GammaLib

The ToF correction factor should be implemented as function of the ToF selection criteria. The correction should be implemented at the level of the GCOMResponse class so that the correction will be directly applied in the response computation.

The ToF selection is stored in the DRE. The best thing is to store the ToF correction factor with the DRE since:

• the DRE is energy dependent, hence a single ToF applies to a given DRE
• the ToF selection criteria are available when computing the DRE

The ToF correction factor should therefore be computed when GCOMDri::compute_dre() is called. The factor should also be written in a DRE FITS file and read back from that file for reference. Selection parameters and minimum Earth horizon angle should also be written into the FITS file and read back. For that purpose, methods GCOMSelection::write(GFitsHDU& hdu) and GCOMSelection::read(const GFitsHDU& hdu) should be implemented that write and read the selection keywords from an HDU. These methods should then be called by the GCOMDri::write_attributes() and GCOMDri::read_attributes() methods. In that way the selection parameters will also be available (this is not strictly needed, yet is desirable).

A method GCOMDri::tof_correction() needs to be added to access the pre-computed ToF correction by reference. If no pre-computation was done the value should be 1.0.

GCOMEventBin needs to store a pointer to the ToF correction value that will be set in GCOMEventCube::init_bin(). In that way the ToF correction is also available for an individual event. A GCOMEventBin::tof_correction() method needs to be added so that the value can be access in the response computation and multiplied to the IRF.

Specifically, this needs to be done in GCOMResponse::irf_ptsrc() (best by changing the IAQ normalisation iaq_norm) and in GCOMResponse::irf() (best as additional multiplier after deadtime correction).