Revolution in Satellite Communication : Most of our work in daily life depends on some kind of satellite. Satellite communication nowadays makes all our needs possible which were not even possible to imagine before - whether you make international calls or check the weather, keep an eye on enemy countries or watch TV from home. Different types of tasks are assigned by different types of satellites. We all use navigation in our mobile or your phone shows you the way, many such tasks depend on satellite. In this article we will discuss what is satellite communication? and importance of satellite communication in human life.
The word 'Satellite' widely know as artificial satellite. A satellite is a machine built and installed by human efforts, which was built for different purposes and placed in Earth's orbit. This machine is called artificial satellite, any artificial satellite revolves around the earth like natural satellite moon. Now many telecom industries have started providing commercial internet service through satellite, due to which the internet speed has become very good.
What is Satellite Communication?
First of all let's try to know what is satellite, Satellites rotate in the Earth's orbit due to their rotational speed and remain unaffected by the force of gravity. A satellite required the speed of 11.2 kilometers per second is to get out of the force of gravity. This is the reason why satellites float in the air in space.
Artificial satellites uses to provide a communication link between the different point on earth and the satellite. An important role played by Satellite Communication in the global telecommunications system. Approx. more than 2,000 artificial satellites revolving about the Earth, that Satellite relay digital and analog signals carrying all types of data like video voice data and internet services from one or several locations around the world.
There are TWO main components of Satellite communication: First is the ground segment, which includes fixed or mobile transmission, reception and accessories, and other is the space segment. which is mainly satellite itself. A typical satellite link arrange to provide the transmission signal from an Earth station to a satellite. Signals received by the the satellite and amplifies the signal and it send back to Earth, Earth stations and terminals received the signals and re-amplified. Signals received at ground by direct-to-home (DTH) satellite equipment and other devices like- mobile reception equipment.
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The exciting journey of satellite communication
Hypothesis of satellite communications via a satellite first appeared in a short story article, "The Brick Moon", author- Edward Everett Hale and published in The Atlantic Monthly in 1869–70. It would not be wrong to say that it was not just an idea, but human being got the direction to turn his fantasies into reality.
The story explained the construction and launch of a satellite 200 feet in diameter and made of bricks into Earth orbit. Brick Moons assisted sailors in navigation, as people jumped up and down on the surface of the satellite to send Morse code signals back to Earth. A 27-year-old Royal Air Force Officer Arthur C. Clark given the first practical concept of satellite communication.
This first practical concept was published in the issue of Wireless World in the October 1945. Clarke, who later became an accomplished science fiction writer. He was proposed that a satellite at an altitude of 35,786 km above Earth's surface would be moving at a speed similar to the Earth's rotation.
Satellite will remain in a fixed position relative to a point on Earth at this altitude. Now this orbit is known as "geostationary orbit". This is ideal for satellite communications, a ground antenna without tracking its position can point a satellite 24 hours a day.
Radio Coverage was calculated by Clark that three satellites located at equal distances in geostationary orbit would be able to provide radio coverage that would be nearly worldwide, with the sole exception of a few polar regions.
The first artificial satellite, Sputnik-1, was successfully launched by the Soviet Union on October 4, 1957. Sputnik-1 diameter was only 58 cm, situated four antennas in sputnik-1 sending the low-frequency radio signals at regular intervals. Then the race to send artificial satellites into space on a global scale started.
Sputnik-1 orbited Earth in a elliptical orbit, to complete one revolution it take 96.2 minutes. Only 22 days it transmitted signals until its battery was exhausted and it stayed in orbit for only three months, but this being the first launch of the Sputnik-1 satellite started a race between the Soviet Union and the United States.
The first time sound signal was relay by satellite was launched on December 19, 1958, from Cape Canaveral, Florida, by the US government's Project SCORE (Signal Communication by Orbiting Relay Equipment). It broadcast a tape message conveying "peace on earth and goodwill to men everywhere". "From the US President. Dwight D. Eisenhower.
John Pierce a American engineers of Bell Laboratories of the American Telephone and Telegraph Company (AT&T) and Harold Rosen of the Hughes Aircraft Company together developed key technologies that made commercial satellites communications possible in the 1950-60.
Pierce was explained the principles of satellite communication in an article "Orbital Radio Relay" published in Jet Propulsion- April 1955. In this article he was calculated the exact power requirements for transmitting signals to satellites in different Earth orbits. The main contribution of Pierce was the development of the traveling wave tube amplifier in the satellite technology, with the help of this technology, enabled the satellite to receive, amplify and transmit radio signals. Also an important technology was developed by Rosen, it was the stability to satellites orbiting in space, this was called the spin- stabilization technology.
