SCIAMACHY

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. GPAS contains a database for the storage and retrieval of calibration parameters computed from the input data. 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.

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 7 of the data processor, which became operational in March 2018, covers the atmosphere parameters listed in the table. The table also includes an overview of the algorithms employed.