Telecommunication satellites are usually placed in geostationary orbit (GEO). which is a circular orbit with an altitude of 35,786 kilometers above the Earth's equator and follows the direction of the Earth's rotation. The object in GEO has an orbital period equal to the period of rotation, therefore, to ground observers, it appears stationary and occupies a fixed position in the sky.
Satellites in GEO allow continuous communicationby transmitting radio frequency signals from fixed antennas. These signals are not very different from those used in broadcast terrestrial television transmissions and are usually 3-50 times higher in frequency. The signal received by the satellite is amplified and transmitted back to Earth, making it possible to establish communication between points located thousands of kilometers apart.
A special feature that makes geostationary satellites extremely attractive is their ability to transmit information... The relayed signal can be received by antennas anywhere in a satellite's coverage area, comparable to the size of a country, region, continent, or even the entire hemisphere. Anyone who has a small antenna 40-50 cm in diameter can become a direct satellite user.
A satellite operating in a geostationary orbit does not need any engine, and its stay in Earth's orbit can last for many years. Friction from the thin upper atmosphere will eventually slow it down and cause it to sink lower and lower, and eventually burn up in the lower atmosphere.
If a satellite is launched with more fuel, it travels faster and has a larger orbital radius. A large orbit means that the satellite's angular motion around the Earth is slower. As an example, the Moon, located 380,000 km from Earth, has an orbital period of 28 days.
Low Earth Orbit (LEO) satellites, such as many scientific and observing satellites, operate at much lower altitudes: they make a complete circle around the Earth in about 90 minutes at altitudes of several hundred kilometers.
Telecommunication satellites can also be on LEO, being visible from anywhere for 10-20 minutes. To guarantee the continuity of information transmission, in this case, it will be necessary to deploy dozens of satellites.
Telecommunications systems on LEO may require 48, 66, 77, 80 or even 288 satellites to provide the required services. Several of these systems have been deployed to provide connectivity for mobile terminals. They use relatively low frequencies (1.5-2.5 GHz), which are in the same range as the frequencies used in mobile networks with GSM. The fact that for of this type satellites do not require any expensive transmitting and receiving devices - plus for them: no careful tracking of the satellite is needed in this case. In addition, the low altitude minimizes signal transit time delay and requires less transmitter power to establish communications.
The star system of the Milky Way galaxy, in which we live, includes the Sun and 8 more planets orbiting it. Scientists are primarily interested in studying the planets closest to Earth. However, the satellites of the planets are also very interesting. What is a satellite? What are their types? Why are they so interesting for science?
What is a satellite?
A satellite is a small body that rotates around the planet under the influence of gravity. We currently know 44 such celestial bodies.
Only the first two planets of our star system, Venus and Mercury, are missing satellites. The Earth has one satellite (the Moon). The "red planet" (Mars) has 2 celestial bodies accompanying it - Deimos and Phobos. The largest planet in our star system - Jupiter - has 16 satellites. Saturn has 17, Uranus has 5, and Neptune has 2.
Types of satellites
All satellites are subdivided into 2 types - natural and artificial.
Artificial - celestial bodies created by humans, which open up the opportunity to observe and explore the planet, as well as other astronomical objects. They are necessary for drawing up maps, weather forecasting, radio transmission of signals. The largest man-made "companion" of the Earth is (ISS). Artificial satellites are not only around our planet. Over 10 such celestial bodies revolve around Venus and Mars.
What is a natural satellite? They are created by nature itself. Their origin has always aroused the genuine interest of scientists. There are several theories, but let's focus on the official versions.
Every planet has a collection of cosmic dust and gases. The planet attracts celestial bodies that fly close to it. As a result of this interaction, satellites are formed. There is also a theory according to which fragments are separated from cosmic bodies that collide with the planet, which subsequently acquire a spherical shape. According to this assumption, there is a fragment of our planet. This is confirmed by the similarity of the terrestrial and lunar chemical compositions.
Satellite orbits
There are 3 types of orbits.
Polaris is tilted to the equatorial plane of the planet at right angles.
The trajectory of the inclined orbit is displaced relative to the equatorial plane by an angle less than 90 0.
