SCIAMACHY has three Earth obsvervation modes: Nadir, Limb and Occultation. At the moment, only Limb and Nadir observation geometries are used for the operational processing. In the processor different types of algorithms developed at different institutions are implemented. In the UV/VIS spectral range, Nadir trace gas retrievals are done with the DOAS (=Differential Optical Absorption Spectroscopy) method, i.e. with the same algorithms as for GOME, adjusted for SCIAMACHY. In the shortwave infrared the direct retrieval method BIRRA (=Beer InfaRed Retrieval Algorithm, developed here at IMF-ATP, is used. In Limb, the retrieval model DRACULA (=aDvanced Retrieval of the Atmosphere with Constrained and Unconstrained Least squares Algorithms) calculates height resolved trace gas profiles. Additionally to the trace gas concentrations, cloud and aerosol parameters are retrieved. Details of the algorithms can be found in the ATBD (pdf, 3.8 MB).
The table below shows an overview of products available with the current version of the Processor (offline and fast delivery):
| Parameter | Spectral Window | Algorithm | Institution | Remark |
|---|---|---|---|---|
| Nadir | ||||
| SO2 VCD | 315.0 - 327.0 nm | SDOAS | BIRA/IUP Bremen | SDOAS Retrieval with IUP Retrieval Settings |
| O3 VCD | 325.0 - 335.0 nm | SDOAS | BIRA | GDP4 DOAS with SCIAMACHY Adjustments (=SDOAS) |
| BrO VCD | 336.0 - 351.0 nm | SDOAS | BIRA | see O3 |
| OClO SCD | 365.0 - 389.0 nm | SDOAS | BIRA/IUP Bremen | see SO2 |
| NO2 VCD | 426.5 - 451.5 nm | SDOAS | BIRA | see O3 |
| HCHO VCD | 328.5 - 346 nm | SDOAS | BIRA | see O3 |
| CHOCHO VCD | 435 - 457 nm | SDOAS | BIRA | see O3 |
| H2O VCD | 688.0 - 700.0 nm | AMC DOAS | IUP Bremen | |
| CO/xCO VCD | 2324.4 - 2335.0 nm | BIRRA | IMF-ATP | |
| xCH4 VCD | 1557.18 - 1594.13 nm/1628.93 - 1670.56 | BIRRA | IMF-ATP | |
| AAI | 340/380 nm | AAIA | KNMI | Ratio of two spectral ranges compared to KNMI DAK model |
| Cloud Fraction | 300.0 - 800.0 nm | OCRA | IMF-ATP | Uses PMDs |
| Cloud Top Height | 758.0 - 772.0 nm | SACURA | IUP Bremen | Uses O2A Band |
| Cloud Opt. Thickness | 758.0 - 772.0 nm | SACURA | IUP Bremen | Uses O2A Band |
| Limb | ||||
| O3 Profile | 520.0 - 590.0 nm | DRACULA | IMF-ATP/IUP Bremen | Operational version of Dracula, Retrieval Settings from IUP |
| NO2 Profile | 420.0 - 470.0 nm | DRACULA | IMF-ATP/IUP Bremen | see Limb O3 |
| BrO Profile | 337.0 - 357.0 nm | DRACULA | IMF-ATP/IUP Bremen | see Limb O3 |
| Limb Clouds | several | SCODA | IUP Bremen | Uses ratio of several wavelength ranges |
| Tropospheric Products | ||||
| trop. BrO | 336.0 - 351.0 nm | - | BIRA | based on climatology BASCOE and ECMWF tropopause height |
| trop. NO2 | 426.5 - 451.5 nm(N)/420 - 470 nm (L) | L/N Matching | see NO2 (N,L) | L: Limb, N: Nadir |