Version 27.0 December 2019 Fine Guidance Sensor Instrument Handbook for Cycle 28 3700 San Martin Drive Baltimore, Maryland 21218 [email protected] Operated by the Association of Universities for Research in Astronomy, Inc., for the National Aeronautics and Space Administration FGS Instrument Handbook . 3 List of Figures . 6 List of Tables . 8 Acknowledgments . 9 Chapter 1: Introduction . 10 1.1 Purpose . 11 1.2 Instrument Handbook Layout . 12 1.3 The FGS as a Science Instrument . 13 1.4 Technical Overview . 14 1.5 Planning and Analyzing FGS Observations . 20 1.6 FGS Replacement in SM4 . 21 Chapter 2: FGS Instrument Design . 22 2.1 The Optical Train . 23 2.2 FGS Detectors . 30 2.3 HST’s Spherical Aberration . 31 2.4 The FGS Interferometric Response . 32 2.5 The FGS1r Articulated Mirror Assembly . 38 2.6 FGS Aperture and Filter . 42 2.7 FGS Calibrations . 48 Chapter 3: FGS Science Guide . 49 3.1 The Unique Capabilities of the FGS . 50 3.2 Position Mode Precision Astrometry . 51 3.3 Transfer Mode Binary Stars and Extended Objects . 52 3.4 Combining FGS Modes Determining Stellar Masses . 58 3.5 Angular Diameters . 60 3.6 Relative Photometry . 62 3.7 Moving Target Observations . 65 3.8 Summary of FGS Performance . 66 3.9 Special Topics Bibliography . 67 Chapter 4: Observing with the FGS . 69 4.1 Position Mode Overview . 70 4.2 Planning Position Mode Observations . 71 4.3 Position Mode Observing Strategies . 80 4.4 Transfer Mode Overview . 83 4.5 Planning a Transfer Mode Observation . 87 4.6 Transfer Mode Observing Strategies . 93 Chapter 5: FGS Calibration Program . 97 5.1 Position Mode Calibrations and Error Sources . 98 5.2 Transfer Mode Calibrations and Error Sources . 108 5.3 Linking Transfer and Position Mode Observations . 114 5.4 Cycle 21 Calibration and Monitoring Program . 115 5.5 Special Calibrations . 116 Chapter 6: Writing a Phase II Proposal . 117 6.1 Phase II Proposals: Introduction . 118 6.2 Instrument Configuration . 119 6.3 Special Requirements . 124 6.4 Overheads . 126 6.5 Proposal Logsheet Examples . 129 Chapter 7: FGS Astrometry Data Processing . 143 7.1 Data Processing Overview . 144 7.2 Exposure-Level Processing . 145 1 7.3 Visit-Level Processing . 148 7.4 Epoch-Level Processing . 151 Appendix A: Target Acquisition and Tracking . 156 A.1 FGS Control . 157 A.2 Target Acquisition and Position Mode Tracking . ..