Detection of the Trajectories of Moving Rectilinearly Air Targets in the Secondary Processing of Radar Information

Introduction. The primary functions of secondary processing of radar information are to detect and maintain the trajectories of air targets (AT). The AT trajectory detection can be characterised by the probability of detecting trajectory and average autocapture time. When the target moves, its distance from the radar station changes, leading to a change in the signal/noise ratio and the probability of detecting AT.

Aim. To assess the impact of a change in the probability of detection of a straight and evenly moving target at consecutive time intervals of radar observation upon the characteristics of trajectory detection during secondary processing of radar information.

Methods and materials. The research aim was achieved using the methods of mathematical statistics, including verification of statistical hypotheses, assessment of distribution parameters and theory of perturbations by small parameters. The ratio of the distance travelled by the AT during the review period to the target range at the initial moment of its detection was chosen as a perturbation parameter.

Results. Analytical expressions were established for the probability of detecting a straight-moving AT and the probability of detecting the trajectory of its movement at interval multiples during the study period. The study illustrated the probability of detecting AT moving away from radar by means of consistent radar observations with reduced signal/noise ratios and angles between the velocity vector and the AT vector radius relative to the radar. The increase in AT speed which causes the z parameter to change from 0.01 to 0.07 reduces the probability of AT detection from 0.727 to 0.52 and leads to a corresponding change in the probability of detecting the trajectory. If the observation time is reduced by one time interval, the probability of detecting the trajectory is from 0.03 to 0.04…0.07 for signal/noise 40 ratio and from 0.06 to 0.08…0.11 for signal/noise 25 ratio (with the probability of false alarm 10–4 ).

Conclusion. The resulting expressions allow for the calculation of directly moving AT trajectory detection, considering changes in the probability of detecting targets in successive time intervals of radar observations.

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