Contents

• List of Tables
• 1 Introduction
  • 1.1 Purpose of Document
  • 1.2 Philosophy of the IUE Final Archive Image Processing
    • 1.2.1 Uniform Archive
    • 1.2.2 New Processing Algorithms and Calibrations
    • 1.2.3 Core Data Item Verifications
    • 1.2.4 Community Involvement
• 2 Description of IUE Data
  • 2.1 Raw Image Data and Label Parameters
  • 2.2 Spectrograph Geometry
  • 2.3 Instrumental Resolution
    • 2.3.1 Low-Dispersion Mode
      • 2.3.1.1 Resolution Along the Dispersion
      • 2.3.1.2 Resolution Perpendicular to the Dispersion
    • 2.3.2 High-Dispersion Mode
      • 2.3.2.1 Resolution Along the Dispersion
      • 2.3.2.2 Resolution Perpendicular to the Dispersion
• 3 Data Quality Flag Description
• 4 Raw Image Screening (RAW_SCREEN)
  • 4.1 Bright-Spot Detection
  • 4.2 Microphonic Noise Detection
  • 4.3 Partial-Read Image Preprocessing
  • 4.4 Missing Minor Frame Detection
  • 4.5 DMU Corrupted Pixel Detection
  • 4.6 Source-Type Determination
  • 4.7 Serendipitous Spectrum Recognition
  • 4.8 Background and Continuum Intensity Estimation
  • 4.9 High-Dispersion Order Registration (ORDERG)
    • 4.9.1 Order Registration Process
      • 4.9.1.1 Step 1: Global Shifts
      • 4.9.1.2 Step 2: Differential Shifts
    • 4.9.2 Potential Problem Areas
  • 4.10 RAW_SCREEN Output
• 5 Raw Image Registration (CROSS-CORR)
  • 5.1 Registration Fiducial
  • 5.2 General Method
  • 5.3 Pattern Matching Algorithm - Step by Step
    • 5.3.1 Intermediate CROSS-CORR Output
  • 5.4 Evaluation of the Raw Correlations
  • 5.5 CROSS-CORR Output
• 6 Photometric Correction (PHOTOM)
  • 6.1 Construction of the ITFs
    • 6.1.1 LWP ITF
    • 6.1.2 LWR ITF
    • 6.1.3 SWP ITF
    • 6.1.4 Periodic Noise
  • 6.2 Determination of the Effective Exposure Times
  • 6.3 Description of the Photometric Correction
    • 6.3.1 Determination of the ITF Pixels
    • 6.3.2 Determination of the Flux Values
  • 6.4 Associated $\nu$ Flags and Reference Images
    • 6.4.1 Non-photometrically Corrected Image Regions
    • 6.4.2 Warning Track
    • 6.4.3 ITF Artifacts
      • 6.4.3.1 Permanent Artifacts and Reseaux
      • 6.4.3.2 The 1515Å Artifact
  • 6.5 PHOTOM Output
• 7 Image Resampling (GEOM)
  • 7.1 Corrections Common to Both Dispersions
    • 7.1.1 Measurement of Distortions
      • 7.1.1.1 Mapping of Raw Science Image to ITF Space
      • 7.1.1.2 Mapping of ITF Space to Geometrically Rectified Space
    • 7.1.2 Image Rotation
    • 7.1.3 Wavelength Linearization
  • 7.2 Additional Corrections for Low Dispersion
    • 7.2.1 Aperture Alignment
    • 7.2.2 Wiggle Corrections
    • 7.2.3 Large-Aperture Tilt Correction
    • 7.2.4 Wavelength and Spatial Normalization
  • 7.3 Additional Corrections for High Dispersion
    • 7.3.1 Order De-splaying
    • 7.3.2 Wavelength and Spatial Normalization
    • 7.3.3 Wiggle Corrections
  • 7.4 Flux Resampling Algorithm
  • 7.5 Data Quality ($\nu$) Flag Resampling
  • 7.6 High-Dispersion Cosmic Ray Detection Algorithm ( COSMIC_RAY )
  • 7.7 GEOM Output
    • 7.7.1 Low-Dispersion
    • 7.7.2 High-Dispersion
