Both types of EPIC cameras, MOS and pn, have high maximum quantum efficiencies (see Fig. 19). Figs. 22 and 23 display the total effective area of the XMM mirror modules with various combinations of EPIC detectors (total, pn only, 2 MOS cameras, 1 MOS only). As mentioned earlier on, all EPIC effective area calculations were performed with the thin filter in place. For comparison, the AXAF effective areas with both the ACIS-I and HRC-I instruments are shown too.
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Note that the above refers to on-axis sources. The mirror vignetting described in § 3.2.2.2 folds into the graphs shown in Figs. 22-23 for off-axis sources. This reduces the EPIC off-axis effective area (not displayed) as displayed in Fig. 14.
Ontop of this, the EPIC MOS effective areas are affected by the presence of the RGAs. The effective area along the RGS dispersion direction differs slightly from that in the cross-dispersion direction.
Note that the EPIC cameras have an effective area of up to 500 cm2 below 0.1 keV (0.05-0.1 keV). However, photons from EPIC observations in this energy range will probably not be scientifically useable, because the EPIC event detection threshold will be somewhere in the range from 70-90 eV. All events below this energy will be filtered out in order to reject spurious events (including electronics noise). Details, in particular the exact level of this threshold, will be determined and set as part of the in-orbit calibration program.