University of Bremen IUP SCIAMACHY M-factors

 correction V8.x



SCIAMACHY M-factors / degradation correction

Degradation correction V8.x      Download      M-Factors V6.x/V7.x       References       Contact

This is the SCIAMACHY m-factors main page. This page refers to the SCIAMACHY Level 0-1b processor version 8.x

Top 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. 

Scannermodel calibration

 I  the Stokes vector of the light in front of the detector,

 I0 the Stokes vector for the incoming light,
 M1 the radiance sensitivity of the OBM,
 mu obm the polarisation sensitivity of the OBM,
 M scanner 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.

SCIAMACHY Monitoring Light Paths

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.
                    Contamination layer thicknesses

Derived thicknesses of the contamination layers of the optical surfaces.

The remaining degradation is then described by a residual m-factor (OBM m-factor nfactor obm 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.

Top 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).

Top 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.

Top References

Top Contact

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

Author of this page: Stefan NoŽl