GIADA: shining a light on the monitoring of the comet dust production from the nucleus of 67P/Churyumov-Gerasimenko

¹ Institute for Space Astrophysics and Planetology (IAPS), National Institute for AstroPhysics (INAF), via Fosso del Cavaliere 100, 00133 Roma, Italy
e-mail: vincenzo.dellacorte@iaps.inaf.it
² Università degli Studi di Napoli “Parthenope”, Dipartimento di Scienze e Tecnologie, CDN IC4, 80143 Naples, Italy
³ Osservatorio Astronomico di Trieste, INAF, via Tiepolo 11, 34143 Trieste, Italy
⁴ Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
⁵ Planetary Science Section, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
⁶ Osservatorio Astronomico di Catania, INAF, via S. Sofia 78, 95123 Catania Italy
⁷ LESIA, Obs. de Paris, CNRS, Univ. Paris 06, Univ. Paris-Diderot, 5 place J. Janssen, 92195 Meudon, France
⁸ Osservatorio Astronomico di Capodimonte, INAF, Salita Moiariello 16, 80133 Naples, Italy
⁹ Osservatorio Astronomico di Roma, INAF, via di Frascati, 33, Monte Porzio Catone, Rome, Italy
¹⁰ Instituto de Astrofsica de Andalucia, Consejo Superior de Investigaciones Cientificas (CSIC), PO Box 3008, 18080 Granada, Spain
¹¹ ESA, European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹² Laboratoire Atmosphères, Milieux, Observations Spatiales, CNRS/ Université de Versailles-Saint-Quentin-en-Yvelines/Institut Pierre-Simon Laplace, 11 boulevard d’Alembert, 78280 Guyancourt, France
¹³ Planetary and Space Sciences, Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
¹⁴ Laboratoire d’Astrophysique de Marseille, UMR 7326, CNRS & Aix Marseille Université, 13388 Marseille Cedex 13, France
¹⁵ The University of Kent, Canterbury, Kent, CT2 7NZ, UK
¹⁶ UnispaceKent, Canterbury, Kent, CT2 8EF, UK
¹⁷ Departamento de Fisica Aplicada, Universidad de Granada, Facultad de Ciencias, Avda. Severo Ochoa, s/n, 18071, Granada, Spain
¹⁸ Observatoire de Haute Provence OSU Pythéas UMS 2244 CNRS-AMU, 04870 Saint-Michel l’Observatoire, France
¹⁹ Dept. of Earth and Planetary Science, MSC 03 2040, 1-University of New Mexico, Albuquerque, NM 87131-0001, USA
²⁰ Centro de Astrobiologia (INTA-CSIC), 28691 Villanueva de la Canada, Madrid, Spain
²¹ International Space Science Institute, Hallerstrasse 6, 3012 Bern, Switzerland
²² Selex-ES, via A. Einstein, 35, 50013 − Campi Bisenzio (Firenze), Italy
²³ Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
²⁴ University of Florida, Gainesville, Florida, FL 32611, USA
²⁵ ESA-ESAC, Camino Bajo del Castillo, s/n., Urb. Villafranca del Castillo, 28692 Villanueva de la Canada, Madrid, Spain

Received: 23 March 2015
Accepted: 23 July 2015

Abstract

Context. During the period between 15 September 2014 and 4 February 2015, the Rosetta spacecraft accomplished the circular orbit phase around the nucleus of comet 67P/Churyumov-Gerasimenko (67P). The Grain Impact Analyzer and Dust Accumulator (GIADA) onboard Rosetta monitored the 67P coma dust environment for the entire period.

Aims. We aim to describe the dust spatial distribution in the coma of comet 67P by means of in situ measurements. We determine dynamical and physical properties of cometary dust particles to support the study of the production process and dust environment modification.

Methods. We analyzed GIADA data with respect to the observation geometry and heliocentric distance to describe the coma dust spatial distribution of 67P, to monitor its activity, and to retrieve information on active areas present on its nucleus. We combined GIADA detection information with calibration activity to distinguish different types of particles that populate the coma of 67P: compact particles and fluffy porous aggregates. By means of particle dynamical parameters measured by GIADA, we studied the dust acceleration region.

Results. GIADA was able to distinguish different types of particles populating the coma of 67P: compact particles and fluffy porous aggregates. Most of the compact particle detections occurred at latitudes and longitudes where the spacecraft was in view of the comet’s neck region of the nucleus, the so-called Hapi region. This resulted in an oscillation of the compact particle abundance with respect to the spacecraft position and a global increase as the comet moved from 3.36 to 2.43 AU heliocentric distance. The speed of these particles, having masses from 10^-10 to 10^-7 kg, ranged from 0.3 to 12.2 m s^-1. The variation of particle mass and speed distribution with respect to the distance from the nucleus gave indications of the dust acceleration region. The influence of solar radiation pressure on micron and submicron particles was studied. The integrated dust mass flux collected from the Sun direction, that is, particles reflected by solar radiation pressure, was three times higher than the flux coming directly from the comet nucleus. The awakening 67P comet shows a strong dust flux anisotropy, confirming what was suggested by on-ground dust coma observations performed in 2008.