Issue |
A&A
Volume 522, November 2010
|
|
---|---|---|
Article Number | A63 | |
Number of page(s) | 17 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/201014928 | |
Published online | 03 November 2010 |
Comet 67P/Churyumov-Gerasimenko: the GIADA dust environment model of the Rosetta mission target
1
INAF – Osservatorio Astronomico di Trieste, via Tiepolo
11, 34143
Trieste,
Italy
e-mail: fulle@oats.inaf.it
2
ESA – ESTEC,
Keplerlaan 1, 2201AZ
Noordwijk, The
Netherlands
3
INAF – Osservatorio Astronomico di Capodimonte,
via Moiariello 16,
80131
Napoli,
Italy
4
Università Parthenope, Dip. Scienze Applicate, Centro Direzionale Isola
C4, 80143
Napoli,
Italy
5
Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117
Heidelberg,
Germany
6
Laboratory for Atmospheric and Space Physics, University of
Colorado, 1234 Innovation
Dr, Boulder,
CO, 80303-7814, USA
7
Seoul National University, Dept. of Physics and Astronomy, Seoul
151-742,
Korea
8 CARA – Unione Astrofili Italiani, UAI
9
Osservatorio di Talmassons, CAST, Italy
10
Instituto de Astrofísica de Andalucía,
CSIC, PO Box,
3004
Granada,
Spain
Received: 4 May 2010
Accepted: 2 July 2010
Context. The ESA Rosetta spacecraft will reach the short-period comet 67P/Churyumov-Gerasimenko in 2014. Orbiting strategy, orbiter safety conditions, landing scenarios and expected results from dust collectors depend on models of the 67P dust environment. Many papers already tackled this matter, analysing a limited set of observations, and therefore often reaching conflicting conclusions.
Aims. We consider a set of observations representative of all ground-based and IR (thermal infrared) Spitzer data collected over the last three perihelion passages, to determine the 67P dust environment after the end of the gas drag on dust (at about 20 nucleus radii) consistent with available 67P gas and dust coma photometry, images of the dust coma, tail and trail, at optical and IR wavelengths.
Methods. In order to obtain the best fit to 67P data, we consider three independent tail and trail simulation codes (developed by three independent groups), which parametrise cometary dust by the quantity β, the ratio between solar radiation pressure and gravity forces. GIADA, the dust monitor instrument of the Rosetta orbiter, will provide an experimental determination of the β-dust mass relation.
Results. A 67P environment model based on a perihelion-symmetric dust velocity and on a perihelion-asymmetric dust size distribution, is consistent with all available data. During most Rosetta operations, the dust cross-section is dominated by mm to cm-sized grains, while the ejected dust mass is dominated by grains larger than a few mm, with a dust-to-gas ratio of 3 around perihelion.
Conclusions. 67P onsets its activity at Sun-distances rh ≥ 3.4 AU; the dust geometric albedo is 0.04 ± 0.02; at 3.0 AU, 10 g grains escape the nucleus gravity field (10 kg grains at perihelion) with a dust mass-loss rate of 10−40 kg s-1 (500 kg s-1 at perihelion); 67P’s activity depends on seasons, with the northern heminucleus (rich in large grains and CN depleted) active before perihelion.
Key words: space vehicles: instruments / comets: individual: 67P/Churyumov-Gerasimenko
© ESO, 2010
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