A.N. Detkov - D.Sc. (Eng.), Professor, Chief Scientific Officer of JSC «SPC NIIDAR»
S.I. Zherebtsov - Head of JSC «SPC NIIDAR»
A.N. Kobuzev - Chief of the laboratory of JSC «SPC NIIDAR»
I.A. Makarov - Ph.D. (Phys.-Math.), senior researcher at the JSC «SPC NIIDAR»

One of the urgent problems of modern radar is the task of providing the required precision trajectory measurements conducted in the near-Earth air-space (the lower atmosphere of the Earth). On this basis, traditionally existing model accounting for refraction correction in the calculation of the route of the radio beam had essentially the original restriction - the goal was considered within the «radio horizon» and with positive initial elevation angles of the electrical axis of the antenna pointing at the target. However, with the development of technologies of radar is very urgent task of calculating the trajectory of the radio beam and its targeting for any distance, including the case of the-horizon radar. In this case, as shown by numerical simulation, for paths with the known initial (non-zero) and final heights are possible modes of «targeting» of the radio beam with initial negative elevation angles. In this case the trajectory of the radio beam may lie at the bottom of the earth's atmosphere, where the refractive index is strongly dependent on the height testing «local disturbances» on the track, and the gradient of refractive index may become alternating. Thus, article design task calculation method of the radio beam propagation path for both the unperturbed and perturbed bottom for Earth's atmosphere at all alternating refractive index gradients and any adjustment, including the initial negative elevation angles electrical axis of the antenna. The algorithm for calculating the trajectories of the radio beam at the bottom of the atmosphere of the Earth using both unperturbed and perturbed strongly dependence of the refractive index of the height of the atmosphere at different initial elevations electrical axis of the antenna, including the negative ones was proposed. The stability of the algorithm for calculating the propagation path of the radio beam at the bottom of the earth's atmosphere, not only in terms of alternating refractive index gradient along the road, but in conditions of substantial disturbance was shown. It was calculated altitude correction characteristic for different distances to the goal. It is established that the perturbation of refractive index may lead to a redistribution of energy in real -sectional antenna beam on the track due to the nonlinear dependence of the final height of the initial elevation in given conditions. It is shown that in the framework of the developed method can be also calculated the initial elevation of the electrical axis antenna for the «target» of the radio beam on a target which at a given height and distance, including the case of the horizon location. Analysis of the results of the calculation algorithms can prevent the possibility of the effective use of resource-intensive real technical problems.