Modern satellite communications, satellite systems. Project "modern satellite communications" Satellite communications one of the types

Subsequently, Clarke, when asked why he did not patent the invention (which was quite possible), replied that he did not believe in the possibility of implementing such a system during his lifetime, and also believed that such an idea should benefit all of humanity.

The first studies in the field of civil satellite communications in Western countries began to appear in the second half of the 50s of the XX century. In the United States, they were driven by the increased demand for transatlantic telephony.

Mail envelope dedicated to the 5th anniversary of the launch of the first Earth satellite

In 1957, the USSR launched the first artificial Earth satellite with radio equipment on board.

Balloon "Echo-1"

On August 12, 1960, US specialists launched an inflatable balloon into orbit at an altitude of 1500 km. This spacecraft was called Echo-1. Its metallized shell, 30 m in diameter, served as a passive repeater.

Engineers work on the world's first commercial communications satellite Early Bird

On August 20, 1964, 11 countries signed an agreement on the creation of the International Telecommunications Satellite organization (Intelsat), but the USSR was not among them for political reasons. On April 6, 1965, the program launched the first commercial communications satellite, Early Bird, manufactured by COMSAT Corporation.

By today's standards, the Early Bird satellite ( INTELSAT I) had more than modest capabilities: with a bandwidth of 50 MHz, it could provide up to 240 telephone communication channels. At any given time, communication could be carried out between an earth station in the United States and only one of three earth stations in Europe (in the UK, France or Germany), which were interconnected by cable communication lines.

Later, the technology stepped forward, and the satellite INTELSAT IX already had a bandwidth of 3456 MHz.

For a long time in the USSR, satellite communications were developed only in the interests of the USSR Ministry of Defense. Due to the greater secrecy of the space program, the development of satellite communications in the socialist countries proceeded differently than in the Western countries. The development of civil satellite communications began with an agreement between 9 countries of the socialist bloc on the creation of the Intersputnik communications system, which was signed only in 1971..

The first artificial satellite of the earth.

The launch of the world's first artificial Earth satellite was carried out in the Soviet Union on October 4, 1957 at 22 h 28 min. 34 s Moscow time. For the first time in history, hundreds of millions of people could observe in the rays of the rising or setting sun an artificial star moving across the dark firmament, created not by gods, but by human hands. And the world community perceived this event as the greatest scientific achievement.

The first satellites with satellite communications.

On May 13, 1946, Stalin signed a decree on the creation in the USSR of the rocket science and industry. In its development, in August 1946, Sergei Korolev (academician since 1958) was appointed chief designer of long-range ballistic missiles. Then none of us foresaw that, working with him, we would be participants in the launch of the world's first satellite, and soon after that, the first half a hundred people in Space - Yuri Gagarin.

Modern satellite communications are one of the directions of development of radio relay communications. In this case, this is the application orbiting satellites as repeaters.

Satellite communication technologies make it possible to use one or more repeaters to provide high-quality radio signal transmission over long distances.

All repeaters can be divided into two categories:

• passive. Currently, they are practically not used. Initially, they were used exclusively as a transmission link between the ground station and the subscriber, they did not amplify the signal and did not convert it;


• active. Such devices additionally amplify the signal and correct it in every possible way before sending it to the subscriber. Most of the world's satellite systems use this type of repeater.

History of satellite communications

At the end of 1945, the world saw a small scientific article devoted to the theoretical possibilities of improving communication (primarily, the distance between the receiver and transmitter) by raising the antenna to its maximum height.

What kind of working principle did you mean?

Everything is quite simple - the scientist proposed to launch a large repeater antenna into low-earth orbit, which would receive signals from a ground source and transmit it further.

The main advantage was the huge coverage area that could be controlled by just one satellite. This would significantly increase the quality of the signal, remove the limit on the number of receiving stations, and additionally would not have to build terrestrial repeaters. The United States is interested in the project as part of solving problems with transatlantic telephone communications.

The development of satellite communication systems began with the launch of the first Echo-1 device (a passive repeater in the form of a metallized ball) into space in August 1960.

Later, key satellite communication standards (operating frequency bands) were developed and are widely used around the world.

Applications of satellite communications

Since the successful implementation, the quality of satellite communications has improved significantly.

