Creating Maps of Ionospheric Electron Density to Support Communication, Surveillance and Navigation Systems

Space based GPS measurements onboard Low Earth Orbiting (LEO) satellites provide a uniquepossibility for exploring the ionosphere on a global scale. Both the radio occultation measurements in thelimb sounding mode and the navigation measurements using a zenith viewing GPS antenna provide theTotal Electron Content (TEC) along numerous ray paths. TEC may effectively be used for reconstructingthe spatial and temporal distribution of the electron density in the ionosphere and plasmasphere.Reported are results obtained from radio occultation measurements on CHAMP which have providedmore than 200,000 vertical electron density profiles so far. These observations contribute to a betterunderstanding of the regular behaviour of the global ionosphere. Furthermore, the radio occultationmeasurements indicate irregular and/or wavelike structures in the ionosphere which may have severeimpact on the functionality of radio systems. A three-dimensional imaging of the electron density distribution near the CHAMP orbit plane betweenCHAMP and GPS orbit height is performed by using link related TEC data derived from dual frequency