Ionospheric Irregularities detected by Radio Occultation Measurements Onboard CHAMP

Ionospheric irregularities causing a severe impact on navigation signals may degrade the performance of Global Navigation Satellite Systems (GNSS) such as GPS and GLONASS and the future GALILEO. Hence, the study of the physical nature of these irregularities and the analysis of their impact on the accuracy and reliability of GNSS is an important issue of current research and discussion. In this paper we focus on the analysis of radio occultation GPS measurements onboard the German geo-research satellite CHAMP which has been launched on July 15, 2000 [1]. Ionospheric Radio Occultation (IRO) measurements onboard GPS equipped LEO satellites can effectively be used for probing the vertical structure of the electron density distribution [2][3]. Since the beginning of the first IRO measurements on CHAMP more than 120000 electron density profiles have been retrieved on a routine basis in DLR Neustrelitz [4]. The paper will present a view on the capabilities of IRO measurements to study the ionospheric impact on GNSS signals causing system performance and discuss preliminary results.