Analyzing existing applied models of the ionosphere for calculating radio wave propagation and possibility of their use for radar systems. I. Classification of applied models and the main requirements imposed on them for radar aids

We review modern HF-X band radars covering over-the-horizon problems. The ionosphere significantly affects wave propagation in all the bands. We describe available correction techniques, which use additional evidence on the ionosphere, as well as models of different degrees of complexity. The fact that the field of view cannot be covered by ground-based instruments as well as the growing requirements to the precision and stability of the radars result in the impossibility of ionospheric correction with up-to-date models, hence the latter require further elaboration. We give a virtually full classification of the models. The article summarizes the requirements to the models for the radars depending on their function.