Thanks to the introduction of mobile ground stations, the subscriber could receive a radio signal regardless of the location of the satellite at any time of the day, automatically moving from one coverage area to another, automatically connecting to the nearest repeater.

The use of satellite communications can be divided into several conventional directions:

• trunk communication. Initially, the task was to transmit a large amount of information (in particular, voice messages), but over time, when switching to digital format, such a need has disappeared, and today from this area satellite communications are being replaced by fiber-optic networks;


• VSAT. The so-called "small" systems with antenna diameters up to 2.4 meters. The technology is developing successfully and is used to create private communication channels;


• mobile communications (the basis of telephony and television broadcasting);


• access to the Internet.

To obtain more information on the development of this area of ​​communication, it is enough to visit a specialized event. The Svyaz International Exhibition, which takes place on the territory of the Expocentre Fairgrounds, is the best industry event of the international level. This guarantees the presence of a wide exposition and participation of well-known international and domestic profile companies.

How modern satellite communication equipment works

Satellite communications are strongly associated in the minds of many people with GPRS navigators and telephony. In fact, this is an invention of mankind and finds its niche in these areas from the point of view of ordinary people.

The very concept of satellite communications originated back in 1945, but at that time few believed that such a data transmission channel could be realized in life. However, now the Earth is surrounded by many satellites, providing a continuous exchange of information between hundreds of people and devices.

It is thanks to the fact that modern satellite communications have such a wide coverage that the ability to make calls from the most remote corners of the world has become a reality. No serious tourist dares to embark on a long and dangerous journey without a satellite phone.

There is also a concept satellite Internet- it makes it possible to access The world wide web even where the light is exclusively due to the generators.

Using the resources and capabilities of satellite transmission of information, many options for navigators have been created for a wide variety of industries.

In fact, modern satellite communication consists of only three elements: a transmitter, a repeater and a receiver. The transmitter and receiver are various devices: mobile phones, computers, antennas and so on.

A repeater is presented in the form of a satellite, which receives an incoming signal from an earth station (or device) and broadcasts it to the entire visible area. Further, the technical and software who cares about this information hit exactly the addressee. The exceptions are cases when the signal must be received by all receivers. For example, satellite TV.

For more bandwidth repeater, the following multiple access (MD) systems have been implemented:

1. MD with frequency division. Each user gets their own frequency.


2. MD with time division. The user has the right to receive or transmit data only within a certain period of time.


3. MD with code division. Each user is given a code. It is superimposed on the data so that signals from different users do not mix even when transmitted on the same frequency.

In general, all of the above systems guarantee frequency reuse, which increases efficiency and throughput.

When transmitting information, the absorption of waves in the atmosphere and the size of the receiving antenna are also taken into account - for each specific case, a different frequency is used.

International satellite communications

International satellite communications Is a type of radio relay communication, which is based on the use of artificial earth satellites as repeaters. Communication takes place between stations located on the ground, which in turn are stationary and mobile. The technology allows you to transmit a radio signal at any distance, even the largest.

By far the most common type is the active repeater. It significantly amplifies and corrects the incoming signal before it reaches the subscriber. Most of the satellite systems in the world use this kind of satellites.

The beginning of this technology was laid by the English scientist Arthur Clarke, who wrote the article "Extraterrestrial Repeaters". The principle was that the antenna had to be brought to the maximum distance in low-earth orbit, which would make it possible to receive signals from ground-based sources and transmit them further. Main feature was that one satellite could control a sufficiently large coverage area of ​​the globe.

The first passive repeater was Echo-1, which was launched into space in 1960. This marked the beginning of the further rapid development of international satellite communications.

Fields of application of international satellite communications

Since the first artificial satellite was launched into space, the quality of technology has improved significantly. Today humanity cannot imagine everyday life without mobile phone(which triumphantly replaced home landlines), without video chats to help communicate with a person at a distance in real time, without television, etc.

The modern use of international satellite communications is divided into the following key areas:

• trunk communication;


• mobile satellite communication system;


• VSAT (a small system with an antenna up to 2.4 m in diameter, used to create a private channel);


• mobile network;


• Internet (most modern technologies work with this system).

International satellite communications is one of the thematic areas of the thematic event, which is annually held within the walls of the Expocentre Central Exhibition Complex.

