Satellites consist of two functional blocks, the first block is the satellite bus, and the second is the payload.
What are the Components of a Satellite Bus?
A satellite bus, also referred to as a spacecraft bus or satellite platform, forms the core of a satellite. It carries and supports the primary systems and subsystems required for the satellite’s operation, while the payload, which varies depending on the satellite’s purpose and mission, is attached to the bus.
The main components of a satellite bus typically include:
Structural Subsystem
This provides the mechanical support for the entire satellite, including the payload and other subsystems. It is designed to withstand the stresses of launch and the harsh conditions of space.
Power Subsystem
This generates, stores, and distributes electrical power to the satellite’s various systems. Solar panels are often used to collect sunlight and convert it into electricity, while batteries store the power for use during periods when the satellite is in Earth’s shadow or during peak power demand.
Attitude Control and Determination Subsystem
This system maintains the satellite’s orientation and position in space, ensuring that antennas, sensors, and solar panels are correctly pointed. It usually consists of sensors to measure the satellite’s attitude and position, and actuators, such as thrusters or reaction wheels, to make adjustments as needed.
Thermal Control Subsystem
This regulates the temperature of the satellite to protect sensitive electronics and other components from extreme temperature fluctuations. It typically employs passive techniques, such as insulation, and active techniques, such as heaters and radiators, to maintain a stable temperature environment.
Propulsion Subsystem
This provides the capability to change the satellite’s orbit or maintain its position. Depending on the mission requirements, propulsion can include chemical, electric, or other propulsion technologies.
Communication Subsystem
This enables communication between the satellite and ground stations, facilitating the transmission of commands, telemetry, and payload data. The communication subsystem typically consists of antennas, transmitters, and receivers.
What Types of Payloads do Satellites Carry?
Satellites carry a variety of payloads depending on their specific mission and purpose. Some common types of payloads that satellites carry include:
Communication Payloads
Satellites designed for communication purposes carry communication payloads such as transponders, antennas, and amplifiers. These payloads enable the satellite to relay voice, data, and video signals between users on the ground.
Remote Sensing Payloads
Satellites designed for remote sensing carry sensors and cameras that capture images and data about the Earth’s surface, atmosphere, and oceans. These payloads are used for applications such as weather forecasting, environmental monitoring, and disaster response.
Navigation Payloads
Satellites designed for navigation carry payloads such as GPS receivers and atomic clocks. These payloads enable the satellite to provide precise location and timing information to users on the ground.
Scientific Payloads
Satellites carrying scientific payloads such as telescopes, spectrometers, and particle detectors are used to study the universe and conduct research in various fields of science.
Defense Payloads
Some satellites carry payloads for military and defense purposes, such as surveillance and reconnaissance equipment.
Technology
Overall, satellites rely on a variety of advanced technologies to carry out their various tasks and functions in space.
NASA regularly publishes a document that provides a comprehensive overview the state-of-the art technology for small spacecraft.
Assembling the Components
A satellite can be custom developed and manufactured, also referred to as bespoke, or can be assembled from standardized components from specialized manufacturers. Satellites were traditionally made bespoke. However, today it is possible for a satellite operator to contract for his satellite missions by selecting from a menu of standardized satellite buses and compatible payload modules. This is described in more detail in this article What is a Satellite Bus and Why is it Important?