Natural satellites of planets. What are satellites for?

The star system of the Milky Way galaxy in which we live includes the Sun and 8 other planets orbiting 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 .

The equatorial plane (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 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, 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. 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 natural satellites of the planets are of particular interest to the world community, 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.

An Earth satellite is any object that moves along 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 the Earth. The path followed by a satellite is an orbit, which sometimes takes the shape of a circle.

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To understand why satellites move the way they do, we have to go back to our friend Newton. exists between any two objects in the Universe. If 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 a strong gravitational attraction directed towards the center of the planet.

Orbits of artificial earth satellites

Sometimes the orbit of an artificial Earth satellite 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 at one of the foci. As a result, the net force applied to the satellite is not uniform throughout the 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 furthest from Earth - a point known as apogee.

There are many different satellite orbits of the Earth. The ones that receive the most attention are geostationary orbits because they are stationary over a specific point on the Earth.

The orbit chosen for an artificial satellite depends on its application. For example, live broadcast television uses the geostationary orbit. Many communications satellites also use geostationary orbit. Other satellite systems, such as satellite phones, may use low-Earth orbits.

Likewise, 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 weather satellites to research satellites. Each will have its own orbit type depending on its application.

The actual Earth satellite orbit chosen will depend on factors including its function, and the area in which it is to serve. In some cases, the Earth satellite's orbit can be as large as 100 miles (160 km) for a LEO low earth orbit, while others can reach over 22,000 miles (36,000 km) as in the case of a GEO low earth 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 the second satellite in orbit and also the first to carry an animal on board, a female dog named Laika. Sputnik 3 suffered the first failure.

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 about the concentration of electrons in the ionosphere. Temperature and pressure were encoded over 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 with a diameter of 58 cm, having four long and thin antennas ranging from 2.4 to 2.9 m in length. The antennas looked like long mustaches. The spacecraft received information about the density of the upper atmosphere and the propagation of radio waves in the ionosphere. Instruments and sources electrical energy were housed in a capsule that also included radio transmitters operating at 20.007 and 40.002 MHz (about 15 and 7.5 m wavelength), the emissions were made in alternate groups of 0.3 s duration. Ground telemetry included temperature data inside and on the surface of the sphere.

Because the sphere was filled with pressurized nitrogen, Sputnik 1 had its first opportunity to detect meteorites, although it did not. The loss of pressure inside, due to penetration to the outer surface, was reflected in the temperature data.

Types of artificial satellites

There are artificial satellites different types, shapes, sizes and play different roles.

Weather satellites help meteorologists predict the weather or see what's happening in at the moment. A good example is the Geostationary Operational Environmental Satellite (GOES). These earth satellites typically contain cameras that can return photographs of Earth's weather, either from fixed geostationary positions or from polar orbits.
Communications satellites allow the transmission of telephone and information conversations via satellite. Typical communications satellites include Telstar and Intelsat. The most important feature of a communications satellite is the transponder, a radio receiver that picks up a conversation on one frequency and then amplifies it and retransmits it back to Earth on a different frequency. A satellite typically contains hundreds or thousands of transponders. Communications satellites are usually geosynchronous.
Broadcast satellites transmit television signals from one point to another (similar to communication satellites).
Scientific satellites, such 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 are GPS satellites NAVSTAR.
Rescue satellites respond to radio interference signals.
Earth observation satellites checking the planet for changes in everything from temperature, forest cover, to ice cover. The most famous are the Landsat series.
Military satellites The Earths are in orbit, but much of the actual information about the position remains secret. Satellites could include encrypted communications relay, nuclear monitoring, surveillance of enemy movements, early warning of missile launches, eavesdropping on terrestrial radio links, radar imaging, and photography (using essentially large telescopes that photograph militarily interesting areas).

Earth from an artificial satellite in real time

Images of the earth from an artificial satellite, broadcast in real time by NASA from the International Space Station. Images are captured by four cameras high resolution, isolated from low temperatures, allowing us to feel closer to space than ever before.

The experiment (HDEV) on board the ISS was activated on April 30, 2014. It is mounted on the external cargo mechanism of the European Space Agency's Columbus module. This experiment involves several high-definition video cameras that are enclosed in a housing.

Advice; put the player in HD and full screen. There are times when the screen will be black, this can be for two reasons: the station is passing through an orbital zone where it is at night, the orbit lasts approximately 90 minutes. Or the screen goes dark when the cameras change.

How many satellites are there in Earth 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 in Earth's orbit, up 4.39% from last year.

221 satellites were launched in 2015, the second most in a single year, although it is lower record number 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 communications satellites last 15 years or more, while small satellites such as CubeSats can only expect a service life of 3-6 months.

How many of these Earth orbiting satellites are operational?

