Figure 12.20: Differences in response as a function of the colour index V − I − 0.5,
for the different channels, as measured over the mission. From top to bottom: B in
the preceding field of view; B in the following field of view; V in the preceding field of
view; V in the following field of view. The two curves in each graph represent transits
through the vertical and inclined slit groups. The grey lines show the instances of
refocusing the telescope.