Figure 4: Analysis of the limb profiles.
From: Using the transit of Venus to probe the upper planetary atmosphere
(a) Intensity profiles (DN rate per pixel) across the planet disk measured from the planet disk centre in the 335-Å channel (see Fig. 3c). The intensity out of the disk (rightwards) depends on the coronal region the planet is crossing. (b) This average intensity profile (4,500 Å) is symmetrical with respect to the middle horizontal line, that is, the 50% level between the out-of-disk intensity and the in-disk intensity (dash-dotted lines). (c) Profiles in the 335-Å channel (Fig. 4a) normalized in the range between the high and low values used to evaluate the 50% intensity level. Only the region around the planet limb is shown. The best radius value is marked (orange dashed lines).
