settings.

The saturation plots (Fig 11) were generated as follows. Signal level is plotted against photometer flux reading for the brightest spot measured. The flux levels of the fainter spots were scaled by the ratio of the signal levels for the lowest two flux settings, compared with that for the brightest spot. In all cases the signals were not saturated for the lowest two fluxes, so this scaling should be good. This leads to points that cover the range of flux and signal quite well. In the case of the subarrays, the number of spots was more limited, so that it was sometimes not possible to cover the ranges as well as we wished.

Figure 12 shows an EM NUV channel saturation plot, derived from the mask with different-sized holes. The saturation curve is different from those of the flight systems because of the different event size and poorer resolution of this detector, illustrating how individual each system is. Figure 12 also shows the flux calibration for VIS channel integrate mode images, whose effective integration time is set by the time gap between pixel row reads (row gap). This low gain INT mode operation is expected to be the default 