ROLE OF RADIATION-HARD SOLAR-CELLS IN MINIMIZING THE COSTS OF GLOBAL SATELLITE COMMUNICATION-SYSTEMS

An analysis embodied in a personal computer program is presented, whic h quantitatively demonstrates how the availability of radiation hard-s olar cells can help to minimize the cost of a global satellite communi cation system. An important distinction between the currently proposed systems, such as lridium, Odyssey and Ellipsat, is the number of sate llites employed and their operating altitudes. Analysis of the major c osts associated with implementing these systems shows that operation a t orbital altitudes within the Earth's radiation belts (10(3)-10(4) km ) can reduce the total cost of a system by several hundred per cent,(1 ,2) so long as radiation-hard components, including solar cells, can b e used. A detailed evaluation of the predicted performance of photovol taic arrays using several different planar solar cell technologies is given, including commercially available Si and GaAs/Ge, and InP/Si whi ch is currently under development. Several examples of applying the pr ogram ave given, which show that the end-of-life (EOL) power density o f different technologies can vary by a factor of ten for certain missi ons. Therefore, although a relatively radiation-soft technology can us ually provide the required EOL power by simply increasing the size of the array, the impact upon the total system budget could be unacceptab le, due to increased launch and hardware costs. In aggregate, these fa ctors can account for move than a 10% increase in the total system cos t. Because the estimated total costs of proposed global-coverage syste ms range from $1 billion to $9 billion, the availability of radiation- hard solar cells could make a decisive difference in the selection of a particular constellation architecture.