What is a satellite bus?
The satellite bus (or spacecraft bus, or service module) is the generic, reusable platform that hosts a mission-specific payload. Think of it as the satellite's infrastructure layer: it provides everything the payload needs to operate in space — power from solar arrays and batteries, pointing accuracy from attitude control systems, thermal regulation, data handling, and the radio links to communicate with the ground.
Key subsystems
A satellite bus integrates six primary subsystems. The power subsystem generates electricity from solar arrays and stores it in lithium-ion batteries for eclipse periods. The ADCS (Attitude Determination and Control System) uses star trackers, gyroscopes, magnetometers, and reaction wheels or thrusters to point the satellite with arc-second precision. The propulsion subsystem uses chemical or electric thrusters for orbit raising, station-keeping, and deorbit. The thermal control subsystem maintains electronics within operating temperature using radiators, heat pipes, and multi-layer insulation. The on-board computer (OBC) runs the flight software that coordinates all subsystems. The TT&C subsystem handles communication with ground stations.
Bus standardisation and smallsat revolution
Standardised bus platforms — Airbus OneWeb satellite bus, Boeing 702 for large GEO, Surrey SSTL-150 for smallsats — dramatically reduce cost and schedule risk compared to custom designs. The CubeSat standard (10×10×10 cm units) created a commodity market for small bus components, enabling university teams and startups to build functional satellites for under $1 million. Modern LEO constellation satellites are designed as expendable, mass-produced buses with 5–7 year lifetimes.