Total electron content modelling for transionosphere propagation applications

It is well known that the ionosphere affects radio waves propagation on Earth-space paths. One of the ionosphere characteristics influencing such propagation is the total electron content (TEC) that the wave encounters in his course. The knowledge of TEC behaviour under different time, geographical and solar activity conditions and its variability is important for satellite communication system planning and for satellite navigation systems operation. A correct estimate of TEC along a trans-ionosphere path depends also on a realistic 3D description of the global ionosphere electron density. The requirements for satellite navigation operation are still more stringent. The paper describes the present state of the art about TEC modelling for satellite system planning and navigation. It summarizes recent results about climate description and variability of the TEC based on global TEC maps obtained from experimental GPS derived data. It describes also the most recent version of the 3D NeQuick model (NeQuick2) adopted by the ITU-R Recommendation P.531-10. This version of the model is fully compatible with the ITU-R coefficients that describe the global peak electron density characteristics of the ionosphere approved in ITU-R Recommendation P.1239-2. The use of the NeQuick model for the single frequency operation of the European satellite navigation system Galileo is also explained as an example of the ability of the model to specify the ionosphere conditions on a regional or global scale.