First observations of SO2 above Venus' clouds by means of Solar Occultation in the Infrared
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Solar Occultation in the Infrared (SOIR) is a part of the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV)/SOIR occultation experiment on board Venus Express dedicated to the study of gaseous and aerosol vertical structure of Venus' mesosphere. SOIR is an echelle spectrometer with acoustooptic selection of diffraction orders operating in the wavelengths range of 2.2-4.3 μm at high spectral resolution (λ/Δλ ∼ 20,000). Detection of minor constituents such as CO, H2O, HDO, HCl, HF, and SO2, at altitudes between 65 and 130 km has been demonstrated. We report results from a series of six occultations with observations of the 4-μm SO2 band at latitudes 69°-88°N and 23°-30°N. It is the first time when the vertical distribution of SO2is retrieved above the clouds with the help of solar occultation direct method. The sulfur dioxide transmission spectrum is measured on a background of strong CO2 absorption. Each retrieved vertical profile of SO2 is characterized by few points; the mixing ratio of SO2 being ∼0.1 ppm with scale height 1 ± 0.4 km for polar measurements (evening observations) and ∼1 ppm with scale height 3 ± 1 km at low latitudes (morning observations) at the altitude of about 70 km. Upper limits of <∼0.05 ppm are established around 75 km.
CitationBelyaev, D.; Korablev, O.; Fedorova, A.; Bertaux, J.-L.; Vandaele, A.-C.; Montmessin, F.; Mahieux, A.; Wilquet, V.; Drummond, R. (2008). First observations of SO2 above Venus' clouds by means of Solar Occultation in the Infrared. , Journal of Geophysical Research E: Planets, Vol. 113, Issue 5, E00B25, DOI: 10.1029/2008JE003143.