  • 7.8 COSMIC_RAWY Output
• 8 Wavelength Calibration (TTDC)
  • 8.1 Image Field-Distortions
  • 8.2 Low-Dispersion Wavelength Calibration
    • 8.2.1 Parameterization of the Dispersion Relations
    • 8.2.2 Application of the Dispersion Relations
    • 8.2.3 1995 Wavelength Calibration Updates
  • 8.3 High-Dispersion Wavelength Calibration
    • 8.3.1 Parameterization of Dispersion Relations
    • 8.3.2 Calculation of the Dispersion Coefficients
    • 8.3.3 Time and THDA Dependence of the Wavelength Zeropoint
    • 8.3.4 Checks Against Other Calibrations
    • 8.3.5 Pertinent Spectrograph Parameters
  • 8.4 TTDC Output
    • 8.4.1 Low-Dispersion
    • 8.4.2 High-Dispersion
• 9 Low-Dispersion Flux Extraction (SWET)
  • 9.1 Noise Models
  • 9.2 Background Flux Extraction
  • 9.3 Spectrum Location and Signal Level
  • 9.4 Profile Fitting
  • 9.5 Extraction of Flux and Cosmic Ray Removal
  • 9.6 One-Dimensional $\nu$ Flag Spectrum
  • 9.7 SWET Output
• 10 High-Dispersion Flux Extraction
  • 10.1 Background Flux Determination (BCKGRD)
    • 10.1.1 Pass 1: Cross-Dispersion Swaths
      • 10.1.1.1 Overview
      • 10.1.1.2 PSF Modeling Details
    • 10.1.2 Pass 2: Dispersion Direction Swaths
    • 10.1.3 Non-continuum images
    • 10.1.4 Data Pathology Assessments
    • 10.1.5 Failure Modes
    • 10.1.6 Caveat
    • 10.1.7 BCKGRD Output
  • 10.2 Spectral Flux Extraction (EXTRACT)
    • 10.2.1 Determination of Echelle-Order Locations
    • 10.2.2 Description of Spectral Flux Extraction Process
    • 10.2.3 Noise Models
    • 10.2.4 One-Dimensional $\nu$ Flag Spectrum
    • 10.2.5 EXTRACT Output
• 11 Calibration of the Net Flux
  • 11.1 Low-Dispersion Absolute Flux Calibration
    • 11.1.1 1985-Epoch Point Source Calibrations
    • 11.1.2 Aperture Response Corrections
    • 11.1.3 Gain Factors
    • 11.1.4 Time-Dependent Degradation Correction
      • 11.1.4.1 Database
      • 11.1.4.2 Analysis
      • 11.1.4.3 Initial Fits to the Ratios
      • 11.1.4.4 Calibration Updates
      • 11.1.4.5 Application of Degradation Correction
    • 11.1.5 Temperature-Dependent Degradation Correction
    • 11.1.6 Application of Calibrations and Corrections
  • 11.2 High-Dispersion Absolute Flux Calibration
    • 11.2.1 Ripple Correction
    • 11.2.2 Absolute Flux Calibration Function
    • 11.2.3 Application of Calibrations and Corrections
• 12 Final Archive Data Products
  • 12.1 FITS File Formats
  • 12.2 FITS Header Format
    • 12.2.1 Basic FITS keywords
    • 12.2.2 Core Data Items
    • 12.2.3 Original IUE VICAR Label
    • 12.2.4 NEWSIPS Image Processing History
      • 12.2.4.1 Low-dispersion Header Example
      • 12.2.4.2 High-dispersion Header Example
  • 12.3 Raw Image FITS File (RILO/RIHI)
  • 12.4 Linearized Image FITS File (LILO/LIHI)
  • 12.5 Vector Displacement FITS File (VDLO/VDHI)
  • 12.6 Low-Dispersion Resampled Image FITS File (SILO)
  • 12.7 High-Dispersion Resampled Image FITS File (SIHI)
  • 12.8 Low-Dispersion Merged Extracted Image FITS File (MXLO)
  • 12.9 High-Dispersion Merged Extracted Image FITS File (MXHI)
• 13 Assessing NEWSIPS Data Quality
