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1. Shape model and spin-state analysis of PHA contact binary (85990) 1999 JV6 from combined radar and optical observations

Author

Rożek, A., primary, Lowry, S. C., additional, Nolan, M. C., additional, Taylor, P. A., additional, Benner, L. A. M., additional, Fitzsimmons, A., additional, Zegmott, T. J., additional, Weissman, P. R., additional, Green, S. F., additional, Rozitis, B., additional, Snodgrass, C., additional, Smythe, W. D., additional, Hicks, M. D., additional, Howell, E. S., additional, Virkki, A. K., additional, Aponte-Hernandez, B., additional, Rivera-Valentín, E. G., additional, Rodriguez-Ford, L. A., additional, Zambrano-Marin, L. F., additional, Brozović, M., additional, Naidu, S. P., additional, Giorgini, J. D., additional, Snedeker, L. G., additional, Jao, J. S., additional, and Ghigo, F. D., additional

Published
2019
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2. Physical model of near-Earth asteroid (1917) Cuyo from ground-based optical and thermal-IR observations

Author

Rożek, A., primary, Lowry, S. C., additional, Rozitis, B., additional, Green, S. F., additional, Snodgrass, C., additional, Weissman, P. R., additional, Fitzsimmons, A., additional, Hicks, M. D., additional, Lawrence, K. J., additional, Duddy, S. R., additional, Wolters, S. D., additional, Roberts-Borsani, G., additional, Behrend, R., additional, and Manzini, F., additional

Published
2019
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3. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs

Author

Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, and Swedish National Space Agency

Subjects
Comets: general, Comets: individual: 67P/Churyumov-Gerasimenko, Methods: observational, individual: 67P/Churyumov-Gerasimenko [Comets], general [Comets], observational [Methods]
Abstract

Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., We directly measured twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimated the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features and the implied previous collapse of another, suggests that they are prone to failure and that the true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of the 67P nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties either with size over the ~10-100 m range studied here or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small body (tens of km)., his project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 686709. This work was supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 16.0008-2. The opinions expressed and arguments employed herein do not necessarily reflect the official view of the Swiss Government. OSIRIS was built by a consortium of the Max-Planck-Institut fur Sonnensystemforschung, Gottingen, Germany; the CISAS University of Padova, Italy; the Laboratoire d'Astrophysique de Marseille, France; the Instituto de Astrofisica de Andalucia, CSIC, Granada, the Universidad Politechnica de Madrid, Spain; the Department of Physics and Astronomy of Uppsala University, Sweden; and the Institut fur Datentechnik und Kommunikationsnetze der Technischen Universitat Braunschweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB), and the ESA Technical Directorate is gratefully acknowledged. We thank the Rosetta Science Operations Centre and the Rosetta Mission Operations Centre for the successful rendezvous with comet 67P/Churyumov-Gerasimenko.

Published
2018

4. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs (Corrigendum)

Author

Attree, N., primary, Groussin, O., additional, Jorda, L., additional, Nébouy, D., additional, Thomas, N., additional, Brouet, Y., additional, Kührt, E., additional, Preusker, F., additional, Scholten, F., additional, Knollenberg, J., additional, Hartogh, P., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, A’Hearn, M. F., additional, Auger, A.-T., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Boudreault, S., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, Deller, J., additional, El-Maarry, M. R., additional, Fornasier, S., additional, Fulle, M., additional, Gutiérrez, P. J., additional, Güttler, C., additional, Hviid, S., additional, Ip, W.-H, additional, Kovacs, G., additional, Kramm, J. R., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, Lopez Moreno, J. J., additional, Lowry, S., additional, Marchi, S., additional, Marzari, F., additional, Mottola, S., additional, Naletto, G., additional, Oklay, N., additional, Pajola, M., additional, Toth, I., additional, Tubiana, C., additional, Vincent, J.-B., additional, and Shi, X., additional

Published
2018
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5. Tensile strength of 67P/Churyumov-Gerasimenko nucleus material from overhangs

Author

European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., Naletto, G., European Commission, State Secretariat for Education, Research and Innovation (Switzerland), German Centre for Air and Space Travel, Centre National D'Etudes Spatiales (France), Agenzia Spaziale Italiana, Agencia Estatal de Investigación (España), European Space Agency, Swedish National Space Agency, Attree, N., Groussin, O., Jorda, L., Nébouy, D., Thomas, N., Brouet, Y., Kührt, E., Preusker, F., Scholten, F., Knollenberg, J., Hartogh, P., Sierks, H., Barbieri, C., Lamy, P., Rodrigo Montero, Rafael, Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M. F., Auger, A.T., Barucci, M.A., Bertaux, J.L., Bertini, I., Bodewits, D., Boudreault, S., Cremonese, G., Da Deppo, Vania, Davidsson, B., Debei, S., De Cecco, M., Deller, J., El-Maarry, M. R., Fornasier, S., Fulle, M., Gutiérrez, Pedro J., Güttler, C., Hviid, S., Ip, W. H., Kovacs, G., Kramm, J.R., Küppers, M., Lara, Luisa María, Lazzarin, M., López-Moreno, José Juan, Lowry, S., Marchi, S., Marzari, F., Mottola, S., and Naletto, G.

Abstract

We directly measured twenty overhanging cliffs on the surface of comet 67P/Churyumov-Gerasimenko extracted from the latest shape model and estimated the minimum tensile strengths needed to support them against collapse under the comet's gravity. We find extremely low strengths of around 1 Pa or less (1 to 5 Pa, when scaled to a metre length). The presence of eroded material at the base of most overhangs, as well as the observed collapse of two features and the implied previous collapse of another, suggests that they are prone to failure and that the true material strengths are close to these lower limits (although we only consider static stresses and not dynamic stress from, for example, cometary activity). Thus, a tensile strength of a few pascals is a good approximation for the tensile strength of the 67P nucleus material, which is in agreement with previous work. We find no particular trends in overhang properties either with size over the ~10-100 m range studied here or location on the nucleus. There are no obvious differences, in terms of strength, height or evidence of collapse, between the populations of overhangs on the two cometary lobes, suggesting that 67P is relatively homogenous in terms of tensile strength. Low material strengths are supportive of cometary formation as a primordial rubble pile or by collisional fragmentation of a small body (tens of km).

