Space Telescope Science Institute
COS Data Handbook 2.00
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Table of Contents

COS Data Handbook
List of Figures
List of Tables
How to Use this Handbook
Handbook Structure
Typographic Conventions
Visual Cues
Chapter 1: COS Overview
1.1 Instrument Capabilities and Design
FUV Spectroscopy
NUV Spectroscopy
Grating Offset Positions (FPPOS)
NUV Imaging
Data Collection Modes
1.2 COS Physical Configuration
1.2.1 The COS Detectors
FUV Channel
NUV Channel
1.3 Basic Instrument Operations
1.3.1 Target Acquisitions
1.3.2 Routine Wavecals
1.3.3 Typical COS Observing Sequence
1.4 COS Coordinate System
Chapter 2: COS Data Files
2.1 Overview
2.2 COS File Names
2.3 COS File Structures
2.3.1 COS FITS Table Extension Files
2.3.2 COS FITS Image Extension Files
2.4 COS Data Products
2.4.1 Uncalibrated Science Data Files
2.4.2 Intermediate Science Data Files
2.4.3 Final Science Data Files (and Product Files)
2.4.4 Auxiliary Data Files
Association Tables (ASN)
Trailer Files (TRL)
Calcos Trailer Files (TRA)
Support Files (SPT)
Acquisition Files (RAWACQ)
Jitter Files (jit)
2-D Spacecraft Pointing Histogram (jif)
2.5 Data Storage Requirements
2.6 Headers, Keywords, and Relationship to Phase II
2.7 Error and Data Quality Array
2.7.1 Error Array
2.7.2 Data Quality Flags
Chapter 3: COS Calibration
3.1 Raw Data Compilation
3.2 Pipeline Processing Overview
3.3 Calcos: Structure and Data Flow
3.4 Descriptions of Spectroscopic Calibration Steps
3.4.1 Initialization
3.4.2 BRSTCORR: Search for and Flag Bursts
3.4.3 BADTCORR: Bad Time Intervals
3.4.4 PHACORR: Pulse Height Filter
3.4.5 WALKCORR: Y-Walk Correction
3.4.6 RANDCORR: Add Pseudo-Random Numbers to Pixel Coordinates
3.4.7 TEMPCORR: Temperature-Dependent Distortion Correction
3.4.8 GEOCORR and IGEOCORR: Geometric Distortion Correction
3.4.9 DOPPCORR: Correct for Doppler Shift
3.4.10 DEADCORR: Nonlinearity Correction
3.4.11 FLATCORR: Flat-field Correction
3.4.12 WAVECORR: Wavecal Correction
Determining the offsets:
Applying the offsets:
3.4.13 DQICORR: Initialize Data Quality File
3.4.14 STATFLAG: Report Simple Statistics
3.4.15 X1DCORR: Locate and Extract 1-D Spectrum
3.4.16 BACKCORR: 1D Spectral Background Subtraction
3.4.17 FLUXCORR/TDSCORR: Conversion to Flux
3.4.18 HELCORR: Correction to Heliocentric Reference Frame
3.4.19 Finalization (making the sum files)
3.5 Descriptions of Imaging Calibration Steps
3.6 Customizing COS Data Calibration
3.6.1 Mechanics of Tailored Recalibration
Set up the Directory Structure for Running calcos
Retrieve Reference Files
Edit the Calibration Header Keywords
Edit the Input Association File
Run Calcos
3.6.2 Using GO Wavecals
3.7 Reference Files
3.7.1 BRSTTAB: Burst Parameters Table
3.7.2 BADTTAB: Bad Time Interval Table
3.7.3 PHATAB: Pulse Height Discrimination Table
3.7.4 PHAFILE: Pulse Height Discrimination File
3.7.5 BRFTAB: Baseline Reference Frame Table
3.7.6 WALKTAB: Y Walk Correction Table
3.7.7 GEOFILE: Geometric Correction File
3.7.8 DEADTAB: Deadtime Table
3.7.9 FLATFILE: Flat-field File
3.7.10 BPIXTAB: Bad Pixel Table
3.7.11 LAMPTAB: Template Calibration Lamp Spectra Table
3.7.12 WCPTAB: Wavecal Parameter Table
3.7.13 DISPTAB: Dispersion Coefficient Table
3.7.14 XTRACTAB: 1-D Spectral Extraction Table
3.7.15 FLUXTAB: Photometric Throughput Table
3.7.16 TDSTAB: Time Dependent Sensitivity Table
3.7.17 GSAGTAB: Gain Sag Table
3.7.18 HVTAB: High Voltage Table
3.7.19 SPWCSTAB: Spectroscopic WCS Parameters Table
Chapter 4: COS Error Sources
4.1 Overview
4.2 Error Sources Associated with Pipeline Processing Steps
4.2.1 FUV Dark Count Rate
4.2.2 Flat Fields
NUV-MAMA Flat Fields
FUV-XDL Flat Fields
4.2.3 Gain Sag
4.2.4 FUV XDL Thermal Drifts
4.3 Factors Limiting Flux and Wavelength Accuracy
4.3.1 Flux Accuracy
4.3.2 Wavelength and Spectral Resolution Accuracies
Chapter 5: COS Data Analysis
5.1 Data Reduction and Analysis Applications
5.1.1 COS-Specific STSDAS Tasks
5.1.2 FITS Table Tasks
5.1.3 General Spectral Display and Analysis Tasks
Plotting COS Spectral Images (flt)
Plotting COS Tabular Spectra (x1d)
5.2 Evaluating Target Acquisitions and Guiding
5.2.1 Types of Target Acquisitions
Undispersed Light (Imaging) Acquisitions (ACQ/IMAGE)
Dispersed-Light Acquisitions (ACQ/PEAKD and ACQ/PEAKXD)
5.2.2 Guiding Errors for Single-Guide-Star Mode
5.3 Working with Extracted Spectra
5.3.1 Working With x1d Files in IDL
5.3.2 Working With x1d Files in Python
5.3.3 Working With x1d Files in IRAF/PyRAF
Using the “Selectors Syntax” to work with 3-D tables
Dumping x1d data to an ASCII File
Plotting COS x1d Data
5.3.4 Redoing Spectral Extraction
Correcting for Shifts Along the Dispersion Direction
Adjusting the Background Subtraction
5.3.5 Splicing Extracted Spectra
5.4 Working with TIME-TAG Data
5.4.1 Displaying TIME-TAG Data in DS9
Spectroscopic Data
Imaging Data
TIME-TAG Animation
5.4.2 Filtering Time-Tag Data
Filtering Events in the Timeline Extension
Manipulating TIME-TAG Data for Variability
Appendix A: COS New Spectra Position
A.1 COS New Lifetime Position
Appendix B: COS High Voltage
B.1 COS High Voltage History

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