• 14 Core Data Items
  • 14.1 The Sources for Core Data Items
  • 14.2 The Core Data Items
• A High-Dispersion Background Determination Algorithm (BCKGRD)
  • A.1 Overview
  • A.2 Background Determination: Step-by-Step
    • A.2.1 Data Screening
    • A.2.2 Pass 1: Cross-Dispersion Swath Grid
      • A.2.2.1 Basic Flow
      • A.2.2.2 Differentiation of Swath Regions
      • A.2.2.3 Swath-Dependent Data Files
      • A.2.2.4 On-the-Fly Pathology Screening
      • A.2.2.5 PSF Modeling
      • A.2.2.6 Post-Solution Pathology Tests
    • A.2.3 Pass 2: Dispersion Direction Swaths
    • A.2.4 Non-continuum images
    • A.2.5 Data Pathology Assessments
  • A.3 Failure Modes
  • A.4 Problem Areas
• B Glossary
• C References

List of Tables

•   Officially Adopted Dimensions for the Apertures in Each Spectrograph, Measured on LWP, LWR, and SWP Images
•   Standard Offsets from the Small to the Large Spectrograph Aperture as used by low-dispersion NEWSIPS (in pixels)
•   Approximate Spectral Scales in Each Dispersion Mode
•   $\nu$ Flag Values
•   Hot Pixels in the LWR Camera
•   Hot Pixels in the SWP Camera
•   Permanent Blemishes in the LWP and LWR Cameras
•   Low-Dispersion Camera Artifacts (Å)
•   High-Dispersion Camera Artifacts
•   Source Type Determination Values (number of pixels)
•   FES Coordinates of the Apertures
•   Low-Dispersion Wavelength Regions for DN Measurements (Å)
•   Number of Fiducial Locations
•   ITF Effective Exposure Times (seconds)
•   LWP True Reseau Positions in Y Direction
•   LWR True Reseau Positions in Y Direction
•   SWP True Reseau Positions in Y Direction
•   Low-Dispersion Pt-Ne Line Libraries
•   LWP and SWP Low-Dispersion Time and THDA Coefficients (pre-1990)
•   LWR Low-Dispersion Time and THDA Coefficients
•   LWP and SWP Low-Dispersion Time and THDA Coefficients (post-1990)
•   IRAF Solutions Used for the Wavelength Linearization Step
•   IRAF Solutions Used for Time and Temperature Correlation Step
•   IUE Spectrograph Parameters
•   Approximate Wavelength Ranges for the Echelle Orders
•   Fiducial Line Positions for the Echelle Orders
•   Extraction Slit Lengths for the Echelle Orders
•   LWP Absolute Calibration
•   LWR ITFA Absolute Calibration
•   LWR ITFB Absolute Calibration
•   SWP Absolute Calibration
•   LWP S/L and T/L Relative Sensitivities$^\ast$
•   LWR ITFA S/L and T/L Relative Sensitivities$^\ast$
•   LWR ITFB S/L and T/L Relative Sensitivities$^\ast$
•   SWP S/L and T/L Relative Sensitivities$^\ast$
•   Temperature Coefficients and Reference THDAs
•   High-Dispersion Ripple Coefficients
•   High-Dispersion Calibration Function Coefficients
•   Low-Dispersion File Formats
•   High-Dispersion File Formats
•   Summary of the IUE Raw Image VICAR Header
•   RILO/RIHI - Basic FITS Keywords
•   RILO Partial Read - Basic FITS Keywords
•   LILO/LIHI - Basic FITS Keywords
•   VDLO/VDHI - Basic FITS Keywords
•   SILO - Basic FITS Keywords
•   SIHI - Basic FITS Keywords
•   MXLO - Basic FITS Keywords
•   MXHI - Basic FITS Keywords
•   Mean ITF THDAs
•   Recourses to Various Pathological Trial Solutions