Wireless communication technology used between subsystems in a micro-satellite design can be quite effective in developing small satellite systems.
Some apparent advantages here include fast assembling, integration, and testing, which are not present in traditional designs that use the conventional wired bus.
In this article, we will look in detail at wireless satellite buses. We will also investigate how and why a satellite bus can be used in micro designs.
What Is A Wireless Satellite Bus?
In 2004, the US launched the tactical satellite program or the TacSat series to focus their development of small satellites with high launch speeds and quick development cycles.
Since there was already a rise in competition in the space industry, rapid testing, integration, and assembly held great significance. Therefore, the cumbersome and complex wired communication interfaces and cables stood as barriers to developing small devices.
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Since all the subsystems to the satellite bus details will traditionally be connected to form a single point, it can potentially prove a threat to the safety of the satellite. Therefore, the idea to replace the traditional wired bus with wireless network technology was proposed in 2006 at the 57th International Astronautical Congress.
Later, this technology caught more attention, and soon the commercial application protocol was proposed for wireless communications.
How Do They Work?
Wireless satellite buses use radio waves to communicate with the satellites that are orbiting the Earth. The communication starts with the satellite and travels through the modem and satellite dish to receive and send data to other devices in space. The data also travels to the Earth’s ground stations, known as network operations centers.
What Are The Applications?
Current applications of wireless satellite buses primarily focus on providing data and voice connectivity worldwide. Most systems utilize inter-satellite links, while others prefer using the ‘bent-pipe’ architecture. Here are some reasons why to use satellite buses:
The earliest attempts at establishing inter-satellite networking have shown the benefits and feasibility of using inter-satellite communication in small devices. The recent developments in satellite bus types are now focusing on adopting commercial off-the-shelf (COTS) technologies that can be used in these satellite networks.
Let us take an example. The Iridium satellite constellation is one of the most well-known satellite constellations that utilize inter-satellite networking. This particular constellation is used to provide satellite-based phone services in all parts of the world.
Some wireless technologies used in this network link include the Quadrature phase-shift keying, the Time Division Multiple Access, and Frequency Division Multiple Access.
With the help of this satellite bus network, phone calls can be done directly between satellites instead of having to depend on ground-based repeaters, thereby cutting the total cost of the phone call.
Another great example is the Cisco Router, orbiting the low Earth orbit. A Cisco 3521 mobile access router was fitted on a satellite to verify whether this COTS router could work in space. It was launched in 2002 and continues to demonstrate that the COTS technology can work for modern satellites with minor modifications.
The bent-pipe networking was considered one of the first contenders for networking systems before inter-satellite networking even came into the picture.
For instance, the Internet on airplanes is a great example. With the help of the bent-pipe architecture, airplanes can provide internet access to in-flight customers. Apart from online work and entertainment, the Internet would allow people to continue with their daily activities in flight. The technology can also be used to provide medical consultations in flight.
What Is The Disadvantage Of Wireless Satellite Bus In Micro-Satellite Designs?
Such technology is often used to reach remote areas. In most cases, these areas do not have the physical infrastructure like fiber cables, telephones, or wireless radio connections. Therefore, these wireless satellite buses are often used as alternatives to wireless radio internet technology.
As we have seen above, such an internet connection is a two-way street – the user will have upload and download capabilities, similar to traditional wireless technology.
However, the difference here is that wireless satellite buses work in an asymmetrical pattern, which means that the download speed will often be faster than the upload speed.
This is compared to a standard optical connection, where the upload and download speeds are symmetrical or the same; therefore, you will be able to get a lot of work done with proportional systems like operating VOIP services, sharing files, etc. Wireless satellite buses on satellite designs will struggle with the asymmetrical load.
Apart from the latency problem, there are also some other significant issues. For instance, the cost related to installation and maintenance is far too expensive.
Therefore, such technologies are only used in industries where there is no requirement for external infrastructure, like air travel or shipping. Alternatively, they can also be used by the military to manage sea, land, and air forces remotely.
Thanks to the recent developments in space technology, spacecraft controls, and design, the boundaries of satellite wireless networking are being pushed further. Replacing the cables with wireless links can significantly reduce the weight of the satellites and, subsequently, launch costs.
It can also increase the focus on modularity, which will divide the satellites into smaller functional units that will be able to network wirelessly. If it is successful, the space devices will start behaving as a group using the inter-satellite wireless networks.
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