Published
2018

6. Distant activity of 67P/Churyumov-Gerasimenko in 2014: Ground-based results during the Rosetta pre-landing phase

Author

Snodgrass, C., Jehin, E., Manfroid, J., Opitom, C., Fitzsimmons, A., Tozzi, G. P., Faggi, S., Yang, B., Knight, M. M., Conn, B. C., Lister, T., Hainaut, O., Bramich, D. M., Lowry, S. C., Rożek, A., Tubiana, C., Guilbert-Lepoutre, A., Snodgrass, C., Jehin, E., Manfroid, J., Opitom, C., Fitzsimmons, A., Tozzi, G. P., Faggi, S., Yang, B., Knight, M. M., Conn, B. C., Lister, T., Hainaut, O., Bramich, D. M., Lowry, S. C., Rożek, A., Tubiana, C., and Guilbert-Lepoutre, A.

Abstract

Context. As the ESA Rosetta mission approached, orbited, and sent a lander to comet 67P/Churyumov-Gerasimenko in 2014, a large campaign of ground-based observations also followed the comet. Aims. We constrain the total activity level of the comet by photometry and spectroscopy to place Rosetta results in context and to understand the large-scale structure of the comet's coma pre-perihelion. Methods. We performed observations using a number of telescopes, but concentrate on results from the 8 m VLT and Gemini South telescopes in Chile. We use R-band imaging to measure the dust coma contribution to the comet's brightness and UV-visible spectroscopy to search for gas emissions, primarily using VLT/FORS. In addition we imaged the comet in near-infrared wavelengths (JHK) in late 2014 with Gemini-S/Flamingos-2. Results. We find that the comet was already active in early 2014 at heliocentric distances beyond 4 au. The evolution of the total activity (measured by dust) followed previous predictions. No gas emissions were detected despite sensitive searches. Conclusions. The comet maintains a similar level of activity from orbit to orbit, and is in that sense predictable, meaning that Rosetta results correspond to typical behaviour for this comet. The gas production (for CN at least) is highly asymmetric with respect to perihelion, as our upper limits are below the measured production rates for similar distances post-perihelion in previous orbits. © ESO, 2016.

Published
2016

7. Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

Author

Ip, W.-H., primary, Lai, I.-L., additional, Lee, J.-C., additional, Cheng, Y.-C., additional, Li, Y., additional, Lin, Z.-Y., additional, Vincent, J.-B., additional, Besse, S., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Agarwal, J., additional, A’Hearn, M. F., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Boudreault, S., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, El-Maarry, M. R., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Gutiérrez, P. J., additional, Güttler, C., additional, Hviid, S. F., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, La Forgia, F., additional, Lara, L. M., additional, Lazzarin, M., additional, López-Moreno, J. J., additional, Lowry, S., additional, Marchi, S., additional, Marzari, F., additional, Michalik, H., additional, Mottola, S., additional, Naletto, G., additional, Oklay, N., additional, Pajola, M., additional, Thomas, N., additional, Toth, E., additional, and Tubiana, C., additional

Published
2016
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8. Observations and analysis of a curved jet in the coma of comet 67P/Churyumov-Gerasimenko

Author

Lin, Z.-Y., primary, Lai, I.-L., additional, Su, C.-C., additional, Ip, W.-H., additional, Lee, J.-C., additional, Wu, J.-S., additional, Vincent, J.-B., additional, La Forgia, F., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Agarwal, J., additional, A’Hearn, M. F., additional, Barucci, M. A., additional, Bertaux, J.–L., additional, Bertini, I., additional, Bodewits, D., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Gutiérrez, P. J., additional, Güttler, C., additional, Hviid, S. F., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, López-Moreno, J. J., additional, Lowry, S., additional, Marzari, F., additional, Michalik, H., additional, Mottola, S., additional, Naletto, G., additional, Oklay, N., additional, Pajola, M., additional, Rożek, A., additional, Thomas, N., additional, and Tubiana, C., additional

Published
2016
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9. Are fractured cliffs the source of cometary dust jets? Insights from OSIRIS/Rosetta at 67P/Churyumov-Gerasimenko

Author

Vincent, J.-B., primary, Oklay, N., additional, Pajola, M., additional, Höfner, S., additional, Sierks, H., additional, Hu, X., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, A’Hearn, M. F., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Besse, S., additional, Bodewits, D., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, El-Maarry, M. R., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Gutiérrez, P. J., additional, Gutiérrez-Marquez, P., additional, Güttler, C., additional, Hofmann, M., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, Lin, Z.-Y., additional, Lopez Moreno, J. J., additional, Lowry, S., additional, Marzari, F., additional, Massironi, M., additional, Moreno, F., additional, Mottola, S., additional, Naletto, G., additional, Preusker, F., additional, Scholten, F., additional, Shi, X., additional, Thomas, N., additional, Toth, I., additional, and Tubiana, C., additional

Published
2016
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10. 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

11. Large-scale dust jets in the coma of 67P/Churyumov-Gerasimenko as seen by the OSIRIS instrument onboard Rosetta

Author

Lara, L.M., Lowry, S., Vincent, J.-B., Gutierrez, P.J., Rożek, A., La Forgia, F., Oklay, N., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., Auger, A.-T., A'Hearn, M.F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Besse, S., Bodewits, D., Cremonese, G., Davidsson, B., Da Deppo, V., Debei, S., De Cecco, M., El-Maarry, M.R., Ferri, F., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez-Marques, P., Güttler, C., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kührt, E., Küppers, M., Lazzarin, M., Lin, Z.-Y., López-Moreno, J.J., Magrin, S., Marzari, F., Michalik, H., Moissl-Fraund, R., Moreno, F., Mottola, S., Naletto, G., Pajola, M., Pommerol, A., Thomas, N., Sabau, M.D., Tubiana, C., Lara, L.M., Lowry, S., Vincent, J.-B., Gutierrez, P.J., Rożek, A., La Forgia, F., Oklay, N., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., Auger, A.-T., A'Hearn, M.F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Besse, S., Bodewits, D., Cremonese, G., Davidsson, B., Da Deppo, V., Debei, S., De Cecco, M., El-Maarry, M.R., Ferri, F., Fornasier, S., Fulle, M., Groussin, O., Gutiérrez-Marques, P., Güttler, C., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kührt, E., Küppers, M., Lazzarin, M., Lin, Z.-Y., López-Moreno, J.J., Magrin, S., Marzari, F., Michalik, H., Moissl-Fraund, R., Moreno, F., Mottola, S., Naletto, G., Pajola, M., Pommerol, A., Thomas, N., Sabau, M.D., and Tubiana, C.

