Fig. 7

Selected global images taken at 0.97 µm on the dayside from the IR1 camera through the 09d filter. Calibrated images are shown in the left column and brightness normalized versions are shown in the middle column and high-pass filtered versions in the right column. Latitude and longitude lines are shown with 45° spacing. (North pole is at the bottom.) In the brightness normalized versions, the shading due to illumination and viewing angles has been removed using a Minnaert function. Local details become more visible in the high-pass filtered versions. In general, contrasts are much lower at 900 nm than at 365 nm as expected and the spatial scales and morphology are similar. However, the global organization is not as apparent as at 365 nm. In images taken closer to the planet which show Venus at ~ 2–6 km/pixel scale, very muted contrasts are seen. This is different from that observed at the ultraviolet wavelengths where the contrasts are much weaker on the very small spatial scales of ~ 5–10 km, and are seen only over scales that are about 10 times larger. Because Akatsuki spends only a short time at close proximity to Venus in its highly elliptic orbit, global coverage at high spatial resolution is not feasible as the camera’s field of view is too small as compared to the angular size of the planet as Akatsuki moves very quickly relative to the planet