Elevation impact on signal to spectral noise density ratio for Low Earth Orbiting satellite ground station at S-band

Ground stations are part of any satellite network, providing communication with satellites. Low Earth Orbit (LEO) satellites are used for public communication and for scientific purposes. The communication quality depends on the performance of the satellite ground station, in addition to that of the satellite. Usually, LEO satellites communicate with ground stations at S-band. Ground stations can communicate with LEO satellites only when the satellite is in their visibility region. The duration of the visibility and so the communication duration vary for each LEO satellite pass over the ground station, since LEO satellites move too fast over the Earth. The range over the same satellite path depends on the look elevation angle from the ground station. The shortest range is achieved under maximal elevation of satellite´s path above the ground station. The range variation causes the free space loss changes impacting on link budget. For the downlink performance, of the greatest interest is receiving system signal to noise ratio (S/N) or (S/N₀). (S/N) depends on the last end receiving device bandwidth. In order to avoid the effect of the last end receiving device bandwidth, within this paper only the impact of elevation on signal to spectral noise density ratio (S/N₀) is considered.