Abstract

During the most recent perihelion passage in 2009 of comet 67P/Churyumov-Gerasimenko (67P), ground-based observations showed an anisotropic dust coma where jet-like features were detected at ~ 1.3 AU from the Sun. The current perihelion passage is exceptional as the Rosetta spacecraft is monitoring the nucleus activity since March 2014, when a clear dust coma was already surrounding the nucleus at 4.3 AU from the Sun. Subsequently, the OSIRIS camera also witnessed an outburst in activity between April 27 and 30, and since mid-July, the dust coma at rh ~ 3.7-3.6 AU preperihelion is clearly non-isotropic, pointing to the existence of dust jet-like features. We aim to ascertain on the nucleus surface the origin of the dust jet-like features detected as early as in mid-July 2014. This will help to establish how the localized comet nucleus activity compares with that seen in previous apparitions and will also help following its evolution as the comet approaches its perihelion, at which phase most of the jets were detected from ground-based observations. Determining these areas also allows locating them in regions on the nucleus with spectroscopic or geomorphological distinct characteristics. Methods. Three series of dust images of comet 67P obtained with the Wide Angle Camera (WAC) of the OSIRIS instrument onboard the Rosetta spacecraft were processed with different enhancement techniques. This was made to clearly show the existence of jet-like features in the dust coma, whose appearance toward the observer changed as a result of the rotation of the comet nucleus and of the changing observing geometry from the spacecraft. The position angles of these features in the coma together with information on the observing geometry, nucleus shape, and rotation, allowed us to determine the most likely locations on the nucleus surface where the jets originate from. Results. Geometrical tracing of jet sources indicates that the activity of the nucleus of 67P gave rise during July and

Published
2015

12. Orbital elements of the material surrounding comet 67P/Churyumov-Gerasimenko

Author

Davidsson, B.J.R., Gutierrez, P.J., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., A'Hearn, M.F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Guttler, C., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kuhrt, E., Kuppers, M., La Forgia, F., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Lowry, S., Magrin, S., Marzari, F., Michalik, H., Moissl-Fraund, R., Naletto, G., Oklay, N., Pajola, M., Snodgrass, C., Thomas, N., Tubiana, C., Vincent, J.-B., Davidsson, B.J.R., Gutierrez, P.J., Sierks, H., Barbieri, C., Lamy, P.L., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., Agarwal, J., A'Hearn, M.F., Barucci, M.A., Bertaux, J.-L., Bertini, I., Bodewits, D., Cremonese, G., Da Deppo, V., Debei, S., De Cecco, M., Fornasier, S., Fulle, M., Groussin, O., Guttler, C., Hviid, S.F., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.-R., Kuhrt, E., Kuppers, M., La Forgia, F., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Lowry, S., Magrin, S., Marzari, F., Michalik, H., Moissl-Fraund, R., Naletto, G., Oklay, N., Pajola, M., Snodgrass, C., Thomas, N., Tubiana, C., and Vincent, J.-B.

Abstract

We investigate the dust coma within the Hill sphere of comet 67P/Churyumov-Gerasimenko. We aim to determine osculating orbital elements for individual distinguishable but unresolved slow-moving grains in the vicinity of the nucleus. In addition, we perform photometry and constrain grain sizes. Methods. We performed astrometry and photometry using images acquired by the OSIRIS Wide Angle Camera on the European Space Agency spacecraft Rosetta. Based on these measurements, we employed standard orbit determination and orbit improvement techniques. Results. Orbital elements and effective diameters of four grains were constrained, but we were unable to uniquely determine them. Two of the grains have light curves that indicate grain rotation. Conclusions. The four grains have diameters nominally in the range 0.14-0.50 m. For three of the grains, we found elliptic orbits, which is consistent with a cloud of bound particles around the nucleus. However, hyperbolic escape trajectories cannot be excluded for any of the grains, and for one grain this is the only known option. One grain may have originated from the surface shortly before observation. These results have possible implications for the understanding of the dispersal of the cloud of bound debris around comet nuclei, as well as for understanding the ejection of large grains far from the Sun.

Published
2015

13. Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko

Author

Groussin, O., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M.F., Auger, A.-T., Barucci, M.A., Bertaux, J.-L., Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., El-Maarry, M.R., Fornasier, S., Fulle, M., Gutiérrez, P.J., Güttler, C., Hviid, S., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Lowry, S., Marchi, S., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Thomas, N., Toth, I., Tubiana, C., Vincent, J.-B., Groussin, O., Sierks, H., Barbieri, C., Lamy, P., Rodrigo, R., Koschny, D., Rickman, H., Keller, H.U., A'Hearn, M.F., Auger, A.-T., Barucci, M.A., Bertaux, J.-L., Bertini, I., Besse, S., Cremonese, G., Da Deppo, V., Davidsson, B., Debei, S., De Cecco, M., El-Maarry, M.R., Fornasier, S., Fulle, M., Gutiérrez, P.J., Güttler, C., Hviid, S., Ip, W.-H., Jorda, L., Knollenberg, J., Kovacs, G., Kramm, J.R., Kührt, E., Küppers, M., Lara, L.M., Lazzarin, M., Lopez Moreno, J.J., Lowry, S., Marchi, S., Marzari, F., Massironi, M., Mottola, S., Naletto, G., Oklay, N., Pajola, M., Pommerol, A., Thomas, N., Toth, I., Tubiana, C., and Vincent, J.-B.

Abstract

Aims. We report on the first major temporal morphological changes observed on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko in the smooth terrains of the Imhotep region. Methods. We used images of the OSIRIS cameras onboard Rosetta to follow the temporal changes from 24 May 2015 to 11 July 2015. Results. The morphological changes observed on the surface are visible in the form of roundish features that are growing in size from a given location in a preferential direction at a rate of 5.6-8.1 x 10-5 m s-1 during the observational period. The location where the changes started and the contours of the expanding features are bluer than the surroundings, which suggests that ices (H2O and/or CO2) are exposed on the surface. However, sublimation of ices alone is not sufficient to explain the observed expanding features. No significant variations in the dust activity pattern are observed during the period of changes. © ESO, 2015.

