On the Implementation of a GPS Based Method for the Real-Time Measurement of the Total Electron Content of the Ionosphere

Kurzfassung

Due to the recent developments towards an European Navigation Satellite System and the actual effords in aviation, a rising interest in the real-time monitoring of the ionosphere is noticed. The crucial task for the estimation of the total electron content (TEC) in real-time is in the separation of the ionospheric delay from the total error budget. Parameters affecting the total error budget have been identified to be the number of epochs before the first ambiguity fixing, elevation cut-off angle, the utilization of either predicted or real-time satellite/receiver instrumental biases, and the handling of multipath effects. In the paper, an operable method for the real-time estimation of TEC is presented. The method is based on the usage of a L1/L2 GPS receiver, preprocessed satellite and receiver biases, and an appropriate ionospheric background model for the preparation of ionospheric maps. A rating of the influences of various processing parameters on the accuracy of the real-time TEC measurements will be given. The evaluation of the accuracy has been obtained by comparing the real-time measurements with TEC obtained by postprocessed data of a receiver at the same location and a subset of the IGS network for reference. The accuracy of the real-time method has been proven to be better than 4 TECU in any case. Depending on actual computer technologies, TEC measurements can be taken up to a sampling rate of 1/3 Hz. The work on the real-time TEC station was done in the framework of the projects DIRES and RAKO under financial support of the German Space Agency (DARA) at DLR Remote Sensing Ground Station Neustrelitz.