We co-registered multi-filter observations of OSIRIS images that are available in reflectance. The Lommel-Seeliger disk function was used to correct for the illumination conditions and the resulting colour cubes were used to perform spectrophotometric analyses on regions of interest. Results. We present a catalogue of 57 exposed bright features observed on the nucleus of the comet, all of which are attributed to the presence of HO ice on the comet. Furthermore, we categorise these patches under four different morphologies and present geometric albedos for each category. Conclusions. Although the nucleus of 67P/Churyumov-Gerasimenko appears to be dark in general, there are localised HO ice sources on the comet. Cometary activity escalates towards the perihelion passage and reveals such volatile ices. We propose that isolated HO ice patches found in smooth terrains in regions, such as Imhotep, Bes, and Hapi, result from frost as an aftermath of the cessation of the diurnal water cycle on the comet as it recedes from perihelion. Upon the comet's return to perihelion, such patches are revealed when sublimation-driven erosion removes the thin dust layers that got deposited earlier. More powerful activity sources such as cometary outbursts are capable of revealing much fresher, less contaminated HO ice that is preserved
Published: 2018

3. The highly active Anhur-Bes regions in the 67P/Churyumov-Gerasimenko comet : results from OSIRIS/ROSETTA observations

Author: Fornasier, S., Feller, C., Lee, J. -C, Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P., Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. -H, Lin, Z. -Y, Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., Vincent, J. -B, Fornasier, S., Feller, C., Lee, J. -C, Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P., Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. -H, Lin, Z. -Y, Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B
Abstract: The Southern hemisphere of the 67P/Churyumov-Gerasimenko comet has become visible from Rosetta only since 2015 March. It was illuminated during the perihelion passage and therefore it contains the regions that experienced the strongest heating and erosion rates, thus exposing the sub-surface most pristine material. In this work we investigate, thanks to the OSIRIS images, the geomorphology, the spectrophotometry and some transient events of two Southern hemisphere regions: Anhur and part of Bes. Bes is dominated by outcropping consolidated terrain covered with fine particle deposits, while Anhur appears strongly eroded with elongated canyon-like structures, scarp retreats, different kinds of deposits and degraded sequences of strata indicating a pervasive layering. We discovered a new 140 m long and 10 m high scarp formed in the Anhur-Bes boundary during/after the perihelion passage, close to the area where exposed CO2 and H2O ices were previously detected. Several jets have been observed originating from these regions, including the strong perihelion outburst, an active pit and a faint optically thick dust plume. We identify several areas with a relatively bluer slope (i.e. a lower spectral slope value) than their surroundings, indicating a surface composition enriched with some water ice. These spectrally bluer areas are observed especially in talus and gravitational accumulation deposits where freshly exposed material had fallen from nearby scarps and cliffs. The investigated regions become spectrally redder beyond 2 au outbound when the dust mantle became thicker, masking the underlying ice-rich layers.
Published: 2017
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4. The opposition effect of 67P/Churyumov-Gerasimenko on post-perihelion Rosetta images

Author: Hasselmann, P. H., Barucci, M. A., Fornasier, S., Feller, C., Deshapriya, J. D. P., Fulchignoni, M., Jost, B., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gaskell, R. W., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Hasselmann, P. H., Barucci, M. A., Fornasier, S., Feller, C., Deshapriya, J. D. P., Fulchignoni, M., Jost, B., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Gaskell, R. W., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: High-resolution OSIRIS/Rosetta images of 67P/Churyumov-Gerasimenko acquired on the night run of 2016 April 9-10 show, at large scale, an opposition effect (OE) spot sweeping across Imhotep as the phase angle ranges from 0 degrees to 17 degrees. In this work, we fitted the phase curve of the whole surface imaged as well as three particular features using both the linear-exponential and Hapke models. These features encompass different types of spectral behaviour: a circular mesa, one venous structure and an assemblage of bright spots, going from red to blue colours. Both the Hapke and linear-exponential parameters indicate a stepwise sharpening of the OE from bright spots to circular mesa. Yet a very broad nonlinear phase curve is verified and no sign of sharp OE associated with a coherent-backscattering mechanism is observed. We estimate that the 67P surface is dominated by opaque, desiccated and larger-than-wavelength irregular grains. Veins and bright spots display photometric properties consistent with surfaces becoming slightly brighter as they are enriched by high-albedo ice grains. We also report the estimation of normal albedo for all cometary regions observed throughout the image sequence. Comparison to pre-perihelion results indicates that far better insolation of northern brighter regions, i.e. Hapi, Hathor and Seth, is sufficient to explain mismatches on the photometric parameters. However, metre-scale photometric analysis of the Imhotep-Ash boundary area advocates for mild darkening (<7 per cent) of the surface at local scale.
Published: 2017
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5. Multivariate statistical analysis of OSIRIS/Rosetta spectrophotometric data of comet 67P/Churyumov-Gerasimenko

Author: Perna, D., Fulchignoni, M., Barucci, M. A., Fornasier, S., Feller, C., Deshapriya, J. D. P., Hasselmann, P. H., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., Deller, J., De Cecco, M., El-Maarry, M. R., Fulle, M., Groussin, O., Gutierrez, P. J., Guttler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuhrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Oklay, N., Thomas, N., Tubiana, C., Vincent, J. -B, Perna, D., Fulchignoni, M., Barucci, M. A., Fornasier, S., Feller, C., Deshapriya, J. D. P., Hasselmann, P. H., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., Deller, J., De Cecco, M., El-Maarry, M. R., Fulle, M., Groussin, O., Gutierrez, P. J., Guttler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuhrt, E., Kuppers, M., Lara, L. M., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Oklay, N., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Context. The ESA Rosetta mission explored comet 67P/Churyumov-Gerasimenko in 2014 2016, following its target before and after the perihelion passage on 13 August 2015. The NAC camera of the OSIRIS imaging system allowed to map the nucleus surface acquiring images with different filters in the visible wavelength range. Aims. Here we study the spectrophotometric behaviour of the nucleus by a multivariate statistical analysis, aiming to distinguish homogeneous groups and to constrain the bulk composition. Methods. We applied the G-mode clustering algorithm to 16 OSIRIS data cubes acquired on 5 6 August 2014 (mostly covering the northern hemisphere) and 2 May 2015 (mostly covering the southern hemisphere), selected to have complete coverage of the comet's surface with similar observing conditions. Results. We found four similar homogeneous groups for each of the analysed cubes. The first group corresponds to the average spectrophotometric behaviour of the nucleus. The second (spectrally redder) and the third (spectrally bluer) groups are found in regions that were already found to deviate from the average terrain of the comet by previous studies. A fourth group (characterised by enhancements of the flux at 700 750 nm and 989 nm, possibly due to H2O+ and /or NH2 emissions) seems connected with the cometary activity rather than with the bulk composition. Conclusions. While our aim in this work was to study the spectrophotometric behaviour of the nucleus of 67P/Churyumov-Gerasimenko as a whole, we found that a follow-up application of the G-mode to smaller regions of the surface could be useful in particular to identify and study the temporal evolution of ice patches, as well as to constrain the composition and physical processes behind the emission of dust jets.
Published: 2017
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6. The highly active Anhur-Bes regions in the 67P/Churyumov - Gerasimenko comet: results from OSIRIS/ROSETTA observations

Author: Fornasier, S., Feller, C., Lee, J. C., Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P, Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. H., Lin, Z. Y., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Agarwal, J., A'Hearn, M., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J ., Kovacs, G., Kramm, R., Kuehrt, E., Kueppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., Vincent, J. -B., Fornasier, S., Feller, C., Lee, J. C., Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P, Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. H., Lin, Z. Y., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Agarwal, J., A'Hearn, M., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J ., Kovacs, G., Kramm, R., Kuehrt, E., Kueppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B.
Abstract: The Southern hemisphere of the 67P/Churyumov-Gerasimenko comet has become visible from Rosetta only since March 2015. It was illuminated during the perihelion passage and therefore it contains the regions that experienced the strongest heating and erosion rate, thus exposing the subsurface most pristine material. In this work we investigate, thanks to the OSIRIS images, the geomorphology, the spectrophotometry and some transient events of two Southern hemisphere regions: Anhur and part of Bes. Bes is dominated by outcropping consolidated terrain covered with fine particle deposits, while Anhur appears strongly eroded with elongated canyon-like structures, scarp retreats, different kinds of deposits, and degraded sequences of strata indicating a pervasive layering. We discovered a new 140 m long and 10 m high scarp formed in the Anhur/Bes boundary during/after the perihelion passage, close to the area where exposed CO$_2$ and H$_2$O ices were previously detected. Several jets have been observed originating from these regions, including the strong perihelion outburst, an active pit, and a faint optically thick dust plume. We identify several areas with a relatively bluer slope (i.e. a lower spectral slope value) than their surroundings, indicating a surface composition enriched with some water ice. These spectrally bluer areas are observed especially in talus and gravitational accumulation deposits where freshly exposed material had fallen from nearby scarps and cliffs. The investigated regions become spectrally redder beyond 2 au outbound when the dust mantle became thicker, masking the underlying ice-rich layers., Comment: 16 pages, 15 figures, published online on 24 May 2017 on Mon. Not. R. Astron. Soc. stx1275, https://doi.org/10.1093/mnras/stx1275
Published: 2017
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7. Evidence for Surface Variegation in Rosetta OSIRIS Images of Asteroid 2867 Steins

