Figure 12.19: Changes in response for the different channels, as measured over the
mission. The responses have been normalized to the value measured for the first
data sets. 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.