Ionospheric Radio Occultation Measurements Onboard CHAMP

Abstract

The GPS radio occultation measurements of the ionosphere have been performed onboard CHAMP since 11 April 2001. More than 115000 vertical electron density profiles have been derived so far by a model assisted retrieval technique. The talk addresses the capabilities of the ionospheric radio occultation (IRO) technique for routinely monitoring the global ionosphere with the purpose of deriving value added data products and studying ionospheric perturbations. Discussed are the model assisted retrieval technique, operational data processing and results from the validation of vertical electron density profiles. These profiles may not only be used to validate other models, but they also provide a good data basis for developing new models of key ionospheric parameters such as the critical frequency, density peak height, and plasma scale height. Such models would help us to improve retrieval procedures and tomographic reconstruction techniques. Travelling ionospheric irregularities (TIDs) and other types of ionospheric irregularities may be studied on the basis of CHAMP radio occultation measurements. Shown are the latitudinal distribution and the diurnal and seasonal dynamics of the irregularities. The most prominent feature is the significant enhancement of winter time TID activities over the polar regions. Thanks to the operational data processing capabilities, the data products may also contribute to the space weather monitoring of the ionosphere.