The aim of the ESA funded FDR4ATMOS (Fundamental Data Records in the domain of satellite Atmospheric Composition) project is the creation and validation of FundamentalData Records (FDR) of GOME and SCIAMACHY Level 1 radiances and irradiances. An FDRconsists of a continuous, harmonized record of calibrated, geolocated, uncertainty-quantifiedsensor observations in geophysical units, together with all ancillary and underlying data used tocalibrate the observations and estimate uncertainty. It can be used by the scientific communityas a common starting point for further analyses to enable a better traceability of uncertaintiesand differences between individual data products.Here we shortly introduce the project itself and describe the individual steps from thecreation of GOME and SCIAMACHY Level 1 FDRs to their final publication, which will bethe first FDR of spectrally resolved radiances and irradiances.Since there is a need for quality assessment and control when creating a FDR, it followsthat the FDR have to be validated to ensure a maximum in accuracy and integrity of the finalproduct. Here, especially the FDR validation process is of interest for the DOAS communityas Level 1 data is planned to be validated with the help of Level 2 products. This procedure isdescribed on the example of NO2, which is derived using the DOAS method. Special emphasisis placed on analyzing the differences between both instruments (e.g. spatial and spectralresolution), such that a consistent NO2time series can be created.The DOAS community can benefit from the FDR products and the methods developedto derive them (e.g. improved error characterization, combination of time series of differentsensors). Especially, problems to be faced within the validation step of the FDR will have astrong similarity to the everyday work of the DOAS community (e.g. handling of correlativedata sets, definition of quality criteria, definition of proper ground scenes and times).