Author: Schröder, S. E., Keller, H. U., Gutierrez, P., Hviid, S. F., Kramm, R., Sabolo, W., Sierks, H., Schröder, S. E., Keller, H. U., Gutierrez, P., Hviid, S. F., Kramm, R., Sabolo, W., and Sierks, H.
Abstract: The OSIRIS camera onboard Rosetta successfully acquired images of asteroid 2867 Steins through a variety of color filters during the flyby on 5 September 2008. The best images of this 5 km diameter asteroid have a resolution of 78 meters per pixel. We process the images by deconvolving with the point spread function and enlarging through the Mitchell-Netravali filter. The enhanced set is analyzed by means of various techniques (PCA, band ratios, stereo anaglyphs) to study surface morphology and search for variegation. We identify a landslide, which supports a YORP origin for Steins' unusual diamond shape. In addition, we find that the interior of one of two large craters on the south pole is bluer than the rest of the body., Comment: 17 pages, 9 figures
Published: 2017
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8. The highly active Anhur-Bes regions in the 67P/Churyumov - Gerasimenko comet: results from OSIRIS/ROSETTA observations

Author: Fornasier, S., Feller, C., Lee, J. C., Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P, Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. H., Lin, Z. Y., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Agarwal, J., A'Hearn, M., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J ., Kovacs, G., Kramm, R., Kuehrt, E., Kueppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., Vincent, J. -B., Fornasier, S., Feller, C., Lee, J. C., Ferrari, S., Massironi, M., Hasselmann, P. H., Deshapriya, J. D. P, Barucci, M. A., El-Maarry, M. R., Giacomini, L., Mottola, S., Keller, H. U., Ip, W. H., Lin, Z. Y., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Agarwal, J., A'Hearn, M., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Jorda, L., Knollenberg, J ., Kovacs, G., Kramm, R., Kuehrt, E., Kueppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Naletto, G., Oklay, N., Pajola, M., Shi, X., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B.
Abstract: The Southern hemisphere of the 67P/Churyumov-Gerasimenko comet has become visible from Rosetta only since March 2015. It was illuminated during the perihelion passage and therefore it contains the regions that experienced the strongest heating and erosion rate, thus exposing the subsurface most pristine material. In this work we investigate, thanks to the OSIRIS images, the geomorphology, the spectrophotometry and some transient events of two Southern hemisphere regions: Anhur and part of Bes. Bes is dominated by outcropping consolidated terrain covered with fine particle deposits, while Anhur appears strongly eroded with elongated canyon-like structures, scarp retreats, different kinds of deposits, and degraded sequences of strata indicating a pervasive layering. We discovered a new 140 m long and 10 m high scarp formed in the Anhur/Bes boundary during/after the perihelion passage, close to the area where exposed CO$_2$ and H$_2$O ices were previously detected. Several jets have been observed originating from these regions, including the strong perihelion outburst, an active pit, and a faint optically thick dust plume. We identify several areas with a relatively bluer slope (i.e. a lower spectral slope value) than their surroundings, indicating a surface composition enriched with some water ice. These spectrally bluer areas are observed especially in talus and gravitational accumulation deposits where freshly exposed material had fallen from nearby scarps and cliffs. The investigated regions become spectrally redder beyond 2 au outbound when the dust mantle became thicker, masking the underlying ice-rich layers., Comment: 16 pages, 15 figures, published online on 24 May 2017 on Mon. Not. R. Astron. Soc. stx1275, https://doi.org/10.1093/mnras/stx1275
Published: 2017
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9. Evidence for Surface Variegation in Rosetta OSIRIS Images of Asteroid 2867 Steins

Author: Schröder, S. E., Keller, H. U., Gutierrez, P., Hviid, S. F., Kramm, R., Sabolo, W., Sierks, H., Schröder, S. E., Keller, H. U., Gutierrez, P., Hviid, S. F., Kramm, R., Sabolo, W., and Sierks, H.
Abstract: The OSIRIS camera onboard Rosetta successfully acquired images of asteroid 2867 Steins through a variety of color filters during the flyby on 5 September 2008. The best images of this 5 km diameter asteroid have a resolution of 78 meters per pixel. We process the images by deconvolving with the point spread function and enlarging through the Mitchell-Netravali filter. The enhanced set is analyzed by means of various techniques (PCA, band ratios, stereo anaglyphs) to study surface morphology and search for variegation. We identify a landslide, which supports a YORP origin for Steins' unusual diamond shape. In addition, we find that the interior of one of two large craters on the south pole is bluer than the rest of the body., Comment: 17 pages, 9 figures
Published: 2017
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10. Evolution Of The Dust Size Distribution Of Comet 67P/Churyumov-Gerasimenko From 2.2 Au To Perihelion

Author: Fulle, M., Marzari, F., Della Corte, V., Fornasier, S., Sierks, H., Rotundi, A., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Lopez-Moreno, J. J., Accolla, M., Agarwal, J., A'Hearn, M. F., Altobelli, N., Barucci, M. A., Bertaux, J. -L, Bertini, I., Bodewits, D., Bussoletti, E., Colangeli, L., Cosi, M., Cremonese, G., Crifo, J. -F, Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Esposito, F., Ferrari, M., Giovane, F., Gustafson, B., Green, S. F., Groussin, O., Gruen, E., Gutierrez, P., Guettler, C., Herranz, M. L., Hviid, S. F., Ip, W., Ivanovski, S. L., Jeronimo, J. M., Jorda, L., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Leese, M. R., Lopez-Jimenez, A. C., Lucarelli, F., Epifani, E. Mazzotta, McDonnell, J. A. M., Mennella, V., Molina, A., Morales, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Ortiz, J. L., Palomba, E., Palumbo, P., Perrin, J. -M, Rietmeijer, F. J. M., Rodriguez, J., Sordini, R., Thomas, N., Tubiana, C., Vincent, J. -B, Weissman, P., Wenzel, K. -P, Zakharov, V., Zarnecki, J. C., Fulle, M., Marzari, F., Della Corte, V., Fornasier, S., Sierks, H., Rotundi, A., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Lopez-Moreno, J. J., Accolla, M., Agarwal, J., A'Hearn, M. F., Altobelli, N., Barucci, M. A., Bertaux, J. -L, Bertini, I., Bodewits, D., Bussoletti, E., Colangeli, L., Cosi, M., Cremonese, G., Crifo, J. -F, Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Esposito, F., Ferrari, M., Giovane, F., Gustafson, B., Green, S. F., Groussin, O., Gruen, E., Gutierrez, P., Guettler, C., Herranz, M. L., Hviid, S. F., Ip, W., Ivanovski, S. L., Jeronimo, J. M., Jorda, L., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Leese, M. R., Lopez-Jimenez, A. C., Lucarelli, F., Epifani, E. Mazzotta, McDonnell, J. A. M., Mennella, V., Molina, A., Morales, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Ortiz, J. L., Palomba, E., Palumbo, P., Perrin, J. -M, Rietmeijer, F. J. M., Rodriguez, J., Sordini, R., Thomas, N., Tubiana, C., Vincent, J. -B, Weissman, P., Wenzel, K. -P, Zakharov, V., and Zarnecki, J. C.
Abstract: The Rosetta probe, orbiting Jupiter-family comet 67P/Churyumov-Gerasimenko, has been detecting individual dust particles of mass larger than 10(-10) kg by means of the GIADA dust collector and the OSIRIS Wide Angle Camera and Narrow Angle Camera since 2014 August and will continue until 2016 September. Detections of single dust particles allow us to estimate the anisotropic dust flux from 67P, infer the dust loss rate and size distribution at the surface of the sunlit nucleus, and see whether the dust size distribution of 67P evolves in time. The velocity of the Rosetta orbiter, relative to 67P, is much lower than the dust velocity measured by GIADA, thus dust counts when GIADA is nadir-pointing will directly provide the dust flux. In OSIRIS observations, the dust flux is derived from the measurement of the dust space density close to the spacecraft. Under the assumption of radial expansion of the dust, observations in the nadir direction provide the distance of the particles by measuring their trail length, with a parallax baseline determined by the motion of the spacecraft. The dust size distribution at sizes > 1 mm observed by OSIRIS is consistent with a differential power index of -4, which was derived from models of 67P's trail. At sizes <1 mm, the size distribution observed by GIADA shows a strong time evolution, with a differential power index drifting from -2 beyond 2 au to -3.7 at perihelion, in agreement with the evolution derived from coma and tail models based on ground-based data. The refractory-to-water mass ratio of the nucleus is close to six during the entire inbound orbit and at perihelion.
Published: 2016
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11. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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12. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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13. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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14. Rosetta's comet 67P/Churyumov-Gerasimenko sheds its dusty mantle to reveal its icy nature

