ICOS handles both observational data (collected by its own networks of measurement stations) and data associated with atmospheric and ecosystem modeling (mainly performed by external research groups). The requirements differ somewhat: the observations are mainly sensor time series data in tabular form, which have to be calibrated, quality controlled, and gap filled. The evaluation of greenhouse gas and energy fluxes involves quite complex calculations. Modelling, on the other hand, involves both, preparation of input data (combination of many different data sources), various calculation steps, and processing of the output data. Model runs typically require access to high-throughput and high-performance computing facilities.