Satellite bus

A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held.

Bus-derived satellites are less customized than specially-produced satellites, but have specific equipment added to meet 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.

Examples
Some satellite bus examples include:
 * Boeing DS&S 702
 * Lockheed Martin Space Systems A2100
 * Alphabus
 * INVAP ARSAT-3K
 * Airbus D&S Eurostar
 * ISRO's I-1K, I-2K, I-3K, I-4K, I-6K, and Indian Mini Satellite bus
 * NASA Ames MCSB
 * SSL 1300
 * Orbital ATK GEOStar
 * Mitsubishi Electric DS2000
 * Spacecraft bus of the James Webb Space Telescope
 * SPUTNIX TabletSat
 * SPUTNIX OrbiCraft-Pro

Components
A bus typically consists of the following subsystems:
 * Command and data handling (C&DH) system
 * Communications system and antennas
 * Electrical power system (EPS)
 * Propulsion
 * Thermal control
 * Attitude control system (ACS)
 * Guidance, navigation, and control (GNC) system
 * Structures and trusses
 * Life support (for crewed missions).