Author: Fornasier, S., Mottola, S., Keller, H. U., Barucci, M. A., Davidsson, B., Feller, C., Deshapriya, J. D. P., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Agarwal, J., Bertaux, J. -L, Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Massironi, M., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., Tubiana, C., Vincent, J. -B, Fornasier, S., Mottola, S., Keller, H. U., Barucci, M. A., Davidsson, B., Feller, C., Deshapriya, J. D. P., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, A'Hearn, M., Agarwal, J., Bertaux, J. -L, Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fulle, M., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W. -H, Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kuppers, M., Lara, M. L., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Massironi, M., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Preusker, F., Scholten, F., Shi, X., Thomas, N., Toth, I., Tubiana, C., and Vincent, J. -B
Abstract: The Rosetta spacecraft has investigated comet 67P/Churyumov-Gerasimenko from large heliocentric distances to its perihelion passage and beyond. We trace the seasonal and diurnal evolution of the colors of the 67P nucleus, finding changes driven by sublimation and recondensation of water ice. The whole nucleus became relatively bluer near perihelion, as increasing activity removed the surface dust, implying that water ice is widespread underneath the surface. We identified large (1500 square meters) ice-rich patches appearing and then vanishing in about 10 days, indicating small-scale heterogeneities on the nucleus. Thin frosts sublimating in a few minutes are observed close to receding shadows, and rapid variations in color are seen on extended areas close to the terminator. These cyclic processes are widespread and lead to continuously, slightly varying surface properties.
Published: 2016
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15. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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16. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

Author: Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., Vincent, J. -B, Deshapriya, J. D. P., Barucci, M. A., Fornasier, S., Feller, C., Hasselmann, P. H., Sierks, H., El-Maarry, M. R., Pajola, M., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B. J. R., Debei, S., Deller, J., De Cecco, M., Fulle, M., Gicquel, A., Groussin, O., Gutierrez, P. J., Guettler, C., Hofmann, M., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Mottola, S., Naletto, G., Oklay, N., Perna, D., Pommerol, A., Thomas, N., Tubiana, C., and Vincent, J. -B
Abstract: Our work focuses on the spectrophotometric analysis of selected terrain and bright patches in the Khonsu region on the comet 67P/Churyumov-Gerasimenko. Despite the variety of geological features, their spectrophotometric properties appear to indicate a similar composition. It is noticeable that the smooth areas in Khonsu possess similar spectrophotometric behaviour to some other regions of the comet. We observed bright patches on Khonsu with an estimation of >40 per cent of normal albedo and suggest that they are associated with H2O ice. One of the studied bright patches has been observed to exist on the surface for more than 5 months without a major decay of its size, implying the existence of potential sub-surface icy layers. Its location may be correlated with a cometary outburst during the perihelion passage of the comet in 2015 August, and we interpret it to have triggered the surface modifications necessary to unearth the stratified icy layers beneath the surface. A boulder analysis on Khonsu leads to a power-law index of -3.1 + 0.2/-0.3 suggesting a boulder formation, shaped by varying geological processes for different morphological units.
Published: 2016
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17. 67P/Churyumov-Gerasimenko : Activity between March and June 2014 as observed from Rosetta/OSIRIS

Author: Tubiana, C., Snodgrass, C., Bertini, I., Mottola, S., Vincent, J. -B, Lara, L., Fornasier, S., Knollenberg, J., Thomas, N., Fulle, M., Agarwal, J., Bodewits, D., Ferri, F., Guettler, C., Gutierrez, P. J., La Forgia, F., Lowry, S., Magrin, S., Oklay, N., Pajola, M., Rodrigo, R., Sierks, H., A'Hearn, M. F., Angrilli, F., Barbieri, C., Barucci, M. A., Bertaux, J. -L, Cremonese, G., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Groussin, O., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Koschny, D., Kramm, R., Kuehrt, E., Kueppers, M., Lazzarin, M., Lamy, P. L., Moreno, J. J. Lopez, Marzari, F., Michalik, H., Naletto, G., Rickman, Hans, Sabau, L., Wenzel, K. -P, Tubiana, C., Snodgrass, C., Bertini, I., Mottola, S., Vincent, J. -B, Lara, L., Fornasier, S., Knollenberg, J., Thomas, N., Fulle, M., Agarwal, J., Bodewits, D., Ferri, F., Guettler, C., Gutierrez, P. J., La Forgia, F., Lowry, S., Magrin, S., Oklay, N., Pajola, M., Rodrigo, R., Sierks, H., A'Hearn, M. F., Angrilli, F., Barbieri, C., Barucci, M. A., Bertaux, J. -L, Cremonese, G., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Groussin, O., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Koschny, D., Kramm, R., Kuehrt, E., Kueppers, M., Lazzarin, M., Lamy, P. L., Moreno, J. J. Lopez, Marzari, F., Michalik, H., Naletto, G., Rickman, Hans, Sabau, L., and Wenzel, K. -P
Abstract: Aims. 67P/Churyumov-Gerasimenko is the target comet of the ESA's Rosetta mission. After commissioning at the end of March 2014, the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard Rosetta, started imaging the comet and its dust environment to investigate how they change and evolve while approaching the Sun. Methods. We focused our work on Narrow Angle Camera (NAC) orange images and Wide Angle Camera (WAC) red and visible-610 images acquired between 2014 March 23 and June 24 when the nucleus of 67P was unresolved and moving from approximately 4.3 AU to 3.8 AU inbound. During this period the 67P - Rosetta distance decreased from 5 million to 120 thousand km. Results. Through aperture photometry, we investigated how the comet brightness varies with heliocentric distance. 67P was likely already weakly active at the end of March 2014, with excess flux above that expected for the nucleus. The comet's brightness was mostly constant during the three months of approach observations, apart from one outburst that occurred around April 30 and a second increase in flux after June 20. Coma was resolved in the profiles from mid-April. Analysis of the coma morphology suggests that most of the activity comes from a source towards the celestial north pole of the comet, but the outburst that occurred on April 30 released material in a different direction.
Published: 2015
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18. Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

Author: Fornasier, S., Hasselmann, P. H., Barucci, M. A., Feller, C., Besse, S., Leyrat, C., Lara, L., Gutierrez, P. J., Oklay, N., Tubiana, C., Scholten, F., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Fulle, M., Groussin, O., Guettler, C., Hviid, S. F., Ip, W., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kueppers, M., La Forgia, F., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Matz, K. -D, Michalik, H., Moreno, F., Mottola, S., Naetto, G., Pajola, M., Pommerol, A., Preusker, F., Shi, X., Snodgrass, C., Thomas, N., Vincent, J-B, Fornasier, S., Hasselmann, P. H., Barucci, M. A., Feller, C., Besse, S., Leyrat, C., Lara, L., Gutierrez, P. J., Oklay, N., Tubiana, C., Scholten, F., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Bertaux, J. -L, Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Fulle, M., Groussin, O., Guettler, C., Hviid, S. F., Ip, W., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kuehrt, E., Kueppers, M., La Forgia, F., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Matz, K. -D, Michalik, H., Moreno, F., Mottola, S., Naetto, G., Pajola, M., Pommerol, A., Preusker, F., Shi, X., Snodgrass, C., Thomas, N., and Vincent, J-B
Abstract: Context. The Rosetta mission of the European Space Agency has been orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014 and is now in its escort phase. A large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted are onboard Rosetta. Aims. We present results for the photometric and spectrophotometric properties of the nucleus of 67P derived from the OSIRIS imaging system, which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). The observations presented here were performed during July and the beginning of August 2014, during the approach phase, when OSIRIS was mapping the surface of the comet with several filters at different phase angles (1.3 degrees-54 degrees). The resolution reached up to 2.1 m/px. Methods. The OSIRIS images were processed with the OSIRIS standard pipeline, then converted into I/F. radiance factors and corrected for the illumination conditions at each pixel using the Lommel-Seeliger disk law. Color cubes of the surface were produced by stacking registered and illumination-corrected images. Furthermore, photometric analysis was performed both on disk-averaged photometry in several filters and on disk-resolved images acquired with the NAC orange filter, centered at 649 ran, using Hapke modeling. Results. The disk-averaged phase function of the nucleus of 67P shows a strong opposition surge with a G parameter value of -0.13 +/- 0.01 in the HG system formalism and an absolute magnitude H-v(1, 1, 0) = 15.74 +/- 0.02 mag. The integrated spectrophotometry in 20 filters covering the 250-1000 nm wavelength range shows a red spectral behavior, without clear absorption bands except for a potential absorption centered at similar to 290 rim that is possibly due to SO2 ice. The nucleus shows strong phase reddening, with disk-averaged spectral slopes increasing from 11%/( 100 nm) to 16%/(100 nm) in the 1.3 degrees-54 degrees phase angle range. The geometric albedo of th
Published: 2015
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19. Rotating dust particles in the coma of comet 67P/Churyumov-Gerasimenko

