The World Data Center for Remote Sensing of the Atmosphere, WDC-RSAT, offers scientists and the general public free access (in the sense of a “one-stop shop”) to a continuously growing collection of atmosphere-related satellite-based data sets (ranging from raw to value added data), information products and services. Focus is on atmospheric trace gases, aerosols, dynamics, radiation, and cloud physical parameters. Complementary information and data on surface parameters (e.g. vegetation index, surface temperatures) is also provided. This is achieved either by giving access to data stored at the data center or by acting as a portal containing links to other providers.