Low Earth Orbit Communication Research Articles

Russian low earth and elliptical orbit satellite communication systems: The competing projects

A number of Russian projects for low earth and elliptical orbit communication satellite systems are struggling for the status of a federal system, which means governmental support. The systems taking part in this competition are reviewed in the light of the published parts of the Russian Federal Space Program. It is shown that some systems included in the plan are old-fashioned and new rivals not included in the Program have a greater chance to become feasible. The current situation concerning Russian non-geostationary communications satellite systems will be examined and their histories, technical specifications, state of readiness and commercial viability discussed. The impact of western systems and companies as collaborators or competitors is assessed.

LEO Satellite System and Communication

The role of Mobile Satellite Services (MSS) shall be immense in the era of the of Personal Communication. Low Earth Orbit (LEO) satellites shall be vehicles for MSS. LEO communication shall be cost effective, wide area and total wireless communication to support man-machine mobility. This may make Personal Communication real revolutionary rather than evolutionary. In the paper, we have reviewed the LEO satellites systems and communication under different ongoing and proposed projects.

Dynamic Momentum BIAS for Yaw Steering

A combination pointing requirement for a low earth orbit communication satellite antenna system and sun orientation for power accumulation can be met with a momentum biased attitude control that maintains nadir pointing and sustains yaw steering simultaneously. During time intervals when direct yaw sensing is not available, momentum bias systems have successfully been used to provide stabilization for nadir pointing satellites. Such systems, however, restrain vehicle yaw rotations to small perturbations about zero without direct yaw sensing. Those systems use a momentum wheel with fixed alignment along the spacecraft pitch axis, horizon sensors to detect pitch and roll attitude errors and mass expulsion devices for actuation. Such systems preclude yaw steering. This paper develops a control algorithm that maintains the advantage of gyroscopic momentum bias stabilization in addition to a controlled open loop yaw steering.