IRAS Explanatory Supplement

Table of Contents

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  1. INTRODUCTION
    1. General Overview
      1. The IRAS Mission
      2. The Explanatory Supplement
      3. Cautionary Notes
    2. Summary Description of Catalogs and Atlases
      1. Point Sources
      2. Small Extended Sources
      3. Sky Brightness Images
      4. Low Resolution Spectra
      5. The Extragalactic Sub-catalog
    3. Overview of Infrared Sky
  2. SATELLITE DESCRIPTION
    1. Introduction
    2. The Spacecraft
      1. Onboard Computers and Software
      2. Attitude Control
      3. Communication
    3. Telescope System Overview
      1. Cryogenics
      2. Thermal Control
      3. Optics
      4. Focal Plane Assembly
      5. Electronics

      Appendix II.1 Data Compression

  3. THE IRAS MISSION
    1. Requirements
    2. Constraints
      1. Introduction
      2. Attitude Control
      3. Solar Radiation
      4. Earth Radiation
      5. Moon and Planets
      6. South Atlantic Anomaly
      7. Station Passes
      8. Constant Sun Angle
      9. Ectipse Operations
    3. Design
      1. Basic Strategy
      2. The Second Six Months
      3. Scan Rate
      4. Strategy during South Atlantic Anomaly Passage
      5. Moon and Jupiter Avoidance Strategy
      6. Strategy of Attitude and Photometric Calibration
      7. Realization of Survey Strategy
      8. Half-Orbit Constraint
      9. Lune Constant
      10. Hole Recovery Strategy
      11. Pre-Survey Observations
    4. In-Flight Modifications
      1. Introduction
      2. Polar Horns
      3. Operations Problems
      4. Saturation
      5. The 5° Gap
      6. Early Eclipse and Warm Up
  4. IN-FLIGHT TESTS
    1. Detector and Focal Plane Performance
      1. Detector Sensitivity and Responsivity
      2. Detector Reliability and Anomalies
      3. Cross-scan Response
      4. Verification of Linearity
      5. Baseline Stability
      6. Particle Radiation Effects
      7. Effects of Bias Boost
      8. Photon Induced Responsivity Enhancement
      9. Feedback Resistor Nonlinearity Analysis
    2. Spectral Passband Verification
      1. Verification of the Relative Consistency
      2. Verification of the Nominal Inband/Out-of-Band Transmission
    3. Optical Performance
      1. Optical Cross Talk due to Bright Sources Crossing the Focal Plane
      2. Optical Cross Talk from Sources not directly on the Focal Plane
      3. Out-of-Field Rejection Monitoring
    4. Internal Reference Source Stability
  5. DATA REDUCTION
    1. Overview
      1. General
      2. IRAS Catalogs and Atlases
      3. Processing Summary
        1. Data Reconstruction
        2. Pointing Reconstruction
        3. Source Detection
        4. Point Source Confirmation
        5. Small Extended Source Confirmation
        6. Asteroids and Comets
        7. Extended Emission Processing
        8. Final Processing Steps
    2. Pointing Reconstruction
    3. Source Detection
      1. Square Wave Filter
      2. Noise Estimator
      3. Timing Estimate
      4. Correlation with Point Source Template
      5. Determination of Templates
      6. Low Signal-to-Noise Detections
      7. Source Shadowing
    4. Point Source Confirmation
      1. Processing Overview
      2. Overview of Seconds-Confirmation
        1. Band Seconds-Confirmation
        2. Position Reconstruction
        3. Optical Crosstalk Removal
        4. In-Band Seconds-Confirmation Decision
        5. Double-Detection Mode
        6. Triple-Detection Mode (Edge Detections)
        7. In-Band Seconds-Confirmation Confusion Processing
        8. In-Band Seconds-Confirmation Position Refinement
        9. In-Band Seconds-Confirmation Photometric Refinement
        10. In-Band Seconds-Confirmation Statistical Processing
      3. Band-Merging
        1. Overview of Band-Merging
        2. Band Filling
        3. Special Considerations Regarding Band-Merging
        4. Focal Plane Geometry Analysis
      4. Known Source Correlation
        1. Known Source Prediction
        2. Correlation of Observations With Predictions
        3. Known Source Flux and Position Discrepancy Analysis
      5. Overview of Hours-Confirmation
        1. Hours-Confirmation Decision
        2. Position Agreement
        3. Photometric Agreement
        4. Hours-Confirmation Confusion Processing
        5. Hours-Confirmation Position and Photometric Refinement
        6. Hours-Confirmation Statistical Processing
        7. Special Considerations Regarding Hours-Confirmation
      6. Overview of Weeks-Confirmation
        1. Weeks-Confirmation Decision
        2. Weeks-Confirmation Position Refinement
        3. Weeks-Confirmation Statistical Processing
      7. Auxiliary Processing for Low Resolution Spectra
      8. Flux and Confusion Status Words
      9. Conversion of Position Uncertainties to Gaussian Approximation
    5. Overview of Small Extended Source Data Processing
      1. Potential Detections
      2. Seconds-Confirmation
      3. Source Construction and Hours-Confirmation
      4. Cluster Analysis Processing
      5. Weeks-Confirmation
      6. Band-Merging
      7. Optimizing the Processor
        1. Choosing the Clustering Threshold
        2. Choosing the Weeks-Confirmation Threshold
        3. Choosing the Band-Merging Threshold
        4. Summary and Discussion
      8. The Small Extended Source Catalog
    6. Asteroids and Comets
    7. Extended Source Products
      1. Processing Overview
      2. Quality Checking, Selection, and Weights
      3. Phasing, Sorting, and Gaps
      4. Conversion to Surface Brightness
      5. Compression and the Time-Ordered Files
      6. Destriping
      7. Projection into Sky Maps
      8. Consistency Checking and Removal of Bad Data
      9. Final Map Image Generation