Author: Fulle, M., Ivanovski, S. L., Bertini, I., Gutierrez, P., Lara, L., Sierks, H., Zakharov, V., Della Corte, V., Rotundi, A., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Fornasier, S., Groussin, O., Guettler, C., Hviid, S. F., Ip, W., Jorda, L., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Michalik, H., Naletto, G., Oklay, N., Sabau, L., Thomas, N., Tubiana, C., Vincent, J. -B, Wenzel, K. -P, Fulle, M., Ivanovski, S. L., Bertini, I., Gutierrez, P., Lara, L., Sierks, H., Zakharov, V., Della Corte, V., Rotundi, A., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, Hans, Keller, H. U., Agarwal, J., A'Hearn, M. F., Barucci, M. A., Bertaux, J. -L, Bodewits, D., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., Fornasier, S., Groussin, O., Guettler, C., Hviid, S. F., Ip, W., Jorda, L., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lazzarin, M., Lopez-Moreno, J. J., Marzari, F., Michalik, H., Naletto, G., Oklay, N., Sabau, L., Thomas, N., Tubiana, C., Vincent, J. -B, and Wenzel, K. -P
Abstract: Context. During September and October 2014, the OSIRIS cameras onboard the ESA Rosetta mission detected millions of single particles. Many of these dust particles appear as long tracks (due to both the dust proper motion and the spacecraft motion during the exposure time) with a clear brightness periodicity. Aims. We interpret the observed periodic features as a rotational and translational motion of aspherical dust grains. Methods. By counting the peaks of each track, we obtained statistics of a rotation frequency. We compared these results with the rotational frequency predicted by a model of aspherical dust grain dynamics in a model gas flow. By testing many possible sets of physical conditions and grain characteristics, we constrained the rotational properties of dust grains. Results. We analyzed on the motion of rotating aspherical dust grains with different cross sections in flow conditions corresponding to the coma of 67P/Churyumov-Gerasimenko qualitatively and quantitatively. Based on the OSIRIS observations, we constrain the possible physical parameters of the grains.
Published: 2015
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20. Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

Author: Fornasier, S., Hasselmann, P. H., Barucci, M. A., Feller, C., Besse, S., Leyrat, C., Lara, L., Gutierrez, P. J., Oklay, N., Tubiana, C., Scholten, F., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Agarwal, J., A'Hearn, M. F., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fulle, M., Groussin, O., Güttler, C., Hviid, S. F., Ip, W., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kührt, E., Küppers, M., La Forgia, F., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Matz, K. -D., Michalik, H., Moreno, F., Mottola, S., Naletto, G., Pajola, M., Pommerol, A., Preusker, F., Shi, X., Snodgrass, C., Thomas, N., Vincent, J. -B., Fornasier, S., Hasselmann, P. H., Barucci, M. A., Feller, C., Besse, S., Leyrat, C., Lara, L., Gutierrez, P. J., Oklay, N., Tubiana, C., Scholten, F., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Agarwal, J., A'Hearn, M. F., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fulle, M., Groussin, O., Güttler, C., Hviid, S. F., Ip, W., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kührt, E., Küppers, M., La Forgia, F., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Matz, K. -D., Michalik, H., Moreno, F., Mottola, S., Naletto, G., Pajola, M., Pommerol, A., Preusker, F., Shi, X., Snodgrass, C., Thomas, N., and Vincent, J. -B.
Abstract: The Rosetta mission of the European Space Agency has been orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014 and is now in its escort phase. A large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted are onboard Rosetta. We present results for the photometric and spectrophotometric properties of the nucleus of 67P derived from the OSIRIS imaging system, which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). The disk-averaged phase function of the nucleus of 67P shows a strong opposition surge with a G parameter value of -0.13$\pm$0.01 in the HG system formalism and an absolute magnitude $H_v(1,1,0)$ = 15.74$\pm$0.02 mag. The integrated spectrophotometry in 20 filters covering the 250-1000 nm wavelength range shows a red spectral behavior, without clear absorption bands except for a potential absorption centered at $\sim$ 290 nm that is possibly due to SO$_2$ ice. The nucleus shows strong phase reddening, with disk-averaged spectral slopes increasing from 11\%/(100 nm) to 16\%/(100 nm) in the 1.3$^{\circ}$--54$^{\circ}$ phase angle range. The geometric albedo of the comet is 6.5$\pm$0.2\% at 649 nm, with local variations of up to $\sim$ 16\% in the Hapi region. From the disk-resolved images we computed the spectral slope together with local spectrophotometry and identified three distinct groups of regions (blue, moderately red, and red). The Hapi region is the brightest, the bluest in term of spectral slope, and the most active surface on the comet. Local spectrophotometry shows an enhancement of the flux in the 700-750 nm that is associated with coma emissions., Comment: 18, pages, 14 figures, Astronomy and Astrophysics, in press
Published: 2015
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21. 67P/Churyumov-Gerasimenko: Activity between March and June 2014 as observed from Rosetta/OSIRIS

Author: Tubiana, C., Snodgrass, C., Bertini, I., Mottola, S., Vincent, J.-B., Lara, L., Fornasier, S., Knollenberg, J., Thomas, N., Fulle, M., Agarwal, J., Bodewits, D., Ferri, F., Güttler, C., Gutiérrez, P.J., La Forgia, F., Lowry, S., Magrin, S., Oklay, N., Pajola, M., Rodrigo, R., Sierks, H., A'hearn, M.F., Angrilli, F., Barbieri, C., Barucci, M.A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., Groussin, O., Hviid, S.F., Ip, W., Jorda, L., Keller, H.U., Koschny, D., Kramm, R., Kührt, E., Küppers, M., Lazzarin, M., Lamy, P.L., Lopez Moreno, J.J., Marzari, F., Michalik, H., Naletto, G., Rickman, H., Sabau, L., Wenzel, K.-P., Tubiana, C., Snodgrass, C., Bertini, I., Mottola, S., Vincent, J.-B., Lara, L., Fornasier, S., Knollenberg, J., Thomas, N., Fulle, M., Agarwal, J., Bodewits, D., Ferri, F., Güttler, C., Gutiérrez, P.J., La Forgia, F., Lowry, S., Magrin, S., Oklay, N., Pajola, M., Rodrigo, R., Sierks, H., A'hearn, M.F., Angrilli, F., Barbieri, C., Barucci, M.A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., Groussin, O., Hviid, S.F., Ip, W., Jorda, L., Keller, H.U., Koschny, D., Kramm, R., Kührt, E., Küppers, M., Lazzarin, M., Lamy, P.L., Lopez Moreno, J.J., Marzari, F., Michalik, H., Naletto, G., Rickman, H., Sabau, L., and Wenzel, K.-P.
Abstract: Aims. 67P/Churyumov-Gerasimenko is the target comet of the ESA's Rosetta mission. After commissioning at the end of March 2014, the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard Rosetta, started imaging the comet and its dust environment to investigate how they change and evolve while approaching the Sun.
Published: 2015

22. Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the sun

Author: Rotundi, A., Sierks, H., Della Corte, V., Fulle, M., Gutierrez, P.J., Lara, L., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., López-Moreno, J.J., Accolla, M., Agarwal, J., A'Hearn, M.F., Altobelli, N., Angrilli, F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Bodewits, D., Bussoletti, E., Colangeli, L., Cosi, M., Cremonese, G., Crifo, J.-F., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Esposito, F., Ferrari, M., Fornasier, S., Giovane, F., Gustafson, B., Green, S.F., Groussin, O., Grün, E., Güttler, C., Herranz, M.L., Hviid, S.F., Ip, W., Ivanovski, S., Jerónimo, J.M., Jorda, L., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lazzarin, M., Leese, M.R., López-Jiménez, A.C., Lucarelli, F., Lowry, S.C., Marzari, F., Epifani, E.M., McDonnell, J.A.M., Mennella, V., Michalik, H., Molina, A., Morales, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Ortiz, J.L., Palomba, E., Palumbo, P., Perrin, J.-M., Rodríguez, J., Sabau, L., Snodgrass, C., Sordini, R., Thomas, N., Tubiana, C., Vincent, J.-B., Weissman, P., Wenzel, K.-P., Zakharov, V., Zarnecki, J.C., Rotundi, A., Sierks, H., Della Corte, V., Fulle, M., Gutierrez, P.J., Lara, L., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., López-Moreno, J.J., Accolla, M., Agarwal, J., A'Hearn, M.F., Altobelli, N., Angrilli, F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Bodewits, D., Bussoletti, E., Colangeli, L., Cosi, M., Cremonese, G., Crifo, J.-F., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Esposito, F., Ferrari, M., Fornasier, S., Giovane, F., Gustafson, B., Green, S.F., Groussin, O., Grün, E., Güttler, C., Herranz, M.L., Hviid, S.F., Ip, W., Ivanovski, S., Jerónimo, J.M., Jorda, L., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lazzarin, M., Leese, M.R., López-Jiménez, A.C., Lucarelli, F., Lowry, S.C., Marzari, F., Epifani, E.M., McDonnell, J.A.M., Mennella, V., Michalik, H., Molina, A., Morales, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Ortiz, J.L., Palomba, E., Palumbo, P., Perrin, J.-M., Rodríguez, J., Sabau, L., Snodgrass, C., Sordini, R., Thomas, N., Tubiana, C., Vincent, J.-B., Weissman, P., Wenzel, K.-P., Zakharov, V., and Zarnecki, J.C.
Abstract: Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency's Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10-10 to 10-7 kilograms, and 48 grains of mass 10-5 to 10-2 kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 ± 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails. © 2015, American Association for the Advancement of Science. All rights reserved.
Published: 2015

23. Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

Author: Fornasier, S., Hasselmann, P. H., Barucci, M. A., Feller, C., Besse, S., Leyrat, C., Lara, L., Gutierrez, P. J., Oklay, N., Tubiana, C., Scholten, F., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Agarwal, J., A'Hearn, M. F., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fulle, M., Groussin, O., Güttler, C., Hviid, S. F., Ip, W., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kührt, E., Küppers, M., La Forgia, F., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Matz, K. -D., Michalik, H., Moreno, F., Mottola, S., Naletto, G., Pajola, M., Pommerol, A., Preusker, F., Shi, X., Snodgrass, C., Thomas, N., Vincent, J. -B., Fornasier, S., Hasselmann, P. H., Barucci, M. A., Feller, C., Besse, S., Leyrat, C., Lara, L., Gutierrez, P. J., Oklay, N., Tubiana, C., Scholten, F., Sierks, H., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., Agarwal, J., A'Hearn, M. F., Bertaux, J. -L., Bertini, I., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Fulle, M., Groussin, O., Güttler, C., Hviid, S. F., Ip, W., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, R., Kührt, E., Küppers, M., La Forgia, F., Lazzarin, M., Moreno, J. J. Lopez, Marzari, F., Matz, K. -D., Michalik, H., Moreno, F., Mottola, S., Naletto, G., Pajola, M., Pommerol, A., Preusker, F., Shi, X., Snodgrass, C., Thomas, N., and Vincent, J. -B.
Abstract: The Rosetta mission of the European Space Agency has been orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014 and is now in its escort phase. A large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted are onboard Rosetta. We present results for the photometric and spectrophotometric properties of the nucleus of 67P derived from the OSIRIS imaging system, which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). The disk-averaged phase function of the nucleus of 67P shows a strong opposition surge with a G parameter value of -0.13$\pm$0.01 in the HG system formalism and an absolute magnitude $H_v(1,1,0)$ = 15.74$\pm$0.02 mag. The integrated spectrophotometry in 20 filters covering the 250-1000 nm wavelength range shows a red spectral behavior, without clear absorption bands except for a potential absorption centered at $\sim$ 290 nm that is possibly due to SO$_2$ ice. The nucleus shows strong phase reddening, with disk-averaged spectral slopes increasing from 11\%/(100 nm) to 16\%/(100 nm) in the 1.3$^{\circ}$--54$^{\circ}$ phase angle range. The geometric albedo of the comet is 6.5$\pm$0.2\% at 649 nm, with local variations of up to $\sim$ 16\% in the Hapi region. From the disk-resolved images we computed the spectral slope together with local spectrophotometry and identified three distinct groups of regions (blue, moderately red, and red). The Hapi region is the brightest, the bluest in term of spectral slope, and the most active surface on the comet. Local spectrophotometry shows an enhancement of the flux in the 700-750 nm that is associated with coma emissions., Comment: 18, pages, 14 figures, Astronomy and Astrophysics, in press
Published: 2015
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24. The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

Author: Mottola, S., Lowry, S., Snodgrass, C., Lamy, P. L., Toth, I., Rozek, A., Sierks, H., A'Hearn, M. F., Angrilli, F., Barbieri, C., Barucci, M. A., Bertaux, J-L, Cremonese, G., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Koschny, D., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Michalik, H., Naletto, G., Rickman, Hans, Rodrigo, R., Sabau, L., Thomas, N., Wenzel, K-P, Agarwal, J., Bertini, I., Ferri, F., Guettler, C., Magrin, S., Oklay, N., Tubiana, C., Vincent, J-B, Mottola, S., Lowry, S., Snodgrass, C., Lamy, P. L., Toth, I., Rozek, A., Sierks, H., A'Hearn, M. F., Angrilli, F., Barbieri, C., Barucci, M. A., Bertaux, J-L, Cremonese, G., Da Deppo, V., Davidsson, Björn, De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutierrez, P., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Knollenberg, J., Koschny, D., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J. J., Marzari, F., Michalik, H., Naletto, G., Rickman, Hans, Rodrigo, R., Sabau, L., Thomas, N., Wenzel, K-P, Agarwal, J., Bertini, I., Ferri, F., Guettler, C., Magrin, S., Oklay, N., Tubiana, C., and Vincent, J-B
Abstract: Aims. Approach observations with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard Rosetta are used to determine the rotation period, the direction of the spin axis, and the state of rotation of comet 67P's nucleus. Methods. Photometric time series of 67P have been acquired by OSIRIS since the post wake-up commissioning of the payload in March 2014. Fourier analysis and convex shape inversion methods have been applied to the Rosetta data as well to the available ground-based observations. Results. Evidence is found that the rotation rate of 67P has significantly changed near the time of its 2009 perihelion passage, probably due to sublimation-induced torque. We find that the sidereal rotation periods P-1 = 12.76129 +/- 0.00005 h and P2 = 12.4043 +/- 0.0007 h for the apparitions before and after the 2009 perihelion, respectively, provide the best fit to the observations. No signs of multiple periodicity are found in the light curves down to the noise level, which implies that the comet is presently in a simple rotation state around its axis of largest moment of inertia. We derive a prograde rotation model with spin vector J2000 ecliptic coordinates lambda = 65 degrees +/- 15 degrees, beta = + 59 degrees +/- 15 degrees, corresponding to equatorial coordinates RA = 22 degrees, Dec = +76 degrees. However, we find that the mirror solution, also prograde, at lambda = 275 degrees +/- 15 degrees, beta = + 50 degrees +/- 15 degrees (or RA = 274 degrees, Dec = +27 degrees), is also possible at the same confidence level, due to the intrinsic ambiguity of the photometric problem for observations performed close to the ecliptic plane.
Published: 2014
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25. The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

Author: Mottola, S., Lowry, S., Snodgrass, C., Lamy, P.L., Toth, I., Rożek, A., Sierks, H., A'Hearn, M.F., Angrilli, F., Barbieri, C., Barucci, M.A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P., Hviid, S.F., Ip, W., Jorda, L., Keller, H.U., Knollenberg, J., Koschny, D., Kramm, R., Kührt, E., Küppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J.J., Marzari, F., Michalik, H., Naletto, G., Rickman, H., Rodrigo, R., Sabau, L., Thomas, N., Wenzel, K.-P., Agarwal, J., Bertini, I., Ferri, F., Güttler, C., Magrin, S., Oklay, N., Tubiana, C., Vincent, J.-B., Mottola, S., Lowry, S., Snodgrass, C., Lamy, P.L., Toth, I., Rożek, A., Sierks, H., A'Hearn, M.F., Angrilli, F., Barbieri, C., Barucci, M.A., Bertaux, J.-L., Cremonese, G., Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez, P., Hviid, S.F., Ip, W., Jorda, L., Keller, H.U., Knollenberg, J., Koschny, D., Kramm, R., Kührt, E., Küppers, M., Lara, L., Lazzarin, M., Lopez Moreno, J.J., Marzari, F., Michalik, H., Naletto, G., Rickman, H., Rodrigo, R., Sabau, L., Thomas, N., Wenzel, K.-P., Agarwal, J., Bertini, I., Ferri, F., Güttler, C., Magrin, S., Oklay, N., Tubiana, C., and Vincent, J.-B.
Abstract: Aims. Approach observations with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard Rosetta are used to determine the rotation period, the direction of the spin axis, and the state of rotation of comet 67P's nucleus. Methods. Photometric time series of 67P have been acquired by OSIRIS since the post wake-up commissioning of the payload in March 2014. Fourier analysis and convex shape inversion methods have been applied to the Rosetta data as well to the available ground-based observations. Results. Evidence is found that the rotation rate of 67P has significantly changed near the time of its 2009 perihelion passage, probably due to sublimation-induced torque. We find that the sidereal rotation periods P1 = 12.76129 ± 0.00005 h and P2 = 12.4043 ± 0.0007 h for the apparitions before and after the 2009 perihelion, respectively, provide the best fit to the observations. No signs of multiple periodicity are found in the light curves down to the noise level, which implies that the comet is presently in a simple rotation state around its axis of largest moment of inertia. We derive a prograde rotation model with spin vector J2000 ecliptic coordinates ? = 65° ± 15°, ? = + 59° ± 15°, corresponding to equatorial coordinates RA = 22°, Dec = + 76°. However, we find that the mirror solution, also prograde, at ? = 275° ± 15°, ? = + 50° ± 15° (or RA = 274°, Dec = + 27°), is also possible at the same confidence level, due to the intrinsic ambiguity of the photometric problem for observations performed close to the ecliptic plane. © 2014 ESO.
Published: 2014

26. Images of Asteroid 21 Lutetia : A Remnant Planetesimal from the Early Solar System

Author: Sierks, H., Lamy, P., Barbieri, C., Koschny, D., Rickman, Hans, Rodrigo, R., A'Hearn, M. F., Angrilli, F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Besse, S., Carry, B., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., De Leon, J., Ferri, F., Fornasier, S., Fulle, M., Hviid, S. F., Gaskell, R. W., Groussin, O., Gutierrez, P., Ip, W., Jorda, L., Kaasalainen, M., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Leyrat, C., Lopez Moreno, J. J., Magrin, S., Marchi, S., Marzari, F., Massironi, M., Michalik, H., Moissl, R., Naletto, G., Preusker, F., Sabau, L., Sabolo, W., Scholten, F., Snodgrass, C., Thomas, N., Tubiana, C., Vernazza, P., Vincent, J. -B, Wenzel, K. -P, Andert, T., Paetzold, M., Weiss, B. P., Sierks, H., Lamy, P., Barbieri, C., Koschny, D., Rickman, Hans, Rodrigo, R., A'Hearn, M. F., Angrilli, F., Barucci, M. A., Bertaux, J. -L, Bertini, I., Besse, S., Carry, B., Cremonese, G., Da Deppo, V., Davidsson, Björn, Debei, S., De Cecco, M., De Leon, J., Ferri, F., Fornasier, S., Fulle, M., Hviid, S. F., Gaskell, R. W., Groussin, O., Gutierrez, P., Ip, W., Jorda, L., Kaasalainen, M., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Leyrat, C., Lopez Moreno, J. J., Magrin, S., Marchi, S., Marzari, F., Massironi, M., Michalik, H., Moissl, R., Naletto, G., Preusker, F., Sabau, L., Sabolo, W., Scholten, F., Snodgrass, C., Thomas, N., Tubiana, C., Vernazza, P., Vincent, J. -B, Wenzel, K. -P, Andert, T., Paetzold, M., and Weiss, B. P.
Abstract: Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 +/- 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.
Published: 2011
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27. Images of Asteroid 21 Lutetia: A Remnant Planetesimal from the Early Solar System

