Characterization of dust aggregates in the vicinity of the Rosetta spacecraft

Carsten Güttler (1) , Pedro H. Hasselmann (2) , Y. Li (3) , Marco Fulle (4) , Cécilia Tubiana (1) , Gabor Kovacs (1) , Jessica Agarwal (1) , Holger Sierks (1) , Sonia Fornasier (2) , Marc Hofmann (1) , Pedro J. Gutiérrez (5) , Theresa Ott (6) , Esther Drolshagen (7) , Ivano Bertini (8) , Cesare Barbieri (9) , Philippe L. Lamy (10) , Rafael Rodrigo (11, 12) , Detlef Koschny (13) , Hans Rickman (14, 15) , Michael F. A'Hearn (16) , Maria Antonella Barucci (2) , Dennis Bodewits (16) , Jean-Loup Bertaux (17) , Steve Boudreault (1) , Gabriele Cremonese (18) , Vania da Deppo (19) , B. Davidsson (20) , S. Debei (21) , M. de Cecco (22) , J. Deller (1) , B. Geiger (23) , O. Groussin (10) , J. Gutiérrez (5) , S. Hviid (24) , W.-H. Ip (25) , L. Jorda (10) , H. U. Keller (24, 26) , J. Knollenberg (24) , J. R. Kramm (1) , Ekkehard Kührt (24) , M. Küppers (23) , Luisa M. Lara (5) , M. Lazzarin (9) , J. J. López-Moreno (5) , F. Marzari (9) , S. Mottola (24) , G. Naletto (19, 8) , N. Oklay (24) , M. Pajola (27) , X. Shi (1) , N. Thomas (28, 29) , J.-B. Vincent (24)

1 MPS - Max-Planck-Institut für Sonnensystemforschung
2 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
3 SSI - Space Science Institute [Macau]
4 OAT - INAF - Osservatorio Astronomico di Trieste
5 IAA - Instituto de Astrofísica de Andalucía
6 University of Oldenburg
7 OFFIS - Carl Von Ossietzky Universität Oldenburg = Carl von Ossietzky University of Oldenburg
8 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
9 Dipartimento di Fisica e Astronomia "Galileo Galilei"
10 LAM - Laboratoire d'Astrophysique de Marseille
11 CAB - Centro de Astrobiologia [Madrid]
12 ISSI - International Space Science Institute [Bern]
13 ESTEC - European Space Research and Technology Centre
14 Department of Physics and Astronomy [Uppsala]
15 CBK - Space Research Centre of Polish Academy of Sciences
16 Department of Astronomy [College Park]
17 PLANETO - LATMOS
18 OAPD - INAF - Osservatorio Astronomico di Padova
19 IFN - CNR Institute for Photonics and Nanotechnologies
20 JPL - Jet Propulsion Laboratory
21 Department of Industrial Engineering [Padova]
22 University of Trento [Trento]
23 Operations Department (ESAC)
24 DLR Institut für Planetenforschung
25 Institute of Space Science [Taiwan]
26 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
27 ARC - NASA Ames Research Center
28 CSH - Center for Space and Habitability
29 Physikalisches Institut [Bern]

In a Rosetta/OSIRIS imaging activity in 2015 June, we have observed the dynamic motion of particles close to the spacecraft. Due to the focal setting of the OSIRIS wide angle camera, these particles were blurred, which can be used to measure their distances to the spacecraft. We detected 109 dust aggregates over a 130 min long sequence, and find that their sizes are around a millimetre and their distances cluster between 2 and 40 m from the spacecraft. Their number densities are about a factor 10 higher than expected for the overall coma and highly fluctuating. Their velocities are small compared to the spacecraft orbital motion and directed away from the spacecraft, towards the comet. From this we conclude that they have interacted with the spacecraft and assess three possible scenarios. In the likeliest of the three scenarios, centimetre-sized aggregates collide with the spacecraft and we would observe the fragments. Ablation of a dust layer on the spacecraft’s z panel (remote instrument viewing direction) when rotated towards the Sun is a reasonable alternative. We could also measure an acceleration for a subset of 18 aggregates, which is directed away from the Sun and can be explain by a rocket effect, which requires a minimum ice fraction of the order of 0.1 per cent.

Keywords: Comets; 67P/Churyumov-Gerasimenko; Image processing

Domains: Earth and Planetary Astrophysics [astro-ph.EP]; Solar and Stellar Astrophysics [astro-ph.SR]; Physics [physics]; Astrophysics [astro-ph]

Carsten Güttler, Pedro H. Hasselmann, Y. Li, Marco Fulle, Cécilia Tubiana, et al.. Characterization of dust aggregates in the vicinity of the Rosetta spacecraft. Monthly Notices of the Royal Astronomical Society, 2017, 469 (Suppl_2), pp.S312 - S320. ⟨10.1093/mnras/stx1692⟩. ⟨insu-01574602⟩