Satellites are no simple invention. They have been a breakthrough technology in discovering much about our planet, the other planets in our solar system, and the rest of our vast universe. However, many people are clueless about the components of satellites since they can be a little complicated. After all, a satellite bus is a complex system that houses equipment for monitoring, capturing, and withstanding complex journeys.
Satellites and Their Components
A satellite is any object that constantly orbits the planet. Different planets have their own natural ones, just like our Earth has the Moon as its natural satellite. However, in this case, we refer to the man-made spacecraft that orbit the planet and collect necessary data. Such a “device” consists of the satellite bus and the payload. What are these components? And how does the satellite bus work, or what are the functions of the payload? Let us answer these questions.
Payload is essentially what makes up a satellite and refers to its instruments needed for a specific space mission. For instance, the Earth Observation satellite has a camera as its payload, which captures pictures of the planet as needed. Similarly, remote sensing systems have radar or some other sensing equipment as their payload.
No matter how necessary a payload is, the essential component of any satellite is its bus. It makes up the structural base of the spacecraft, and it holds the payload along with all the scientific instruments necessary for a space mission.
Much like how a simple city bus transports passengers, a satellite bus transports the payload. The payload can differ depending on the mission. However, the structure of a bus remains the same for almost all devices. Let us dig deeper into satellite bus details.
A satellite bus comprises several subsystems, and all these subsystems have their own functions and purposes. For instance, a typical bus is made up of structure blocks, electrical power, thermal control, tracking and commanding, attitude control, and telemetry.
The electrical power subsystem offers power for the technology, whereas the thermal subsystem maintains the temperatures of the different components inside it. Similarly, the attitude control subsystem of a satellite panel determines its precise position, along with the direction in which it must observe.
However, one of the most critical subsystems for any satellite bus is the structure panel or the structure subsystem.
Functions of the Structure Panel of a Satellite Bus
So, what is the structure of a satellite bus, or what are its functions? The structure subsystem supplies the mechanical structure required to endure launch vehicle forces, orbital movements, and loads given by landing into the Earth’s atmosphere or another celestial body.
The structural subsystem comprises the satellite’s basic structure and holds all of its hardware, such as the payload equipment. The structure, which can take numerous forms depending on the mission objectives, must be built to reduce bulk while still surviving the tremendous stresses placed on it during launching and the brief journey to space.
The structural subsystem’s tasks include enclosing, protecting, and supporting other satellite subsystems and providing a mechanical link with the launch system. These tasks are critical during spacecraft construction, handling, and transit from the production site to the launch site. Mating, along with attachment sites, for subsystem parts like batteries, electronics modules, propellant tanks, and so on are provided by structural members.
The structure should also withstand the strains and pressures encountered during analytical procedures, launch, perigee, apogee firings, boom, solar array, and antenna deployment. Vibrations and noises can be powerful when the satellite is subjected to high gravitational forces during the launch. Acoustic noise is at its peak during the initial phases of the launching. The noise is carried by the air from the rocket motors via the housing and inside the spacecraft.
As the engines drive the satellites to the high speeds necessary for entry into orbit, steady loads are transferred through the structure. The rocket engines transmit a broad array of vibrations through the spaceship supports. The separation ring and other pyrotechnic devices provide potent shocks to the structure.
The loads on the satellite are substantially decreased inside the zero-gravity atmosphere once it has reached its final orbit location, but the requirements for alignment are more stringent. The developer must meet all needs while minimizing structural bulk and expense while keeping the likelihood of failure near zero.
The satellite will be exposed to brutal circumstances during its lifespan. Mechanical strains, vibrations, heat shocks, radiation, and a chemical and particle environment. The materials selected for the structural subsystem meet the yield standards, strength, toughness and hardness, specific stiffness, ductility, creep resistance, thermal expansion, and melting point.
Importance of the Structure Subsystem
As seen, the structure subsystem has vital importance regarding a satellite bus. It considers aspects of any space mission and forms the rudimentary basis for any bus. It communicates with launch vehicles and satisfies the parameters of those launch vehicles.
Moreover, the launch vehicle is subjected to significant degrees of acceleration and tremors — conveyed to the payload on the satellite. Launch loads include vibration, static, and acoustic loads, all of which impose rigorous restrictions on the spacecraft’s construction.
The structural subsystem ensures that the satellite can withstand all these loads during the launch and that all its parts are stable and operational after the launch. Hence, it can be concluded that the structural subsystem is the elementary part of satellite bus systems that looks over the workings of the other subsystems.
The design of satellites is becoming more complex with the growing demands of space technology. Regardless, the structural panel of a satellite bus offers several roles and looks over the components to ensure it reaches the launch site safely.