    8. The Point Source Catalog
      1. Processing Overview
      2. Clean-Up Processing
      3. Neighbor Tagging
      4. Cirrus Flagging
      5. Average Flux Computation and Variability Analysis
      6. High Source Density Regions
        1. Location of High Source Density Regions
        2. Catalog Selection Criteria in High Source Density Regions
        3. Weaker Neighbors
        4. Confused Neighbors
        5. Very Near Neighbors
        6. Moderate Quality Fluxes
        7. Low Quality Fluxes (Upper limits)
        8. Flux Averaging and Uncertainties
      7. Catalog Source Selection
      8. Low-Resolution Spectral Associations
      9. Associations
  6. FLUX RECONSTRUCTION AND CALIBRATION
    1. Processing - Removal of Telescope Transfer Function
      1. Digital Electronics
      2. Analog Electronics Amplifiers
      3. Trans-impedance Amplifier
      4. Removal of Coherent Detector Noise
      5. Feedback Resistor
      6. Summary
    2. Determination of Relative Flux
      1. Overall Procedure to Determine Relative Photometry
      2. Photometry of Point Sources and Small Extended Sources
      3. Photometry of Extended Emission
        1. Determination of F[TFPR]
        2. Determination of the TFPR Annual Variation
      4. Problems
        1. Rejected Internal Reference Source Flashes
        2. Radiation
        3. Photon Induced Responsivity Enchancement
          1. Point Sources
          2. Extended Emission
        4. Variation of Frequency Response with Total Flux
    3. Absolute Calibration
      1. General Philosophy
      2. Point Source Calibration
        1. Stellar Calibration
        2. Asteroid Calibration
        3. Estimated Accuracy
      3. Color Correction
      4. Absolute Calibration of Extended Emission
    4. Comparison of IRAS Observations with Ground Based Observations
  7. ANALYSIS OF PROCESSING
    1. Overview
    2. General Statistics of the Point Source Processing and Catalog
      1. The Generation of Reliable Point Sources
      2. Distribution of Sources in the Catalog
    3. Positional Accuracy
      1. Positional Accuracy of Catalog Sources
        1. Accuracy of Absolute Positions
        2. The Quoted Position Uncertainties
      2. Accuaracy of Scan-by-Scan Pointing Reconstruction
    4. Photometric Accuracy
      1. Absolute Calibration Uncertainty Checks
      2. Relative Photometric Accuracy
        1. Relative Photometric Accuracy of HCONs
        2. The Quoted Flux Density Uncertainties
      3. Variable Sources
      4. Discrepant Fluxes
    5. Point Source Processing Considerations
      1. The Nature of Rejected Sources
        1. Single HCONs
        2. Rejected Weeks-Confirmed Sources
      2. Bright Source Problems
      3. Sources of Incompleteness
      4. Effects of Failed Detectors
      5. Setting the Seconds-Confirmation Threshold
    6. Asteroids and Comets
      1. Number Present in Catalog (Asteroid Source Density)
    7. Associations
    8. Meaning of Point Source Flags
      1. Confusion Flags
        1. Point Source Neighbors
        2. Small Extended Source Neighbors
        3. Confuse Flag
        4. Summary
      2. Cirrus Flags
    9. The Small Extended Source Catalog
    10. Extended Source Products
      1. Zodiacal Emission Effects
      2. Effective Resolution
      3. Tests of Extended Source Calibration Consistency
    11. Appendix
  8. SKY COVERAGE, CONFUSION, COMPLETENESS AND RELIABILITY
    1. Introduction
    2. Sky Coverage
    3. Point Source Confusion
    4. Reliability and Completeness of Point Source Catalog
      1. Definitions, Assumptions and Limitations
      2. Formalism for the Determination of Completeness and Reliability
        1. Completeness
        2. Reliability
      3. Estimation of Parameters
      4. Completeness and Reliability Outside of the Galactic Plane
        1. Estimates from Minisurvey Data
        2. Verification of the Completeness from Source Counts
        3. Reliability of Point Sources with Flux densities of Moderate Quality
      5. Completeness and Reliability in the Galactic Plane
      6. Galactic Plane Shadow
    5. Completeness and Reliability of the Catalog of Small Extended Sources
  9. THE LOW RESOLUTION SPECTRA
    1. Instrumentation
      1. Introduction
      2. Optical Properties
      3. Electronics
      4. Effects of the Zero-Clamp
      5. Summary of Instrumental Characteristics
    2. Performance and Calibration
      1. Detectors
      2. Wavelength Scale
      3. Cross-Scan Responsivity
      4. Wavelength-Dependent Responsivity
      5. Radiation Effects
      6. Multiplexer Glitches
      7. Confusion
      8. Photon Induced Responsivity Enhancement
      9. Memory Effects
      10. Linearity Checks
      11. Overall Flux-Density Scale
    3. Data Processing
      1. The Database
      2. Processing the Individual Spectra
      3. Averaging Spectra, Quality Checks
      4. Final Selection of Spectra
    4. Classification
      1. Introduction
      2. Classification Scheme
      3. Performance of the Classification Scheme
    5. Some Characteristics of the Catalog
      1. Completeness
      2. Checks on the Shape of the Spectra
  10. THE FORMATS OF THE IRAS CATALOGS AND ATLASES
    1. Introduction
    2. Point Sources
      1. The Machine Readable Version of the Point Source Catalog
      2. The Printed Version of the Point Source Catalog
      3. The Working Survey Data Base
    3. The Small Extended Source Catalog
    4. Extended Emission
      1. Introductory Comments
      2. Map Projections and Transformation Equations
      3. 16.5° Images
      4. Galactic Plane Maps
      5. Low-Resolution Al1-Sky Maps
      6. Zodiacal Observation History File
      7. Coordinate Overlays
    5. Low-Resolution Spectra
      1. Catalog Header File
      2. Spectra Records

