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Satellite Communications

What is Satellite Communications?

Satellite communications (satcom) refers to any transmission of information and data such as voice, audio, video between any two points on Earth through a satellite. A communication satellite typically comprises a transponder, antenna, communication payload, switching systems, telemetry command, and control system. It is basically a microwave repeater-transponder orbiting in space. What it does is to amplify or increase the strength of a signal it receives, change its frequency band before relaying it to other locations known as terminals/stations on Earth. 

The Sun is the main energy source for satellites which explains the wings where solar panel arrays are mounted. Each array contains thousands of small solar cells. These solar arrays have to be big because only 20% of sunlight is actually converted to solar power.

 

 

Satellites are launched with 300kg of fuel in their tanks which can maintain their orbits for up to 10 years. The fuel is needed for space manoeuvres by firing thrusters to keep the satellite in positon to compensate for the moon’s gravity or atmospheric drag in the case of low-orbiting satellites. Some manoeuvres may require up to 20kg of fuel due to the speed the satellites are travelling – as much as 8.5 km/sec.

Communication satellites can range from as big as a small school bus to the size of a toaster, a handheld cube or even smaller. The weight varies from more than 5000 kg for larger satellites to less than a kilogram. The term small satellite or mini-satellite often refers to those with a wet mass (including fuel) between 100 and 500 kg; while microsatellite or microsat is usually applied to those with a wet mass between 10 and 100 kg. Smaller ones are classified as nanosatellites (nanosat also known as picosatellites) with those less than 500 grams sometimes referred to as femtosatellite (femtosat). Multiple nanosats are usually deployed in formation (also known as a satellite swarm) controlled by a larger ‘mother’ satellite which is linked to ground controllers.

  • Advantages of Satcom

    One of the key advantages satcoms has over terrestrial communication systems – such as landlines and undersea fibre optics cables – is the wider connectivity across borders, vast lands and wide oceans, as well as for mobile uses. 

    High amounts of data can be transmitted in which speed and uniformity in performance are better and reliable. As it is less vulnerable than other forms of communication, satcoms is often deployed during times of disasters and for defence purposes. By adding encryption technology, satellite networks can provide more secure connections than terrestrial networks, making it ideal for government, military and enterprise VPN (virtual private network) applications.

    Besides enabling wider global coverage, satcoms also has the advantage of scalability and fast deployment from the quick installation of Very Small Aperture Terminals (VSAT). These are two-way ground stations that can both transmit and receive data from satellites. These are essentially the satellite dishes seen on top of houses or office buildings. The “very small” refers to the size of the antenna reflector or dish, typically less than 3.8 meters in diameter.

    VSAT networks are ideal for providing connectivity to remote work sites such as exploratory drilling sites or vessels that need to relay daily logs back to headquarters. They are independent of local telecommunications networks, which makes them ideal as back-up to reduce business recovery risks. If the normal wired network goes down, businesses can continue using the VSAT network.

  • Types of Satellites

    Low Earth Orbit (LEO) satellites

    These are small satellites that orbit the Earth at a low altitude of 160-2,000 km and take as little as 1.5 to 3 hours to complete their orbit. Being closer to the ground, they are often deployed for high-resolution remote sensing or surveillance as well as communications for disaster relief and maritime operations. The short distance from the station means less power is needed to transmit data and lower latency (time between a signal being sent and received). This enables real-time interactive activities such as trading and banking or some video games. It usually requires a constellation of satellites and ground stations for effective communication. LEO satellites are growing in popularity due to their ability to offer increased bandwidth capacity at reduced operating cost, as well as low data latency. The drag in lower orbits gradually lowers the altitude of the satellite until it burns into the atmosphere at the end of their useful life.

     

    Medium Earth Orbit (MEO)

    These typically operated at altitudes of 6,000-20,000 km and are often used for defence industry applications and navigation systems that require GPS tracking and mobile telephone communications over a large global footprint. Good for interactive broadband transmission due to low power requirements and high bandwidth. Orbital period of 4-12 hours.

    Geostationary Orbit (GEO)

    These satellites are located at the highest altitude of 35,700 km or more and takes a day to orbit round the earth which means their positions are fixed relative to the Earth. They have a coverage of an area the size of continents and are hence often deployed for TV broadcasting and weather forecast.