Equatorial (also called geostationary) is located in the plane of the same name, along its trajectory, the celestial body moves at the speed of the planet's rotation around its axis.
Also, the orbits of satellites in their shape are divided into two basic types - circular and elliptical. In a circular orbit, a celestial body moves in one of the planes of the planet with a constant distance above the planet's surface. If the satellite is moving in an elliptical orbit, this distance varies within the period of one revolution.
Natural satellites of the planets of the solar system: interesting facts
Saturn's moon Titan has its own dense atmosphere. There are lakes on its surface, which contain liquid hydrocarbon compounds.
Following the USSR and the United States, satellites were launched by France (1965), Australia (1967), Japan (1970), China (1970), and Great Britain (1971).
The implementation is based on international scientific and technical cooperation. So, for example, countries friendly to the USSR carried out launches of satellites from Soviet cosmodromes. Some satellites, manufactured in Canada, France, Italy, have been launched since 1962 using US-developed launch vehicles.
What is a cosmic body rotating in an orbit around a planet? By origin, they are natural and artificial. The special interest of the world community is caused by the natural satellites of the planets, because they conceal many more mysteries in themselves, and most of them are still awaiting discovery. There are projects for their study of private, state and global significance. Artificial satellites make it possible to solve applied and scientific problems both on the scale of an individual planet and the entire outer space.
In our VK group (vk.com/posterspbru), one of the users left such a playfully sarcastic comment:
- Monya, where are you looking?
- To the stars. Believe it or not, there are 8000 satellites!
- And sho, it became easier to breathe?
He gave us the idea of \u200b\u200bthis article.
Perhaps Moni's friend is right - in the literal sense of the word, satellites do not help people breathe. Although this is a moot point, since satellites are able to save from situations in which people can suffocate. Probably, many of us rarely think about how much satellites affect our lives.
Here are some of the applications that satellites provide us with.
1. Satellites send television signals to homes, but they are also the basis for cable and network TV. In other words, no satellites - no news, no broadcasts of sports matches, no Olympics in live etc. Satellites transmit signals from a central station, which generates programs for smaller stations, which transmit signals to local level... All direct connections are possible thanks to satellites.
2. Satellites provide telephone communications on airplanes and are often the only channel telephone connection for many rural areas and areas where telephone lines damaged by natural disasters. Satellites also provide the primary timing source for cell phones and pagers. In 1998, a satellite failure demonstrated this addiction - 80% of pagers in the United States temporarily fell silent, public national radio was unable to distribute its broadcasts to affiliates and only broadcast via a website, and a video picture was frozen on the CBS evening news and only broadcast audio.
3. Satellite navigation systems allow any user to navigate the terrain. GPS navigators are part of modern world, whether they are used in private vehicles or for commercial or military purposes for navigation on land, at sea or in the air. And by the way, GPS navigation plays a decisive role in many situations, for example when a ship is heading for harbor in bad weather.
4. Satellites connect companies to suppliers, are the basis for international video conferencing, provide instant credit card authorization and banking. Without a satellite in orbit, you will not be able to pay for goods in the hypermarket with your bank card.
5. Satellites provide meteorologists with weather data, with the help of which they monitor not only whether it will be cloudy or sunny today, but also for volcanic eruptions, hurricanes, gas leaks, and the like. Returning to the question of Mona and his friend, in some cases, satellites will help a person breathe, simply because they will warn him that a cloud of toxic gases is moving to the place where he is. Or a satellite can rescue him at sea or on land by transmitting a beacon signal to rescue services.
Sputniks are one of the main sources of data for climate change research. Satellites monitor ocean temperatures and currents. They can point out air pollution, help organize rescue operations in disaster regions, help locate people in remote areas, send distress signals, and more.
6. The satellite can detect groundwater and mineral springs, monitor the transfer of nutrients and pollutants from the earth to water sources, measure the temperature of the land and water, measure the growth of algae in the seas and erosion of the topsoil on land. They can effectively monitor large-scale infrastructures such as fuel lines that need to be checked for leaks using satellites rather than manual labor (which will take many hours). Satellite imagery is helping a variety of industries, and even you can take advantage of Google Earth thanks to satellites.
