Instrument Distortion Calibration File Transformation

The current generation of detectors on board the Hubble Space Telescope (HST) suffer from extreme optical distortion - some of them have deviations as high as 11% across their field of view. This large effect must be accurately calibrated to obtain high precision astrometry and accurate alignment of any HST images. Corrections for the geometric distortion in the form of high-order polynomial coefficients can be found in the Instrument Distortion Coefficients Table reference file. Here we describe the transformation of polynomial coefficients of geometric distortion from the raw detector coordinate system into the HST coordinate system in the context of the IDC table.