GPS radio occultation measurements onboard geo research satellites such as CHAMP and GRACE are used for retrieving vertical electron density profiles of the ionosphere. At present, only GPS measurements from GRACE are available. These data are routinely provided by GFZ Potsdam. Thus, the derived electron density profiles retrieved in SWACI are a common data product of DLR and GFZ Potsdam. Users are asked to acknowledge this in a proper way.