The spacecraft consists of a number of systems and subsystems for different functions. It is generally divided into two categories: specialized systems and safeguard systems. The former is used to directly perform specific tasks; the latter is used to guarantee the normal work of the specialized system. Generally include: ① structural subsystems. It is used to support and fix the instruments and equipments on the spacecraft, make the subsystems form a whole, and bear the mechanical and space environment loads. It is generally composed of shells, frames, partitions and brackets. Temperature control subsystem. Used to ensure that the instrumentation in the space environment in the allowable temperature range. Commonly used temperature control materials and components, temperature control coatings, insulation materials, temperature control shutters, heat pipes, heaters and heat exchangers. ③ Power supply subsystem. It is used to provide electric power for the instruments and equipment on the spacecraft. It is generally composed of primary power supply, controller, power converter and cable network. The primary power supply includes solar battery, silver oxide battery, fuel cell and nuclear battery. ④ Attitude control subsystem. It is used to maintain or change the operating attitude of the spacecraft to meet the needs of the mission, for example, to make the camera lens point to the ground, to make the communication antenna point to a certain region on the earth, etc. Commonly used attitude control methods are Commonly used attitude control methods include three-axis control, spin stabilization, gravity gradient stabilization and magnetic moment control. ⑤ Orbital control subsystem. It is used to maintain or change the orbit of the spacecraft, usually powered by the orbit maneuvering engine and controlled by the program control device or remotely controlled by the ground measurement and control station. (6) Radio measurement and control subsystem. It includes three parts of radio tracking, telemetry and remote control on the spacecraft. The tracking part is mainly composed of a beacon machine and a transponder, which are used to send out signals so that the ground measurement and control station can track the spacecraft and measure its orbit. The telemetry section consists mainly of sensors, modulators and transmitters, which are used to measure and send various parameters of the spacecraft to the ground. Remote control part is generally composed of receivers and decoders, used to receive radio instructions from the ground measurement and control station, transmitted to the relevant subsystem implementation. (7) computer subsystem. Used to store a variety of programs, information processing and coordinated management of spacecraft on the relevant subsystems. (8) return subsystem. Used to ensure that the return spacecraft safe and accurate return to the ground. It is generally composed of braking rockets, parachutes, landing buffer devices, labeling devices and control devices. Manned spacecraft in addition to the above subsystems, there are also life support subsystems to maintain the life and work of the astronauts, as well as instrumentation, display and hand control, communications and emergency life-saving subsystems.