In the dark, the charge generation in the detectors is not due to thermal effects, but to tunnel effects. It increases slowly as the logarithm of the integration time, so that very long integration times are possible without saturation.
Due to the very long stabilization time at low signal level, the dark
frame of the SW array is very difficult to determine. It is not
foreseen to measure it after each observation, but only once per
orbit, with an accuracy of 0.5 ADU rms. This library dark frame
will be available in the standard data products. An example of SW
dark frame is given in Figure 
. More accurate dark
frames might nevertheless be obtained, if needed by the observer,
by using a specific procedure (cf. section ).