XMM-Newton
Users Handbook
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3.3.1.1 EPIC MOS chip geometry
The MOS chip arrays consist of 7 individual identical, front-illuminated chips.
The individual CCDs are not co-planar, but offset with respect to each
other, following closely the slight curvature of the focal surface of the
Wolter telescopes. Technically, this leaves space for the connections to
the central CCD. The numbering scheme for the EPIC MOS chip array, the
individual chip coordinate frames and the directions of the detector
coordinates are displayed in Figs. 20 and
21. Not visible
in the figures is that the MOS chips have a frame store region which serves
as a data buffer for storage before they are read out through the
readout nodes, while the rest of the chip is obtaining the next exposure.
As indicated above, the MOS cameras are mounted on those X-ray telescopes
that also carry RGS instruments. Therefore, they receive only 44% of
the reflected light.
Figure 20:
The layout of the EPIC MOS cameras as presented in SAS:
MOS1 (here) and MOS2 (next figure).
The orientation of the DETX/DETY axes are shown, to highlight that the RGS
dispersion axes are parallel within spacecraft physical co-ordinates, but
the EPIC MOS cameras are orthogonally aligned.
The readout node of each CCD is located with a small box. The RAWX and RAWY
co-ordinates in each CCD decrease towards the readout. The orientation of
the CCD specific RAWX/RAWY coordinate systems is visible e.g. via the SAS
task calview under View
LinCoord
FocalPlane.
Note: Since the MOS1 event in XMM-Newton revolution 961 (see
§ 3.3) and at the time of writing, scientific observations
are performed with MOS1 CCD6 switched off.
![\begin{figure}\begin{center}
\leavevmode
\epsfig{width=.95\hsize, file=figs/MOS1_UHB_16.ps}
\end{center}
\end{figure}](https://webarchive.library.unt.edu/eot2008/20090830074109im_/http://xmm.esac.esa.int/external/xmm_user_support/documentation/uhb/img98.png) |
Figure 21:
The layout of the EPIC MOS cameras as presented in SAS
(cntd. from previous figure): MOS2.
![\begin{figure}\begin{center}
\leavevmode
\epsfig{width=.95\hsize, file=figs/MOS2_UHB_16.ps}
\end{center}
\end{figure}](https://webarchive.library.unt.edu/eot2008/20090830074109im_/http://xmm.esac.esa.int/external/xmm_user_support/documentation/uhb/img99.png) |
Next: 3.3.1.2 EPIC pn chip geometry
Up: 3.3.1 Two types of EPIC camera: MOS and pn
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European Space Agency - XMM-Newton Science Operations Centre