Artificial Satellites

We explain what artificial satellites are and the types of satellites that exist. Also, what are its general characteristics and functions.

What are artificial satellites?

Artificial satellites are objects that human beings make and throw into outer space with the aim of orbiting a celestial body (a planet) or a natural satellite (for example, the moon). They differ from natural satellites, which are celestial bodies that orbit a planet.

The purpose of these satellites is to obtain certain useful information about the celestial body or natural satellite that they observe. Satellites orbiting planet Earth are used to improve telecommunicationssince they emit signals and allow the operation of telephones, the Internet and digital television. They are also used to generate weather reports and obtain information about the Earth’s surface.

Satellites are launched into space and They must pass through the Earth’s atmosphere and achieve orbit around a celestial bodywhich is usually Earth. Once there, they must follow a specific route depending on their objective. The satellites have an energy recharge that allows them to extend their useful life. However, after power depletion, the satellite is discarded in outer space as space debris.

The first artificial satellite and the space race

The first space satellite It was sent in October 1957 by the Soviet Union and was called Sputnik I. Its objective was to collect information about the highest layers of the atmosphere.

This occurred within the framework of the space race that began in the mid-1950sbetween the United States and the Soviet Union, which aimed at space exploration with the development of satellites and sending humans into space. The United States managed to send its first artificial satellite, called Explorer Iin 1958 and had as one of its greatest successes the discovery of the Van Allen belts.

Later other countries managed to place artificial satellites in Earth’s orbit. It is believed that there are currently almost 5,000 satellites orbiting the Earth. and more than half are already inactive and constitute the so-called space junk.

Due to scientific development and the necessary financial support, few countries in the world sent satellites into space. Those leading the list of shipments are: Russia, the United States, France, Japan and China.

Characteristics of artificial satellites

The main characteristics of artificial satellites are:

• They are created by humans. Satellites are launched for a specific purpose that varies depending on each case.
• They usually orbit planet Earth. Most of the satellites that are built are used to obtain information about planet Earth or fulfill certain purposes that contribute to human and social development.
• They can be spherical, cylindrical or conical.. Inside they have highly delicate and sensitive materials.
• They can be observed from Earth. The most suitable times are two hours before sunrise and two hours after sunset.
• They can be scientific or applied. Scientific satellites have the function of studying space, radiation or planets, and applied satellites have a specific function on Earth, such as meteorological observation, military espionage or telecommunications.
• They are made up of certain fundamental parts. Satellites are made up of: solar panels, which absorb solar energy and convert it into electrical energy (in some cases they can be made up of batteries); antennas, which are responsible for transmitting and receiving information; a control center, which processes the stored information, and a camera or mechanism that collects information.
• They must have a route or trajectory to follow. When a satellite has a path around a planet, it is called an orbit. If this orbit is elliptical, it will have a farther point called “apogee” and a closer point called “perigee.”
• They can be active or inactive. Satellites have a certain useful life, so after a while, or due to certain factors, they become obsolete. In some cases they remain in Earth’s orbit as space debris, but in others they can re-enter the atmosphere, where they disintegrate and return to Earth.
• They are launched in a rocket. In order to place a satellite that orbits the Earth, a powerful driving mechanism is required, since the satellite must reach a speed of 8 km per second. For this, it is necessary to build a rocket that has the satellite inside, which will be dropped once the desired location is reached.

Types of satellites

Satellites can be classified according to two main criteria:

According to its purpose:

• Communication satellites. They are satellites that help transmit the signals necessary for telecommunications. They usually emit television and radio signals from one point to another. The first satellite of this type was Telstar 1.
• Weather satellites. They are satellites used to evaluate, measure and predict climatic conditions on Earth. The first satellite of this type was Shots-1released in 1960.
• Navigation satellites. They are satellites that are used to know the precise and exact position of something or someone on Earth. They are, for example, those used by the GPS system, Galileo and GLONASS.
• Reconnaissance satellites. They are better known as spy satellites and are used in the military or intelligence services.
• Astronomical satellites. They are satellites that are manufactured to observe galaxies, planets, asteroids or other astronomical objects.
• Solar energy satellites. They are satellites that serve as a power source. They receive energy from the sun and redirect it to the antennas of homes on Earth.

Depending on the type of orbit:

• Low Earth Orbit. They are satellites that are located at a short distance from the Earth’s surface, between 700 and 1400 km, and their orbital period is between 80 and 150 minutes.
• Middle Earth orbit or intermediate circular orbit. They are satellites that are located between 9,000 and 20,000 km and their orbital period can be between 10 and 14 hours.
• Geostationary orbit. They are satellites that are 35,786 km away above the equator. These satellites always remain over the same place on Earth, that is, they do not rotate.

Space junk

After its useful life or the collection of necessary data, an artificial satellite can remain orbiting a celestial body without any use. Therefore, it is said to become space junk.

Space debris is often a risk for spacecraft that are launched from Earth into space, because these loose satellite remains can damage or destroy them.

In case the satellite is at a low altitude, it can disintegrate and enter the Earth’s atmosphere in portions.

