Clear-Sky Availability for Satellite Communications in a Subtropical Region—Australia

Cloud cover provides a significant difficulty for effective ground-to-satellite optical communication. While the Australian continent is positioned in the midlatitudes and is the second most arid continent in the world, there is not any location that can achieve year-round, 24-h, clear-sky communications. In order to achieve a high level of clear-sky availability (greater than 90%) in Australia, multisite networks (site diversity) will perform better than any single site. In considering the global demand for weather-resilient and high-bandwidth communications, it is important to have networks that also permit cross-hemisphere linkages. In the Southern Hemisphere, Australia's longitudinal extent offers a significant siting advantage when compared to South Africa and South America. In this research, we identify this advantage with selections of several combinations of sites. Lowly correlated spatially well-separated sites with low amounts of cloud are ideally suited for inclusion in ground station networks to increase the probability of clear-sky communication opportunities. Many sites across Australia, being well separated spatially, are well suited to achieve these selection criteria. The selected spatially separated sites across Australia were prescreened for low cloud cover levels using a recent decadal satellite dataset. Of these selected sites, seven were chosen to participate in an investigation of multisite networks. Approximately two-thirds of the two-site network combinations analyzed achieved an average clear-sky probability greater than 0.90. Combinations containing the site at Learmonth performed best. Any combination of three sites (from the seven analyzed) achieved an average clear-sky probability greater than 0.94 with some combinations as high as 0.99.