David J. Osip 1, R. G. Walker 2, D. Lien 2, & S. M. Lederer 3
1 Massachusetts Institute of Technology
2 Vanguard Research Inc.
3 University of Florida
In the fall of 1996 we observed the periodic comet P/IRAS across a broad range of wavelengths from visible through far-infrared. Narrowband visible imaging and photometry from Lowell Observatory along with near and thermal-infrared imaging and photometry from the NASA/IRTF were coordinated with two mid- and far-IR observing runs using the Infrared Space Observatory (ISO) and the Midcourse Space Experiment (MSX). The ISO observations were scheduled to closely match the observational geometry of the comet when observed in 1983 by the Infrared Astronomical Satellite (IRAS) The broad spectral energy distribution observations obtained by ISO and IRAS match remarkably well indicating little change in the comet's dust coma production from apparition to apparition. Beyond the broadband photometry that IRAS obtained, we were also able to obtain simultaneous 2-12 micron spectroscopy with the ISOPHOT-S sub-instrument. These spectroscopic data have provided clear evidence of a strong silicate feature in this short period comet and current analysis also indicates the presence of the 11.2 micron feature associated with crystalline olvine in comets Halley and Hale-Bopp. The data from the Spirit III instrument on MSX are presently being reduced and calibrated. Both spectral and dynamical modeling of the combined data sets are being used to investigate the composition, particle size distribution, and emission history of the dust particles emitted by this comet.