Satellites are of great importance to developing countries, as they provide their populations in remote regions with access to data, educational information, medical information, and the like. A person can only get the right treatment because their doctor consults with a more experienced companion colleague.
7. Space exploration is impossible without satellites. Telescopic satellites play a critical role in understanding many space phenomena.
Anthropogenic satellites in Earth's orbit strongly affect our modern lifealthough many do not realize it. To some extent, satellites help us breathe freely, providing us with data, timely help, and opportunities. Satellites make life safer, provide a host of modern amenities, and help broadcast entertainment and explore Earth and space.
Who among us did not shout joyfully, looking into the deep starry sky: - Look, look, the satellite is flying! And this satellite was not at all associated with anything other than space.
But now - a completely different story! Satellites are communications, television, determination of coordinates, security, and the Internet. And many more things people will come up with for space technologists to serve for the benefit of man.
And we will tell you why and what are the most popular ways of using satellite systems today.
Why sometimes only satellite technology can be the only development option?
When installing land lines, wires are used - fiber optic or copper, or when wireless technology – cellular networks or radio internet.
All these rather costly work always have significant disadvantages:
Territory coverage limitation. Any transmitter or receiver of a signal has a certain area of \u200b\u200bwork, which depends on the power and terrain of the area;
issues of network modernization always relate to technical capabilities and feasibility of spending financial resources;
it is often impossible to quickly dismantle equipment and deploy a station to a new location.
And in some cases, the most justified in a technical and financial sense to ensure reliable and high-quality communication is the use of satellite systems.
Satellites will always find us
Without satellite technology, we would never be able to find each other on our large planet.
The global coordinate system allows you to accurately determine the location of objects (longitude, latitude, and even height above sea level), as well as the direction and speed of this object.
The famous American GPS (Global Positioning System) system includes 24 artificial satellites, a wide network of ground stations, which have unlimited connectivity to user terminals.
GPS - the system works continuously. Anyone on the planet can use it, you just need to purchase a GPS navigator. Manufacturers offer portable, automotive, aviation, marine models. Search work and rescue operations in no country in the world are complete without the help of GPS.
Satellites guard us
This is especially true in the automotive industry. The main security system is successfully combined with channels satellite communications, GPS and traditional radar methods.
How do satellite security systems work?
The central unit with security sensors is discreetly installed on the car. In the event of an emergency, the signal from the central unit is transmitted via communication channels to the owner or dispatcher. GPS system helps to track route, location, driving mode in real time.
Satellites entertain us
The most relevant and well-known topic is satellite TV. But we are already so used to the plates in our houses that we practically do not notice it. But only three devices: an antenna, a receiver, a converter give us extraordinary pleasure from watching our favorite TV programs.
Difference from traditional television antenna in that, instead of a tower, a satellite appears and transmits digital signal... This results in a large selection of channels and image quality.
Satellites connect us with friends
The most widespread and well-known global satellite communication systems (GSSS): Globalstar, Inmarsat, Iridium, Thuraya. At the very beginning of their creation, it was assumed that these systems organize a mobile and fixed telephony where there are no communication lines. In the further development, new opportunities appeared: access to the Internet, transfer of information in various formats. And GSSS have become multi-service.
If you describe the operation of these systems in a nutshell, it will turn out like this.
The satellite receives the subscriber's signal and transmits it to the nearest station on Earth. The station determines the signal, selects a route and sends it over terrestrial networks or satellite channel to the point of reception.
The difference between global satellite communication systems in the cost of traffic, the size and cost of subscriber terminals, coverage areas, and technical features the concept of the system itself.
Satellites help us live comfortably
Satellite system is actively developing Very Small Aperture Terminal - VSAT... This system - as a basis for the constructor: you can add equipment and access the Internet, other equipment - and have already been combined local area networks users in different territories. And you can also collect data, reserve communication channels, manage various production processes, organize remote video and audio conferences.
Such a system is easy to deploy and get started. The quality of communication, ease of content and use have already been appreciated by financial institutions, retail chains, and large industrial enterprises.
The VSAT-based network consists of a central control station (NCC), subscriber terminals and a satellite relay.
With further development, all systems will inevitably become more accessible, cheaper, more convenient and easier to manage and understand the ongoing processes of assimilation of our everyday life with satellite technologies.
