Prediction of the noise immunity of the Cospas-Sarsat satellite system based on the results of GPS-monitoring of small-scale ionospheric disturbances

A method for predicting the interference immunity of the satellite system Cospas-Sarsat under conditions of small-scale ionospheric disturbances has been developed based on the results of GPS-monitoring of small-scale fluctuations in the total electron content of the ionosphere. Within this method, the problem of developing a technique for determining the dependence of the probability of erroneous signal reception in satellite communication systems on the choice of the carrier frequency and the signal-to-noise ratio at the receiver input, as well as fluctuations in the total electron content of the ionosphere determined by GPS-monitoring methods on the navigation path of radio wave propagation, has been solved. Based on the obtained dependence, the features of the structure and algorithm of the interference immunity prediction complex of the satellite system Cospas-Sarsat based on GPS-monitoring of small-scale fluctuations in the total electron content are justified. These features include that the inclination angle of the radio wave propagation path in the satellite radio line is initially unknown but can be calculated after solving the problem of determining the coordinates of the radio buoy at the receiver of the spacecraft. Furthermore, a hardware and software implementation of the interference immunity prediction complex of the satellite system Cospas-Sarsat based on the results of GPS ionospheric monitoring has been developed. Experimental results have been obtained regarding the change in the probability of erroneous signal reception in the Cospas-Sarsat satellite system during specified signal-to-noise ratios under conditions of small-scale ionospheric disturbances and increasing levels of ionospheric scintillation. Based on this, estimates of the energy reserve have been obtained to ensure an acceptable error probability in the Cospas-Sarsat satellite system for various values of fluctuations in the total electron content of the ionosphere (0.01 TECU; 0.015 TECU; 0.03 TECU) and levels of scintillation index (0.35; 0.55; 0.85). It has been established that to maintain an acceptable level of signal reception error probability during the formation of small-scale ionospheric disturbances over a 4-minute period, accompanied by an increase in the scintillation index to a moderate level (0.55), an increase in the energy reserve of 4.6 dB will be required. In the event of strong scintillations lasting for 20 seconds (at a level of 0.85), it will be necessary to raise the energy reserve of the Cospas-Sarsat satellite system by 13 dB.