Building a spacecraft
A satellite is made up of two main parts: a platform (or bus) and a payload (instruments or experiments).
The platform is the basic metal structure. This has to be strong, but light. It includes the framework around which everything is built and the various spacecraft systems – thrusters, main engine, fuel tanks and power supply. The payload includes the equipment to communicate with the ground, as well as cameras and other scientific instruments.
The parts of a satellite are made in many different places. They are all sent to one centre, where they are assembled and tested in special clean rooms. Only then is the spacecraft sent to the launch centre.
Since there are no garages in space, many satellites carry their own 'spare parts'. If a breakdown occurs, ground controllers can order the spacecraft to switch to a back-up piece of hardware.
Last update: 10 December 2004