Why are satellites needed? What is a satellite? Types of artificial satellites
Galaxy star system Milky Way, in which we live, includes the Sun and 8 other planets revolving around it. First of all, scientists are 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 a planet under the influence of gravity. Currently, we know of 44 such celestial bodies.
Only the first two planets of our star system, Venus and Mercury, have no 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 divided into 2 types - natural and artificial.
Artificial - celestial bodies created by people, which open up the opportunity to observe and explore the planet, as well as other astronomical objects. They are necessary for drawing maps, weather forecasts, and radio broadcasting of signals. The largest man-made "fellow traveler" of the Earth is (ISS). Artificial satellites are not only found on our planet. More than 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 genuine interest among scientists. There are several theories, but we will focus on the official versions.
Near each planet there is an accumulation of cosmic dust and gases. The planet attracts celestial bodies that fly close to it. As a result of such interaction, satellites are formed. There is also a theory according to which fragments are separated from cosmic bodies colliding with a 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.
The polar plane is inclined to the equatorial plane of the planet at a right angle.
The trajectory of the inclined orbit is shifted relative to the equatorial plane by an angle of less than 90 0 .
Equatorial (also called geostationary) is located in the plane of the same name, along its trajectory heavenly body moves at the speed of the planet's revolution around its axis.
Also, the orbits of satellites according to their shape are divided into two basic type- 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 surface of the planet. If the satellite moves in an elliptical orbit, this distance changes within the period of one orbit.
Natural satellites of the planets of the solar system: interesting facts
Saturn's moon Titan has its own dense atmosphere. On its surface there are lakes containing 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. For example, countries friendly to the USSR launched satellites from Soviet spaceports. Some satellites, manufactured in Canada, France, and Italy, have been launched since 1962 using launch vehicles developed by the United States.
What is a cosmic body rotating in orbit around a particular planet? By origin they are natural and artificial. The world community is of particular interest natural satellites planets, because they still conceal many mysteries, and most of them are still waiting to be discovered. There are projects to study them 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.
Telecommunications satellites are typically 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 Earth's rotation. An object in GEO has an orbital period equal to its rotation period, so to observers on the ground it appears stationary and occupies a fixed position in the sky.
Satellites in GEO allow constant communication , transmitting radio frequency signals from fixed antennas. These signals are not very different from those used in terrestrial broadcast television transmission and are typically 3 to 50 times higher in frequency. The signal received by the satellite is amplified and transmitted back to Earth, allowing communication between points located thousands of kilometers apart.
A special property that makes geostationary satellites extremely attractive is their ability to transmit information. The relayed signal can be received by antennas anywhere within the satellite's coverage area, comparable to the size of a country, region, continent or even an entire hemisphere. Anyone who has a small antenna 40-50 cm in diameter can become a direct user of the satellite.
A satellite operating in geostationary orbit does not need any engine and its stay in Earth orbit can last for many years. Friction from the thin upper atmosphere will eventually slow it down and cause it to sink lower and eventually burn up in the lower atmosphere.
If a satellite is launched with more fuel, it moves faster and its orbital radius is larger. 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 science and observation satellites operate at much lower altitudes: they orbit the Earth in approximately 90 minutes at altitudes of several hundred kilometers.
Telecommunications satellites can also be on LEO, being visible from any location for 10-20 minutes. To guarantee the continuity of information transmission in this case, the deployment of dozens of satellites will be necessary.
LEO telecommunications systems may require 48, 66, 77, 80 or even 288 satellites to provide the required services. Several of these systems have been deployed to provide communications 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 - a plus for them: no careful tracking of the satellite is necessary in this case. In addition, low altitude minimizes signal travel time delay and requires less transmitter power to establish communications.
In a broad sense, a companion is a fellow traveler or comrade, someone who accompanies someone on a journey. But not only people have satellites. Planets also have their “fellow travelers”. What are they? When did the artificial satellite first appear?
The emergence of satellites
In astronomy, the concept of “satellite” first appeared thanks to the scientist Johannes Kepler. He used it back in 1611 in his work Narratio de Iovis Satellitibus. In the usual sense, planetary satellites are cosmic bodies that revolve around planets. They rotate in their own orbit under the influence of the gravitational forces of their “senior companion”.
Natural satellites are bodies that appeared naturally, without human intervention. They can be formed from gas and dust or from a fragment of a celestial body, captured by the gravitational forces of the planet. When they come under the influence of gravitational forces, they are transformed, for example, they compress and become denser, acquire a spherical shape (not always), etc.
It is assumed that most of the modern satellites of the planets are their fragments, broken off as a result of a collision, or former asteroids. As a rule, they consist of ice and minerals, unlike planets, do not have a metallic core, and are dotted with craters and faults.
When you open a satellite, it is assigned a number. Then the discoverer has the right to name it at his own discretion. Traditionally, their names are associated with mythology. Only Uranus has them named after literary characters.
Satellites of the planets
Planets can have a wide variety of “companions.” The Earth has only one - the Moon, but Jupiter has 69 of them. Venus and Mercury have no satellites. Claims about their discovery appear from time to time, but all of them are soon refuted.
Jupiter's moon Ganymede is considered the largest in the solar system. It consists of silicates and ice, and reaches a diameter of 5,268 kilometers. It takes him 7 days and 3 hours to complete a revolution around Jupiter.