Published
2015

14. Morphology and dynamics of the jets of comet 67P/Churyumov-Gerasimenko: Early-phase development

Author

Lin, Z.-Y., primary, Ip, W.-H., additional, Lai, I.-L., additional, Lee, J.-C., additional, Vincent, J.-B., additional, Lara, L. M., additional, Bodewits, D., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Agarwal, J., additional, A’Hearn, M. F., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Gutiérrez, P. J., additional, Güttler, C., additional, Hviid, S. F., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, La Forgia, F., additional, Lazzarin, M., additional, López-Moreno, J. J., additional, Lowry, S., additional, Marzari, F., additional, Michalik, H., additional, Mottola, S., additional, Naletto, G., additional, Oklay, N., additional, Pajola, M., additional, Rożek, A., additional, Thomas, N., additional, Liao, Y., additional, and Tubiana, C., additional

Published
2015
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15. OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

Author

Pommerol, A., primary, Thomas, N., additional, El-Maarry, M. R., additional, Pajola, M., additional, Groussin, O., additional, Auger, A.-T., additional, Oklay, N., additional, Fornasier, S., additional, Feller, C., additional, Davidsson, B., additional, Gracia-Berná, A., additional, Jost, B., additional, Marschall, R., additional, Poch, O., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, La Forgia, F., additional, Keller, H. U., additional, Kührt, E., additional, Lowry, S. C., additional, Mottola, S., additional, Naletto, G., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Agarwal, J., additional, A’Hearn, M. F., additional, Bertini, I., additional, Boudreault, S., additional, Cremonese, G., additional, Da Deppo, V., additional, De Cecco, M., additional, Debei, S., additional, Güttler, C., additional, Fulle, M., additional, Gutierrez, P. J., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Küppers, E., additional, Lara, L., additional, Lazzarin, M., additional, Lopez Moreno, J. L., additional, Marzari, F., additional, Michalik, H., additional, Preusker, F., additional, Scholten, F., additional, Tubiana, C., additional, and Vincent, J.-B., additional

Published
2015
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16. Orbital elements of the material surrounding comet 67P/Churyumov-Gerasimenko

Author

Davidsson, B. J. R., primary, Gutiérrez, P. J., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Agarwal, J., additional, A’Hearn, M. F., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Bodewits, D., additional, Cremonese, G., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Güttler, C., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, La Forgia, F., additional, Lara, L. M., additional, Lazzarin, M., additional, Lopez Moreno, J. J., additional, Lowry, S., additional, Magrin, S., additional, Marzari, F., additional, Michalik, H., additional, Moissl-Fraund, R., additional, Naletto, G., additional, Oklay, N., additional, Pajola, M., additional, Snodgrass, C., additional, Thomas, N., additional, Tubiana, C., additional, and Vincent, J.-B., additional

Published
2015
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17. Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko

Author

Groussin, O., primary, Sierks, H., additional, Barbieri, C., additional, Lamy, P., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, A’Hearn, M. F., additional, Auger, A.-T., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Besse, S., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, Debei, S., additional, De Cecco, M., additional, El-Maarry, M. R., additional, Fornasier, S., additional, Fulle, M., additional, Gutiérrez, P. J., additional, Güttler, C., additional, Hviid, S., additional, Ip, W.-H, additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J. R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L. M., additional, Lazzarin, M., additional, Lopez Moreno, J. J., additional, Lowry, S., additional, Marchi, S., additional, Marzari, F., additional, Massironi, M., additional, Mottola, S., additional, Naletto, G., additional, Oklay, N., additional, Pajola, M., additional, Pommerol, A., additional, Thomas, N., additional, Toth, I., additional, Tubiana, C., additional, and Vincent, J.-B., additional

Published
2015
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18. Large-scale dust jets in the coma of 67P/Churyumov-Gerasimenko as seen by the OSIRIS instrument onboard Rosetta

Author

Lara, L. M., primary, Lowry, S., additional, Vincent, J.-B., additional, Gutiérrez, P. J., additional, Rożek, A., additional, La Forgia, F., additional, Oklay, N., additional, Sierks, H., additional, Barbieri, C., additional, Lamy, P. L., additional, Rodrigo, R., additional, Koschny, D., additional, Rickman, H., additional, Keller, H. U., additional, Agarwal, J., additional, Auger, A.-T., additional, A’Hearn, M. F., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Bertini, I., additional, Besse, S., additional, Bodewits, D., additional, Cremonese, G., additional, Davidsson, B., additional, Da Deppo, V., additional, Debei, S., additional, De Cecco, M., additional, El-Maarry, M. R., additional, Ferri, F., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Gutiérrez–Marques, P., additional, Güttler, C., additional, Hviid, S. F., additional, Ip, W.-H., additional, Jorda, L., additional, Knollenberg, J., additional, Kovacs, G., additional, Kramm, J.-R., additional, Kührt, E., additional, Küppers, M., additional, Lazzarin, M., additional, Lin, Z.-Y., additional, López-Moreno, J. J., additional, Magrin, S., additional, Marzari, F., additional, Michalik, H., additional, Moissl–Fraund, R., additional, Moreno, F., additional, Mottola, S., additional, Naletto, G., additional, Pajola, M., additional, Pommerol, A., additional, Thomas, N., additional, Sabau, M. D., additional, and Tubiana, C., additional

Published
2015
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19. 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

20. 67P/Churyumov-Gerasimenko: Activity between March and June 2014 as observed from Rosetta/OSIRIS

Author

Tubiana, C., primary, Snodgrass, C., additional, Bertini, I., additional, Mottola, S., additional, Vincent, J.-B., additional, Lara, L., additional, Fornasier, S., additional, Knollenberg, J., additional, Thomas, N., additional, Fulle, M., additional, Agarwal, J., additional, Bodewits, D., additional, Ferri, F., additional, Güttler, C., additional, Gutierrez, P. J., additional, La Forgia, F., additional, Lowry, S., additional, Magrin, S., additional, Oklay, N., additional, Pajola, M., additional, Rodrigo, R., additional, Sierks, H., additional, A’Hearn, M. F., additional, Angrilli, F., additional, Barbieri, C., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, De Cecco, M., additional, Debei, S., additional, Groussin, O., additional, Hviid, S. F., additional, Ip, W., additional, Jorda, L., additional, Keller, H. U., additional, Koschny, D., additional, Kramm, R., additional, Kührt, E., additional, Küppers, M., additional, Lazzarin, M., additional, Lamy, P. L., additional, Lopez Moreno, J. J., additional, Marzari, F., additional, Michalik, H., additional, Naletto, G., additional, Rickman, H., additional, Sabau, L., additional, and Wenzel, K.-P., additional

