Beyond the horizon ionospheric propagation experiment from an equatorial orbiting satellite to a middle latitude station

Abstract

Results of the long range propagation experiment carried out with the HF radio signals emitted by the San Marco 2 satellite, and received at the Florence station, Italy, are presented. The satellite, launched in April 1967, had a low equatorial orbit with a perigee of 204 km and an apogee of 632 km. From June 26, for a period of 11 days, an emission on 20.005 MHz was utilized for the experiment. Relative reception occurrence observations are presented as a function of subsatellite-station range, satellite local time and ground station local time. Due to the orbit and station position, the explored ranges are 5000–15,000 km. During the total of 172 orbits, the signal was received at the Florence station (43°48'N; 11°12'E) for 82 per cent of the orbits from ranges of 5000–10,000 km and 51 per cent of the orbits from ranges of 10,000–15,000 km. A typical reception occurrence of the order of 70–80 per cent was found at both satellite and station sunset (with satellite at low altitude) over ranges of about 10,000km. During the experiment, some measured values of path losses vary between 132 and 147.5 dB. Comments are given on the factors influencing the possibility of ionospheric long range propagation.