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NASA's contribution to satellite communication
NASA was established in 1958 in USA, NASA began working on satellite technology very quickly and soon put its flag on the moon. Echo-1 satellite was the first project of NASA which was developed in Bell Labs with coordination AT&T's.
Pierce and his team member developed the Echo-1 satellite at Bell Labs, this Echo-1 satellite was launched on August 12, 1960. The length of Echo-1 satellite was 30.5-metre aluminum-coated balloon with no instruments, but it was capable of reflecting signals from the base.
Since Echo-1 was only reflecting signals, it was considered a passive satellite. Echo-2 was managed by NASA's GSFC and was launched on January 25, 1964. NASA excluded passive satellite communications systems after Echo-2, and focused in favor of active satellites. The Echo-1 and Echo-2 satellites were credited with improving satellite tracking and ground station technology that later proved indispensable in the development of active satellite systems.
The first active communications satellite was developed by Pierce's team at Bell Labs which was "Telstar-1". This was capable of two-way communication. Telstar-1 was launched into low Earth orbit on 10 July 1962 by a Delta rocket.
This satellite was very developed with features like- launch services and some tracking and telemetry support. It was a wonderful miracle by NASA that developed Telstar-1 and it was the first satellite that transmit live television images between North America and Europe. Infect the first phone call was also transmitted via satellite Telstar-1.
Another Satellite Syncom-1 was launched on February 14, 1963 by Rosen's team at Hughes Aircraft attempted to place the first satellite in geostationary orbit, but Syncom-1 was lost shortly after launch. After Syncom-1 satellite a successful launch was completed of Syncom-2, it was the first satellite in a geosynchronous orbit launched on on July 26, 1963. After Syncom-2, Syncom-3 was the first satellite in geostationary orbit which was launched on August 19, 1964.
There is no broadcasting evidence of Syncom-1 and Syncom-2, but Syncom-3 broadcast the 1964 Olympic Games from Tokyo-Japan to the United States. It was the first major sporting event to be broadcast via satellite.
After the broadcast of Syncom-3 satellite, it was the successful development of the satellite era. And it was considered successful development of satellite technology. Successful Satellite communication technology open the way for the global communications satellite industry.
Development of the satellite communications industry led by The United States with Communications Satellites Act formed in 1962. COMSAT- (Communications Satellite Corporation) formation authorized by the act, a private company Intelsat that was represent the United States in an international satellite communications.
Intelsat was established on August 20, 1964, Intelsat formation was based on 11 signatories to the Intelsat Interim Agreement. Those 11 signatories were from different countries like- Austria, Canada, Japan, Netherlands, Norway, Spain, Switzerland, United Kingdom, United States, Vatican and West Germany.
The first Intelsat satellite was launched by the name Early Bird (also known as Intelsat-1). It was launched on April 6, 1965. it was developed at Hughes Aircraft Company and built by Rosen’s team. It was the first operational commercial satellite. Early Bird satellite was able to provide regular communications and broadcasting between Europe and North America.
After the launch of Early Bird, Intelsat 2B and 2D was launched in 1967 and Pacific Ocean region was covered by it, and Intelsat 3 F-3, launched in 1969 and covering the Indian Ocean region. All satellite of Intelsat was established in geostationary orbit and that was providing near-global coverage. Nineteen days later, the Intelsat 3 F-3 was placed over the Indian Ocean, the first man landing on the Moon on July 20, 1969, broadcast live to over 600 million television viewers via the global network of Intelsat satellites.
The Soviet Union, moving very fast in the development of satellite technology, launched a series of satellites named Molniya, The first Molniya-1 satellite was launched on 23 April 1965. In 1967 there were six Molniya satellites launched and they provided the coverage throughout the Soviet Union. During the 50th anniversary of the Soviet Union on October 1, 1967, first time the annual parade in Red Square was broadcast nationwide through the Molniya satellite network. In 1971 The Intersputnik International Organization of Space Communications was formed by several communist countries led by the Soviet Union.
Canada was also not behind in the race of satellite communication, after the Soviet Union and the United States, Canada was the first country to launch a satellite, named Anik-1, which was launched on 9 November 1972. Then many countries jumped into the race of satellite communication and launched their own satellites.
India was also not behind in the satellite race and it launched the first satellite Aryabhata on 19 April 1975.
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How does satellite work?
Different types of satellites are made for different tasks, so their work is also different. But their basic structure remains the same. Satellites have two main parts, an antenna part and a power source part. To meet the energy requirement of the satellite, solar panels are used on either side of it and the antenna does the job of sending and receiving information.
