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C.C.C. Tsang, F.W. Taylor, P.J. Irwin, C.F. Wilson (Atmospheric, Oceanic and Planetary Physics, Oxford University, Clarendon Laboratory, Parks Road, Oxford, OX13PU)
Venus Express, ESAs orbiter mission to explore Venus, is in its final stages of preparation for launch in October 2005. Its arrival in the early half of 2006 will bring about a greater understanding of this mysterious planet, first visited by the American probe Mariner 2 in 1962. Covered by thick sulphuric acid clouds, in a super-rotating atmosphere, above a 90 bar, 740K surface, Venus has not had a dedicated orbiter since NASAs Magellan radar mapper, some fifteen years ago. With the arrival of Venus Express and the seven science instruments on-board, a two year long campaign of monitoring the atmosphere will begin.
One of the major advances in the past few decades concerning the Venusian atmosphere is the discovery of the near-infrared emission windows, centred at 1.01, 1.18, 1.73 and 2.3 microns. Radiation at these wavelengths is able to escape to space, giving information such as temperature and composition of the atmosphere at varying heights above the surface. Continual monitoring of these parameters will give us a better understanding of the chemistry and the physical processes occurring on Venus in the larger context of addressing specific scientific topics, such as whether there is still active volcanism on the surface.
A radiative transfer model used for retrieving properties of the Jovian planets is in the process of being adapted for use on Venus. Absorption coefficients can be derived explicitly from line-by-line calculations, or by pre-tabulation using the correlated-k method. Conditions in the Venusian atmosphere have been taken into account, such as collision induced absorption, pressure broadening and sub-Lorentzian lineshapes. Model output has been compared with ground-based spectra of Venus and used to determine the sensitivity of near-IR measurements to the abundances of key trace species, particularly those associated with volcanic activity.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.