ITAL]Submillimeter Wave Astronomy Satellite[/ITAL] Observations of Water Vapor toward Comet C/1999 H1 (Lee)

Abstract

We have detected the 110-101 pure rotational transition of water vapor toward comet C/1999 H1 using the Submillimeter Wave Astronomy Satellite. Over the period 1999 May 19.01-23.69 UT, the average integrated antenna temperature was 1.79 ± 0.03 K km s-1 within a 33 × 45 (FWHM) elliptical beam. For an assumed ortho-to-para ratio of 3, we estimate the total water production rate as 8 × 1028 s-1. This value lies approximately 50% above the value estimated by Biver et al. from contemporaneous radio observations of hydroxyl molecules. The observed line width of 1.8 km s-1 (FWHM) is broader than the instrumental profile and suggests an intrinsic line width of about 1.4 km s-1 (FWHM). The data, taken during a portion of every 97 minute spacecraft orbit over a 4.68 day period, provide no evidence for variability.