University of Bremen IUP SCIAMACHY M-factors

 correction V8.x


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    M-Factors at
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Introduction       Short-Term Concept       Long-Term Concept       Data       References       Contact

This is the SCIAMACHY m-factors main page. This pages refers to the SCIAMACHY Level 0-1b processor versions 6.xx and 7.xx.

Top Introduction

M–factors are used in the 0-1b processor to compensate for the radiometric degradation of SCIAMACHY. In general, an m-factor is defined as the ratio between a measured spectrum of a constant light source (typically the sun) at a certain time to a spectrum obtained for the same optical path at a reference time. M-factors therefore provide an end-to-end degradation correction for each individual light path.

SCIAMACHY Monitoring Light Paths

Schematic view of the different SCIAMACHY monitoring light paths.

M–factors have an impact on the polarization correction and on the absolute radiometric calibration.
The m–factors for the science detectors are multiplicative factors to the absolute radiometric calibration of SCIAMACHY.
The m–factors for the PMDs influence in a non-linear way the polarization correction of SCIAMACHY.
Regarding the m–factors for the polarization requires re-processing of the full mission, as the calculation of the polarization correction has to be done by the Level 0-1b processor.
The concept for calculation and provision of m-factors foresees two steps:
  • A short-term solution where only science detector readouts are corrected.
  • A long-term solution where all light paths are corrected.
Details about the generation of m-factors are given in a corresponding Technical Note.

SCIAMACHY long-term monitoring results based on partly calibrated Level 0 data are also available.

Top Short-Term Concept

The m-factor impact on polarization correction is neglected within the short–term solution.
The m–factors are provided by an external database, which than can be applied by a modified Level 1b-1c applicator.
Advantages of this approach are:
  • The application of m-factors can be switched on and off by the Level 1 data users.
  • M-factors are decoupled from the operational 0-1b processing, therefore a fast implementation is possible.
  • Updates of the m-factor data base are possible independent from a Level 1 re-processing.
Only the m-factors describing the degradation of the science channels are needed here; the PMD m-factors are set to 1.

Top Long-Term Concept

On long-term, a full set of m-factors including PMDs can be set up. For this concept, changes of the Level 0-1b processor are necessary.
The m-factors are included in the Level 1 product and cannot be switched off, if polarization correction or absolute radiometric calibration is needed.
Advantage of this approach is full consistency for reprocessed products.

Top Data

Currently only m-factors for the short-term solution are available. Click here to download the data base.

Top References

  • K. Bramstedt, Calculation of SCIAMACHY M-Factors, Technical Note, IFE-SCIA-TN-2007-01-CalcMFactor, Issue: 1, 2008. (PDF file, ca. 1.3 MB)

Top Contact

If you are interested in more information on SCIAMACHY m-factors contact Stefan Noël or Klaus Bramstedt.

Author of this page: Stefan Noël