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E.F. Young (Southwest Research Institute), M.W. Buie (Lowell Observatory), L.A. Young (Southwest Research Institute)
We examine the 384 dithered images of Pluto and Charon taken with the Hubble Space Telescope's High Resolution Camera (HRC) under program GO-9391. We have deconvolved the individual images with synthetic point spread functions (PSF) generated with TinyTim v6.3 using PIXON processing (Puetter and Yahil 1999).
We reconstruct a surface albedo map of Pluto using a backprojection algorithm. At present, this algorithm does not include Hapke phase function or backscattering parameters. We compare this albedo map to earlier maps based on HST and mutual event observations (e.g., Stern et al. 1997, Young et al. 2001), looking for changes in albedo distribution and B-V color distribution.
Pluto's volatile surface ices are closely tied to its atmospheric column abundance, which has doubled in the interval between 1989 and 2002 (Sicardy et al. 2003, Elliot et al. 2003). A slight rise (1.5 K) in the temperature of nitrogen ice would support the thicker atmosphere. We examine the albedo distribution in the context of Pluto's changing atmosphere.
Finally, a side effect of the PIXON processing is that we are better able to search for additional satellites in the Pluto-Charon system. We find no satellites within a 12 arcsec radius of Pluto brighter than a 5-sigma upper limit of B=25.9. In between Pluto and Charon this upper limit is degraded to B=22.8 within one Rp of Pluto's surface, improving to B=25.1 at 10 Rp (Charon's semimajor axis).
This research was supported by a grant from NASA's Planetary Astronomy Program (NAG5-12516) and STScI grant GO-9391.
Elliot, J.L., and 28 co-authors (2003), ``The recent expansion of Pluto's atmosphere," Nature 424, 165-168.
R. C. Puetter and A. Yahil (1999), ``The Pixon Method of Image Reconstruction" in Astronomical Data Analysis Software and Systems VIII, D. M. Mehringer, R. L. Plante & D. A. Roberts, eds., ASP Conference Series, 172, pp. 307-316.
Sicardy, B. and 40 co-authors (2003), ``Large changes in Pluto's atmosphere as revealed by recent stellar occultations," Nature 424, 168-170.
Stern, S.A., Buie, M.W., and Trafton, L.M. (1997), ``HST High-Resolution Images and Maps of Pluto," AJ 113, 827.
Young, E.F., Binzel, R.P., and Crane, K. (2001), ``A Two-Color Map of Pluto's Sub-Charon Hemisphere," AJ 121, 552.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.