Stardust-NExT,Deep Impact,and the accelerating spin of 9P/Tempel 1 |
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| Authors: | Michael JS Belton Karen J Meech Steven Chesley Jana Pittichová Brian Carcich Michal Drahus Alan Harris Stephen Gillam Joseph Veverka Nicholas Mastrodemos William Owen Michael F A’Hearn S Bagnulo J Bai L Barrera Fabienne Bastien James M Bauer J Bedient BC Bhatt Hermann Boehnhardt H Zhao |
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| Institution: | 1. Belton Space Exploration Initiatives, LLC, 430 S. Randolph Way, Tucson, AZ 85716, USA;2. Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, USA;3. Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109, USA;4. Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, USA;5. Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA;6. Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA;7. Department of Astronomy, University of Maryland, College Park, MD 20742, USA;8. Armagh Observatory, College Hill, Armagh BT61 9DG, United Kingdom;9. Yunnan Astronomical Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming 65011, Yunnan, PR China;10. Universidad Metropolitana de Ciencias de la Educac?´on, Dep. Fisica, Avda. Jose Pedro Alessandri 774, Santiago, Chile;11. University of Hawaii, Honolulu, HI 96822, USA;12. Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560 034, India;13. Max-Planck Institut für Sonnensystemforschung, Max-Planck Str. 2, 37191 Katlenburg-Lindau, Germany;14. Dept. Geophysics and Planetary Sciences, Tel Aviv University, 69978 Te-Aviv, Israel;15. Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302, USA;p. Gemini Observatory, c/o AURA, casilla 603, La Serena, Chile;q. Grad. Inst. Of Astronomy, National Central Univ., 300 Jhongda Road, Jhongli 32001, Taiwan;r. Korea Astronomy and Space Science Institute, 776 Daedukdaero, Yuseong-gu, Daejeon 305-348, South Korea;s. Univ. Texas, Dept. of Astronomy, 1 University Station, C1400, Austin, TX 78712, USA;t. Centre for Astrophysics and Planetary Science School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK;u. Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816-2385, USA;v. Instituto de Astrofisica de Andalucia – CSIC, Box 3004, E-18080 Granada, Spain;w. European Southern Observatory, Casilla 19001, Santiago 19, Chile;x. Geophysical Institute, Univ. AK, 903 Koyukuk Dr., Fairbanks, AK 99775-7320, USA;y. Lowell Observatory, 1400 Mars Hill Rd., Flagstaff, AZ 86001, USA;z. Department of Astronomy, College of Science, 134 Sinchon-dong, Sodaemun-gu, Seoul 120-749, South Korea;11. Texas A&M University, Department of Physics, College Station, TX 77843, USA;12. National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719, USA;13. Instituto de Astrofisica de Canarias, Via Lactea, 38200 La Laguna, Tenerife, Spain;14. Departmento de Astrofisica, Universidad de la laguna, E-38205 La Laguna, Tenerife, Spain;15. Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA;16. NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA;17. Dept. of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA;18. Planetary Science Institute, 1700 E. Ft. Lowell Rd., #106, Tucson, AZ 85719-2395, USA;19. National Astronomical Observatory, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan;110. Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA;111. INAF Osservatorio Astrofisico di Arcetri, Firenze, I-50125, Italy;112. HAS, 47-728 Hui Kelu St. #9, Kaneohe, HI 96744, USA;113. Purple Mountain Obs. Chinese Academy of Sciences, 2# West Beijing Road, Nanjing 210008, PR China;1. University of Southampton, Faculty of Engineering and Environment, Southampton, UK;2. Lancaster University, Faculty of Science and Technology, Lancaster, UK;3. University of Utrecht, Faculty of Geosciences, Utrecht, The Netherlands;4. University of Southampton, Geography and Environment, Southampton, UK;5. Queen''s University Belfast, School of Geography, Archaeology and Palaeoecology, Belfast, UK;1. Université de Lyon, Lyon, F-69003, France; Université Lyon 1, Observatoire de Lyon, 9 avenue Charles André, Saint-Genis Laval, F-69230, France; CNRS, UMR 5574, Centre de Recherche Astrophysique de Lyon; École Normale Supérieure de Lyon, Lyon, F-69007, France;2. School of Physics and Astronomy, University of Saint Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK;3. Centre for Astrophysics and Supercomputing, Swinburne Institute of Technology, PO Box 218, Hawthorn, VIC 3122, Australia;4. UMI-FCA, CNRS/INSU France (UMI 3386), and Departamento de Astronomía, Universidad de Chile, Casilla 36-D Santiago, Chile;5. UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble, UMR 5274, Grenoble, F-38041, France;1. Department of Astronomy, Cornell University, Ithaca, NY 14853, United States;2. Department of Astronomy, Wellesley College, Wellesley, MA 02481, United States;3. Department of Physics, University of Idaho, Moscow, ID 83844, United States;4. Department of Electrical Engineering, San Jose State University, San Jose, CA 95192, United States;5. Department of Physics, University of Central Florida, Orlando, FL 32816, United States |
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| Abstract: | The evolution of the spin rate of Comet 9P/Tempel 1 through two perihelion passages (in 2000 and 2005) is determined from 1922 Earth-based observations taken over a period of 13 year as part of a World-Wide observing campaign and from 2888 observations taken over a period of 50 days from the Deep Impact spacecraft. We determine the following sidereal spin rates (periods): 209.023 ± 0.025°/dy (41.335 ± 0.005 h) prior to the 2000 perihelion passage, 210.448 ± 0.016°/dy (41.055 ± 0.003 h) for the interval between the 2000 and 2005 perihelion passages, 211.856 ± 0.030°/dy (40.783 ± 0.006 h) from Deep Impact photometry just prior to the 2005 perihelion passage, and 211.625 ± 0.012°/dy (40.827 ± 0.002 h) in the interval 2006–2010 following the 2005 perihelion passage. The period decreased by 16.8 ± 0.3 min during the 2000 passage and by 13.7 ± 0.2 min during the 2005 passage suggesting a secular decrease in the net torque. The change in spin rate is asymmetric with respect to perihelion with the maximum net torque being applied on approach to perihelion. The Deep Impact data alone show that the spin rate was increasing at a rate of 0.024 ± 0.003°/dy/dy at JD2453530.60510 (i.e., 25.134 dy before impact), which provides independent confirmation of the change seen in the Earth-based observations.The rotational phase of the nucleus at times before and after each perihelion and at the Deep Impact encounter is estimated based on the Thomas et al. (Thomas et al. 2007]. Icarus 187, 4–15) pole and longitude system. The possibility of a 180° error in the rotational phase is assessed and found to be significant. Analytical and physical modeling of the behavior of the spin rate through of each perihelion is presented and used as a basis to predict the rotational state of the nucleus at the time of the nominal (i.e., prior to February 2010) Stardust-NExT encounter on 2011 February 14 at 20:42.We find that a net torque in the range of 0.3–2.5 × 107 kg m2 s?2 acts on the nucleus during perihelion passage. The spin rate initially slows down on approach to perihelion and then passes through a minimum. It then accelerates rapidly as it passes through perihelion eventually reaching a maximum post-perihelion. It then decreases to a stable value as the nucleus moves away from the Sun. We find that the pole direction is unlikely to precess by more than ～1° per perihelion passage. The trend of the period with time and the fact that the modeled peak torque occurs before perihelion are in agreement with published accounts of trends in water production rate and suggests that widespread H2O out-gassing from the surface is largely responsible for the observed spin-up. |
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