The in-flight spectroscopic calibration of the Swift XRT CCD camera

The Swift X-ray Telescope (XRT) focal plane camera houses a front-illuminated MOS CCD, providing a spectral response of 145 eV FWHM at 5.9 keV. We describe the status of the CCD X-ray spectral redistribution matrices, which are made using a Monte-Carlo simulation technique based on physical models of the CCD response. We emphasize how the model has been refined following in-flight experience with celestial and on-board calibration sources. Residuals less than 10% are typically observed for astrophysical sources.