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N. Biver, D. Bockelée-Morvan, J. Boissier, P. Colom, J. Crovisier, A. Lecacheux, R. Moreno (Observatoire de Paris-Meudon, France), G. Paubert (IRAM, Spain), D.C. Lis, M. Sumner (Caltech, USA), U. Frisk (Swedish Space Corporation, Sweden), A. Hjalmarsson (Onsala Space Observatory, Sweden), Aa. Sandqvist (Stokholm Observatory, Sweden), S. Kwok (Inst. of Astron. and Astrophys., Taipei, Taiwan), H. Rickman (Upsala Observatory, Sweden), M.F. A'Hearn (Univ. of Maryland, USA), K. Meech (Univ. of Hawaii, USA)
In order to characterize the chemical composition of comet 9P/Tempel 1 and the effect of the impactor released onto the comet on July 4, 2005 a two-step observing campaign at radio wavelengths has been set. Pre-perihelion, the water outgassing of the comet has been monitored through observations of OH radical lines at 18 cm with the Nançay radiotelescope (IAUC 8512) from March to May, followed by Odin observations of H2O line at 557 GHz in June. Molecular lines were also observed at the IRAM 30-m on May 4-9, 2005. The HCN:H2S:CH3OH:CO:CS relative production rates (or thier upper limits) were found to be typical of short period comets. The HCN line profile shows evidence for preferential outgassing towards the Sun. The HCN production rate presents a possible 1.7-day periodic time variation, likely related to the rotation and aspherical shape of the nucleus (IAUC8538). The second step was the observations at or near impact time. Lines of OH (with Nancay), H2O (with Odin), HCN, CH3OH, H2S, CO and CS (with IRAM-30m and CSO-10m) have been monitored: \begin{enumerate} \item to characterize the amount of volatiles released following impact and obtain information on the gas velocity and spatial distribution; \item to look for variations in molecular abundances ratio in order to investigate whether pristine material with different molecular composition has been released from deeper layers in the comet. \end{enumerate}
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.