SCIAMACHY Data Processing



Die Operational data processing is designed to provide users with Level 1 and Level 2 data continuously. The levels are defined as follows:

  • Level 1b: data containing all the auxiliary data need for calibration as well as the geographical coordinates of the recorded ground pixels,
  • Level 1c: calibrated data, in other words, solar radiance intensity and the intensity of the part of Earth’s atmosphere under observation as a function of wavelength,
  • Level 2: geophysical values such as trace gas content of the atmosphere or extent of cloud cover.

There are two processing stages – Level 0-1b with an optional Level 1c, and Level 1b-2.

In general, the recording of the calibration data required for Level 0-1b processing does not take place at the same time as the atmosphere measurements themselves. It is therefore necessary to process both types of data separately. With the SciCal software package developed by the IMF Atmospheric Processors department the calibration data can be processed with the specified algorithms and then centrally managed. For any given atmosphere data set, appropriate calibration data—usually that which is closest in time—can be defined and incorporated in a Level 1b data set along with geolocation information. The calibration algorithms were developed together with SRON (Netherlands Institute of Space Research), whereas the operational processor initially was provided by industry (Jena Optronik) according to IMF specifications and since 2010 it is directly providet by DLR.

Many users require Level 1c data for their own purposes. This requirement can be met with the software package SciaL1c, which was developed for ESA by the IMF Atmospheric Processors department. It permits the selection of all, individual, or any combination of calibration steps for Level 1b data in order to generate a customized Level 1c product.

Atmosphere Parameters from SCIAMACHY Measurement Data
Parameter Wavelength Range (nm)

Algorithm (Institute)

Ozone (O3) 325-335 GDP4/SDOAS (BIRA)
Nitrogen dioxide (NO2) 426.5-451.5 GDP4/SDOAS (BIRA)
Bromine oxide (BrO) 336-351 GDP4/SDOAS (BIRA)
Sulfur dioxide(SO2) 315-327 GDP4/SDOAS (BIRA/IUP Bremen)
Water vapor (H2O) 688-700 AMC-DOAS (IUP Bremen)
Chlorine dioxide (OClO) 365-389 GDP4/SDOAS (BIRA/IUP Bremen)
Carbon monoxide (CO) 2324.4 -2335 BIRRA (MF-ATP)
Absorbing Aerosol Index 340 - 380 Algorithmus von KNMI
Extent of cloud cover 300 - 800 OCRA (MF-ATP)
Cloud top and optical density 758 - 772 SACURA (IUP Bremen)
Limb Profile    
Ozone (O3) 520 -590 DRACULA (MF-ATP)
Nitrogen dioxide (NO2) 420 - 470 DRACULA (MF-ATP)
Bromine oxide (BrO) 337 - 357 DRACULA (MF-ATP)
Cloud detection (high resolution) Varies with cloud type SCODA (IUP Bremen)

Operational Level 1b-2 processing begins with internal processing to Level 1c, in other words, to calibrated spectra. After deriving parameters for use when later calculating trace gas concentrations (for example, the extent of cloud cover), a classification is made according to the observation geometry—limb or nadir. Only then does the actual retrieval (determination of trace gas concentrations) take place, with the results being collected in a Level 2 data set for each orbit. The new Version 5 of the data processor, which became operational in September 2009, covers the atmosphere parameters listed in the table. The table also includes an overview of the algorithms employed.

There is more information about calibrating absorption spectrometers on the calibration page of the "Team Sensor-specific Methods" of the "Atmospheric Processors Department".


Contact
Dr.rer.nat. Günter Lichtenberg
German Aerospace Center (DLR)

Remote Sensing Technology Institute
, Atmospheric Processors
Tel: +49 8153 28-1331

Fax: +49 8153 28-1446

E-Mail: Guenter.Lichtenberg@dlr.de
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