Thematic diversity covers all categories of the communications industry:

• Internet technologies;


• software;


• data networks;


• startups;


• telecommunication infrastructure;


• services in the field of IT technologies;


• communication equipment and modern technologies.

Possibilities of modern international satellite communications

Modern high-tech international satellite communications provide the following opportunities:

• exchange information;


• manage and coordinate aircraft and ships, as well as land transport;


• the ability to transfer large amounts of information to the other side of the world;


• receive high and stable signal quality;


• carry out secure communications, etc.

Novelties of satellite communications of the Russian Federation

Satellite connection has an inevitable impact on the development of various industrial spheres, the economic growth of the state and the standard of living of nations.

Today, the formation of a market segment of satellite communications is unimaginable without a connection with a terrestrial networked system... Any changes to the network structure can have a profound effect on the performance of the satellites.

Satellite communication has the following latest innovations:

• fiber-optic networks have led to the partial displacement of satellite backbones;


• distribution of antenna stations VSAT (Very Small Aperture Terminal);


• improvement of the energy equipment of space vehicles and their ability to transmit remote signals from points of the earth;


• broadband satellites equipped with a repeater;


• facilities with large frequency ranges;


• development of medium-altitude orbits.

All of these innovative adaptations have led to the ability to process multiple signals in space by means of inter-beam switches.

Thanks to the latest mechanisms for transferring images of video files, free online communication has become commonplace in the present time.

Market segments of satellite communications of the Russian Federation

Satellite communications in the Russian Federation are economically divided into three large market segments information technologies and communications.

1. The first segment was founded thanks to the connection of ground stations on the territory of the state with the developing satellite complexes Global Star, Inmarsat, Ellipse. They form compact terminals for personal communication, interfaced with mobile broadcasting devices. The satellites of the system are located over the oceans to provide high-quality Internet signals for large radii of the earth. The system has a telephone that is tuned to one of the satellites. Communication terminals with large antennas pick up the signal and distribute it to subscribers anywhere in the world.


2. In the second segment, the emphasis is placed on the production of small satellite terrestrial terminals (VSAT), designed to form corporate networks with secure access. Now on the territory of the Russian Federation, according to the National Union of Satellite Communications, there are about 3.2% of the total number of such stations in the world (500 thousand).


3. In the third segment, satellites, small-format stations and their systems are invented and introduced into production, which determine television and radio broadcasting, remote online communications. The cost of equipment for this market niche is several times lower than the terminals of the previous two segments. Taking into account the geographical advantage of small settlements relative to the entire area of ​​the country, television infrastructure brings the maximum profit among all types of contacts.

On Russian market communications are of no small importance for the economic development of the zone where signals processed by multi-mode terminals are distributed.

The signal from the Remote Administration Tool (RAT) network is split into codes in CDMA (Code Division Multiple Access) channels and, by scanning, facilitates paging in loops connected to each other in a separate RAT. It is beneficial to communicate with these areas where there is no cellular signal reception.

Multi-mode subscriber terminals wireless able to improve the efficiency of interconnection, increase access to various services.

Modern equipment for receiving and transmitting satellite communications at the exhibition

Modern satellite communications serves as a wonderful way of transferring information, but puts forward increased demands on the equipment.

Exhibition "Communication" provides an opportunity to get acquainted with the latest developments and offers from various manufacturers of equipment for satellite communications.

A wide range of samples of various price categories is exhibited within the walls of Expocentre, so that anyone can find the most optimal option in terms of quality and price.

Exhibition "Communication" has been carried out for more than three decades and serves as a powerful engine in the effective development of this technical field.

Space or satellite communication is essentially a kind of radio relay (tropospheric) communication and differs in that its repeaters are located not on the surface of the Earth, but on satellites in outer space.