Published
2014
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21. The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

Author

Mottola, S., primary, Lowry, S., additional, Snodgrass, C., additional, Lamy, P. L., additional, Toth, I., additional, Rożek, A., additional, Sierks, H., additional, A’Hearn, M. F., additional, Angrilli, F., additional, Barbieri, C., additional, Barucci, M. A., additional, Bertaux, J.-L., additional, Cremonese, G., additional, Da Deppo, V., additional, Davidsson, B., additional, De Cecco, M., additional, Debei, S., additional, Fornasier, S., additional, Fulle, M., additional, Groussin, O., additional, Gutiérrez, P., additional, Hviid, S. F., additional, Ip, W., additional, Jorda, L., additional, Keller, H. U., additional, Knollenberg, J., additional, Koschny, D., additional, Kramm, R., additional, Kührt, E., additional, Küppers, M., additional, Lara, L., additional, Lazzarin, M., additional, Lopez Moreno, J. J., additional, Marzari, F., additional, Michalik, H., additional, Naletto, G., additional, Rickman, H., additional, Rodrigo, R., additional, Sabau, L., additional, Thomas, N., additional, Wenzel, K.-P., additional, Agarwal, J., additional, Bertini, I., additional, Ferri, F., additional, Güttler, C., additional, Magrin, S., additional, Oklay, N., additional, Tubiana, C., additional, and Vincent, J.-B., additional

Published
2014
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23. Continued activity in P/2013 P5 PANSTARRS

Author

Hainaut, O. R., primary, Boehnhardt, H., additional, Snodgrass, C., additional, Meech, K. J., additional, Deller, J., additional, Gillon, M., additional, Jehin, E., additional, Kuehrt, E., additional, Lowry, S. C., additional, Manfroid, J., additional, Micheli, M., additional, Mottola, S., additional, Opitom, C., additional, Vincent, J.-B., additional, and Wainscoat, R., additional

Published
2014
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24. The nucleus of Comet 67P/Churyumov-Gerasimenko: A new shape model and thermophysical analysis

Author

Lowry, S., Duddy, S.R., Rozitis, B., Green, S.F., Fitzsimmons, A., Snodgrass, C., Hsieh, H.H., Hainaut, O., Lowry, S., Duddy, S.R., Rozitis, B., Green, S.F., Fitzsimmons, A., Snodgrass, C., Hsieh, H.H., and Hainaut, O.

Abstract

Context. Comet 67P/Churyumov-Gerasimenko is the target of the European Space Agency Rosetta spacecraft rendez-vous mission. Detailed physical characteristation of the comet before arrival is important for mission planning as well as providing a test bed for ground-based observing and data-analysis methods. Aims. To conduct a long-term observational programme to characterize the physical properties of the nucleus of the comet, via ground-based optical photometry, and to combine our new data with all available nucleus data from the literature. Methods. We applied aperture photometry techniques on our imaging data and combined the extracted rotational lightcurves with data from the literature. Optical lightcurve inversion techniques were applied to constrain the spin state of the nucleus and its broad shape. We performed a detailed surface thermal analysis with the shape model and optical photometry by incorporating both into the new Advanced Thermophysical Model (ATPM), along with all available Spitzer 8-24 ?m thermal-IR flux measurements from the literature. Results. A convex triangular-facet shape model was determined with axial ratios b/a = 1.239 and c/a = 0.819. These values can vary by as much as 7% in each axis and still result in a statistically significant fit to the observational data. Our best spin state solution has Psid = 12.76137 ± 0.00006 h, and a rotational pole orientated at Ecliptic coordinates ? = 78°(±10°), ? = + 58°(±10°). The nucleus phase darkening behaviour was measured and best characterized using the IAU HG system. Best fit parameters are: G = 0.11 ± 0.12 and H R(1,1,0) = 15.31 ± 0.07. Our shape model combined with the ATPM can satisfactorily reconcile all optical and thermal-IR data, with the fit to the Spitzer 24 ?m data taken in February 2004 being exceptionally good. We derive a range of mutually-consistent physical parameters for each thermal-IR data set, including effective radius, geometric albedo, surface thermal inertia and roughness

Published
2012

26. Asteroid 2867 Steins II. Multi-telescope visible observations, shape reconstruction, and rotational state

Author

Lamy, P.L., Kaasalainen, M., Lowry, S., Weissman, P., Barucci, M.A., Carvano, J., Choi, Y.-J., Colas, F., Faury, G., Fornasier, S., Groussin, O., Hicks, M.D., Jorda, L., Kryszczynska, A., Larson, S., Toth, I., Warner, B., Lamy, P.L., Kaasalainen, M., Lowry, S., Weissman, P., Barucci, M.A., Carvano, J., Choi, Y.-J., Colas, F., Faury, G., Fornasier, S., Groussin, O., Hicks, M.D., Jorda, L., Kryszczynska, A., Larson, S., Toth, I., and Warner, B.

Abstract

Context. Asteroid 2867 Steins is the first target of the Rosetta space mission with a flyby scheduled in September 2008. Aims.An early physical characterization is needed to optimize the flyby parameters and the science operations, and to maximize the scientific return. The aim of this article is to characterize the shape and rotational state of this asteroid. Methods. We compile a set of 26 visible light curves whose phase angle coverage extends from 7.5 degs to 41.7 degs, and perform their simultaneous inversion relying on convex modeling. Results.The full three-dimensional solution for asteroid 2867 Steins is rather spherical with axial ratios a/b = 1.17 and a/c = 1.25. The rotational state is characterized by a sidereal period of 6.04681 ± 0.00002 h, and the pole direction defined by its ecliptic coordinates lambda ~ 250 degs and beta ~ -89 degs has an uncertainty of about 5 degs. It is therefore almost exactly perpendicular to the ecliptic plane, and the viewing geometries are thus restricted to only ± 20 degs about Steins' equator. Consequently, the shape model is not strongly constrained, and the polar flattening has an uncertainty of about 10%. Inversion is basically scale-free, and absolute scaling comes from a measurement of its thermal emission with the Spitzer Space Telescope (Lamy et al. 2008, A&A, 487, 1187), yielding overall dimensions of 5.73 ± 0.52, 4.95 ± 0.45, and 4.58 ± 0.41 km. © ESO 2008.

