Some of the best and most up-to-date communication satellites in the world are designed and built in Stevenage in Britain. With exclusive access to specialist manufacturer Astrium, this program shows step-by-step how to assemble one of the most complicated machines in the world. The team is followed as they construct a massive communication satellite; from the inner carbon-fibre skeleton to the fuel tanks and engines. At the Portsmouth site, the electronic 'payload' is built and then tested. It has to operate for a minimum of fifteen years - guaranteed, and so precision is everything; these machines are built inside rooms cleaner than the cleanest operating theatre. Once the satellite is built and tested, it is sent to France where solar arrays and antenna dishes are added before it is boxed up and sent for launch in French Guiana in South America. Finally, there is the tense countdown to lift-off - the most dangerous moment of the satellite's life.