New Absorption Bands of the Carbon Dioxide Isotopologues in Venus Spectra

International audience; We present new absorption bands of carbon dioxide isotopologues detected by the SOIR instrument on board Venus Express. The SOIR instrument combines an echelle spectrometer and an Acousto-Optical Tunable Filter for the order selection. It performs solar occultation measurements in the IR region (2.2 - 4.3 μm) at a resolution of 0.12 - 0.18 cm-1. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer (65 to 150 km) with an emphasis on vertical distribution of the gases. The sensitivity of the SOIR instrument and the high concentration of CO2 on Venus, coupled with the long absorption paths sounded during solar occultation, enable us to detect weak absorption bands of the rare CO2 isotopologues in the Venus atmosphere. A systematic study of the recorded spectra is under way and preliminary results will be discussed. So far we have identified the 20001 - 00001 band of 16O13C18O isotopologue and the 21101 - 01101 band of 16O12C18O isotopologue in the SOIR spectra. Rotational analyses were performed for these two new bands and also for the 01111 - 00001 band of 16O12C18O, already reported in [1]. Additional bands are under analysis as well. . 1. Wilquet, V., et al., Line parameters for the 01111-00001 band of 16O12C18O from SOIR measurements of the Venus atmosphere. Journal of Quantitative Spectroscopy and Radiative Transfer, 2008. 109: p. 895-905.