Maintaining the FGS3 optical field angle distortion calibration

To date four OFAD (Optical Field Angle Distortion) calibrations have been performed on FGS3 in M35 and analyzed by the Astrometry Science Team. Two have been performed since the last HST (Hubble Space Telescope) Calibra- tion Workshop. The ongoing Long Term Stability Tests have also been analyzed and incorporated into the calibration. A lateral color calibration has been derived from calibration and science data. Descriptions of these tests and the results of our analysis of the resulting data are given. The astrometric science supported by these calibrations is briefly reviewed.