The Union of Scientists (UCS) is clarifying which of these orbiting satellites are working, and it's not as much as you think! There are currently only 1,419 operational Earth satellites - only about one third of the total number in orbit. This means there is a lot of useless metal around the planet! That's why there's a lot of interest from companies looking at how they capture and return space debris, using techniques like space nets, slingshots or solar sails.

What are all these satellites doing?

According to UCS, the main objectives of operational satellites are:

Communications - 713 satellites
Earth observation/science - 374 satellites
Technology demonstration/development using 160 satellites
Navigation & GPS - 105 satellites
Space science - 67 satellites

It should be noted that some satellites have multiple purposes.

Who owns the Earth's satellites?

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 purpose of developing technologies such as Earth and space science. Observations account for another 43%.
579 belong to commercial users: commercial organizations and government organizations who want to sell the data they collect. 84% of these satellites are focused on communication services and global positioning; 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% is focused on Earth observation. Of the remainder, the development of space science and technology accounts for 12% and 10%, respectively.
345 satellites belong to the military: again the focus here is communications, Earth observation and global positioning systems, with 89% of the satellites having one of these three purposes.

How many satellites do countries have?

According to UNOOSA, about 65 countries have launched satellites, although the UCS database only has 57 countries recorded using satellites, and some satellites are listed with joint/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 operated by the European Space Agency.

Remember when you look!
Next time you look at the night sky, remember that between you and the stars there are about two million kilograms of metal surrounding the Earth!

Who among us has not shouted 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 it’s a completely different story! Satellites provide communications, television, coordinate determination, security, and the Internet. And people will come up with many more things to make space technologies serve for the benefit of people.
And we will tell you why and what methods of using satellite systems are most popular today.

Why can sometimes only satellite technologies be the only development option?
When installing land lines, wires are used - fiber optic or copper, or when wireless technology – cellular networks or radioethernet.

All this rather expensive work always has significant disadvantages:

Limitation of territory coverage. Any signal transmitter or receiver has a certain operating area, which depends on the power and terrain of the area;
network modernization issues always concern technical capabilities and the feasibility of spending financial resources;
It is often impossible to quickly dismantle equipment and set up a station in a new location.

And in some cases, the most justified in a technical and financial sense for ensuring reliable and high-quality communications is the use of satellite systems.

Satellites will always find us

Without satellite technology, we would never have the opportunity to find each other on our big planet.
The global coordinate system allows you to accurately determine the location of objects (longitude, latitude, and even altitude above sea level), as well as the direction of movement and speed of this object.
Famous American system GPS (Global Positioning System) includes 24 artificial satellites, a wide network of ground stations that have unlimited opportunity for connecting user terminals.
The GPS system operates continuously. Anyone on the planet can use it, you just need to purchase a GPS navigator. Manufacturers offer portable, automotive, aviation, and marine models. Search work and rescue operations in no country in the world are complete without the help of GPS.

Satellites protect us

This is especially true in the automotive industry. The main security system is successfully combined with satellite communication channels, GPS system 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, a signal from the central unit is transmitted via communication channels to the owner or dispatcher. The GPS system helps track the route, location, and driving mode in real time.
Satellites entertain us
The most current and most famous topic is satellite television. But we are already so accustomed to the plates on our houses that we practically do not notice it. But just three devices: an antenna, a receiver, a converter give us extraordinary pleasure from watching our favorite television programs.
Difference from traditional TV antenna in which, instead of a tower, a satellite acts and transmits digital signal. This results in a large selection of channels and image quality.

Satellites connect us with friends

The most common and well-known global satellite communication systems (GCSS): Globalstar, Inmarsat, Iridium, Thuraya. At the very beginning of their creation, it was assumed that these systems would organize mobile and landline telephony where there were no communication lines. In further development, new opportunities appeared: access to the Internet, transfer of information to various formats. And the GSSS became multi-service.
If we describe the operation of these systems in a nutshell, it will look like this.
The satellite receives the subscriber's signal and transmits it to the nearest station on Earth. The station detects the signal, selects a route and routes it through terrestrial networks or satellite channel to the reception point.
The differences between global satellite communication systems are in the cost of traffic, the size and cost of user terminals, coverage areas, as well as technical features concept of the system itself.

Satellites help us live comfortably

Actively developing satellite system Very Small Aperture Terminal - VSAT. This system is like a basis for a designer: you can add equipment and get access to the Internet, other equipment - and already combined local networks users in different territories. 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 start working. The quality of communication, ease of maintenance and use have already been appreciated by financial institutions, retail chains, large industrial enterprises.

A VSAT-based network consists of a central control station (CCS), user terminals and a relay satellite.
WITH further development inevitably all systems will 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, looking dreamily at the night sky and seeing a moving star, you will think that they, satellites, greatly facilitate and diversify life. And this is wonderful.

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.

