The files describe the PSFs of the flight mirror modules xrt1, xrt2 or xrt3 vs field angle, energy and field azimuth. The xrt1, xrt2 or xrt3 telescopes are respectively associated with the MOS1, MOS2 and PN EPIC cameras. Each file will consist of a header, a table section and an image section.

- an alignment correction table is provided. It contains correction factors which account for the mirror module field curvature, EPIC defocus, mirror module tilt with respect to the boresight and EPIC decenter with respect to the average focal point of the mirror modules. Initially these correcting factors will be set to 0.
- a second table section contain a three dimensional table of 6 fitting coefficients provided as a function of 6 energies and 6 field angles. These coefficient will be used by the CCF access layer to generate analytical PSF descriptions using a simple bi-dimensional Gaussian fit.
- a third table section contain a table of 21 fitting coefficients. These coefficient will be used by the CCF access layer to generate analytical PSF descriptions using the bi-dimensional multi-Gaussian fit. The validity range of this analytical fit is limited to the central 10 arcmin of the field of view and to energies lower than 4.5 keV.
- the image section contains a collection of 36 FITS images obtained at 6 energies and 6 field angles. Theses images can be interpolated by the CCF access layer to any energy, field angle or field azimuth.
- table
`KING_PARAMS`provides the parameters of the King function tabulated against Energy and off-axis angle.`ENERGY`- Photon energy in eV.
`THETA`- Off-axis angle in radians.
`PARAMS`- Two parameters, core radius and slope for each ENERGY/THETA pair.

- table
`BETAPSF`provides a set of parameters of the PSF as a function of RGS dispersion coordinate (Z-coordinate in`SACOORD`, being integrated in cross-dispersion. This is required for the RGS response generation. The table has the following columns:`TYPE`- a flag on which function these parameters act;
either 'G' or 'L' for
*Gaussian*of*Lorentzian*parameterization, respectively. `NORM`- Amplitude of Gaussian and normalization of Lorentzian, as described by parameters and in section 3.4.33, respectively.
`WIDTH`- either Gaussian , or Lorentzian FWHM, as described by parameters and in section 3.4.33, respectively.
`CENTER`- Center of the distribution with respect to zero, as described by parameters and in section 3.4.33, respectively.

Note: Inversion due to the mirroring effect of the gratings takes place as part of the CAL function

`CAL_rgsgetXRTFigure`(see section 3.4.33).