IRAS serendipitous survey observations of Pluto and Charon

by: Sykes, Mark V.; Cutri, Roc M.; Lebofsky, Larry A.; Binzel, Richard P.

ABSTRACT

On Aug. 16, 1983, the Infrared Astronomical Satellite made two separate
pointed observations of Pluto and its moon Charon. Because of the small
angular displacement of the system between the times of measurement, the
Pluto-Charon system was identified as a source in the Serendipitous Survey
(SSC 140290518). Detections were made at 60 and 100 micrometers with color-
corrected flux densities of 581 or - 58 and 721 or - 123 millijanskys,
respectively. Pluto is best described as having a dark equatorial band,
and brighter polar caps of methane ice extending to or - 45 deg latitude,
at most. An upper limit of approximately 9 meter-amagats is placed on the
column abundance of a methane atmosphere on Pluto, which is comparable to
recent upper limits based on independent ground-based spectroscopy.

Science, ISSN 0036-8075, vol. 237, Sept. 11, 1987, p. 1336-1340.