EPOXI: Comet 103P/Hartley 2 observations from a worldwide campaign


K. J. Meech, University of Hawaiʻi System
M. F. A'Hearn, University of Maryland, College Park (UMD)
J. A. Adams, Cornell University
P. Bacci, Centro Astronomico di Libbiano
J. Bai, National Astronomical Observatories Chinese Academy of Sciences
L. Barrera, Universidad Metropolitana de Ciencias de la Educación
M. Battelino, Swedish Space Corporation
J. M. Bauer, Jet Propulsion Laboratory
E. Becklin, Universities Space Research Association
B. Bhatt, Indian Institute of Astrophysics
N. Biver, L'Observatoire de Paris
D. Bockelée-Morvan, L'Observatoire de Paris
D. Bodewits, University of Maryland, College Park (UMD)
H. Böhnhardt, Max Planck Institute for Solar System Research
J. Boissier, Istituto Di Radioastronomia, Bologna
B. P. Bonev, Catholic University of America
W. Borghini, Osservatorio Astronomico Naturalistico di Casasco
J. R. Brucato, Osservatorio Astrofisico Di Arcetri
E. Bryssinck, Brixiis Observatory
M. W. Buie, Space Science and Engineering Division
H. Canovas, Sterrekundig Instituut Utrecht
D. Castellano, INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, Rome
S. B. Charnley, NASA Goddard Space Flight Center
W. P. Chen, National Central University Taiwan
P. Chiang, Korea Astronomy and Space Science Institute
Y. J. Choi, Korea Astronomy and Space Science Institute
D. J. Christian, California State University, Northridge
Y. L. Chuang, National Taiwan Normal University
A. L. Cochran, The University of Texas at Austin
P. Colom, L'Observatoire de Paris
M. R. Combi, University of Michigan, Ann Arbor
I. M. Coulson, Joint Astronomy Centre
J. Crovisier, L'Observatoire de Paris

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Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was 16.4hr. Starting in 2010 August the period changed from 16.6hr to near 19hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO -driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production. © 2011. The American Astronomical Society. All rights reserved.. 2

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Astrophysical Journal Letters

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