SEPARATE LIGHTCURVES OF PLUTO AND CHARON

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 ima ges in the F439W filter. From these data we extracted individual light curves, phase coefficients, and colors for Pluto and Charon. These lig htcurves have peak-to-peak variations of 0.33 and 0.08 mag, respective ly. The lightcurve for Charon is consistent with its suspected synchro nous 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, s panning a range of phase angles from 0.6 degrees to 2.0 degrees. Charo n'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 a lso confirmed a reddish B-V color for Pluto of 0.873 +/- 0.002 and 0.8 62 +/- 0.002 mag at 123 degrees and 289 degrees east longitude, respec tively, These colors are consistent with prior mutual event observatio ns but the higher precision measurement indicates that the surface of Pluto is slightly redder near minimum light. (C) 1997 Academic Press.