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G. Sonnabend (NAS/NRC/NASA GSFC), F. Schmuelling (KOSMA/University of Cologne), Th. Kostiuk (NASA GSFC), T. A. Livengood (USRA NCSEFSE), J. N. Annen, D. Buhl, K. E. Fast (NASA GSFC), J. D. Delgado, T. Hewagama (University of Maryland)
OCS plays a significant role in the chemistry of the atmosphere of Venus. While it is a well known constituent of the lower Venusian atmosphere as well as the cloud layer its abundance in the middle atmosphere (i.e. above the cloud deck) is still in doubt. OCS spectra near 11.8 micron can be used to probe this region of the atmosphere.
We present new observations of Venus acquired with the NASA GSFC Heterodyne Instrument for Planetary Wind And Composition (HIPWAC) at the IRTF on Mauna Kea, Hawaii during August 2004. The high spectral resolution (R~107) data shows a weak emission feature consistent with an OCS abundance profile by Mills and standard temperature/pressure profiles for Venus (F.P. Mills, PhD Thesis, California Institute of Technology, May 1999). A comparison to previous data from February 2001 that does not show this emission feature suggests temporal variability in the temperature and/or the height of the cloud deck. Radiative transfer calculations using the GSFC BEAMINT code provided temperature and OCS abundance limits based on HITRAN data as well as laboratory data acquired using the HIPWAC instrument.
While the current data is only consistent with upper limits for OCS in the middle atmosphere, it shows the need for further investigation, especially to understand the possible temporal variability of the Venusian atmosphere.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.