The EMI image intensifier used in the IPCS has a dark
current of about 4 counts/cm
/s. The noise level per pixel
due to the dark current is proportional to the area of each pixel.
The pixel size of
the CCD-IPCS in standard spectroscopic format is 10.5
42 microns.
implying a dark current of only 2 counts per pixel per 10
seconds.