The Status of the FDR4ATMOS Project

Kurzfassung

The Fundamental Data Record for ATMOSpheric Composition (FDR4ATMOS) project is part of the ESA Long Term Data Preservation (LTDP) programme and has two objectives: First, update the SCIAMACHY processing chain for better Ozone total column data: After the full re-processing of the SCIAMACHY mission with the updated processor versions, the validation showed that the total Ozone column drifted downward by nearly 2% over the mission lifetime. This drift is likely caused by changes in the degradation correction in the Level 1 processor, that led to subtle changes in the spectral structures. These are misinterpreted as an atmospheric signature. FDR4ATMOS updated the Level 0-1 processor accordingly and a full mission re-processing hast started. In an addition to the original plan, we also incorporated lunar data in the SCIAMACHYLevel 1b product. The instrument performed regular lunar observations buiding up a unique 10 year data set of lunar spectra from the UV to the SWIR with moderately high spectral resolution. In the project we calibrated these data. The results show an agreement within the error with other lunar data (e.g. ROLO). The second objective of the FDR4ATMOS project is to develop a cross-instrument Level 1 product for GOME-1 and SCIAMACHY for the UV, VIS and NIR spectral range, with focus on the spectral windows used for O3, SO2, NO2 total column retrieval and the determination of cloud properties. FDR4ATMOS aims to build a Fundamental Data Record (FDR) of Level 1 products, i.e. radiances and reflectances. The GOME-1 and SCIAMACHY instruments together span 17 years of spectrally highly resolved data essential for air quality, climate, ozone trend and UV radiation applications. We plan to generate harmonised data sets that allows to directly use it in long-term trend analysis, independently of the instrument. Since this was never done for highly resolved spectrometers, new methods have to be developed that e.g. take into account the different observation geometries and observation times of the instrument without impacting the spectral structures that are used for the retrieval of the atmospheric species. The resulting algorithms and the processor should also be as generic as possible to be able to easily transfer the methodology to other instruments (e.g. GOME-2 and Sentinel-5p) for a future extension of the time series. We will present the current status of the project, including results for the updated SCIAMACHY processor, the uncertainty analyses and will report the status of the data analysis for the harmonisation of data.