Seasonal variations in the instrument background in counts per second on node C of CCD9, as function of orbit. The different phases of the orbit are shown from bottom to top with a different offset for clarity (indicated by the dashed lines). The phases for the perigee passage are omitted (1/8 and 8/8). The others are shown for increasing phase (bottom to top; for clarity the labels of phases 3/8 to 5/8 are left out). The large scale trend of increasingly smaller maxima in later years, shows the decreasing solar activity over the 11 year solar cycle.