Exposure Correction

The exposure correction program, xrtcorr performs dead-time corrections, correction for the mirror vignetting, and correction for the quantum efficiency of the detector. All corrections are carried out according to formulae given in the Calibration Report. The one slight exception to this is the quantum efficiency correction. The QE of the detector is provided as a 2-D map in detector coordinates. To apply this to data binned in world coordinates it is radially binned, and the averaged correction applied only as a function of radial offset from the centre of the FOV.