A SENSITIVE UPPER LIMIT TO OCS IN COMET AUSTIN (1989C1) FROM A SEARCH FOR NU-3 EMISSION AT 4.85 MU-M

We observed the dynamically new Comet Austin (1989c1) UT 1990 May 18, at λ/Δλ ∼ 104, using a cryogenic echelle grating spectrometer. Our observations encompassed the P(1) through P(14) line frequencies of the ν3 band of carbonyl sulfide (OCS). Although OCS was not detected in our data, we derive a 3σ upper limit to the OCS abundance (relative to H2O) of 5.5. × 10-3 for an assumed coma temperature of 50 K. Our value falls between previously reported (3σ) upper limits of 2 × 10-3, obtained from IRAM observations of Comet Levy (1990c), and ∼8 × 10-3 for Comet P/Halley, based on IKS measurements aboard Vega 1. © 1992.