a) Evolution of the dark signal in CCD column (image row) #1341 for an integration time T′ equal to 7.4 s. The Box-Cox transformed dark signal of this CCD column are represented horizontally (after Step 1), and the information from all frames with T′ = 7.4 s has been stacked vertically. The presence or advent of hot pixels can be seen as bright semi-infinite vertical lines, telemetry holes as black horizontal segments, cosmic-ray hits as white dots. It can be verified that the pixels in the right part of the figure exhibit higher dark current since they dwell for a longer duration in the memory zone. We note that in this particular column #1341, a hot pixel in the MZ generates a dark signal excess that affects the last ~10% of the CCD column, on the right side of the figure. b) The same data, but after Step 3.