For the first time the idea of ​​satellite communications was presented in 1945 by the Englishman Arthur Clarke. In a radio engineering journal, he published an article on the prospects of rockets like the V-2 for launching earth satellites for scientific and practical purposes. The last paragraph of this article is significant: “An artificial satellite at a certain distance from the Earth will make one revolution in 24 hours. It will remain stationary over a certain place and within the optical visibility range from almost half of the earth's surface. Three repeaters, placed in the correct orbit with an angular separation of 120 °, will be able to cover the entire planet with television and VHF broadcasting; I am afraid that those who are planning post-war work will not find it easy, but I consider this path to be the final solution to the problem. "

On October 4, 1957, the USSR launched the world's first artificial Earth satellite, the first space object whose signals were received on Earth. This satellite marked the beginning of the space age. The signals emitted by the satellite were used not only for direction finding, but also for transmitting information about the processes on the satellite (temperature, pressure, etc.). This information was transmitted by changing the duration of the messages emitted by the transmitters (pulse-width modulation). On April 12, 1961, for the first time in the history of mankind, a manned flight into outer space was carried out in the Soviet Union. The Vostok spacecraft with the pilot-cosmonaut Yu. A. Gagarin on board was launched into the orbit of the Earth satellite. To measure the parameters of the orbit of the spacecraft and control the operation of its onboard equipment, numerous measuring and radiotelemetric equipment was installed on it. For direction finding of the spacecraft and transmission of telemetric information, the Signal radio system operating at a frequency of 19.955 MHz was used. The cosmonaut's two-way communication with the Earth was provided by a radiotelephone system operating in the short (19.019 and 20.006 MHz) and ultrashort (143.625 MHz) wave bands. The television system transmitted the cosmonaut's image to Earth, which made it possible to have visual control over his condition. One of the television cameras transmitted a full-face image of the pilot, and the other - from the side.

The achievements of Russian science in the field of space exploration made it possible to implement the predictions of Arthur Clarke. At the end of the 50s of the last century, experimental studies of the possibilities of using artificial earth satellites as radio repeaters (active and passive) in terrestrial communication systems began to be carried out in the USSR and the USA. Theoretical developments in the field of energy capabilities of satellite communication lines made it possible to formulate tactical and technical requirements for satellite repeater devices and ground devices, based on the real characteristics of the technical means that existed at that time.

Considering the identity of the approaches, we will present experimental studies in the field of creating satellite communication lines using the example of the United States. The first active radio relay "Score" was launched on December 18, 1958 into an inclined elliptical orbit with an apogee height of 1481 km, a perigee of 177 km. The satellite equipment consisted of two transceivers operating at frequencies 132.435 and 132.095 MHz. The work was carried out in slow retransmission mode. The storage of the signal sent by the ground transmitting station was carried out by recording it on a magnetic tape. Silver-zinc batteries with a capacity of 45 amperes - an hour at a voltage of 18 volts were used as power sources. The duration of the connection was approximately 4 minutes per 1 satellite revolution. Retransmission of 1 telephone or 7 teletype channels was carried out. The satellite's service life was 34 days. The satellite burned up upon entering the atmosphere on January 21, 1959. The second active radio relay "Courier" was launched on October 4, 1960 into an inclined elliptical orbit with an apogee of 1270 km and a perigee of 970 km. The satellite equipment consisted of 4 transceivers (150 MHz for command transmission and 1900 MHz for communication), magnetic memory devices and power sources - solar cells and chemical batteries. Silicon solar cells in the amount of 19,152 were used as the primary power source. Nickel-cadmium batteries with a capacity of 10 ampere-hour at a voltage of 28-32 volts were used as a buffer stage. The duration of the communication session was 5 minutes per satellite revolution. The satellite service life was 1 year. On July 10, 1962, an active Telstar repeater was launched into an inclined elliptical orbit with an apogee of 5600 km and a perigee of 950 km, which was intended for active relaying of radio signals in real time. At the same time, he relayed either 600 simplex telephone channels, or 12 duplex telephone channels, or one television channel. In all cases, the work was carried out using the frequency modulation method. Communication frequencies: on the satellite-Earth line 4169.72 MHz, on the Earth-satellite line 6389.58 MHz. The duration of a communication session on the US-Europe line via this satellite was about 2 hours a day. The quality of the transmitted television images ranged from good to excellent. The project envisaged a very significant service life of the satellite - 2 years, but after four months of successful operation, the command line failed. It was found that the causal failure was surface damage due to the action of radiation when the satellite passed the inner radiation belt.