Published
2008

27. Surface properties of Rosetta's targets (21) Lutetia and (2867) Steins from ESO observations

Author

Carvano, J.M., Barucci, M.A., Delbo, M., Fornasier, S., Lowry, S., Fitzsimmons, A., Carvano, J.M., Barucci, M.A., Delbo, M., Fornasier, S., Lowry, S., and Fitzsimmons, A.

Abstract

Aims. The aim of this work is to constrain the size, composition and surface properties of asteroids (2867) Steins and (21) Lutetia, targets of the Rosetta mission. Rosetta is en route to rendezvous with comet 67P/Churyumov-Gerasimenko. Methods.Thermal-Infrared N-band observations for Lutetia and Steins were obtained using, respectively, TIMMI2 on the ESO 3.6-m telescope at La Silla and VISIR at the UT3 VLT telescope on Cerro Paranal; visible light curves for Steins were obtained using NTT+SUSI2, while -band photometry for Lutetia was obtained with the 2.0-m Faulkes Telescope North on Haleakala. For Steins, the NEATM model was used to constrain its visible geometric albedo and beaming parameter. A detailed thermophysical model was implemented and used to analyze our set of observations of Lutetia as well as previous reported measurements.Results. The visible photometry of Steins was used along with data from the literature to yield a slope parameter of. Problems during the observations led to the loss of measurements on two of the three -band filters requested for Steins. Using the remaining data and the polarimetric albedo recently published, we were able to constrain the thermal beaming parameter as 1.2$, which is more similar to near-Earth asteroids and suggests either high thermal inertia or a very rough surface. For Lutetia, the best fit visible geometric albedo obtained with our model and the reported observation is , significantly lower than that obtained if one applies the same model to previously reported measurements. The discrepancy cannot be explained solely by assuming inhomogeneities in the surface properties and we suggest that the most plausible explanation is the presence of one or more large craters on the northern hemisphere. For both sets of measurements, the implied single scattering albedo of Lutetia is compatible with laboratory measurements of carbonaceous chondrite meteorites. © 2008 ESO.

Published
2008

31. CCD photometry and model of MUSES-C target (25143) 1998 SF36

Author

Kaasalainen, M., Kwiatkowski, T., Abe, M., Piironen, J., Nakamura, T., Ohba, Y., Dermawan, B., Farnham, T., Colas, F., Lowry, S., Weissman, P., Whiteley, R.J., Tholen, D.J., Larson, S.M., Yoshikawa, M., Toth, I., Velichko, F.P., Kaasalainen, M., Kwiatkowski, T., Abe, M., Piironen, J., Nakamura, T., Ohba, Y., Dermawan, B., Farnham, T., Colas, F., Lowry, S., Weissman, P., Whiteley, R.J., Tholen, D.J., Larson, S.M., Yoshikawa, M., Toth, I., and Velichko, F.P.

Abstract

We present photometric observations of the near-Earth asteroid (25143) 1998 SF36 from the 2001 apparition campaign, and we discuss the corresponding physical model. The asteroid's photometric behaviour is consistent with an S-type object, it has a retrograde pole at lambda = 355°, beta = -84° ± 5°, and its sidereal rotation period is P = 12.132 ± 0.0005 hours. 1998 SF36 is elongated, with rough global dimension ratios a/b = 2.0, b/c = 1.3, but the elongation is not due to a bifurcated shape. The surface is not likely to contain major concavities. No significant albedo variegation was detected.

Published
2003

32. Spitzer observations of the asteroid-comet transition object and potential spacecraft target 107P (4015) Wilson-Harrington

Author

Licandro, J., primary, Campins, H., additional, Kelley, M., additional, Fernández, Y., additional, Delbó, M., additional, Reach, W. T., additional, Groussin, O., additional, Lamy, P. L., additional, Toth, I., additional, A'Hearn, M. F., additional, Bauer, J. M., additional, Lowry, S. C., additional, Fitzsimmons, A., additional, Lisse, C. M., additional, Meech, K. J., additional, Pittichová, J., additional, Snodgrass, C., additional, and Weaver, H. A., additional

Published
2009
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33. Asteroid 2867 Steins

Author

Jorda, L., primary, Lamy, P. L., additional, Faury, G., additional, Weissman, P., additional, Barucci, M. A., additional, Fornasier, S., additional, Lowry, S., additional, Toth, I., additional, and Küppers, M., additional

Published
2008
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34. Asteroid 2867 Steins

Author

Lamy, P. L., primary, Kaasalainen, M., additional, Lowry, S., additional, Weissman, P., additional, Barucci, M. A., additional, Carvano, J., additional, Choi, Y.-J., additional, Colas, F., additional, Faury, G., additional, Fornasier, S., additional, Groussin, O., additional, Hicks, M. D., additional, Jorda, L., additional, Kryszczynska, A., additional, Larson, S., additional, Toth, I., additional, and Warner, B., additional

Published
2008
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35. New photometric observations of asteroids (1862) Apollo and (25143) Itokawa – an analysis of YORP effect

Author

Ďurech, J., primary, Vokrouhlický, D., additional, Kaasalainen, M., additional, Weissman, P., additional, Lowry, S. C., additional, Beshore, E., additional, Higgins, D., additional, Krugly, Y. N., additional, Shevchenko, V. G., additional, Gaftonyuk, N. M., additional, Choi, Y.-J., additional, Kowalski, R. A., additional, Larson, S., additional, Warner, B. D., additional, Marshalkina, A. L., additional, Ibrahimov, M. A., additional, Molotov, I. E., additional, Michałowski, T., additional, and Kitazato, K., additional

Published
2008
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40. CCD photometry and model of MUSES-C target (25143) 1998 SF36

Author

Kaasalainen, M., primary, Kwiatkowski, T., additional, Abe, M., additional, Piironen, J., additional, Nakamura, T., additional, Ohba, Y., additional, Dermawan, B., additional, Farnham, T., additional, Colas, F., additional, Lowry, S., additional, Weissman, P., additional, Whiteley, R. J., additional, Tholen, D. J., additional, Larson, S. M., additional, Yoshikawa, M., additional, Toth, I., additional, and Velichko, F. P., additional

Published
2003
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43. Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

