the german research satellite champ had been launched in summer 2000. its modern instruments and near earth orbit allow for the first time to collect data of the gravitational and magnetic fields and in addition to sound out the atmosphere and ionosphere by using gps techniques. the book is the result of the first meeting of the international champ research groups gathering 18 months later at the geoforschungszentrum potsdam. besides technical information the volume offers a comprehensive overview over the use of champ data for earth system research in the fields of geodesy, geophysics and meteorology.