Exploiting the Link: Improving Satellite Communication through Higher Elevation Links

Most small satellites operations, including those in the CubeSat community, maximize the duration of single communication passes with ground stations, but, in doing so, do not maximize the total data transferred. In this paper we examine methods to maximize data download by waiting to begin transmission at a non-intuitive high elevation angle. This elevation angle reduces the slant distance and allows the link to be closed at a higher fixed data rate. Though the transmission duration is shorter, the total data downloaded is greater. We examine this method for a variety of pass configurations and compare it to distributions of passes for known ground stations around the world. The results of this study (analytic and numerical) are presented along with recommendations for strategies for maximizing the amount of data transmitted for a given satellite orbit. These methods rely on the ability to alter the data rate of a radio while on-orbit, enabled through the use of flexible-rate radios. We expand this study by examining the amount of data transferred for individual groundstations over the course of a year. It is shown that an optimal fixed data rate can be found such that the amount of data downloaded is maximized for the year. Finally, recommendations for radio development are given for the small satellite community.