DPS 35th Meeting, 1-6 September 2003
Session 47. Comets IV: Nuclei, Atmospheres and Dust
Oral, Chairs: S. C. Lowry and J. Pittichova, Saturday, September 6, 2003, 1:30-3:00pm, DeAnza III

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[47.01] Visual Colors of the Nucleus of Periodic Comet 2P/Encke

S.C. Lowry (QUB), P.R. Weissman (JPL)

Comet 2P/Encke has been observed extensively in the past and was one of the planned flyby targets of the recently failed CONTOUR mission [1]. We present results for comet Encke based on observations with Steward Observatory's 2.3-m Bok telescope at Kitt Peak and Palomar Observatory's 1.5-m telescope. Our observations consist of time-series BVR photometry obtained under photometric conditions in October 2002, when the comet was at an inbound heliocentric distance of 3.93 AU. From these data we obtain the nucleus color indices and search for signs of color variation with rotation, which may provide evidence of nucleus surface inhomogeniety. We also provide an update of our analysis of observations obtained in September 2002, which include time-series R filter photometry of Encke when it was at a heliocentric distance of 3.97 AU. From these data we have derived an estimate of the rotation period and limits on the nuclear size and shape. The September rotational lightcurve is highly asymmetric - a feature also observed by Meech et al. and Fernandez et al. [2,3] - with a periodicity of ~11.03 hours. We also discuss our previously reported visual wavelength detection of comet Encke's dust trail [4]. The Encke dust trail had only been detected at IR wavelengths [5,6]. This visual detection was achieved by co-adding four nights of continuous R filter observations from the September 2002 run. Combining photometric measurements at visual and IR wavelengths will allow us to constrain the physical properties of the dust particles within the trail. This work was supported in part by the NASA Planetary Astronomy program, and was performed jointly at the Jet Propulsion Laboratory and Queen's University Belfast.

[1] Bell, J.F., and 18 colleagues. 2000. M&PS 35, A23. [2] Meech, K.J., Y. Fernandez, and J. Pittichova. 2001. BAAS 33, 1075 (abstract). [3] Fernandez, Y.R., S.C. Lowry, P.R. Weissman, and K.J. Meech. 2002. BAAS 34, 887 (abstract). [4] Lowry, S.C., P.R. Weissman, M.V. Sykes, and W.T. Reach. 2003. LPSC XXXIV, 2056 (abstract). [5] Sykes, M.V., and R.G. Walker. 1992. Icarus 95, 180-210. [6] Reach, W.T., M.V. Sykes, D. Lien, and J.K. Davies. 2000. Icarus 148, 80-94.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.