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

¹ Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
e-mail: tubiana@mps.mpg.de
² Planetary and Space Sciences, Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
³ Center of Studies and Activities for Space (CISAS) “G. Colombo”, University of Padova, via Venezia 15, 35131 Padova, Italy
⁴ Institute of Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany
⁵ Instituto de Astrofísica de Andalucía – CSIC, 18080 Granada, Spain
⁶ LESIA, Obs. de Paris, CNRS, Univ Paris 06, Univ. Paris-Diderot, 5 Place J. Janssen, 92195 Meudon, France
⁷ Physikalisches Institut, Sidlerstrasse 5, University of Bern, 3012 Bern, Switzerland
⁸ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
⁹ Department for Astronomy, University of Maryland, College Park, MD 20742-2421, USA
¹⁰ Department of Physics and Astronomy “G. Galilei”, University of Padova, Vic. Osservatorio 3, 35122 Padova, Italy
¹¹ Centre for Astrophysics and Planetary Science, School of Physical Sciences, The University of Kent, Canterbury, CT2 7NH, UK
¹² Centro de Astrobiología, CSIC-INTA, 28850 Torrejón de Ardoz, Madrid, Spain
¹³ International Space Science Institute, Hallerstrasse 6, 3012 Bern, Switzerland
¹⁴ University of Padova, Department of Physics and Astronomy, vicolo dell’Osservatorio 3, 35122 Padova, Italy
¹⁵ LATMOS, CNRS/UVSQ/IPSL, 11 Boulevard d’Alembert, 78280 Guyancourt, France
¹⁶ INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹⁷ CNR–IFN UOS Padova LUXOR, via Trasea 7, 35131 Padova, Italy
¹⁸ Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
¹⁹ UNITN, Universitá di Trento, via Mesiano 77, 38100 Trento, Italy
²⁰ Department of Mechanical Engineering – University of Padova, via Venezia 1, 35131 Padova, Italy
²¹ Aix Marseille Université, CNRS, LAM (Laboratoire d’Astro-physique de Marseille) UMR 7326, 13388 Marseille, France
²² Institute for Space Science, National Central University, 32054 Chung-Li, Taiwan
²³ Institute for Geophysics and Extraterrestrial Physics, TU Braunschweig, 38106 Braunschweig, Germany
²⁴ Research and Scientific Support Department, European Space Agency, 2201 Noordwijk, The Netherlands
²⁵ ESA/ESAC, PO Box 78, 28691 Villanueva de la Cañada, Spain
²⁶ Dept. Physics, University of Padova, 35122 Padova, Italy
²⁷ Institut für Datentechnik und Kommunikationsnetze, 38106 Braunschweig, Germany
²⁸ Department of Information Engineering – University of Padova, via Gradenigo 6, 35131 Padova, Italy
²⁹ PAS Space Reserch Center, Bartycka 18A, 00716 Warszawa, Poland
³⁰ Instituto Nacional de Técnica Aeroespacial, 28850 Torrejon de Ardoz, Spain

Received: 1 August 2014
Accepted: 27 October 2014

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.