Separate lightcurves of Pluto and Charon.

M. W. Buie, D. J. Tholen, and L. H. Wasserman. Icarus 125, 233-244 (1997) .


We present new Hubble Space Telescope observations of the Pluto-Charon system taken with WFPC1 (PC6) between 1992 May 21 and 1993 August 18. Our observations consist of 52 images with the F555W filter and 8 images in the F439W filter. From these data we extracted individual lightcurves, phase coefficients, and colors for Pluto and Charon. These lightcurves have peak-to-peak variations of 0.33 and 0.08 mag, respectively. The lightcurve for Charon is consistent with its suspected synchronous rotation about Pluto. The linear phase coefficients are 0.0294 +/- 0.0011 mag/deg for Pluto and 0.0866 +/- 0.0078 mag/deg for Charon, spanning a range of phase angles from 0.6 deg to 2.0 deg. Charon's lightcurve has far less structure than Pluto's with minimum light corresponding to the anti-Pluto hemisphere. We found the B-V color of Charon to be 0.710 +/- 0.011 mag. Combined with previous mutual event measurements, the color of Charon is seen to be globally uniform. We also confirmed a reddish B-V color for Pluto of 0.873 +/- 0.002 and 0.862 +/- 0.002 mag at 123 deg and 289 deg east longitude, respectively. These colors are consistent with prior mutual event observations but the higher precision measurement indicates that the surface of Pluto is slightly redder near minimum light.

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