Abstract. A space-based satellite system suited for long-term monitoring of the Earth's ionosphere/plasmasphere systems is proposed. The monitoring system consists of a network of radio beacon satellites capable of measuring the ionospheric and plasmaspheric electron content on a continuous base with high time resolution. It takes advantage of the geometrical relationship between the orbit of geostationary satellites and the position of the plasmapause region characterized by a steep electron density gradient. A combination of geostationary and nongeostationary satellites may explore the three-dimensional structure of the plasmasphere. Taking into account plasmaspheric characteristics some criteria for an effective arrangement of the satellites are derived and discussed. Since the plasmapause position is very sensitive to changes or distortions in the solar wind and the related geomagnetic activity, a continuous monitoring of the position of the plasmapause would be helpful in understanding solar-terrestrial relationships.