Observational study of Venus atmosphere dynamics

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Planetary atmospheres were observed many times using large telescopes, such as the Subaru telescope at Hawaii, and new knowledge about composition and movement of the Venus atmosphere were acquired. Moreover, new observation equipment for planetary probes, such as an infrared detector array, was developed. Techniques to analyze imaging-spectral data of planetary atmospheres were studied, and applied to the data obtained so far. The data analysis system for the Japanese Venus atmosphere mission 'PLANET-C' or 'Venus Climate Orbiter' has been developed. More specifically, the following studies have been performed.(1) To study the photochemical reaction chain in the Venus atmosphere, the spatial distribution of HCl in the Venus stratosphere was observed using the IRTF telescope at Hawaii. The roloe of HCl as a catalyst reaction was constrained.(2) The thermal radiation from the cloud top of Venus was observed at middle infrared wavelengths using the Subaru Telescope and the IRTF telescope, and the temporal variation in the fine structures of the cloud top was detected for the first time. Information on the thermal convection in the cloud layer and the characteristics of planetary-scale waves were acquired.(3) Instruments onboard planetary probes need to have tolerance to the energetic radiation in space. A new infrared detector was developed and tested for such radiation environment.(4) The technique of deriving wind velocities from successive cloud images of high spatial resolution was studied for future ground-based observations or spacecraft missions. The wind determination accuracy of several meters per second, which is needed in meteorological study, was achieved.