The use of DORIS as a tool to study the Earth ionosphere

Abstract

Space Geodetic techniques based on dual frequency signals have already proven their usefulness for the study of the ionosphere and are nowadays widely used by the ionosphere community. The so-called “geometric free” combination of the measurements made on these dual frequency signals allows to retrieve the Total Electron Content which is the integral of the electron concentration along the receiver-to-satellite path from the bottom of the ionosphere (about 50 km) up to the altitude of the satellite considered. This geodetic technique does not give a direct access to the electron concentration which is the most interesting data for ionospherists. Nevertheless, the combination of several techniques at the same location allows to retrieve more detailed information. The paper illustrates the interest of such collocations for ionospheric studies. First, the collocation of GPS (altitude 20 000 km) and DORIS (altitude from 800 to 1336 km) allows to give information about the integrated electron content of the protonosphere (ionised atmosphere above 1 000 km) by simply making the difference between GPS and DORIS electron contents. In addition, the collocation of GPS, DORIS and an ionosonde allows to retrieve the electron concentration profile which could be used to validate ionospheric models. The installation of a DORIS beacon at the Geophysical Centre of Dourbes (Belgium) would allow to take profit of such a collocation.