Author: Sierks, H., Lamy, P., Barbieri, C., Koschny, D., Rickman, H., Rodrigo, R., A'Hearn, M. F., Angrilli, F., Barucci, M. A., Bertaux, J. -L., Bertini, I., Besse, S., Carry, B., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., De Leon, J., Ferri, F., Fornasier, S., Fulle, M., Hviid, S. F., Gaskell, R. W., Groussin, O., Gutierrez, P., Ip, W., Jorda, L., Kaasalainen, M., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Leyrat, C., Lopez Moreno, J. J., Magrin, S., Marchi, S., Marzari, F., Massironi, M., Michalik, H., Moissl, R., Naletto, G., Preusker, F., Sabau, L., Sabolo, W., Scholten, F., Snodgrass, C., Thomas, N., Tubiana, C., Vernazza, P., Vincent, J. -B., Wenzel, K. -P., Andert, T., Paetzold, M., Weiss, B. P., Sierks, H., Lamy, P., Barbieri, C., Koschny, D., Rickman, H., Rodrigo, R., A'Hearn, M. F., Angrilli, F., Barucci, M. A., Bertaux, J. -L., Bertini, I., Besse, S., Carry, B., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., De Leon, J., Ferri, F., Fornasier, S., Fulle, M., Hviid, S. F., Gaskell, R. W., Groussin, O., Gutierrez, P., Ip, W., Jorda, L., Kaasalainen, M., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Leyrat, C., Lopez Moreno, J. J., Magrin, S., Marchi, S., Marzari, F., Massironi, M., Michalik, H., Moissl, R., Naletto, G., Preusker, F., Sabau, L., Sabolo, W., Scholten, F., Snodgrass, C., Thomas, N., Tubiana, C., Vernazza, P., Vincent, J. -B., Wenzel, K. -P., Andert, T., Paetzold, M., and Weiss, B. P.
Abstract: Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 +/- 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.
Published: 2011

28. Images of Asteroid 21 Lutetia: A Remnant Planetesimal from the Early Solar System

Author: Sierks, H., Lamy, P., Barbieri, C., Koschny, D., Rickman, H., Rodrigo, R., A'Hearn, M. F., Angrilli, F., Barucci, M. A., Bertaux, J. -L., Bertini, I., Besse, S., Carry, B., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., De Leon, J., Ferri, F., Fornasier, S., Fulle, M., Hviid, S. F., Gaskell, R. W., Groussin, O., Gutierrez, P., Ip, W., Jorda, L., Kaasalainen, M., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Leyrat, C., Lopez Moreno, J. J., Magrin, S., Marchi, S., Marzari, F., Massironi, M., Michalik, H., Moissl, R., Naletto, G., Preusker, F., Sabau, L., Sabolo, W., Scholten, F., Snodgrass, C., Thomas, N., Tubiana, C., Vernazza, P., Vincent, J. -B., Wenzel, K. -P., Andert, T., Paetzold, M., Weiss, B. P., Sierks, H., Lamy, P., Barbieri, C., Koschny, D., Rickman, H., Rodrigo, R., A'Hearn, M. F., Angrilli, F., Barucci, M. A., Bertaux, J. -L., Bertini, I., Besse, S., Carry, B., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., De Leon, J., Ferri, F., Fornasier, S., Fulle, M., Hviid, S. F., Gaskell, R. W., Groussin, O., Gutierrez, P., Ip, W., Jorda, L., Kaasalainen, M., Keller, H. U., Knollenberg, J., Kramm, R., Kuehrt, E., Kueppers, M., Lara, L., Lazzarin, M., Leyrat, C., Lopez Moreno, J. J., Magrin, S., Marchi, S., Marzari, F., Massironi, M., Michalik, H., Moissl, R., Naletto, G., Preusker, F., Sabau, L., Sabolo, W., Scholten, F., Snodgrass, C., Thomas, N., Tubiana, C., Vernazza, P., Vincent, J. -B., Wenzel, K. -P., Andert, T., Paetzold, M., and Weiss, B. P.
Abstract: Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 +/- 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.
Published: 2011

29. Microscopy analysis of soils at the Phoenix landing site, Mars: Classification of soil particles and description of their optical and magnetic properties

Author: Goetz, W. (author), Pike, W.T. (author), Hviid, S.F. (author), Madsen, M.B. (author), Morris, R.V. (author), Hecht, M.H. (author), Staufer, U. (author), Leer, K. (author), Sykulska, H. (author), Hemmig, E. (author), Marshall, J. (author), Morookian, J.M. (author), Parrat, D. (author), Vijendran, S. (author), Bos, B.J. (author), El Maarry, M.R. (author), Keller, H.U. (author), Kramm, R. (author), Markiewicz, W.J. (author), Drube, L. (author), Blaney, D. (author), Arvidson, R.E. (author), Bell, J.F. (author), Reynolds, R. (author), Smith, P.H. (author), Woida, P. (author), Woida, R. (author), Tanner, R. (author), Goetz, W. (author), Pike, W.T. (author), Hviid, S.F. (author), Madsen, M.B. (author), Morris, R.V. (author), Hecht, M.H. (author), Staufer, U. (author), Leer, K. (author), Sykulska, H. (author), Hemmig, E. (author), Marshall, J. (author), Morookian, J.M. (author), Parrat, D. (author), Vijendran, S. (author), Bos, B.J. (author), El Maarry, M.R. (author), Keller, H.U. (author), Kramm, R. (author), Markiewicz, W.J. (author), Drube, L. (author), Blaney, D. (author), Arvidson, R.E. (author), Bell, J.F. (author), Reynolds, R. (author), Smith, P.H. (author), Woida, P. (author), Woida, R. (author), and Tanner, R. (author)
Abstract: The optical microscope onboard the Phoenix spacecraft has returned color images (4 ?m pixel?1) of soils that were delivered to and held on various substrates. A preliminary taxonomy of Phoenix soil particles, based on color, size, and shape, identifies the following particle types [generic names in brackets]: (1) reddish fines, mostly unresolved, that are spectrally similar to (though slightly darker than) global airborne dust [red fines], (2) silt? to sand?sized brownish grains [brown sand], (3) silt? to sand?sized black grains [black sand], and (4) small amounts of whitish fines, possibly salts [white fines]. Most particles have a saturation magnetization in the range 0.5?2 Am2 kg?1 as inferred from their interaction with magnetic substrates. The particle size distribution has two distinct peaks below 10 ?m (fines) and in the range 20–100 ?m (grains), respectively, and is different from that of ripple soils in Gusev crater. In particular medium to large sand grains appear to be absent in Phoenix soils. Most sand grains have subrounded shape with variable texture. A fractured grain (observed on sol 112) reveals evidence of micrometer?sized crystal facets. The brown sand category displays a large diversity in color including shiny, almost colorless particles. Potential source regions for these grains may be the Tharsis volcanoes or Heimdal crater (20 km east of the landing site). The black grains are suggested to belong to a more widespread population of particles with mafic mineralogy. The absence of black/brown composite grains is consistent with different formation pathways and source regions for each grain type., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering
Published: 2010
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30. Microscopy analysis of soils at the Phoenix landing site, Mars: Classification of soil particles and description of their optical and magnetic properties

