High Throughput Data Relay Satellite Link at Ka/Q/W Bands for Earth Observation Missions

Abstract

Captured data by earth observing low earth orbit satellites are downlinked to the gateways at very low data rates limited by the congested X and S bands. A data relay link by a geostationary orbit satellite was proposed to collect the captured data from several low earth orbit satellites from its higher altitude and feeds it to the gateways. A high throughput feeder downlink was achieved by migration to higher and less congested Q and W frequency bands aiming to achieve higher data rates. The achieved data rates by the modelled data relay links at Ka, Q and W bands were very promising in clear sky conditions never the less the satellite channel was an obstacle specifically at Q and W bands, where the satellite link showed a very poor availability and significantly deteriorated capacity. Hence propagation channel models were derived for each band and fade mitigation techniques were investigated and employed. The links at Q and W bands employed site diversity fade mitigation technique being the only possible strategy within the existing technology together with variable code and modulation. Selective, equal gain and maximum gain combining site diversity techniques were modelled and evaluated for three diversity scenarios for all the European earth observation programme gateways. The designed data relay link at Q and W bands achieved the high throughput data demand by Copernicus European Earth observation programme while maintaining the system's ground segment complexity. This solution could be extended to provide a near live streaming service which is limited by the low earth orbit satellites constellation design and number of geostationary orbit satellites.