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

Mottola, S.; Lowry, S.; Snodgrass, Colin; Lamy, P. L.; Toth, I.; Rożek, A.; Sierks, H.; A’Hearn, M. F.; Angrilli, F.; Barbieri, C.; Barucci, M. A.; Bertaux, J.-L.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P.; Hviid, S. F.; Ip, W.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Rickman, H.; Rodrigo, R.; Sabau, L.; Thomas, N.; Wenzel, K.-P.; Agarwal, J.; Bertini, I.; Ferri, F.; Güttler, C.; Magrin, S.; Oklay, N.; Tubiana, C. and Vincent, J.-B. (2014). The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta. Astronomy & Astrophysics, 569, article no. L2.

DOI: https://doi.org/10.1051/0004-6361/201424590

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.

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About

  • Item ORO ID
  • 43020
  • Item Type
  • Journal Item
  • ISSN
  • 1432-0746
  • Project Funding Details
  • Funded Project NameProject IDFunding Body
    Seventh Framework Programme (FP7/2007-2013)Grant agreement No. 268421EU
    Not SetNot SetNational Funding Agency of Germany (DLR)
    Not SetNot SetNational Funding Agency of France (CNES)
    Not SetNot SetNational Funding Agency of Italy (ASI)
    Not SetNot SetNational Funding Agency of Spain (MEC)
    Not SetNot SetNational Funding Agency of Sweden (SNSB)
    Not SetNot SetESA Technical Directorate
  • Keywords
  • comets-general; comets-individual-67P/Churyumov-Gerasimenko; techniques-photometric
  • Academic Unit or School
  • Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
    Faculty of Science, Technology, Engineering and Mathematics (STEM)
  • Research Group
  • Space
  • Copyright Holders
  • © 2014 ESO
  • Depositing User
  • Colin Snodgrass

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