Contents

• Contents
• List of Figures
• List of Tables
• 1. Introduction
  • 1.1 Purpose of this manual
  • 1.2 Document change history
  • 1.3 References
• 2. How to use this manual
  • 2.1 Overview of the document
  • 2.2 Where to go now
• 3. Instrument and AOT overview
  • 3.1 The LWS Instrument
  • 3.2 The LWS AOTs and operations
    • 3.2.1 LWS operations
    • 3.2.2 Transparent Data
    • 3.2.3 The LWS Instrument Commands Sequences (ICSs)
    • 3.2.4 Internal Illuminators
    • 3.2.5 Raster scans
    • 3.2.6 Grating operations
    • 3.2.7 Fabry Perot operations
• 4. Instrument Characteristics
  • 4.1 Introduction
  • 4.2 Behavior of the Detector Circuit
  • 4.3 Grating Characteristics
  • 4.4 Fabry-Perot Characteristics
• 5. Calibration and Accuracy
  • 5.1 Calibration philosophy
  • 5.2 Instrument characterisation procedure
    • 5.2.1 Detector characteristics
    • 5.2.2 Electronics characteristics
    • 5.2.3 Fabry Perot characteristics
    • 5.2.4 Optical characteristics
  • 5.3 Astronomical Calibration procedure
    • 5.3.1 Wavelength calibration
    • 5.3.2 Relative Response and Flux calibration
  • 5.4 Calibration sources and achieved accuracy
    • 5.4.1 Spectroscopic calibration
    • 5.4.2 Photometric calibration
• 6. Data processing
  • 6.1 Processing overview
  • 6.2 Quality Check of the data
  • 6.3 Derive SPD Processing steps
    • 6.3.1 Introduction
    • 6.3.2 Construction of ramps and discarding unusable readouts.
    • 6.3.3 Conversion of read-outs to voltages
    • 6.3.4 Flag saturated ramps
    • 6.3.5 First level deglitching
    • 6.3.6 Extraction of ramp slopes and conversion to photocurrent
    • 6.3.7 Illuminator processing
  • 6.4 Auto Analysis Processing Steps
    • 6.4.1 Dark Current/Background Stray-light Subtraction
    • 6.4.2 Grating Scan Wavelength Calibration
    • 6.4.3 Grating Spectral Responsivity Calibration
    • 6.4.4 Spectral bandwidth correction
    • 6.4.5 Fabry Perot Scan Wavelength Calibration
    • 6.4.6 Fabry Perot Spectral Responsivity Calibration
    • 6.4.7 Velocity correction to wavelength
    • 6.4.8 Write LSNR data product
    • 6.4.9 Absolute responsivity correction and responsivity drift correction
    • 6.4.10 Calculation of uncertainties
• 7. Caveats in the data processing
  • 7.1 Glitches
  • 7.2 Ramp slope order switching
  • 7.3 Last ramp in format
  • 7.4 Non-linear detector behaviour.
    • 7.4.1 The Strong Source Correction
  • 7.5 Grating wavelength calibration
  • 7.6 Spurious features in LWS spectra.
    • 7.6.1 Introduction
    • 7.6.2 Determination of filter profiles.
    • 7.6.3 Spurious Features in the Filter Profiles
  • 7.7 FP wavelength calibration
  • 7.8 Invalid data in FP products
  • 7.9 Correction for the LWS aperture size for point sources and extended sources
  • 7.10 Fringes in the data
  • 7.11 Straylight features in the data
    • 7.11.1 Introduction
    • 7.11.2 The NIR leak
    • 7.11.3 Straylight features on the long wavelength detectors
  • 7.12 Differences between overlapping spectra
  • 7.13 Correction for responsivity drift
  • 7.14 Removal of the grating spectral element
  • 7.15 Darkcurrent subtraction
• 8. Guide to instrument related data products.
  • 8.1 Inventory and naming convention
  • 8.2 Description of content and use
    • 8.2.1 Timing information in the products; the ITK
    • 8.2.2 General FITS header keywords for LWS Data
    • 8.2.3 Edited Raw Data
    • 8.2.4 Standard Processed Data
    • 8.2.5 LSPD and LIPD Status words
    • 8.2.6 SPD calibration files
    • 8.2.7 Auto Analysis results
    • 8.2.8 LSAN Status words
    • 8.2.9 Auto-analysis calibration files
• 9. Getting started with LWS data
  • 9.1 How to read to data
  • 9.2 Where to find instrumental calibration parameters (SPD calibration)
  • 9.3 Where to find astronomical calibration parameters (AA calibration)
• 10. Post-processing
  • 10.1 Introduction
  • 10.2 Invalid data points in LSPD and LSAN files.
  • 10.3 Strong source correction
    • 10.3.1 How do you know if you have saggy data.
    • 10.3.2 What to do if you have saggy data.
  • 10.4 Rebinning of wavelength to standard scale
  • 10.5 Co-adding repeated scans
  • 10.6 Fitting together LWS subspectra
  • 10.7 Subtraction of the astronomical background
  • 10.8 Performing absolute responsivity correction on LSNR data.
  • 10.9 Generation of maps for raster scans
• A. Detector theory
• B. List of acronyms