Volume 60 (2012) Pages 193-202
An automated cloud tracking system for processing data obtained by the Japanese Venus Climate Orbiter, Akatsuki, has been developed. Accurate pointing information for the satellite is essential for deriving cloud motion vectors, which may be regarded approximately as wind velocities, by the cloud tracking technique. In the proposed method, pointing direction errors are reduced by an ellipse fitting technique. By mapping images onto regularly spaced grids with longitude-latitude coordinates, cloud motion vectors cloud be obtained in a format suitable for meteorological analysis. A new method for correction of optical distortions was implemented, and the cloud motion vectors were determined using a cloud tracking technique. In this paper, we show preliminary results obtained by the system using Venus Express data, including meridional speeds. The results show that the easterly wind reaches a maximum in the morning and evening. The northerly wind is relatively strong in a region extending from the northeast to the southwest on the dayside. The results were found to be independent of the size of the target area. Finally, there appears to be a correlation between the zonal and meridional wind speeds.