Author: Goetz, W. (author), Pike, W.T. (author), Hviid, S.F. (author), Madsen, M.B. (author), Morris, R.V. (author), Hecht, M.H. (author), Staufer, U. (author), Leer, K. (author), Sykulska, H. (author), Hemmig, E. (author), Marshall, J. (author), Morookian, J.M. (author), Parrat, D. (author), Vijendran, S. (author), Bos, B.J. (author), El Maarry, M.R. (author), Keller, H.U. (author), Kramm, R. (author), Markiewicz, W.J. (author), Drube, L. (author), Blaney, D. (author), Arvidson, R.E. (author), Bell, J.F. (author), Reynolds, R. (author), Smith, P.H. (author), Woida, P. (author), Woida, R. (author), Tanner, R. (author), Goetz, W. (author), Pike, W.T. (author), Hviid, S.F. (author), Madsen, M.B. (author), Morris, R.V. (author), Hecht, M.H. (author), Staufer, U. (author), Leer, K. (author), Sykulska, H. (author), Hemmig, E. (author), Marshall, J. (author), Morookian, J.M. (author), Parrat, D. (author), Vijendran, S. (author), Bos, B.J. (author), El Maarry, M.R. (author), Keller, H.U. (author), Kramm, R. (author), Markiewicz, W.J. (author), Drube, L. (author), Blaney, D. (author), Arvidson, R.E. (author), Bell, J.F. (author), Reynolds, R. (author), Smith, P.H. (author), Woida, P. (author), Woida, R. (author), and Tanner, R. (author)
Abstract: The optical microscope onboard the Phoenix spacecraft has returned color images (4 ?m pixel?1) of soils that were delivered to and held on various substrates. A preliminary taxonomy of Phoenix soil particles, based on color, size, and shape, identifies the following particle types [generic names in brackets]: (1) reddish fines, mostly unresolved, that are spectrally similar to (though slightly darker than) global airborne dust [red fines], (2) silt? to sand?sized brownish grains [brown sand], (3) silt? to sand?sized black grains [black sand], and (4) small amounts of whitish fines, possibly salts [white fines]. Most particles have a saturation magnetization in the range 0.5?2 Am2 kg?1 as inferred from their interaction with magnetic substrates. The particle size distribution has two distinct peaks below 10 ?m (fines) and in the range 20–100 ?m (grains), respectively, and is different from that of ripple soils in Gusev crater. In particular medium to large sand grains appear to be absent in Phoenix soils. Most sand grains have subrounded shape with variable texture. A fractured grain (observed on sol 112) reveals evidence of micrometer?sized crystal facets. The brown sand category displays a large diversity in color including shiny, almost colorless particles. Potential source regions for these grains may be the Tharsis volcanoes or Heimdal crater (20 km east of the landing site). The black grains are suggested to belong to a more widespread population of particles with mafic mineralogy. The absence of black/brown composite grains is consistent with different formation pathways and source regions for each grain type., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering
Published: 2010
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31. Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta

Author: Keller, H.U., Kuppers, M., Fornasier, S., Gutiérrez, P.J., Hviid, S.F., Jorda, L., Knollenberg, J., Lowry, S.C., Rengel, M., Bertini, I., Cremonese, G., Ip, W.-H., Koschny, D., Kramm, R., Kührt, E., Lara, L.-M., Sierks, H., Thomas, N., Barbieri, C., Lamy, P., Rickman, H., Rodrigo, R., A'Hearn, M.F., Angrilli, F., Barucci, M.-A., Bertaux, J.-L., da Deppo, V., Davidsson, B.J.R., de Cecco, M., Debei, S., Fulle, M., Gliem, F., Groussin, O., Lopez Moreno, J.J., Marzari, F., Naletto, G., Sabau, L., Sanz Andrés, A., Wenzel, K.-P., Keller, H.U., Kuppers, M., Fornasier, S., Gutiérrez, P.J., Hviid, S.F., Jorda, L., Knollenberg, J., Lowry, S.C., Rengel, M., Bertini, I., Cremonese, G., Ip, W.-H., Koschny, D., Kramm, R., Kührt, E., Lara, L.-M., Sierks, H., Thomas, N., Barbieri, C., Lamy, P., Rickman, H., Rodrigo, R., A'Hearn, M.F., Angrilli, F., Barucci, M.-A., Bertaux, J.-L., da Deppo, V., Davidsson, B.J.R., de Cecco, M., Debei, S., Fulle, M., Gliem, F., Groussin, O., Lopez Moreno, J.J., Marzari, F., Naletto, G., Sabau, L., Sanz Andrés, A., and Wenzel, K.-P.
Abstract: The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel 1 from 5 days before to 10 days after it was hit by the Deep Impact projectile. The Narrow Angle Camera (NAC) monitored the cometary dust in 5 different filters. The Wide Angle Camera (WAC) observed through filters sensitive to emissions from OH, CN, Na, and OI together with the associated continuum. Before and after the impact the comet showed regular variations in intensity. The period of the brightness changes is consistent with the rotation period of Tempel 1. The overall brightness of Tempel 1 decreased by about 10% during the OSIRIS observations. The analysis of the impact ejecta shows that no new permanent coma structures were created by the impact. Most of the material moved with ~200 m s-1. Much of it left the comet in the form of icy grains which sublimated and fragmented within the first hour after the impact. The light curve of the comet after the impact and the amount of material leaving the comet (4.5 - 9 x 10^6 kg of water ice and a presumably larger amount of dust) suggest that the impact ejecta were quickly accelerated by collisions with gas molecules. Therefore, the motion of the bulk of the ejecta cannot be described by ballistic trajectories, and the validity of determinations of the density and tensile strength of the nucleus of Tempel 1 with models using ballistic ejection of particles is uncertain. © 2006 Elsevier Inc. All rights reserved.
Published: 2007

32. The imager for mars pathfinder (IMP) experiment

Author: Smith, P.H., Britt, D.T., Tomasko, M.G., Singer, R.B., Doose, L.R., Chinohara, C., Reynolds, R., Crowe, D.G., Reid, R., Hoppa, G., Chabot, N., Keller, H.U., Thomas, N., Koschny, D., Kramm, R., Gliem, F., Rabe, F., Rueffer, P., Sullivan, R.P., Greeley, R., Wilson, G., Knudsen, Jens Martin, Madsen, M.B., Hviid, S.F., Goetz, W., Gunnlaugsson, Haraldur Pall, Soderblom, L., Gaddis, L., Kirk, R., Ward, W., Herkenhoff, K., Smith, P.H., Britt, D.T., Tomasko, M.G., Singer, R.B., Doose, L.R., Chinohara, C., Reynolds, R., Crowe, D.G., Reid, R., Hoppa, G., Chabot, N., Keller, H.U., Thomas, N., Koschny, D., Kramm, R., Gliem, F., Rabe, F., Rueffer, P., Sullivan, R.P., Greeley, R., Wilson, G., Knudsen, Jens Martin, Madsen, M.B., Hviid, S.F., Goetz, W., Gunnlaugsson, Haraldur Pall, Soderblom, L., Gaddis, L., Kirk, R., Ward, W., and Herkenhoff, K.
Published: 1997

33. The imager for mars pathfinder (IMP) experiment

Author: Smith, P.H., Britt, D.T., Tomasko, M.G., Singer, R.B., Doose, L.R., Chinohara, C., Reynolds, R., Crowe, D.G., Reid, R., Hoppa, G., Chabot, N., Keller, H.U., Thomas, N., Koschny, D., Kramm, R., Gliem, F., Rabe, F., Rueffer, P., Sullivan, R.P., Greeley, R., Wilson, G., Knudsen, Jens Martin, Madsen, M.B., Hviid, S.F., Goetz, W., Gunnlaugsson, Haraldur Pall, Soderblom, L., Gaddis, L., Kirk, R., Ward, W., Herkenhoff, K., Smith, P.H., Britt, D.T., Tomasko, M.G., Singer, R.B., Doose, L.R., Chinohara, C., Reynolds, R., Crowe, D.G., Reid, R., Hoppa, G., Chabot, N., Keller, H.U., Thomas, N., Koschny, D., Kramm, R., Gliem, F., Rabe, F., Rueffer, P., Sullivan, R.P., Greeley, R., Wilson, G., Knudsen, Jens Martin, Madsen, M.B., Hviid, S.F., Goetz, W., Gunnlaugsson, Haraldur Pall, Soderblom, L., Gaddis, L., Kirk, R., Ward, W., and Herkenhoff, K.
Published: 1997

