A Study of the Relative Speed and Doppler Effects in Space-Based Networks

Abstract

In many space network architectures, such as those intended for the military, there will be numerous types of air, ground and sea terminals communicating with each other over a complex system consisting of both Geostationary Earth Orbit (GEO) and Low Earth Orbit (LEO) satellites. These architectures would require highspeed communication links to be established between GEO satellite pairs, and even a GEO and a LEO satellite. With relative speeds approaching or exceeding 8 km/sec., Doppler effects can play a significant role in SONET timing and synchronization, especially when one takes into account satellite repositioning, inclinations, and other perturbations and anomalies. 1 2The intent of this study is to analyze the relative speed and Doppler effects in space-based SONET networks. To this end, we start with a simplified kinematics model to analyze the worst-case scenarios. For the proposed model, we will find the locus of the maximal relative speeds, compute the associated Doppler effects at these maxima, and determine the amount of Doppler compensation necessary to establish and maintain SONET timing and synchronization at various links. Subsequently, we will look at effects of GEO satellite repositioning, possible GEO orbital inclinations (for geosynchronous orbits) and other second order deviations on the proposed model and conclude that the utilized model is adequate for our qualitative analysis.