The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

S. Mottola 1 S. Lowry 2 C. Snodgrass 3 P. L. Lamy 4 I. Toth 5 A. Rożek 2 H. Sierks 3 M. F. A'Hearn 6 F. Angrilli 7 C. Barbieri 7 M. A. Barucci 8, 9 Jean-Loup Bertaux 10 G. Cremonese 11 V. Da Deppo 12 B. Davidsson 13 M. De Cecco 14 S. Debei 15 S. Fornasier 8 M. Fulle 16 O. Groussin 4 P. Gutiérrez 17 S. F. Hviid 1 W. Ip 18 L. Jorda 4 H. U. Keller 19 J. Knollenberg 1 D. Koschny 20 R. Kramm 3 E. Kührt 1 M. Küppers 21 L. Lara 17 M. Lazzarin 7 J. J. Lopez Moreno 17 F. Marzari 22 H. Michalik G. Naletto 23 H. Rickman 13 R. Rodrigo 24, 25 L. Sabau 26 N. Thomas 27 K.-P. Wenzel 20 J. Agarwal 3 I. Bertini 12 F. Ferri 12 C. Güttler 3 S. Magrin 6 N. Oklay 3 C. Tubiana 3 J.-B. Vincent 3
Abstract : Aims: Approach observations with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard Rosetta are used to determine the rotation period, the direction of the spin axis, and the state of rotation of comet 67P's nucleus. Methods: Photometric time series of 67P have been acquired by OSIRIS since the post wake-up commissioning of the payload in March 2014. Fourier analysis and convex shape inversion methods have been applied to the Rosetta data as well to the available ground-based observations. Results: Evidence is found that the rotation rate of 67P has significantly changed near the time of its 2009 perihelion passage, probably due to sublimation-induced torque. We find that the sidereal rotation periods P1 = 12.76129 ± 0.00005 h and P2 = 12.4043 ± 0.0007 h for the apparitions before and after the 2009 perihelion, respectively, provide the best fit to the observations. No signs of multiple periodicity are found in the light curves down to the noise level, which implies that the comet is presently in a simple rotation state around its axis of largest moment of inertia. We derive a prograde rotation model with spin vector J2000 ecliptic coordinates λ = 65° ± 15°, β = + 59° ± 15°, corresponding to equatorial coordinates RA = 22°, Dec = + 76°. However, we find that the mirror solution, also prograde, at λ = 275° ± 15°, β = + 50° ± 15° (or RA = 274°, Dec = + 27°), is also possible at the same confidence level, due to the intrinsic ambiguity of the photometric problem for observations performed close to the ecliptic plane. Table 1 is available in electronic form at http://www.aanda.org
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https://hal.archives-ouvertes.fr/hal-01065970
Contributeur : Catherine Cardon <>
Soumis le : jeudi 18 septembre 2014 - 18:36:58
Dernière modification le : jeudi 5 octobre 2017 - 17:38:01

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S. Mottola, S. Lowry, C. Snodgrass, P. L. Lamy, I. Toth, et al.. The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta. Astronomy and Astrophysics - A&A, EDP Sciences, 2014, 569, pp.L2. 〈10.1051/0004-6361/201424590〉. 〈hal-01065970〉

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