34. Evolution of the Dust Size Distribution of Comet 67P/Churyumov–Gerasimenko from 2.2 au to Perihelion

Author: Fulle, M., Marzari, F., Della Corte, V., Fornasier, S., Sierks, H., Rotundi, A., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., López-Moreno, J. J., Accolla, M., Agarwal, J., A’Hearn, M. F., Altobelli, N., Barucci, M. A., Bertaux, J.-L., Bertini, I., Bodewits, D., Bussoletti, E., Colangeli, L., Cosi, M., Cremonese, G., Crifo, J.-F., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Esposito, F., Ferrari, M., Giovane, F., Gustafson, B., Green, S. F., Groussin, O., Grün, E., Gutierrez, P., Güttler, C., Herranz, M. L., Hviid, S. F., Ip, W., Ivanovski, S. L., Jerónimo, J. M., Jorda, L., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, L., Lazzarin, M., Leese, M. R., López-Jiménez, A. C., Lucarelli, F., Mazzotta Epifani, E., McDonnell, J. A. M., Mennella, V., Molina, A., Morales, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Ortiz, J. L., Palomba, E., Palumbo, P., Perrin, J.-M., Rietmeijer, F. J. M., Rodríguez, J., Sordini, R., Thomas, N., Tubiana, C., Vincent, J.-B., Weissman, P., Wenzel, K.-P., Zakharov, V., Zarnecki, J. C., Fulle, M., Marzari, F., Della Corte, V., Fornasier, S., Sierks, H., Rotundi, A., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., López-Moreno, J. J., Accolla, M., Agarwal, J., A’Hearn, M. F., Altobelli, N., Barucci, M. A., Bertaux, J.-L., Bertini, I., Bodewits, D., Bussoletti, E., Colangeli, L., Cosi, M., Cremonese, G., Crifo, J.-F., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Esposito, F., Ferrari, M., Giovane, F., Gustafson, B., Green, S. F., Groussin, O., Grün, E., Gutierrez, P., Güttler, C., Herranz, M. L., Hviid, S. F., Ip, W., Ivanovski, S. L., Jerónimo, J. M., Jorda, L., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, L., Lazzarin, M., Leese, M. R., López-Jiménez, A. C., Lucarelli, F., Mazzotta Epifani, E., McDonnell, J. A. M., Mennella, V., Molina, A., Morales, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Ortiz, J. L., Palomba, E., Palumbo, P., Perrin, J.-M., Rietmeijer, F. J. M., Rodríguez, J., Sordini, R., Thomas, N., Tubiana, C., Vincent, J.-B., Weissman, P., Wenzel, K.-P., Zakharov, V., and Zarnecki, J. C.
Abstract: The Rosetta probe, orbiting Jupiter-family comet 67P/Churyumov–Gerasimenko, has been detecting individual dust particles of mass larger than 10^(−10) kg by means of the GIADA dust collector and the OSIRIS Wide Angle Camera and Narrow Angle Camera since 2014 August and will continue until 2016 September. Detections of single dust particles allow us to estimate the anisotropic dust flux from 67P, infer the dust loss rate and size distribution at the surface of the sunlit nucleus, and see whether the dust size distribution of 67P evolves in time. The velocity of the Rosetta orbiter, relative to 67P, is much lower than the dust velocity measured by GIADA, thus dust counts when GIADA is nadir-pointing will directly provide the dust flux. In OSIRIS observations, the dust flux is derived from the measurement of the dust space density close to the spacecraft. Under the assumption of radial expansion of the dust, observations in the nadir direction provide the distance of the particles by measuring their trail length, with a parallax baseline determined by the motion of the spacecraft. The dust size distribution at sizes >1 mm observed by OSIRIS is consistent with a differential power index of −4, which was derived from models of 67P’s trail. At sizes <1 mm, the size distribution observed by GIADA shows a strong time evolution, with a differential power index drifting from −2 beyond 2 au to −3.7 at perihelion, in agreement with the evolution derived from coma and tail models based on ground-based data. The refractory-to-water mass ratio of the nucleus is close to six during the entire inbound orbit and at perihelion.

35. Evolution of the Dust Size Distribution of Comet 67P/Churyumov–Gerasimenko from 2.2 au to Perihelion

Author: Fulle, M., Marzari, F., Della Corte, V., Fornasier, S., Sierks, H., Rotundi, A., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., López-Moreno, J. J., Accolla, M., Agarwal, J., A’Hearn, M. F., Altobelli, N., Barucci, M. A., Bertaux, J.-L., Bertini, I., Bodewits, D., Bussoletti, E., Colangeli, L., Cosi, M., Cremonese, G., Crifo, J.-F., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Esposito, F., Ferrari, M., Giovane, F., Gustafson, B., Green, S. F., Groussin, O., Grün, E., Gutierrez, P., Güttler, C., Herranz, M. L., Hviid, S. F., Ip, W., Ivanovski, S. L., Jerónimo, J. M., Jorda, L., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, L., Lazzarin, M., Leese, M. R., López-Jiménez, A. C., Lucarelli, F., Mazzotta Epifani, E., McDonnell, J. A. M., Mennella, V., Molina, A., Morales, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Ortiz, J. L., Palomba, E., Palumbo, P., Perrin, J.-M., Rietmeijer, F. J. M., Rodríguez, J., Sordini, R., Thomas, N., Tubiana, C., Vincent, J.-B., Weissman, P., Wenzel, K.-P., Zakharov, V., Zarnecki, J. C., Fulle, M., Marzari, F., Della Corte, V., Fornasier, S., Sierks, H., Rotundi, A., Barbieri, C., Lamy, P. L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H. U., López-Moreno, J. J., Accolla, M., Agarwal, J., A’Hearn, M. F., Altobelli, N., Barucci, M. A., Bertaux, J.-L., Bertini, I., Bodewits, D., Bussoletti, E., Colangeli, L., Cosi, M., Cremonese, G., Crifo, J.-F., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Esposito, F., Ferrari, M., Giovane, F., Gustafson, B., Green, S. F., Groussin, O., Grün, E., Gutierrez, P., Güttler, C., Herranz, M. L., Hviid, S. F., Ip, W., Ivanovski, S. L., Jerónimo, J. M., Jorda, L., Knollenberg, J., Kramm, R., Kührt, E., Küppers, M., Lara, L., Lazzarin, M., Leese, M. R., López-Jiménez, A. C., Lucarelli, F., Mazzotta Epifani, E., McDonnell, J. A. M., Mennella, V., Molina, A., Morales, R., Moreno, F., Mottola, S., Naletto, G., Oklay, N., Ortiz, J. L., Palomba, E., Palumbo, P., Perrin, J.-M., Rietmeijer, F. J. M., Rodríguez, J., Sordini, R., Thomas, N., Tubiana, C., Vincent, J.-B., Weissman, P., Wenzel, K.-P., Zakharov, V., and Zarnecki, J. C.
Abstract: The Rosetta probe, orbiting Jupiter-family comet 67P/Churyumov–Gerasimenko, has been detecting individual dust particles of mass larger than 10^(−10) kg by means of the GIADA dust collector and the OSIRIS Wide Angle Camera and Narrow Angle Camera since 2014 August and will continue until 2016 September. Detections of single dust particles allow us to estimate the anisotropic dust flux from 67P, infer the dust loss rate and size distribution at the surface of the sunlit nucleus, and see whether the dust size distribution of 67P evolves in time. The velocity of the Rosetta orbiter, relative to 67P, is much lower than the dust velocity measured by GIADA, thus dust counts when GIADA is nadir-pointing will directly provide the dust flux. In OSIRIS observations, the dust flux is derived from the measurement of the dust space density close to the spacecraft. Under the assumption of radial expansion of the dust, observations in the nadir direction provide the distance of the particles by measuring their trail length, with a parallax baseline determined by the motion of the spacecraft. The dust size distribution at sizes >1 mm observed by OSIRIS is consistent with a differential power index of −4, which was derived from models of 67P’s trail. At sizes <1 mm, the size distribution observed by GIADA shows a strong time evolution, with a differential power index drifting from −2 beyond 2 au to −3.7 at perihelion, in agreement with the evolution derived from coma and tail models based on ground-based data. The refractory-to-water mass ratio of the nucleus is close to six during the entire inbound orbit and at perihelion.

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35 results on '"Kramm, R."'

1. Exposed bright features on the comet 67P/Churyumov-Gerasimenko : distribution and evolution

2. Exposed bright features on the comet 67P/Churyumov-Gerasimenko: Distribution and evolution

3. The highly active Anhur-Bes regions in the 67P/Churyumov-Gerasimenko comet : results from OSIRIS/ROSETTA observations

4. The opposition effect of 67P/Churyumov-Gerasimenko on post-perihelion Rosetta images

5. Multivariate statistical analysis of OSIRIS/Rosetta spectrophotometric data of comet 67P/Churyumov-Gerasimenko

6. The highly active Anhur-Bes regions in the 67P/Churyumov - Gerasimenko comet: results from OSIRIS/ROSETTA observations

7. Evidence for Surface Variegation in Rosetta OSIRIS Images of Asteroid 2867 Steins

8. The highly active Anhur-Bes regions in the 67P/Churyumov - Gerasimenko comet: results from OSIRIS/ROSETTA observations

9. Evidence for Surface Variegation in Rosetta OSIRIS Images of Asteroid 2867 Steins

10. Evolution Of The Dust Size Distribution Of Comet 67P/Churyumov-Gerasimenko From 2.2 Au To Perihelion

11. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

12. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

13. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

14. Rosetta's comet 67P/Churyumov-Gerasimenko sheds its dusty mantle to reveal its icy nature

15. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

16. Spectrophotometry of the Khonsu region on the comet 67P/Churyumov-Gerasimenko using OSIRIS instrument images

17. 67P/Churyumov-Gerasimenko : Activity between March and June 2014 as observed from Rosetta/OSIRIS

18. Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

19. Rotating dust particles in the coma of comet 67P/Churyumov-Gerasimenko

20. Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

21. 67P/Churyumov-Gerasimenko: Activity between March and June 2014 as observed from Rosetta/OSIRIS

22. Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the sun

23. Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

24. The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

25. The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

26. Images of Asteroid 21 Lutetia : A Remnant Planetesimal from the Early Solar System

27. Images of Asteroid 21 Lutetia: A Remnant Planetesimal from the Early Solar System

28. Images of Asteroid 21 Lutetia: A Remnant Planetesimal from the Early Solar System

29. Microscopy analysis of soils at the Phoenix landing site, Mars: Classification of soil particles and description of their optical and magnetic properties

30. Microscopy analysis of soils at the Phoenix landing site, Mars: Classification of soil particles and description of their optical and magnetic properties

31. Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta

32. The imager for mars pathfinder (IMP) experiment

33. The imager for mars pathfinder (IMP) experiment

34. Evolution of the Dust Size Distribution of Comet 67P/Churyumov–Gerasimenko from 2.2 au to Perihelion

35. Evolution of the Dust Size Distribution of Comet 67P/Churyumov–Gerasimenko from 2.2 au to Perihelion

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35 results on '"Kramm, R."'

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