Satellites and planets of the solar system

The natural satellites of planets play a huge role in the life of these space objects. Moreover, even we humans are capable of feeling the influence of our planet’s only natural satellite – the Moon.

The natural satellites of the planets of the solar system have aroused keen interest among astronomers since ancient times. To this day, scientists are studying them. What are these space objects?

Natural satellites of planets are cosmic bodies of natural origin that orbit around planets. The most interesting for us are the natural satellites of the planets of the solar system, since they are in close proximity to us.

There are only two planets in the solar system that do not have natural satellites. These are Venus and Mercury. Although it is assumed that Mercury previously had natural satellites, this planet lost them in the process of its evolution. As for the rest of the planets in the solar system, each of them has at least one natural satellite. The most famous of them is the Moon, which is our planet’s faithful cosmic companion. Mars has, Jupiter -, Saturn -, Uranus -, Neptune -. Among these satellites we can find both very unremarkable objects, consisting mainly of stone, and very interesting specimens that deserve special attention, and which we will discuss below.

Classification of satellites

Scientists divide planetary satellites into two types: satellites of artificial origin and natural ones. Satellites of artificial origin or, as they are also called, artificial satellites- These are spacecraft created by people that make it possible to observe the planet around which they orbit, as well as other astronomical objects from space. Typically, artificial satellites are used to monitor the weather, radio broadcasts, changes in the topography of the planet's surface, and also for military purposes.

The ISS is the largest artificial satellite of the Earth

It should be noted that not only the Earth has satellites of artificial origin, as many people believe. More than a dozen artificial satellites created by mankind revolve around the two closest planets to us - Venus and Mars. They allow you to monitor climate conditions, changes in terrain, and also receive other relevant information regarding our space neighbors.

Ganymede is the largest moon in the solar system

The second category of satellites - natural satellites of planets - is of great interest to us in this article. Natural satellites differ from artificial ones in that they were created not by man, but by nature itself. It is believed that most of the satellites of the solar system are asteroids that were captured by the gravitational forces of the planets of this system. Subsequently, the asteroids took on a spherical shape and, as a result, began to revolve around the planet that captured them as a constant companion. There is also a theory that says that the natural satellites of planets are fragments of these planets themselves, which for one reason or another broke away from the planet itself during the process of its formation. By the way, according to this theory, this is how the Earth’s natural satellite, the Moon, came into being. This theory is confirmed by chemical analysis of the composition of the Moon. He showed that the chemical composition of the satellite is practically no different from chemical composition our planet, where the same chemical compounds are present as on the Moon.

Interesting facts about the most interesting satellites

One of the most interesting natural satellites of the planets of the solar system is the natural satellite. Charon, in comparison with Pluto, is so huge that many astronomers call these two space objects nothing more than a double dwarf planet. The planet Pluto is only twice the size of its natural satellite.

The natural satellite is of keen interest to astronomers. Most of the natural satellites of the solar system's planets are composed primarily of ice, rock, or both, resulting in them lacking an atmosphere. However, Titan has this, and quite dense one, as well as lakes of liquid hydrocarbons.

Another natural satellite that gives scientists hope for discovering extraterrestrial life forms is Jupiter’s satellite. It is believed that under the thick layer of ice that covers the satellite there is an ocean, inside of which there are thermal springs - exactly the same as on Earth. Since some deep-sea life forms on Earth exist thanks to these sources, it is believed that similar life forms may exist on Titan.

The planet Jupiter has another interesting natural satellite -. Io is the only satellite of a planet in the solar system on which astrophysicists first discovered active volcanoes. It is for this reason that it is of particular interest to space researchers.

Natural satellite research

Research on the natural satellites of the planets of the Solar System has interested the minds of astronomers since ancient times. Since the invention of the first telescope, people have been actively studying these celestial objects. The breakthrough in the development of civilization made it possible not only to discover a colossal number of satellites of various planets of the solar system, but also to set man on the main, closest to us, satellite of the Earth - the Moon. On July 21, 1969, American astronaut Neil Armstrong, together with the crew of the Apollo 11 spacecraft, first set foot on the surface of the Moon, which caused rejoicing in the hearts of humanity at that time and is still considered one of the most important and significant events in space exploration.

In addition to the Moon, scientists are actively studying other natural satellites of the planets of the solar system. To do this, astronomers use not only visual and radar observation methods, but also use modern spacecraft, as well as artificial satellites. For example, the “” spacecraft for the first time transmitted to Earth images of several of Jupiter’s largest satellites:,. In particular, it was thanks to these images that scientists were able to record the presence of volcanoes on the moon Io, and the ocean on Europa.

Today, the global community of space researchers continues to be actively engaged in the study of the natural satellites of the planets of the solar system. In addition to various government programs, there are also private projects aimed at studying these space objects. In particular, the world-famous American company Google is currently developing a tourist lunar rover, on which many people could take a walk on the Moon.