This is the SCIAMACHY m-factors main page. This
pages refers to the SCIAMACHY Level
0-1b processor versions 6.xx and 7.xx.
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.
Schematic view of the different SCIAMACHY monitoring
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
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
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
Details about the generation of m-factors are given in a
on partly calibrated Level 0 data
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
- 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.
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
m-factors for the short-term solution are available. Click
to download the data
- K. Bramstedt, Calculation of SCIAMACHY M-Factors,
Technical Note, IFE-SCIA-TN-2007-01-CalcMFactor,
Issue: 1, 2008. (PDF file, ca. 1.3 MB)
If you are interested in more information on SCIAMACHY
m-factors contact Stefan
Author of this page: Stefan