A satellite bus or spacecraft bus is a general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of the spacecraft, usually providing locations for the payload (typically space experiments or instruments).
Bus-derived satellites are opposed to one-off, or specially produced satellites. Bus-derived satellites are usually customized to customer requirements, for example with specialized sensors or transponders, in order to achieve a specific mission.
They are commonly used for geosynchronous satellites, particularly communications satellites, but are also used in spacecraft which occupy lower orbits, occasionally including low Earth orbit missions.