A MEASUREMENT OF THE RELATIVE REFLECTANCE OF PLUTO AT 0.86 MICRON.

We have examined Pluto's near infrared reflectance by means of photoelectric photometry using a filter whose effective wavelength is 0.86 micron. The ratio of Pluto's reflectance at 0.86 micron to that at 0.55 micron is 1.33 plus or minus 0.04. Our measurements, combined with the UBVR colors of Pluto as measured by Hardie, show that Pluto's reflectance increases almost linearly with wavelength in the region between 0.36 micron and 0.86 micron. Pluto's reflectance in the spectral region resembles the reflectance of the asteorid 5 Astrae as well as some stony-iron meteorites and iron meteorites having low nickel content.