ECS - Evolution on a satellite system design

Design changes and improvements in the European Communications Satellites (ECS) Program started in 1970 are outlined. The two major objectives were development of technology and expertise in Europe and implementation of a communications satellite system for Europe. The basic satellite design was hexagonal three-axis stabilized box with folding sun-tracking solar arrays and carrying 12 repeater chains. In 1975, the design of ECS was completely revised, with the main objective of providing maximum possible communications capability within the same basic satellite design and using the same TD 3914 launcher as an orbital test satellite. The major changes were adoption of a free-drift orbit inclination, an entire change of the spot beam coverage pattern, and a new repeater redundancy scheme. The future will show how reusable launchers may change the constraints on satellite system design.