Now, dreamily looking at the night sky and seeing a moving star, you will think that they, satellites, greatly facilitate and diversify life. And that is great.
A satellite of the Earth is any object that moves in a curved path around a planet. The Moon is the original, natural satellite of the Earth, and there are many artificial satellites, usually in close orbit to Earth. The satellite's path is an orbit, which sometimes takes the form of a circle.
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To understand why the satellites move in this way, we must return to our friend Newton. exists between any two objects in the universe. If it were not for this force, a satellite moving near the planet would continue to move at the same speed and in the same direction - in a straight line. However, this rectilinear inertial path of the satellite is balanced by the strong gravitational attraction directed towards the center of the planet.
Orbits of artificial earth satellites
Sometimes the orbit artificial satellite The earth looks like an ellipse, a squashed circle that moves around two points known as foci. The same basic laws of motion apply, except that the planet is in one focus. As a result, the net force applied to the satellite is not uniform throughout its orbit, and the satellite's speed is constantly changing. It moves fastest when it is closest to Earth - a point known as perigee - and slowest when it is farthest from Earth - a point known as apogee.
There are many different satellite orbits for the Earth. The ones that receive the most attention are geostationary orbits, as they are stationary over a specific point on the Earth.
The orbit chosen for the artificial satellite depends on its application. For example, a geostationary orbit is used for live broadcast television. Many communications satellites also use geostationary orbit. Other satellite systems, such as satellite telephones, can use low earth orbits.
Similarly, satellite systems used for navigation, such as Navstar or Global Positioning (GPS), occupy a relatively low Earth orbit. There are also many other types of satellites. From meteorological satellites to research satellites. Each of them will have their own own type orbits depending on its application.
The actual chosen orbit of an Earth satellite will depend on factors including its function and the area in which it is intended to serve. In some cases, the Earth satellite's orbit can reach 100 miles (160 km) for LEO, while others can reach over 22,000 miles (36,000 km), as in the case of the GEO-orbiting GEO orbit.
The first artificial earth satellite
The first artificial earth satellite was launched on October 4, 1957 by the Soviet Union and was the first artificial satellite in history.
Sputnik 1 was the first of several satellites launched by the Soviet Union in the Sputnik program, most of which were successful. Satellite 2 followed a second satellite in orbit and also the first one to carry an animal on board, a bitch named Laika. The first failure was Sputnik 3.
The first earth satellite had an approximate mass of 83 kg, had two radio transmitters (20.007 and 40.002 MHz) and orbited the Earth at a distance of 938 km from its apogee and 214 km at its perigee. Analysis of radio signals was used to obtain information on the concentration of electrons in the ionosphere. Temperature and pressure were encoded for the duration of the radio signals it emitted, indicating that the satellite was not perforated by a meteorite.
The first earth satellite was an aluminum sphere 58 cm in diameter with four long and thin antennas ranging in length from 2.4 to 2.9 m. The antennas looked like long whiskers. The spacecraft received information about the density of the upper atmosphere and the propagation of radio waves in the ionosphere. The devices and sources of electrical energy were placed in the capsule, which also included radio transmitters operating at 20.007 and 40.002 MHz (about 15 and 7.5 m at a wavelength), emissions were made in alternative groups of 0.3 s duration. Telemetry grounding included temperature data inside and on the surface of the sphere.
Since the sphere was filled with nitrogen under pressure, Sputnik 1 had its first opportunity to detect meteorites, although it did not. The pressure loss inside, due to penetration on the outer surface, was reflected in the temperature data.
Types of artificial satellites
Artificial satellites are different types, shapes, sizes and play different roles.
- Weather satellites help meteorologists predict the weather or see what is happening at the moment. A good example is a Geostationary Operational Environmental Satellite (GOES). These earth satellites usually contain cameras that can return photographs of the earth's weather, either from fixed geostationary positions or from polar orbits.
- Communication satellites allow the transmission of telephone and informational conversations via satellite. Typical communications satellites include Telstar and Intelsat. The most important feature of a communications satellite is a transponder - a radio receiver that picks up a conversation on one frequency and then amplifies it and re-transmits it back to Earth on a different frequency. A satellite usually contains hundreds or thousands of transponders. Communication satellites are usually geosynchronous.
