RESISTANCE TO SATELLITE FAILURES OF LEO COMMUNICATION SYSTEMS

This paper presents a satellite failure analysis for Low Earth Orbit (LEO) constellations with continuous global coverage. Worst case failure configurations are identified for polar orbit constellations and the coverage performance deterioration 'is evaluated by computer simulations. Then, the probability of having a number of satellite failures in a given constellation is evaluated as a function of satellite reliability. It is shown that the probability of occurence of a worst case failure configuration is very low, and that the most probable configuration is a uniform distribution of the defective satellites. As a consequence, the maximum tolerable number of satellite failures occuring simultaneously in a constellation can be determined, for a specified minimum coverage performance. Therefore, assuming a given launch delay for the replacement of satellites, one can estimate the necessary overall satellite reliability. Finally, a constellation deployment and maintenance strategy based on those results is proposed. 1