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Fine Guidance Sensor (FGS) Instrument Handbook Version 26.0 January 2019 Fine Guidance Sensor Instrument Handbook for Cycle 27 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 User Support Please contact the HST Help Desk for assistance. We encourage users to access the new web portal where you can submit your questions directly to the appropriate team of experts. • Web portal: http://hsthelp.stsci.edu • E-mail: [email protected] World Wide Web Information and other resources are available on the FGS World Wide Web pages: • URL: http://www.stsci.edu/hst/fgs/ FGS Instrument Contact Name Title Phone e-mail Ed Nelan Instrument Scientist (410) 338-4992 [email protected] Revision History Version Date Editor Version Date Editor 26.0 January 2019 E. P. Nelan 25.0 May 2018 E. P. Nelan 14.0 October 2005 E. P. Nelan 24.0 January 2017 E. P. Nelan 13.0 October 2004 E. P. Nelan 23.0 January 2016 E. P. Nelan 12.0 October 2003 E. P. Nelan and J. Younger 22.0 January 2015 E. P. Nelan 11.0 October 2002 E. P. Nelan and R. B. Makidon 21.0 January 2014 E. P. Nelan 10.0 June 2001 E. P. Nelan and R. B. Makidon 20.0 December 2012 E. P. Nelan 9.0 June 2000 E. P. Nelan and R. B. Makidon 19.0 December 2011 E. P. Nelan 8.0 June 1999 E. P. Nelan and R. B. Makidon 18.0 December 2010 E. P. Nelan 7.0 June 1998 O. L. Lupie & E. P. Nelan 17.0 January 2010 E. P. Nelan 6.0 June 1996 S. T. Holfeltz 16.0 December 2007 E. P. Nelan 5.0 June 1995 S. T. Holfeltz, E. P. Nelan, L. G. Taff, and M. G. Lattanzi 15.0 October 2006 E. P. Nelan 1.0 October 1985 Alain Fresneau Citation In publications, refer to this document as: Nelan, E., et al. 2019, “Fine Guidance Sensor Instrument Handbook”, Version 26.0, (Baltimore: STScI) Send comments or corrections to: Space Telescope Science Institute 3700 San Martin Drive Baltimore, Maryland 21218 E-mail:[email protected] Table of Contents List of Figures................................................................................................. viii List of Tables.......................................................................................................x Acknowledgments........................................................................................ xii Chapter 1: Introduction............................................................................1 1.1 Purpose..............................................................................................................2 1.2 Instrument Handbook Layout .....................................................................2 1.3 The FGS as a Science Instrument ..............................................................3 1.4 Technical Overview.......................................................................................4 1.4.1 The Instrument ...............................................................................................4 1.4.2 Spectral Response ..........................................................................................5 1.4.3 The S-Curve: The FGS’s Interferogram.........................................................5 1.4.4 FGS1r and the AMA ......................................................................................5 1.4.5 Field of View..................................................................................................6 1.4.6 Modes of Operation........................................................................................7 1.5 Planning and Analyzing FGS Observations............................................8 1.5.1 Writing an FGS Proposal ...............................................................................8 1.5.2 Data Reduction...............................................................................................8 1.6 FGS Replacement in SM4 ...........................................................................9 Chapter 2: FGS Instrument Design..............................................10 2.1 The Optical Train .........................................................................................10 2.1.1 The Star Selectors ........................................................................................10 2.1.2 The Interferometer........................................................................................12 2.2 FGS Detectors ...............................................................................................15 2.3 HST’s Spherical Aberration ......................................................................16 2.4 The FGS Interferometric Response .........................................................16 2.4.1 The Ideal S-Curve ........................................................................................17 2.4.2 Actual S-Curves ...........................................................................................17 iii iv Table of Contents 2.5 The FGS1r Articulated Mirror Assembly ..............................................20 2.6 FGS Aperture and Filters ...........................................................................23 2.6.1 FOV and Detector Coordinates....................................................................23 2.6.2 Filters and Spectral Coverage ......................................................................25 2.7 FGS Calibrations ..........................................................................................27 Chapter 3: FGS Science Guide .........................................................28 3.1 The Unique Capabilities of the FGS .......................................................28 3.2 Position Mode: Precision Astrometry.....................................................29 3.3 Transfer Mode: Binary Stars and Extended Objects...........................29 3.3.1 Observing Binaries: The FGS vs. HST’s Cameras ......................................30 3.3.2 Transfer Mode Performance.........................................................................32 3.4 Combining FGS Modes: Determining Stellar Masses........................................................................................................34 3.5 Angular Diameters.......................................................................................36 3.6 Relative Photometry ....................................................................................36 3.7 Moving Target Observations.....................................................................38 3.8 Summary of FGS Performance.................................................................38 3.9 Special Topics Bibliography .....................................................................39 3.9.1 STScI General Publications .........................................................................39 3.9.2 Position Mode Observations ........................................................................39 3.9.3 Transfer Mode Observations........................................................................40 3.9.4 Miscellaneous Observations.........................................................................40 3.9.5 Web Resources.............................................................................................40 Chapter 4: Observing with the FGS ............................................41 4.1 Position Mode Overview............................................................................41 4.1.1 The Position Mode Visit ..............................................................................41 4.1.2 The Position Mode Exposure .......................................................................42 4.2 Planning Position Mode Observations....................................................42 4.2.1 Target Selection Criteria ..............................................................................42 4.2.2 Filters............................................................................................................43 4.2.3 Background ..................................................................................................47 4.2.4 Position Mode Exposure Time Calculations................................................48 4.2.5 Exposure Strategies for Special Cases .........................................................48 4.2.6 Sources Against a Bright Background .........................................................50 4.2.7 Crowded Field Sources ................................................................................50 Table of Contents v 4.3 Position Mode Observing Strategies .......................................................51 4.3.1 Summary of Position Mode Error Sources ..................................................51 4.3.2 Drift and Exposure Sequencing....................................................................52 4.3.3 Cross Filter Observations.............................................................................53 4.3.4 Moving Target Observation Strategy...........................................................53 4.4 Transfer Mode Overview ...........................................................................53 4.4.1 The FGS Response to a Binary ....................................................................53 4.4.2 The Transfer Mode Exposure.......................................................................56 4.5 Planning a Transfer Mode Observation..................................................56 4.5.1 Target Selection Criteria ..............................................................................56 4.5.2 Transfer Mode
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