Chapter 2:
FGS Instrument Design

2.1 The Optical Train

2.1.1 The Star Selectors

2.1.2 The Interferometer

2.2 FGS Detectors

2.3 HST’s Spherical Aberration

2.4 The FGS Interferometric Response

2.4.1 The Ideal S-Curve

2.4.2 Actual S-Curves

2.5 The FGS1r Articulated Mirror Assembly

2.6 FGS Aperture and Filters

2.6.1 FOV and Detector Coordinates

2.6.2 Filters and Spectral Coverage

2.7 FGS Calibrations