    Satellite constellation

    This refers to a group of LEO or MEO satellites working in concert. LEO satellites are often deployed in satellite constellations as the coverage provided by each satellite covers a limited footprint, and hence many are needed to maintain continuous coverage over an area. Examples of satellite constellations include the Global Positioning System (GPS), Galileo constellation for navigation; Iridium and Globalstar for telephony services and RapidEye for remote sensing services.

    High Throughput Satellites

    These offer more through or bandwidth capacity – from 20 to 100 times – compared to than traditional satellites. The higher capacity is achieved by focusing multiple narrowly spot beams compared to traditional satellites which utilizes a broad single beam to cover wide regions or even entire continents. 

  • Satellite Frequency Bands

    Satellite Bandwidth refers to the amount of data that can be received, processed, and transmitted by a satellite. It is commonly expressed in megabits per second or gigabits per second (one billion bits per second). An analogy would be a river; the wider it is – the more water flows through the channel.

    Satellites transmit information within frequency bands with the higher frequency spectrum typically having wider bandwidths, but are also more susceptible to signal degradation due to the absorption of radio signals by atmospheric rain, snow or ice (known as rain fade). Most commercial satellites operate in C-band, Ku-band, Ka-band, S-band or L-band range. Of these, the C-band and Ku-band are the most commonly used by commercial satcoms services. 

    • L-band (1–2 GHz) is used for mobile applications such as Global Positioning System (GPS) carriers and satellite mobile phones employed in land, maritime and aerospace communications.
    • S-band (2–4 GHz) is used for weather radar, surface ship radar, and some communications satellites, especially those of NASA to communicate with the International Space Station (ISS) and space shuttles.
    • C-band (4–8 GHz) is primarily used for satellite TV networks, public switch networks (PSN), internet trunking and mobile feeder links. Commonly deployed in areas that are subject to tropical rainfall, since it is less susceptible to rain fade. The earth stations will have to be relatively large – typically 4.5 to 18 m in diameter. Inmarsat, Intelsat and SES are examples of satellite operators using this bandwidth.
    • X-band (8–12 GHz) radar frequency sub-bands are used in civil, military and government institutions for weather monitoring, air traffic control, maritime vessel traffic control, defence tracking and vehicle speed detection for law enforcement.
    • Ku-band (12–18 GHz) The higher power compared to C-band allows for smaller earth stations (4m or less) to be deployed. It is generally used for internet trunking, satellite news gathering, video distribution, rural telephony and fixed services such as VSAT networks popular with corporates and small businesses.
    • Ka-band (26–40 GHz) With higher power compared to Ku-brand, it is used for interactive, high-bandwidth and high-resolution services such as high-speed Internet, videoconferencing and multimedia applications

The Convergence of Satcom and 5G

Satcom will likely play an increasing role in upcoming 5G mobile networks in the coming years. Firstly, while the coverage provided by cellular networks has expanded, there are still many places where coverage drops off dramatically, especially in remote regions. This is where satellite’s longer range and bigger footprints can be deployed to complement 5G in areas where setting up terrestrial networks for enhanced broadband services is simply too costly.

Secondly, in the digital age of the Internet of Things (IoT), there will be a need for increasingly higher capacity and better connectivity to handle the voluminous data from millions of smart devices and sensors embedded in urban infrastructures and unmanned vehicles, as they become more prevalent in smart cities of the future.

An intelligent 5G network will need to automatically engage satellite links — seamlessly and quickly – in order to offer end-users with consistent, reliable, high performance experiences. Service providers will have to determine how best they can deliver – whether it’s through satellite, terrestrial or mobile networks, or all a combination of them – to their customers.

ST Engineering is an industry leader in the aviation and maritime segments of the global satcom business. It is the largest enterprise vendor for Very Small Aperture Terminals (VSAT) systems and hardware with more than a third of the global market share.

The increasing use of High Throughput Satellite (HTS) which allows service providers to deliver connectivity to specific locations, enabling them to tailor their data services will be another growth driver. It will open new opportunities and capabilities in many vertical markets including aviation, maritime, connected cars and Smart Cities applications.

ST Engineering is well poised to ride these growing opportunities to shape the future of how the world connects. 

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