Most of ASA's satellites have cameras and scientific sensors, which keep their eyes on large areas of Earth and movement in space. In between the satellites are transmitters and receivers, which receive and send signals and commands. Mostly Satellites are made for communication system, because they are at a higher altitude away from the Earth, so satellites cover more area than radio and ground web.
Basically satellite is a self-contained communication system. A Satellite able to receive signals from Earth and send it back with the help of a transponder. Transponder is an integrated system for receiver and transmitter of radio signals.
A satellite is subjected to the shock of being accelerated to an orbital velocity of 28,100 km per hour during launch and a hostile space environment where it may be subject to radiation and extreme temperatures for much of its estimated operational life, which may last up to 20 years.
In addition, satellites need to be light, as the cost of launching a satellite is quite expensive and is based on weight. To achieve the target, satellites should be small and made of lightweight and durable materials. They have to operate at a high reliability of over 99.9 percent in the vacuum of space without any possibility of maintenance or repair.
The satellite have two main component include the communication system, which consist of antennas and transponders that receive and retransmit signals, which also includes solar panels that provide power, and the propulsion system, Including rockets that propel satellites.
A satellite required to have its own driving force system to propel itself into the correct orbital position and occasionally improve upon that position. A satellite in geostationary orbit may deviate by one degree from north to south or east to west of its location every year due to the gravitational pull of the Moon and the Sun.
A satellite consists of propellants that are sometimes ejected to make adjustments to their position. Maintenance of the satellite's orbital position is called "station keeping" and corrections made using the satellite's thrusters are called "attitude control".
The life span of a satellite is determined by the amount of fuel needed to power these thrusters. Once the fuel runs out, the satellite eventually goes into space and goes out of operation, becoming a space debris.
A satellite in orbit has to work continuously throughout its life time. All type satellite have internal power to operate its communication payloads and also electronic systems . The main source of power is sunlight, which is used by the satellite's solar panels. A satellite also has a battery to provide power when the Sun is blocked by the Earth. The batteries are recharged by the additional current generated by the solar panels when exposed to sunlight.
Temperature tolerance range of satellites are from −150 °C to 150 °C and may be subject to radiation in space. Satellite and satellite components is made capable of withstanding radiation so that the satellite cannot be destroyed due to radiation so it is shielded with aluminium and other radiation-resistant material.
A strong thermal system of satellite protects its sensitive electronic and as well as mechanical components and maintains it at its optimum working temperature to ensure its continued operation. A satellite's thermal system also protects sensitive satellite components from extreme changes in temperature, when it gets too hot or the heating system activates the cooling system when it gets too cold.
The satellite has a very powerful system which is called Tracking Telemetry and Control (TT&C) system. It perform two-way communication link between the satellite and TT&C on the ground. This allows a ground station to track the position of the satellite and control the satellite's propulsion, thermal and other systems. It can also monitor a satellite's temperature, electrical voltage and other important parameters.
The smallest communication satellite weighs less than 1 kg and the largest satellite can weigh up to 6,500 kg.. The miniaturization and digitalization issues have grown the capacity of satellites significantly over the years.
Early Bird satellite was consist of just one transponder it was capable of sending just one TV channel. In contrast, Boeing 702 series satellites can have more than 100 transponders, and each transponder can have 16 channels using digital compression technology, providing more than 1,600 TV channels via a single satellite.
There are three different orbits in which satellites work: 1. low Earth orbit (LEO), 2. Medium Earth orbit (MEO), and 3. Geostationary or geosynchronous orbit (GEO). LEO satellite position range are at an altitude between 160 km and 1,600 km above Earth.
MEO satellites operate at a distance of 10,000 to 20,000 km from the Earth. (here important to note that Satellites do not functioned between LEO and MEO because that region has not suitable environment for electronic components, caused by the Van Allen radiation belts.) GEO satellites are located 35,786 km above Earth, where they travel in 24 hours. complete one orbit and thus remain fixed at one place.
As mentioned above, it only takes three GEO satellites to provide global coverage, whereas it takes 20 or more satellites to cover the entire Earth from LEO and 10 or more satellites to MEO. In addition, required tracking antenna on the ground for communicating with satellites in LEO and MEO to ensure a seamless connection between the satellites.
When a signal collides with a satellite and bounces, it takes 0.22 seconds for that signal to travel from the ground to the satellite and back, this bounced signal travels at the speed of light. The delay of 0.22 seconds causes problems in services like voice services and mobile phone. Using LEO or MEO satellites is most commonly used to avoid signal delay because of latency inherent in GEO satellites. GEO satellites are commonly used for broadcast and data applications because they can cover a large area on the ground.