Author

Debei, S., Vincent, J.-B., Barbieri, C., Güttler, C., Jorda, L., Besse, S., Knollenberg, J., Sierks, H., Hviid, S. F., Bertaux, J.-L., Boudreault, S., Lowry, S., Lamy, P. L., Pajola, M., Keller, H. U., Rodrigo, R., Marzari, F., Fulle, M., Lazzarin, M., Fornasier, S., Bodewits, D., Kührt, E., Cremonese, G., Lee, J.-C., Tubiana, C., Koschny, D., Li, Y., La Forgia, F., Kramm, J.-R., Bertini, I., Küppers, M., Lin, Z.-Y., Oklay, N., Mottola, S., Toth, E., Ip, W.-H., El-Maarry, M. R., Agarwal, J., Barucci, M. A., López-Moreno, J. J., A’Hearn, M. F., Marchi, S., Da Deppo, V., Davidsson, B., Rickman, H., Cheng, Y.-C., De Cecco, M., Naletto, G., Lara, L. M., Michalik, H., Kovacs, G., Groussin, O., Lai, I.-L., Thomas, Nicolas, and Gutiérrez, P. J.

Subjects
13. Climate action, 530 Physics
Abstract

Aims. We aim to characterize the circular depressions of comet 67P/Churyumov-Gerasimenko and investigate whether such surface morphology of a comet nucleus is related to the cumulative sublimation effect since becoming a Jupiter family comet (JFC). Methods. The images from the Rosetta/OSIRIS science camera experiment are used to construct size frequency distributions of the circular depression structures on comet 67P and they are compared with those of the JFCs 81P/Wild 2, 9P/Tempel 1, and 103P/Hartley 2. The orbital evolutionary histories of these comets over the past 100 000 yr are analyzed statistically and compared with each other. Results. The global distribution of the circular depressions over the surface of 67P is charted and classified. Descriptions are given to the characteristics and cumulative size frequency distribution of the identified features. Orbital statistics of the JFCs visited by spacecraft are derived. Conclusions. The size frequency distribution of the circular depressions is found to have a similar power law distribution to those of 9P/Tempel 1 and 81P/Wild 2. This might imply that they could have been generated by the same process. Orbital integration calculation shows that the surface erosion histories of 81P/Wild 2, and 9P/Tempel 1 could be shorter than those of 67P, 103 P/Hartley 2 and 19P/Borrelly. From this point of view, the circular depressions could be dated back to the pre-JFC phase or the transneptunian phase of these comets. The north-south asymmetry in the distribution of the circular depressions could be associated with the heterogeneous structure of the nucleus of comet 67P and/or the solar insolation history.

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

Author

Wenzel, K.-P., Magrin, S., Gutiérrez, P., Rickman, H., Debei, S., Hviid, S. F., Rożek, A., Koschny, D., Ferri, F., Jorda, L., Knollenberg, J., Mottola, S., A’Hearn, M. F., Lazzarin, M., Fornasier, S., Da Deppo, V., Angrilli, F., Vincent, J.-B., Marzari, F., Barucci, M. A., Sabau, L., Groussin, O., Kramm, R., Lamy, P. L., Oklay, N., Ip, W., Davidsson, B., Sierks, H., Toth, I., Lara, L., Michalik, H., Cremonese, G., Tubiana, C., De Cecco, M., Fulle, M., Thomas, Nicolas, Agarwal, J., Küppers, M., Bertini, I., Lopez Moreno, J. J., Naletto, G., Kührt, E., Güttler, C., Keller, H. U., Barbieri, C., Lowry, S., Rodrigo, R., Bertaux, J.-L., and Snodgrass, C.

Subjects
13. Climate action, 530 Physics, 520 Astronomy
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 λ = 65° ± 15°, β = + 59° ± 15°, corresponding to equatorial coordinates RA = 22°, Dec = + 76°. However, we find that the mirror solution, also prograde, at λ = 275° ± 15°, β = + 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.

45. Are fractured cliffs the source of cometary dust jets? Insights from OSIRIS/Rosetta at 67P/Churyumov-Gerasimenko

Author

Hu, X., De Cecco, M., Lamy, P. L., Rickman, H., Lopez Moreno, J. J., Sierks, H., Rodrigo, R., Lowry, S., Keller, H. U., Moreno, F., Davidsson, B., Toth, I., Bodewits, D., Barucci, M. A., Lara, L. M., Lazzarin, M., Kueppers, M., Vincent, J. B., Gutierrez, P. J., Guettler, C., Tubiana, C., Barbieri, C., Da Deppo, V., Elmaarry, Mohamed Ramy, Kuehrt, E., Ip, W. H., Koschny, D., Bertaux, J. L., Kramm, J. R., Massironi, M., Gutierrez-Marquez, P., Mottola, S., Bertini, I., Cremonese, G., Oklay, N., Pajola, M., Fornasier, S., A'Hearn, M. F., Marzari, F., Besse, S., Lin, Z. Y., Scholten, F., Hofmann, M., Fulle, M., Hoefner, S., Groussin, O., Naletto, G., Knollenberg, J., Shi, X., Debei, S., Preusker, F., Kovacs, G., Hviid, S. F., Jordan, L., and Thomas, Nicolas

Subjects
13. Climate action, 530 Physics, 520 Astronomy
Abstract

Context. Dust jets (i.e., fuzzy collimated streams of cometary material arising from the nucleus) have been observed in situ on all comets since the Giotto mission flew by comet 1P/Halley in 1986, and yet their formation mechanism remains unknown. Several solutions have been proposed involving either specific properties of the active areas or the local topography to create and focus the gas and dust flows. While the nucleus morphology seems to be responsible for the larger features, high resolution imagery has shown that broad streams are composed of many smaller jets (a few meters wide) that connect directly to the nucleus surface. Aims. We monitored these jets at high resolution and over several months to understand what the physical processes are that drive their formation and how this affects the surface. Methods. Using many images of the same areas with different viewing angles, we performed a 3-dimensional reconstruction of collimated jets and linked them precisely to their sources on the nucleus. Results. We show here observational evidence that the northern hemisphere jets of comet 67P/Churyumov-Gerasimenko arise from areas with sharp topographic changes and describe the physical processes involved. We propose a model in which active cliffs are the main source of jet-like features and therefore of the regions eroding the fastest on comets. We suggest that this is a common mechanism taking place on all comets.

