This provides the shape of the XRT along the dispersion direction (integrated in cross-dispersion).
This function can have two modes of operations:
The functions are selected by a flag in the CCF. The parameters of
the centers ( and ) are given with respect to a common
center to allow for an assymetric parameterizations. The common
center is calculated by
The value of the input argument CENTER_CHAN is added to , in order to provide the PSF correctly centered.
The width of the PSF of the telescope scales as a function of angle of
incidence on the gratings and diffration angle of the RGA by the
chromatic magnification function . The chromatic magnification
which is an imaging effect by the gratings that scales the width of
the PSF in the dispersion direction as a function of angle of
incidence and diffraction angle. It is defined as
The function returns the probability distribution which
calculated from by integration per channel
Note: The CAL inverts the parameterization that is in XRT_XPSF along the dispersion axis, because the RGA acts as a mirorr in this respect.