      Appendix X.Ap.1 Regions of High Source Density
      Appendix X.Ap.2 Location of 16.5° Image Fields
      Appendix X.Ap.3 Sample FITS Headers
      Appendix X.Ap.4 Zodiacal Observation History File (ZOHF) Format

  11. KNOWN PROCESSING ANOMALIES
    1. Processing of Extended ("Cirrus") Sources as Point Sources
    2. Instability and Lag of the Noise Estimator
    3. Frequency Dependence of Responsivity with Amplitude
    4. Errors in Cross-Scan Uncertainties Related to Failed Detectors
    5. Photon-Induced Responsivity Enhancement
    6. Artifacts in the Digital Image Data Base
    7. Photometric Processing
    8. Insufficient Specification of HCON Coverage
    9. Position Uncertainties
    10. Overestimated Weak Fluxes
    11. Minor Problems
  12. ERRATA AND REVISIONS AS OF 1987
    1. Version 2.0 of the Point Source Catalog
      1. The Flux Overestimation Correction
      2. Additional Flux Density Changes
      3. New and Deleted Sources
      4. Revised Completeness Estimates for Version 2.0
      5. Associations
      6. Source Names
      7. Revised Positional Uncertainties for Bright Sources
      8. Correction of Point Source Neighbor Counts
      9. Spurious 25 µm Only Sources
      10. Working Survey Data Base and Ancillary File
    2. Total Intensity Data
      1. Total Intensity Maps
      2. Version 2.0 of the Zodiacal Observation History File
    3. Low Resolution Spectrometer
    4. Other Anomalies Fixed in This Release
  13. CONTRIBUTORS TO IRAS (Formerly Chapter XII)
  14. AREA COVERAGE PLOTS (Formerly Chapter XIII)
  15. INDEX
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