FGS1r: Final AMA Adjustment
The final adjustment to FGS1r's AMA was performed on October 12, 1998. The results included near-ideal S-curves, essentially similar to those displayed in Figure A2.4. Since then, STScI has continued to monitor the temporal stability of these interferograms. Small changes in the amplitude and morphology of the y-axis S-curve have been seen. These appear to be due to a continuing, but very slow, shift of the y-axis Koester prism w.r.t. HST's OTA. To assure the reliability of measurements made by FGS1r on close (< 25mas) binary systems, standard calibration reference stars are observed once per cycle (if that spectral type is needed by GO programs during the cycle).
