NOAO >   Observing Info >   Approved Programs >   2009B-0363

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Proposal Information for 2009B-0363


PI: Beatrice Mueller, Planetary Science Institute, muller@psi.edu
Address: 1700 E. Ft. Lowell, Suite 106, Tucson, AZ 85719

CoI: Yanga Fernandez, University of Central Florida
CoI: Nalin Samarasinha, Planetary Science Institute

Title: Confirmation of the change in rotation period of comet 2P/Encke

Abstract: We observed comet 2P/Encke just pre-aphelion in August and September 2008 and deduced three possible rotation periods (due to aliasing) from those data. None of these periods are compatible with the rotation period deduced by Fernandez et al. (2005) for the 2001/2002 data. The difference in period cannot be explained by synodic effects. This indicates either a change in rotation period or a manifestation of a non- principal axis (NPA) rotation. We propose to observe comet Encke in two observing runs, about two months apart between August and October 2009 while the comet is post-aphelion. The observations will be used to confirm the period deduced from our 2008 data. The proposed observations will also be used to investigate if the comet is in a NPA spin state as was claimed by Belton et al. (2005). This is the last opportunity to observe Encke before it becomes too active to obtain a rotational lightcurve. The next opportunity to observe Encke near aphelion will be in 2011 after its perihelion passage where we expect to see another change in the rotation period. We therefore need to confirm the change in the rotation period between the 2001/2002 and the 2008 data with the proposed observations.


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