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HST Data Handbook for NICMOS Version 7.0 April, 2007 HST Data Handbook for NICMOS Space Telescope Science Institute 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 For prompt answers to any question, please contact the STScI Help Desk. • E-mail: [email protected] • Phone: (410) 338-1082 (800) 544-8125 (U.S., toll free) World Wide Web Information and other resources are available on the Web site: • URL: http://www.stsci.edu. Revision History Version Date Editors 7.0 April 2007 Helene McLaughlin & Tommy Wiklind 6.0 July 2004 Bahram Mobasher & Erin Roye, Editors, NICMOS Data Handbook, Diane Karakla, Chief Editor and Susan Rose, Technical Editor, HST Data Handbook 5.0 January 2002 Mark Dickinson 4.0 December 1999 Mark Dickinson 3.0 October 1997 Daniela Calzetti Contributors STScI NICMOS Group (past & present members), including: Santiago Arribas, Eddie Bergeron, Torsten Boeker, Howard Bushouse, Daniela Calzetti, Luis Colina, Mark Dickinson, Sherie Holfeltz, Lisa Mazzuca, Bahram Mobasher, Keith Noll, Antonella Nota, Erin Roye, Chris Skinner, Al Schultz, Anand Sivaramakrishnan, Megan Sosey, Alex Storrs, Anatoly Suchkov, Chun Xu. ST-ECF: Wolfram Freudling. Send comments or corrections to: Space Telescope Science Institute 3700 San Martin Drive Baltimore, Maryland 21218 E-mail:[email protected] Table of Contents Preface .....................................................................................xi Part I: Introduction to Reducing the HST Data Chapter 1: Getting HST Data............................. 1-1 1.1 Archive Overview ....................................................... 1-2 1.1.1 Archive Registration................................................. 1-3 1.1.2 Archive Documentation and Help ............................ 1-4 1.2 Getting Data with StarView...................................... 1-4 1.2.1 Downloading and Setting Up StarView.................... 1-4 1.2.2 Simple Use of StarView........................................... 1-5 1.2.3 Marking and Retrieving Data with StarView ............ 1-9 1.2.4 Using StarView to Retrieve Calibration Files and Proposal Information and for Duplication Checking .................................................................... 1-10 1.2.5 Advanced Features of StarView ............................ 1-12 1.2.6 StarView and the Visual Target Tuner................... 1-14 1.2.7 Quick Proprietary Data Retrieval with StarView .... 1-14 1.3 Getting Data with the World Wide Web .............. 1-15 1.3.1 WFPC2 Associations............................................. 1-17 1.3.2 High Level Science Products................................. 1-19 1.4 Reading HST Data Disks ....................................... 1-20 Chapter 2: HST File Formats............................. 2-1 2.1 FITS File Format ........................................................ 2-2 2.1.1 Working with FITS Image Extensions...................... 2-3 2.1.2 Working with FITS Table Extensions....................... 2-8 iii iv Table of Contents 2.2 GEIS File Format...................................................... 2-11 2.2.1 Converting FITS to GEIS....................................... 2-13 2.2.2 GEIS Data Groups................................................. 2-13 2.2.3 Working with GEIS Files........................................ 2-15 2.2.4 The “waiver” FITS Format...................................... 2-17 Chapter 3: Analyzing HST Data ...................... 3-1 3.1 Alternative Means of Accessing HST Data.......... 3-2 3.1.1 Interactive Data Language (IDL) ............................. 3-2 3.1.2 Python...................................................................... 3-2 3.1.3 Fortran and C........................................................... 3-3 3.1.4 Java ......................................................................... 3-3 3.1.5 PyRAF ..................................................................... 3-3 3.2 Navigating STSDAS .................................................. 3-4 3.2.1 STSDAS Structure................................................... 3-4 3.2.2 Packages of General Interest .................................. 3-6 3.3 Displaying HST Images ............................................ 3-7 3.3.1 The Display Task..................................................... 3-7 3.3.2 Working with Image Sections ................................ 3-10 3.4 Analyzing HST Images ........................................... 3-11 3.4.1 Basic Astrometry.................................................... 3-12 3.4.2 Examining and Manipulating Image Data.............. 3-14 3.4.3 Working with STIS, ACS, and NICMOS Imsets..... 3-16 3.4.4 Photometry ............................................................ 