On February 14, 1963, the first synchronous satellite of the Sinkom system was launched with orbital parameters: apogee altitude 37,022 km, perigee altitude 34185, orbital period 1426.6 minutes. The operating frequency on the Earth-to-satellite link is 7360 MHz, and on the satellite-to-Earth link, 1820 MHz. Solar cells in the amount of 3,840 units with a total power of 28 W at a voltage of 27.5 volts were used as the primary power source on the satellite. Communication with the satellite was maintained for only 20,077 seconds, after which the observations were carried out by astronomical methods.

On April 23, 1965, the first communications satellite Molniya-1 was launched in the USSR. With the launch of the second communications satellite "Molniya-2" on October 14, 1965, the regular operation of the long-distance communication line through the satellite began. Later, the Orbita long-range space communications system was created. It consisted of a network of ground stations and artificial earth satellites "Molniya", "Raduga", "Horizon". Below, in Chapter 7, it will be shown that modifications of the Horizon satellites continue to function in the 21st century. This indicates the high reliability of domestic equipment compared to foreign ones.

The first satellite communication stations were built, tested and put into operation in the town of Shchelkovo near Moscow and in Ussuriisk. They were connected by cable and relay communication lines, respectively, with television centers and telephone intercity stations in Moscow and Vladivostok.

The most suitable for the equipment of earth stations of the satellite system turned out to be the tropospheric communication equipment TR-60/120, in which, as is known, high-power transmitters and highly sensitive receivers with low-noise parametric amplifiers were used. On its basis, a receiving and transmitting complex "Horizon" is being developed, installed at ground stations of the first satellite communication line between Moscow and Vladivostok.

Specially developed transmitters for communication and command and measurement lines, parametric amplifiers with a noise temperature of 120 K for installation in the antenna under the mirror cabin, as well as completely new equipment that provides docking with local television centers and long-distance telephone exchanges.

In those years, the designers of the earth station, fearing the influence of powerful transmitters on the receivers, installed them on different antennas and in different buildings (receiving and transmitting). However, the experience of using one common antenna for receiving and transmitting, obtained on tropospheric communication lines, made it possible to transfer the receiving equipment to the transmitting antenna in the future, which greatly simplified and reduced the cost of operating satellite communication stations.

In 1967, through the communication satellite "Molniya-1", an extensive television network of receiving earth stations "Orbita" with a central transmitting station near Moscow was created. This made it possible to organize the first communication channels between Moscow and the Far East, Siberia, Central Asia, transmit the program of Central Television to remote regions of our Motherland and additionally reach more than 30 million TV viewers.

However, the Molniya satellites revolved around the Earth in elongated elliptical orbits. To track them, the antennas of the ground receiving stations must constantly rotate. It is much easier to solve this problem by satellites rotating in a stationary circular orbit, which is located in the equatorial plane at an altitude of 36,000 km. They make one revolution around the Earth in 24 hours and therefore seem to a terrestrial observer hanging motionless over one point of our planet. Three such satellites are enough to provide communications for the entire Earth.

In the 80s of the last century, communication satellites "Raduga" and television satellites "Ekran" effectively operated in stationary orbits. No sophisticated ground stations were needed to receive their signals. Television transmissions from such satellites are received directly on simple collective and even individual antennas.

In the 1980s, the development of personal satellite communications began. In this connection, the satellite phone is directly connected to a satellite in low-earth orbit. From the satellite, the signal enters the ground station, from where it is transmitted to the regular telephone network. The number of satellites required for stable communication anywhere on the planet depends on the orbital radius of a particular satellite system.

The main disadvantage of personal satellite communication is its relative high cost in comparison with cellular communication. In addition, high-power transmitters are built into satellite phones. Therefore, they are considered unsafe for the health of users.

The most reliable satellite phones operate on the Inmarsat network, which was established over 20 years ago. Satellite phones of the Inmarsat system are a suitcase with a hinged lid the size of the first laptop computers... The satellite phone cover is also an antenna, which must be turned towards the satellite (the signal strength is displayed on the phone display). Most of these phones are used on ships, trains or heavy vehicles. Every time when you need to make or answer someone's call, you will need to install the satellite phone on some flat surface, open the lid and twist it, determining the direction of the maximum signal.

At present, satellite systems still account for about 3% of world traffic in the overall balance of communications. But the demand for satellite lines continues to grow, since with a range of more than 800 km, satellite channels become economically more profitable compared to other types of long-distance communications.