- Broadcast satellites transmit television signals from one point to another (similar to communication satellites).
- Scientific satellitessuch as the Hubble Space Telescope carry out all kinds of scientific missions. They look at everything from sunspots to gamma rays.
- Navigation satellites help ships and planes navigate. The most famous satellites are GPS NAVSTAR.
- Rescue satellites react to radio interference signals.
- Earth observation satellites they check the planet for changes in everything: from temperature, afforestation, to ice cover. The most famous are the Landsat series.
- Military satellites The earths are in orbit, but most of the actual position information remains classified. Satellites can include encrypted communication relaying, nuclear monitoring, surveillance of enemy movements, early warning of missile launches, eavesdropping on ground radio links, radar imaging, and photography (using essentially large telescopes that photograph militarily interesting areas).
Earth from artificial satellite in real time
Satellite imagery of the earth, broadcast in real time by NASA from the International Space Station. Images are captured by four cameras high resolutionisolated from cold temperatures, allowing us to feel closer to space than ever before.
Experiment (HDEV) aboard the ISS was activated on April 30, 2014. It is mounted on the external cargo vehicle of the European Space Agency's Columbus module. This experiment includes several high definition video cameras that are enclosed in a housing.
Council; place the player in HD and full screen. There are times when the screen will be black, this may be for two reasons: the station passes through the orbit zone, where it is at night, the orbit lasts approximately 90 minutes. Or, the screen gets dark when the cameras change.
How many satellites are in Earth's orbit 2018?
According to the United Nations Office for Outer Space Affairs (UNOOSA) Index of Objects Launched into Outer Space, there are currently some 4,256 satellites orbiting the Earth, up 4.39% from last year.
221 satellites were launched in 2015, the second largest in one year, although below the record 240 launched in 2014. The increase in the number of satellites orbiting the Earth is less than the number launched last year because satellites have a limited lifespan. Large communication satellites are 15 or more years old, while small satellites such as CubeSat can only count on a service life of 3-6 months.
How many of these Earth orbiting satellites are in operation?
The Union of Scientists (UCS) is clarifying which of these orbiting satellites are working, and that's not as much as you might think! Currently, there are only 1,419 operational Earth satellites, only about one third of the total in orbit. This means there is a lot of useless metal around the planet! This is why there is a lot of interest from companies watching them capture and recover space debris using techniques such as space nets, slingshots or solar sails.
What are all these satellites doing?
According to UCS data, the main targets of operational satellites are:
- Communication - 713 satellites
- Earth observation / science - 374 satellites
- Technological demonstration / development using 160 satellites
- Navigation & GPS - 105 satellites
- Space Science - 67 satellites
It should be noted that some satellites have multiple targets.
Who owns the satellites of the Earth?
It is interesting to note that there are four main types of users in the UCS database, although 17% of satellites are owned by multiple users.
- 94 satellites registered by civilians: these are usually educational institutions, although there are other national organizations. 46% of these satellites have the goal of developing technologies such as earth and space science. Observation is another 43%.
- 579 are owned by commercial users: commercial organizations and government organizations that want to sell the data they collect. 84% of these satellites are focused on communications and global positioning services; of the remaining 12% are Earth observation satellites.
- 401 satellites are owned by government users: mainly national space organizations, but also other national and international bodies. 40% of them are communications and global positioning satellites; another 38% are focused on Earth observation. Of the rest, the development of space science and technology is 12% and 10%, respectively.
- 345 satellites belong to the military: communications, Earth observation and global positioning systems are again concentrated here, with 89% of satellites serving one of these three targets.
How many satellites countries have
According to UNOOSA, about 65 countries have launched satellites, although there are only 57 countries registered using satellites in the UCS database and some satellites are listed with co-operative / multinational operators. The biggest:
- USA with 576 satellites
- China with 181 satellites
- Russia with 140 satellites
- The UK is listed as having 41 satellites, plus participates in an additional 36 satellites held by the European Space Agency.
Remember when you look!
The next time you look at the night sky, remember that there are about two million kilograms of metal that surrounds the Earth between you and the stars!
