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Wavelength calibration of spectra measured by
the Global Ozone Monitoring Experiment by use
of a high-resolution reference spectrum

Jos H.G.M. van Geffen and Roeland F. van Oss
Applied Optics  42, 2739-2753 (2003).

Abstract

Earthshine spectra measured by the nadir-viewing Global Ozone Monitoring Experiment (GOME) spectrometer aboard the ERS-2 satellite in the range 240-790 nm are widely in use for the retrieval of concentrations and vertical profiles of atmospheric trace gases. For the near-real time delivery of ozone columns and profiles at KNMI, a tailor-made wavelength calibration method was developed. The method uses a high-resolution (0.01 nm) solar spectrum as reference spectrum and applies both a shift and a squeeze to the wavelengths in selected windows to find the optimal wavelength grid per window. This provides a calibration accuracy of 0.002 nm below and 0.001 nm above 290 nm.

The new wavelength calibration method can be used on any wavelength window, for example to improve the calibration of spectra from the GOME Data Processor (GDP). A software package called GomeCal which performs this re-calibration, along with an improved polarisation and radiometric correction, has been made and is released via the WWW. The method can be used for any high-resolution (ir)radiance spectrometer, such as the satellite instruments SCIAMACHY, OMI and GOME-2.

contents

   Abstract
   1. Introduction
      1.1 GOME Fast Delivery Service
      1.2 Wavelength calibration
   2. The wavelength calibration method
      2.1 The reference spectrum
      2.2 The wavelength grid
      2.3 The calibration procedure
      2.4 Scaling the spectra 
   3. Wavelength calibration in the EGOI windows
      3.1 Wavelength window 9
      3.2 Initial wavelength grid
      3.3 Re-calibration of GDP spectra
      3.4 Simulated GOME earthshine spectra
      3.5 Accuracy of the calibration method
      3.6 Systematic offset
      3.7 Variation of the calibration results along orbits and in time 
   4. The GomeCal package: re-calibraton of GDP spectra
      4.1 Wavelength re-calibration in GomeCal
      4.2 Other corrections in GomeCal 
   5. Concluding remarks
   Acknowledgements
   References
Note: Section 4 introduces the GomeCal package; see the GomeCal home page

===> PDF file of the paper in own typesetting (28 pages; 367 kB)

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created: 16 August 2002
last modified: 19 August 2020