Satellite Subsystems
Given the complexity of a satellite, they are often split of multiple specialised subsystems. Each individual subsystem is designed to perform a specific set of functions that contribute to the overall mission of a satellite.
Attitude Determination & Orbit Control System (AOCS)
The attitude determination and orbit control system, or AOCS, is responsible for controlling the satellite's orientation (attitude) and orbit. Star trackers, gyroscopes, and magnetometers are used as sensors to determine the satellite's current attitudem while actuators like reaction wheels, gyroscopes, and magnetic torques are used to change it.
Payload
The payload subsystem houses mission-specific instuments and equiptment. For example, in Earth observation satellites, the payload might consist of high-resoultion cameras, spectrometers, and radar. In communication satellites, the payload usually consists of transponders that relay signals between ground stations.
Command & Data Handling System (CDHS)
The command and data handling system, or CDHS, is the "control center" of the satellite. It includes a centeral computer, data storage devices, and a command decoder. This subsystem is able to interpret and execute commands received from ground control, manage task scheduling, and oversee data collection and storage.
Communications (COM)
The communications subsystem serves as the primary interface between the satellite and ground control (and sometimes other satellites). This system contains equipment such as antennas for transmission and reception, transmitters to send data to Earth, and receivers to collect incoming data from ground control. Signal processing units handle the modulation and demodulation of data, as well as the encoding and decoding of data.
More advanced communication subsystems may employ adaptive modulation techniques, beamforming, and onboard data processing to improve reliability and data throughput.
Telemetry Subsystem
The telemetry subsystem is crucial for monitoring the health and performace of the satellite. It collects data from sensors embedded in other subsystems and transmits this information back to ground control.
References
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