Degradation
correction V8.x
M-Factors
(V6.x/7.x)
SCIAMACHY
SCIAMACHY
M-factors / degradation correction
This is the SCIAMACHY m-factors main page. This page refers to the SCIAMACHY Level 0-1b processor version 8.x
Degradation
correction V8.x
With version 8 of the Level 0-1b processor, a new
common approach for the radiometric calibration
(including polarisation correction) and the degradation
correction of SCIAMACHY has been introduced.
For the calculation of polarisation and radiance
response we start with the following formula, which
describes the light by a Stokes vector and the
instrument by a series of matrices.
with:
the Stokes vector of the light in front of the detector,
the Stokes vector for the
incoming light,
the radiance sensitivity of
the OBM,
the polarisation sensitivity
of the OBM,
the Mueller
matrix of the scanner unit.
The Mueller matrix of scanner unit depends on the
scanner angle of the ESM mirror, the scanner angle of
the ASM mirror or the sun elevation angle (depending on
the light path in the instrument). This Mueller matrix
is based on a physical model, which describes the
reflections on the mirrors or the diffuser surfaces
using the Fresnel equations. The model includes a
contamination layer on top of the optical surfaces. The
thicknesses of these contamination layers are derived
from the regular measurements of the different
monitoring light pathes.
Schematic view of the different SCIAMACHY monitoring light paths.
The derived thicknesses describe to a large extend the radiometric degradation of the instrument with time.
Derived thicknesses of the contamination layers of the optical surfaces.
The remaining degradation is then described by a residual m-factor (OBM m-factor
in the above equation), mainly describing the degradation
of the optical bench module (OBM).This degradation correction is now integrated in the Level 0-1b processor as part of the radiometric calibation, i.e. calibrated SCIAMACHY spectra of version 8 or higher are always degradation corrected.
The physical details of the scanner model are described in Krijger et. al., the implementation for the degradation correction is descibed in this technical note.
Download m-factor
files V8.x
The m-factor files for version 8 (containing the
derived thicknesses of the contamination layers, the
used refractive indicees and the residual m-factors in a
binary format) are used by the L0-1b processor and
usually not relevant for the users of SCIAMACHY data.
These files are stored here for reference only (m-factor_08.31_20130830.tgz,
735 MB).
M-Factors V6.x/V7.x
The Level 0-1b processor V6.x/V7.x degradation
correction is an end-to-end correction with the so-called
monitoring factors (m-factors). This approach is described
on the V6.x/V7.x m-factor pages,
including download possibilities for the m-factor files. References
- K. Bramstedt, Scan-angle dependent degradation correction with the scanner model approach, Technical Note, IUP-SCIA-TN-Mfactor, Issue: 1, 2014.
- Krijger, J. M., Snel, R., van Harten, G., Rietjens, J. H. H., and Aben, I.: Mirror contamination in space I: approach, Atmos. Meas. Tech. Discuss., 7, 1213-1246, doi:10.5194/amtd-7-1213-2014, 2014.
Contact
If you are interested in more information on SCIAMACHY
m-factors contact Stefan
Noël or Klaus
Bramstedt. Author of this page: Stefan Noël
©2008