Satellite communications use a high frequency range of 1–50 GHz (gigahertz; 1 GHz = 1,000,000,000 Hz) to transmit and receive signals. The frequency range or band is identified by the letters: (in order of low to high frequency) L-, S-, C-, X-, Ku-, Ka- and V-bands.
Satellite communications use a high frequency range of 1–50 GHz (gigahertz; 1 GHz = 1,000,000,000 Hz) to transmit and receive signals. The frequency band is identified by the letters: L-, S-, C-, X-, Ku-, Ka- and V-bands.
Signals in the lower range are transmitted with less power of the satellite frequency spectrum (L-, S-, and C-bands), and to receive these signals, require larger antennas. Higher signal spectrum (X-, Ku-, Ka-, and V-bands) required more power; Therefore, smaller dishes up to 45 cm in diameter can receive them. Ideal band for the direct-to-home (DTH) broadcasting is the Ku-band and Ka-band, also suitanle for the broadband data communications, and mobile telephony and data applications.
A specialized agency of the United Nations is the International Telecommunication Union (ITU), Hope that all of you know that the ITU, which is based in Switzerland - city Geneva. Applications for use of orbital slots for satellites receives and approves by the ITU .Every 2–4 years the ITU organizes the World Radio Communications Conference, which is responsible for specifying frequencies for various applications in different regions of the world. Regulatory agencies of all countries follow the rules together and also enforce the rules and grants licenses to users of different frequencies. The regulatory body governing frequency allocation and licensing in the United States is the Federal Communications Commission.
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Applications of Satellites
Advances in satellite technology have provided strong satellite services that provides a variety of services to broadcasters, like- governments, the military, Internet Service Providers (ISPs), and so many other sectors. There are three types of services provided by the Satellites communication : Internet & voice, broadcast and data communications. Nowadays many telecom companies are going to provide internet, as well as wireless, mobile and cellular network facilities through satellite. Telecom companies claim that satellite communication will provide very high internet speed.
Satellite broadcast services directly delivered to the consumer end which includes radio, television and mobile services. Other services of satellite like- Satellite television, DirecTV and Dish Network also received directly by households. Satellite networks are delivered to local stations and affiliates via cable and network programming. Important role of Satellites is for the providing the services to the cell phones and other mobile devices.
Data communication involves transferring data from one point to another. Many organization that require the exchange of information between their various locations use satellites to facilitate the transfer of data through the VSAT network. With the development of the Internet, a significant portion of Internet traffic goes through satellites, making ISPs one of the largest customers for satellite services.
Satellite communication technology is very helpful during the natural disasters when land-based communication services are shut down. To provide emergency communication services mobile satellite equipment can be deployed in disaster areas.
A big technical drawback of satellites communication is that, especially in geostationary orbit, there are 0.22 second delay in transmission. While solution of this problem is already available to compensate for this delay, but some applications are require real-time transmission and feedback, so we can say that voice communications, not ideal for satellites.
The satellite faces competition from other networks spread across the Earth. Media on earth are fiber optics, cable, microwaves and even power lines. We can consider as a big advantages that satellite distribute signals from one point to many locations . Strong benefits of satellite technology is vey ideal for "point-to-multipoint" communications. Do not require extra investments on the ground for Satellite communications. It is best for low and isolated areas with scattered populations.
Satellites communication, fiber optics, cables and other terrestrial networks are not very different to each other. A combination of different delivery mechanisms may be required, which has led to various hybrid solutions where satellites may be one of the links in the chain in conjunction with other media. Service providers on the ground is called "teleports" have the ability to receive and transmit signals from satellites to other terrestrial networks.
What is the future of satellite communication?
It is true that satellite technology has progressed a lot in a short span of time, from Sputnik in 1957 till today, there has been a lot of improvement in satellite communication, due to which human life has become completely dependent on technology. Mega-constellations of thousands of satellites designed to provide Internet access anywhere on Earth are in development.
In the future, satellite communication will be developed more so that some additional technology can be provided in human life. Satellite communication will have more power and larger aperture antennas to provide proper bandwidth. Due to the considerable improvement in the satellite, the life span of the satellite can be increased, on which the work is going on very fast, for this type of improvement, the power system of the satellite is being improved more and more.
Some other technological innovations are under developments as low-cost reusable launch vehicles. With growing video, voice and data traffic requiring vast amounts of bandwidth, due to no shortage of emerging applications, satellite communication can be in great demand in the future. Greater demand of more bandwidth, going on continuous improvement and development of satellite technology, will ensure the long-term viability of the commercial satellite industry in the 21st century.
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Last Word
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