46. 67P/Churyumov-Gerasimenko: Activity between March and June 2014 as observed from Rosetta/OSIRIS

Author

Oklay, N., Koschny, D., Barbieri, C., Hviid, S. F., Davidsson, B., Fornasier, S., Lara, L., Keller, H. U., Lazzarin, M., Groussin, O., Pajola, M., Bodewits, D., Lowry, S., Debei, S., Tubiana, C., Güttler, C., A’Hearn, M. F., Thomas, Nicolas, Kramm, R., Bertini, I., Ip, W., Magrin, S., Gutierrez, P. J., Barucci, M. A., Snodgrass, C., Da Deppo, V., Bertaux, J.-L., Fulle, M., De Cecco, M., Naletto, G., Küppers, M., Lamy, P. L., Rickman, H., Vincent, J.-B., La Forgia, F., Ferri, F., Cremonese, G., Marzari, F., Rodrigo, R., Agarwal, J., Knollenberg, J., Kührt, E., Sabau, L., Sierks, H., Angrilli, F., Mottola, S., Michalik, H., Jorda, L., Wenzel, K.-P., and Lopez Moreno, J. J.

Subjects
13. Climate action, 530 Physics, 520 Astronomy
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.

47. Large-scale dust jets in the coma of 67P/Churyumov-Gerasimenko as seen by the OSIRIS instrument onboard Rosetta

Author

Guettler, C., Da Deppo, V., Lopez-Moreno, J. J., Kuehrt, E., Magrin, S., Elmaarry, Mohamed Ramy, Keller, H. U., Rickman, H., Debei, S., Gutierrez-Marques, P., Marzari, F., Rodrigo, R., Auger, A. T., Bodewits, D., Kueppers, M., Cremonese, G., Lara, L. M., Koschny, D., Gutierrez, P. J., Hviid, S. F., Pajola, M., Michalik, H., Rozek, A., Thomas, Nicolas, Kovacs, G., Kramm, J. R., Lowry, S., Moreno, F., Barucci, M. A., Vincent, J. B., A'Hearn, M. F., Jorda, L., De Cecco, M., Ferri, F., Oklay, N., Agarwal, J., Davidsson, B., Ip, W. H., Bertaux, J. L., Mottola, S., Lazzarin, M., Tubiana, C., Fulle, M., Knollenberg, J., Sierks, H., Moissl-Fraund, R., Bertini, I., Besse, S., Naletto, G., Lamy, P. L., Barbieri, C., La Forgia, F., Sabau, M. D., Fornasier, S., Pommerol, Antoine, Lin, Z. Y., and Groussin, O.

Subjects
13. Climate action, 530 Physics
Abstract

Context. During the most recent perihelion passage in 2009 of comet 67P/Churyumov-Gerasimenko (67P), ground-based observations showed an anisotropic dust coma where jet-like features were detected at similar to 1.3 AU from the Sun. The current perihelion passage is exceptional as the Rosetta spacecraft is monitoring the nucleus activity since March 2014, when a clear dust coma was already surrounding the nucleus at 4.3 AU from the Sun. Subsequently, the OSIRIS camera also witnessed an outburst in activity between April 27 and 30, and since mid-July, the dust coma at rh similar to 3.7-3.6 AU preperihelion is clearly non-isotropic, pointing to the existence of dust jet-like features. Aims. We aim to ascertain on the nucleus surface the origin of the dust jet-like features detected as early as in mid-July 2014. This will help to establish how the localized comet nucleus activity compares with that seen in previous apparitions and will also help following its evolution as the comet approaches its perihelion, at which phase most of the jets were detected from ground-based observations. Determining these areas also allows locating them in regions on the nucleus with spectroscopic or geomorphological distinct characteristics. Methods. Three series of dust images of comet 67P obtained with the Wide Angle Camera (WAC) of the OSIRIS instrument onboard the Rosetta spacecraft were processed with different enhancement techniques. This was made to clearly show the existence of jet-like features in the dust coma, whose appearance toward the observer changed as a result of the rotation of the comet nucleus and of the changing observing geometry from the spacecraft. The position angles of these features in the coma together with information on the observing geometry, nucleus shape, and rotation, allowed us to determine the most likely locations on the nucleus surface where the jets originate from. Results. Geometrical tracing of jet sources indicates that the activity of the nucleus of 67P gave rise during July and August 2014 to large-scale jet-like features from the Hapi, Hathor, Anuket, and Aten regions, confirming that active regions may be present on the nucleus localized at 60. northern latitude as deduced from previous comet apparitions. There are also hints that large-scale jets observed from the ground are possibly composed, at their place of origin on the nucleus surface, of numerous small-scale features.

48. Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko

Author

Davidsson, B., Lara, L. M., A'Hearn, M. F., Toth, I., Kovacs, G., Kuehrt, E., Debei, S., Pajola, M., Fornasier, S., Kramm, J. R., Oklay, N., De Cecco, M., Kueppers, M., Koschny, D., Rickman, H., Barbieri, C., Vincent, J. B., Tubiana, C., Lazzarin, M., Besse, S., Elmaarry, Mohamed Ramy, Auger, A. T., Lopez Moreno, J. J., Marzari, F., Jorda, L., Keller, H. U., Massironi, M., Lowry, S., Rodrigo, R., Lamy, P., Cremonese, G., Mottola, S., Thomas, Nicolas, Knollenberg, J., Bertaux, J. L., Gutierrez, P. J., Fulle, M., Ip, W. H., Groussin, O., Barucci, M. A., Naletto, G., Sierks, H., Hviid, S., Bertini, I., Pommerol, Antoine, Marchi, S., Da Deppo, V., and Guettler, C.

Subjects
13. Climate action, 530 Physics, 520 Astronomy
Abstract

Aims. We report on the first major temporal morphological changes observed on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko in the smooth terrains of the Imhotep region. Methods. We used images of the OSIRIS cameras onboard Rosetta to follow the temporal changes from 24 May 2015 to 11 July 2015. Results. The morphological changes observed on the surface are visible in the form of roundish features that are growing in size from a given location in a preferential direction at a rate of 5.6-8.1 x 10(-5) m s(-1) during the observational period. The location where the changes started and the contours of the expanding features are bluer than the surroundings, which suggests that ices (H2O and/or CO2) are exposed on the surface. However, sublimation of ices alone is not sufficient to explain the observed expanding features. No significant variations in the dust activity pattern are observed during the period of changes.

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