3-19 3.4.5 Combining Dithered HST Datasets with MultiDrizzle ......................................................... 3-22 3.5 Displaying HST Spectra ......................................... 3-24 3.5.1 Specview ............................................................... 3-24 3.5.2 STIS Spectra ......................................................... 3-25 3.5.3 FOS and GHRS Spectra........................................ 3-26 3.5.4 Producing Hardcopy .............................................. 3-27 3.6 Analyzing HST Spectra........................................... 3-29 3.6.1 Preparing STIS Spectra for Analysis in IRAF/STSDAS or Pyraf .......................................... 3-29 3.6.2 Preparing FOS and GHRS Data............................ 3-32 3.6.3 Photometry ............................................................ 3-35 3.6.4 General Tasks for Spectra..................................... 3-35 3.6.5 STSDAS Fitting Package ...................................... 3-38 3.6.6 Specfit.................................................................... 3-41 Table of Contents v 3.7 References ................................................................ 3-41 3.7.1 Available from STScI ............................................. 3-41 3.7.2 Available from NOAO ............................................ 3-42 3.7.3 Other References Cited in This Chapter ............... 3-42 Part II: NICMOS Data Handbook NICMOS Introduction.................................................. 3 How to Use this Handbook ................................................. 3 Chapter 1: Instrument Overview.................... 1-1 1.1 Instrument Overview ................................................. 1-1 1.2 Detector Readout Modes ......................................... 1-3 1.2.1 MULTIACCUM......................................................... 1-4 1.2.2 ACCUM.................................................................... 1-5 1.2.3 BRIGHTOBJ ............................................................ 1-5 1.2.4 RAMP ...................................................................... 1-6 Chapter 2: Data Structures ................................. 2-1 2.1 NICMOS Data Files ................................................... 2-1 2.1.1 File Name Suffixes................................................... 2-2 2.1.2 Science Data Files................................................... 2-3 2.1.3 Auxiliary Data Files.................................................. 2-9 2.2 Header Keywords..................................................... 2-10 2.3 Working with NICMOS Files.................................. 2-18 2.4 From the Phase II Proposal to Your Data .......... 2-21 2.5 Paper Products ......................................................... 2-23 Chapter 3: Calibration ............................................. 3-1 3.1 Pipeline Processing, OTFR, and the HST Archive .................................................... 3-1 3.2 NICMOS Calibration Software ................................ 3-3 3.2.1 The Calibration Pipeline .......................................... 3-3 3.2.2 Software for Grism Data Reduction......................... 3-4 3.3 Basic Data Reduction: calnica ................................ 3-5 vi Table of Contents 3.4 Mosaicing: calnicb.................................................... 3-16 3.4.1 Input Files .............................................................. 3-17 3.4.2 Output Files ........................................................... 3-18 3.4.3 Processing............................................................. 3-19 3.5 Recalibration ............................................................. 3-23 3.5.1 Why Recalibrate? .................................................. 3-23 3.5.2 Recalibrating the Data ........................................... 3-25 3.6 Calibration Goals and Plans.................................. 3-28 3.6.1 Calibration Accuracies........................................... 3-29 3.6.2 Monitoring Programs ............................................. 3-30 3.6.3 Special Programs .................................................. 3-30 3.6.4 Calibration in Previous Cycles............................... 3-31 3.6.5 Special Calibrations............................................... 3-31 Chapter 4: Anomalies and Error Sources........................................................................... 4-1 4.1 NICMOS Dark Current and Bias ............................ 4-3 4.1.1 Dark Current ............................................................ 4-4 4.1.2 Bias, Shading, and “Pedestal” ................................. 4-7 4.1.3 Dark Reference Files............................................. 4-12 4.1.4 Cures: How
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