Mars has two “fellow travelers” with the impressive names Deimos and Phobos, which are translated from Greek as “horror” and “fear”. They have a shape close to a triaxial ellipsoid (the length of the semi-axes is not the same). Scientists say that the speed of Phobos is gradually decreasing, and it is approaching the planet. One day it will simply fall to Mars or collapse, forming a planetary ring.
Moon
The only natural satellite of the earth is the Moon. This is the closest and most studied celestial body by us outside of planet Earth. It has a core, lower, middle, upper mantle and crust. The Moon also has an atmosphere.
The satellite's crust consists of regolith - residual soil made of dust and rocky fragments of meteorites. The surface of the Moon is covered with mountains, furrows, ridges, as well as seas (large lowlands covered with solidified lava). Its atmosphere is very rarefied, which is why the sky above it is always black and starry.
The movement of the Moon around the Earth is complex. It is influenced not only by the gravity of our planet, but also by its oblate shape, as well as the gravity of the Sun, which attracts the Moon more strongly. Its complete circulation takes 27.3 days. Its orbit is in the ecliptic plane, while most other satellites are located in the equator.
The moon also rotates around its own axis. However, this movement is synchronized in such a way that it always faces the same side towards the Earth. The same phenomenon is observed in Pluto and its satellite Charon.
Artificial satellites
Artificial satellites are devices created by man and sent into near-planetary orbit. Inside they contain various instruments necessary for research.
As a rule, they are unmanned and controlled from earthly space stations. To launch them into space, special manned vehicles are used. Satellites are:
- research - for studying space and celestial bodies;
- navigation - to determine the location of Earth objects, determine the speed and direction of the signal receiver (GPS, Glonas);
- communications satellites - transmit radio signals between distant points on Earth;
- meteorological - receives data on the state of the atmosphere for weather forecasting.
The first artificial Earth satellite was launched during the Cold War in 1957. It was sent from the USSR and was called Sputnik 1. A year later, the United States released Explorer 1. Only a few years later they were followed by Great Britain, Canada, Italy, France, Australia and many other countries.
In our VK group (vk.com/posterspbru) one of the users left the following playfully sarcastic comment:
- Monya, where are you looking?
- To the stars. You won’t believe it, there are 8000 satellites there!
- So, did it become easier to breathe?
He gave us the idea for this article.
Perhaps Monya’s friend is right - in the literal sense of the word, satellites do not help people breathe. Although this is a controversial issue, because satellites can save people from situations in which people could suffocate. Probably many of us rarely think about how much our companions influence our lives.
These are some of the applications that satellites provide us.
1. Satellites send television signals into 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 and so on. Satellites transmit signals from central station, which generates programs for smaller stations that transmit signals locally. All direct broadcasts are possible thanks to satellites.
2. Satellites provide telephone communications on airplanes and are often the only link telephone communication for many rural regions and areas where telephone lines damaged as a result of natural disasters. Satellites also provide the primary timing source for cell phones and pagers. In 1998, a satellite failure demonstrated this dependence - 80% of pagers in the United States were temporarily silenced, National Public Radio was unable to distribute its broadcasts to affiliates and transmitted only through its website, and the CBS Evening News video was frozen and broadcast only audio.
3. Satellite navigation systems allow any user to navigate the terrain. GPS navigators are part modern world, regardless of whether they are used in private cars or for commercial or military purposes for navigation on land, sea or in the air. And by the way, GPS navigation plays a decisive role in many situations, such as when a ship is heading towards a harbor in bad weather.
4. Satellites connect companies with suppliers, are the basis for international video conferencing, and provide instant authorization credit card and conducting banking operations. Without a satellite in orbit, you will not be able to pay for goods in a hypermarket with your bank card.
5. Satellites provide meteorologists with weather data, with which they monitor not only whether it will be cloudy or sunny today, but also volcanic eruptions, hurricanes, gas leaks, and the like. Returning to the question about Monet 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 towards the place where he is. Or a satellite can rescue him at sea or on land by transmitting a beacon signal to rescue services.
Satellites are one of the main sources of data for climate change research. Satellites monitor ocean temperatures and currents. They can indicate air pollution, help organize rescue operations in disaster areas, help locate people in remote regions, transmit distress signals, etc.
6. The satellite can be detected The groundwater and mineral springs, monitor the transfer of nutrients and pollutants from land to water sources, measure land and water temperatures, measure algae growth in the seas and topsoil erosion on land. They can effectively monitor large-scale infrastructure, such as fuel pipelines, which need to be checked for leaks using satellites rather than manual labor (which would take many hours). Satellite imagery helps various industries and even you can benefit Google Earth thanks to satellites.
Satellites provide great importance on developing countries, as they provide their populations in remote regions with access to data, educational information, medical information, etc. A person can receive the correct treatment only because his doctor has consulted with a more experienced colleague.
7. Space research is impossible without satellites. Telescope satellites play a critical role in understanding many cosmic phenomena.
Man-made satellites orbiting the Earth greatly influence our modern lives, although many do not realize it. To some extent, satellites help us breathe freely by providing us with data, timely assistance, and opportunities. Satellites make life safer, provide many modern conveniences, and also help broadcast entertainment and study the Earth and space.