There has been a rapid growth of Low-Earth-Orbit technology, which is simply known as LEO, constellation technology in recent years. This was triggered by with start of the new space revolution.
Despite this rapid growth, people still have a better understanding of the LEO constellation. They are not quite so conversant with the new satellite innovations and technologies. So there is a need to give people more insights about this innovation and technologies.
The LEO industry is not slowing down any time soon, in fact, the industry is projected to skyrocket in the near future due to the advancement and arising of new technologies which are being utilized in the ground-breaking opportunities.
The LEO industry can also be referred to as the Fourth Industrial Revolution or Space Revolution.
Here you are about to get some great information about the LEO industry, as well as the technology and the innovation that has been utilized in the industry.
The purpose of the large LEO constellations.
The large LEO constellation is there to serve one obvious purpose, which is to have a constant 100% global coverage. Data shows that there are slightly less than 4 billion current internet users in the world, and this means that another 4 billion people do not have internet access.
This a problem that the new developments in the LEO satellite constellations are seeking to address. While the new LEO constellations have been developed with the intention to achieve or get closer to 100% internet access, they also want to provide 100% coverage in certain areas such as the constant worldwide surveillance and imaging.
- There are many smaller LEO satellites that are used. These numerous smaller satellites are launched to the low-earth-orbit so that they can work together and operate effectively as one large satellite. On the other hand, the large constellations are launched to provide a global coverage given their location relative to earth.
Traditional satellites have always been GEO satellites. GEO means Geosynchronous Equatorial Orbit, which is a circular orbit 35,786 kilometres above the earth’s equator and follows the direction of the earth’s rotation.
The traditional satellites, being GEO satellites are, therefore, fixed at a position on the GEO belt which moves with the earth as it rotates. Since they are placed at a larger distance than the LEO satellites they are able to cover larger areas of Earth- the land mass and water bodies.
Traditional satellites are associated with several limitations as opposed to LEO satellites. The limitations include:
- GEO satellites do not offer coverage around the polar caps.
- The entire frequency spectrum is shared across the entire coverage area.
- The mobile antennas on the ground that point to a GEO satellite experiences limitations and challenges. This happens as the mobile antenna moves further away in longitude from the orbital slot location.
Currently, it is not clearly known what frequency spectrum will be used by the LEO satellites. However, it is confirmed that if they were to use the C-band, it would be necessary to use larger antennas on the ground in order to support the C-band LEO constellation. Therefore, this would present some limits to the new LEO constellations in terms of providing global internet access to anyone at home across the globe.
C-band is currently widely used, thus it would not need interferences since it would lead to some problem. It is always known n that the higher the band, the more bandwidth is available. Additionally, the higher the frequency the less widely it is used. This leads to less interference.
The best thing about selecting the right frequency band to be used in any constellation is that there are guidelines that are set and frequency spectrums that are allocated which help in the decision about which bands can be used and which cannot be used for various applications.
The frequency spectrum that is being used in the LEO satellite is based on approval from government ran regulatory bodies such as the Federal Communications Commission (FCC) and the International Telecommunications Union (ITU).
The spectrum that any company chooses to use in their development of their LEO satellite constellation should not interfere with any existing satellite constellation systems and terrestrial networks. This can be ensured by filing an application to get an approval, which can also be put in the public domain so that users can raise concerns if any.
Some of the LEO constellations such as the Leo sat and OneWeb filed with the FCC for approval to use the Ku-band for the RF links between the satellites and the user terminals, and Ka-band for RF links between the satellites and gateway earth stations. Similarly, SpaceX had filed for the same in 2016, but later in the Spring of 2017, they refiled for the approval to use a V-band solution for all satellite uplinks and downlinks.
In 2015, Elon Musk announced the SpaceX Starlink program which would revolutionize the satellite side of things. Thus in 2016, SpaceX filed the FCC application, which wanted an approval for 1600 satellites to go up until 2021. The satellites were later reduced to 800.
These satellites would fly between 1,100 km and 1,325 km above the ground, and go round the Earth in 83 distinct orbital planes. The satellites will communicate with one another via onboard optical links such that data could be bounced along the sky rather than coming back to the ground.
On the ground consumers will be required to mount a new terminal with electronic antennas that will automatically connect to whichever satellite that is offering the best signal. As I stated earlier, LEO satellites move relative to the Earth, thus the system will switch between the consumers and the satellites every 10 minutes or so.
There will be thousands of satellites in the sky, therefore, this means that there will be not less than 20 available to choose from.
The communication of these satellites will be based on two frequency bands: Ka and Ku. These bands appear on the radio spectrum, but at higher frequencies. Ka-band has higher frequencies between 26.5GHz and 40GHz, while Ku-band has frequencies ranging from 12GHz to 18GHz.
In February, SpaceX actually launched its first two Starlink satellites which are shaped like cylinders and have solar panels for wings. They are referred to as Tintin A and B which were confirmed to be successfully communicating. If these prototypes continue to work, other numerous satellites would be launched to join them in 2019. If this system will operational they will replace the decommissioned satellites, in which they would be instructed to lower their orbits such that they would fall toward Earth and burn up on re-entry, and in the process, this would help reduce space debris.
Latency is the amount of time it takes information to travel from your computer to its destination and then back to your computer. The GSO satellites have a latency of about 700 milliseconds which is quite high compared to the LEO satellites.
The LEO satellite is much closer to the users and that’s why SpaceX and LeoSat have chosen to develop their LEO satellites. They are anticipating a latency of about 20 to 30 milliseconds. So the latency that is associated with the LEO satellites is very low compared to other satellites.
However, the LEO system actually is a trade-off such that you get a lower latency but the system is complex. You will have to launch hundreds of satellites in order to ensure you have a complete constellation. Also, you need to have an antenna system that is able to track them.
Competition in the LEO system
There are about 12 companies that are actively taking part in the development of LEO constellation the Richard Branson’s OneWeb is actually launching its satellites, and their services are expected to start in 2019. They are also planning to launch several more constellations in 2021 and 2023, where they are targeting 1,000 terabits by 2025.
There is also Telesat which operates GSO satellites but has plans on LEO system for 2021 which will feature optical links with expected latency of 30 milliseconds to 50 milliseconds.
LeoSat is planning to launch its first round of satellites in 2019 which would go through to 2022. These satellites will move round the Earth at 1,400km high. They will connect to other satellites in the mesh through optical communications and beam information up and down in Ku-band.
LeoSat is actually setting up 78 satellites that weigh about 1,200Kg featuring four panels and four lasers that will help connect to other neighbouring satellites. This connection is very important as it will help satellites to pass data along faster.
Every company that is pursuing the LEO system, has its own innovation and technology which might be more supreme than the other. One thing to note is that these companies have different target markets and they are actually working together in various aspects so that they can reach their target markets. Some are targeting the planes, ships and military bases while others are focusing on developing nations or rural consumers. However, the ultimate goal of all these companies is one: to provide internet access to all the areas where there is none or where it’s insufficient at a cost low enough to sustain their business model.