Importance of artificial satellites

Artificial satellites that manage to position themselves in Earth orbit are fundamental for the development of the human species and life in society. They are used both in the field of scientific research and development, as well as in telecommunications and meteorology.

On the one hand, satellites are used for scientific research since many of them are sent into space with the aim of explore other planets or bodies and detect meteorites. In addition, they allow us to observe life on Earth and study phenomena such as deforestation, different types of relief, sea level, pollution and explore regions that are inhospitable or difficult to access for humans.

Satellites are essential for obtaining useful information, such as climate data at a specific point on the planet or that necessary for creating maps. They are also in charge of development of GPS type technology which allows knowing the almost exact position of any object on the Earth’s surface.

Artificial satellites are of great importance in the field of telecommunications because transmit messages and information from one point on the planet to another. Communication satellites send and receive signals that allow the development of communication technologies and media such as television, radio, cell phones and the Internet.

Natural satellites

Unlike artificial satellites, which are created by humans, natural satellites are those that They exist naturally in space.

Natural satellites are celestial bodies (objects located in space) that orbit around a planet (although bodies that orbit around other celestial bodies are also often called satellites). The most recognized case of a natural satellite is the Moonwhich is the only natural satellite that orbits planet Earth. In many cases the term moon is often used as a synonym for a natural satellite.

Other natural satellites are: the four main satellites of Jupiter: Io, Europa, Ganymede and Callisto; the largest satellite of Saturn – Titan; the two satellites of Mars: Deimos and Phobos; and the main satellites of Uranus: Titania, Miranda, Ariel, Umbriel and Oberon.

Types of artificial satellites

Broadly speaking, artificial satellites are classified into two:

• Observation satellites. For astronomical or geolocation work,
• Telecommunications satellites

However, according to their specific function, several subtypes can be distinguished:

• Communications satellites Employees in telephone, radio, television, etc. work.
• Meteorological satellites In constant observation of the weather, atmospheric conditions and other important details of non-military cartography.
• Navigation satellites Necessary for geolocation and GPS.
• Reconnaissance satellites Also called spy satellites, they are used for military or intelligence purposes.
• Astronomical satellites They serve as orbiting telescopes to observe regions of outer space without the interference of the atmosphere.
• Space stations Structures of greater size and complexity than simple satellites, which allow human beings to live in space and conduct scientific experiments there.

What are artificial satellites used for?

Before we have talked about the specific functions of satellites, that is, the tasks to which they can dedicate their resources. However, the essential function of satellites can be explained by the interest of human beings in having a better point of view of our planet and outer space than from the ground.

This allows not only a more global perspective of the planet which is key in a world of globalized economy and interests, but also to be able overcome the distortions inherent to the Earth’s atmosphere and take a look outside.

On the other hand, satellites have been thought of as war artifacts since their inception, since they could be equipped with extra-atmospheric weapons that allow them to attack rivals from unreachable positions on the border with space.

Likewise, thinking about less destructive purposes, the design and construction of solar energy collecting satellites has been proposed, which could serve as gigantic solar panels in space and supply constant and almost free energy to the Earth.

How do artificial satellites work?

Artificial satellites must be put into orbit by some type of space launch which once the desired region of the atmosphere is reached, leaves the device forever. Although there are hundreds of possible orbits, satellites are generally located on three types of trajectories:

• Low Earth orbit (Low Earth Orbit) Between 700 and 1,400 km high, with an orbital period of 80 to 150 minutes.
• Middle Earth orbit (Medium Earth Orbit) Between 9000 and 20,000 km altitude, with an orbital period of 10 to 14 hours.
• High Earth Orbit (High Earth Orbit) At a height of 37,786 km above the Earth’s equator, with an orbital period of 24 hours over the same place on the planet.

Once in orbit, the satellites deploy their solar panels, which allows them to capture energy from the Sun to send and receive information and instructions from the Earth, using microwave antennas for the latter.

Artificial Earth satellites

Currently, Our planet is being orbited by more than 5,600 artificial satellites of different nature, as well as by 21,000 satellite fragments of more than 10 centimeters, about 500,000 of around one centimeter and more than one billion particles sized at one centimeter.

All of the latter makes up the so-called “space junk” and represents a real danger for future space missions and future satellites. This space debris ranges from astronaut gloves to broken telescopes and fragments of disused spacecraft, nuts, bolts, fragments of matter, etc.

Through the website http://stuffin.space you can observe all the satellites and space debris on the planet in real time.

Natural satellites

Unlike artificial satellites, natural satellites were born together with the astronomical body they orbit (generally planets) or became trapped in their orbit as a result of some type of cosmic or astronomical phenomenon.

The most obvious case of natural satellites is our Moon but there are many more on other planets in the Solar System. Some are similar in size and shape to ours, and others consist of rocks of different shapes or groups of asteroids that form “rings” around the planet, as happens with Saturn.

References:

• “Components of a satellite” at Space Foundation.
• “What is a satellite?” at NASA.
• “How satellites work” in Britannica.
• “Sputnik, the first satellite that launched the space race between the USSR and the United States 60 years ago” on BBC.