The variation in the detector response throughout the mission, as determined from photometric checks, was below 5%. While for bands 1 and 2 this change was of a random nature, the band 3 responses showed a slight anti-correlation with dark currents, and the band 4 response increased by a small amount.
During a revolution, the band 1 response was stable to within 2%, whereas for band 2 the response was higher by 40% at the start of a revolution, decreasing with time. For bands 3 & 4 this effect was only at the 10% level.
Again, normally all detector response changes will be automatically corrected during the OLP processing, see section 8.3.5