Modeling of the Inner Coma of Comet 67P/Churyumov-Gerasimenko Constrained by VIRTIS and ROSINA Observations

Nicolas Fougere (1) , Michael Combi (1) , Valeriy Tenishev (1) , André Bieler (1) , Alessandra Migliorini (2) , Dominique Bockelée-Morvan (3) , Gabor Toth (1) , Zhenguang Huang (1) , Tamas I. Gombosi (1) , Kenneth Hansen (1) , Fabrizio Capaccioni (2) , Gianrico Filacchione (2) , Giuseppe Piccioni (2) , Vincent Debout (3) , Stéphane Erard (3) , Cedric Leyrat (3) , Uwe Fink (4) , Martin Rubin (5) , Kathrin Altwegg (5, 6) , Chia-Yu Tzou (5) , Léna Le Roy (6) , Ursina Calmonte (5) , Jean-Jacques Berthelier (7) , Henri Rème (8) , Myrtha Hässig (9) , Stephen Fuselier (9) , Björn Fiethe (10) , Johan de Keyser (11)

1 AOSS - Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor]
2 IAPS - Istituto di Astrofisica e Planetologia Spaziali - INAF
3 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
4 LPL - Lunar and Planetary Laboratory [Tucson]
5 Physikalisches Institut [Bern]
6 CSH - Center for Space and Habitability
7 PLANETO - LATMOS
8 IRAP - Institut de recherche en astrophysique et planétologie
9 Space Science Division [San Antonio]
10 IDA - Institute of Computer and Network Engineering [Braunschweig]
11 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique

As it orbits around comet 67P/Churyumov-Gerasimenko (CG), the Rosetta spacecraft acquires more information about its main target. The numerous observations made at various geometries and at different times enable a good spatial and temporal coverage of the evolution of CG’s cometary coma. However, the question regarding the link between the coma measurements and the nucleus activity remains relatively open notably due to gas expansion and strong kinetic effects in the comet’s rarefied atmosphere. In this work, we use coma observations made by the ROSINA-DFMS instrument to constrain the activity at the surface of the nucleus. The distribution of the H2O and CO2 outgassing is described with the use of spherical harmonics. The coordinates in the orthogonal system represented by the spherical harmonics are computed using a least squared method, minimizing the sum of the square residuals between an analytical coma model and the DFMS data. Then, the previously deduced activity distributions are used in a Direct Simulation Monte Carlo (DSMC) model to compute a full description of the H2O and CO2 coma of comet CG from the nucleus’ surface up to several hundreds of kilometers. The DSMC outputs are used to create synthetic images, which can be directly compared with VIRTIS measurements. The good agreement between the VIRTIS observations and the DSMC model, itself constrained with ROSINA data, provides a compelling juxtaposition of the measurements from these two instruments.

Domains: Earth and Planetary Astrophysics [astro-ph.EP]; Instrumentation and Methods for Astrophysic [astro-ph.IM]; Solar and Stellar Astrophysics [astro-ph.SR]

Nicolas Fougere, Michael Combi, Valeriy Tenishev, André Bieler, Alessandra Migliorini, et al.. Modeling of the Inner Coma of Comet 67P/Churyumov-Gerasimenko Constrained by VIRTIS and ROSINA Observations. AGU Fall Meeting 2015, Dec 2015, San Francisco, United States. pp.P31E-2105, 2015. ⟨insu-01248321⟩