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Satellite is revolving around a larger object in space. There are two types of satellites: natural and artificial. Natural satellites such as the moon, which revolves around the earth. And Artificial satellites or human-made satellites revolve around the earth to transmit data. Communication alludes to the sharing of data between at least two substances, through any medium or channel.

Along these lines, satellite communication is characterized as the communication that happens between any two earth stations through a satellite. Electromagnetic waves are utilized as transporter signals. These signs convey data like voice, sound, video or some other information among ground and space.

Satellite communication is utilized to relay and enhance radio telecom signals through a transponder; it makes a communication channel between a source transmitter and a receiver at various areas on Earth. The first artificial Earth satellite was Sputnik 1 which was placed into space by the Soviet Union on October 4, 1957. It was created by Mikhail Tikhonravov and Sergey Korolev, expanding on work by Konstantin Tsiolkovsky. Satellite Communications are utilized for TV, phone, radio, web, and military applications.

Passive and active satellites communication:

There are two significant classes of satellite communications, passive and active. Passive satellites only reflect the signal toward the direction of the receiver. With passive satellites, the reflected signal is not enhanced at the satellite, and only a very small amount of the communicated energy arrives at the collector. Since the satellite is so far above Earth, the radio signal is attenuated due to free-space path loss, so the signal received on Earth is extremely weak. Active satellites enhance the strength of the received signal before retransmitting it to the receiver on the ground. Passive satellites were the first communications satellites, however, are minimally utilized at this point.

Requirement of Satellite Communication

The following two sorts of propagation are used before for correspondence dependent upon some distance.

Ground wave propagation − Ground wave propagation is appropriate for recurrence up to 30MHz. This technique of satellite communication utilizes the lower atmosphere states of the earth.

Skywave propagation − The appropriate data transmission for this kind of communication is extensively between 30-40 MHz and it utilizes the ionosphere properties of the earth.

The most extreme station distance is restricted to 1500 KM only in both ground wave propagation and skywave propagation. Satellite communication overcomes this limitation. In this technique, satellites provide communication for significant distances. 

The communication takes place between any two earth stations effectively through satellite, as the satellites are situated at a specific height above the earth. In this way, it conquers the restriction of correspondence between two earth stations because of the earth’s curvature.

Work of satellites:

Three phases are involved which clarify the working of satellite communications.

These are:

  • Uplink
  • Transponders
  • Downlink

Uplink: In the first stage, the signal from the television broadcast on the opposite side of the earth is first radiated up to the satellite from the ground station on the earth. This process is known as uplink.

Transponders: These transponders are utilized for amplifying the approaching signal and to change their recurrence so that the outgoing signals are not adjusted. The transponders vary contingent upon the approaching signal sources. The transponders, for example, receivers, amplifiers, and transmitters.

Downlink: The last stage includes a downlink in which the information is transmitted to the receiver on the earth. There are one uplink and many downlinks.

Satellite communication

A repeater enhances the strength of the received signal and afterwards sends it. However, this repeater works as a transponder, Which changes the recurrence band of the transmitted signal. 

Satellite orbits:

  • Geostationary Earth Orbiting (GEO): GEO has an equatorial orbit around Earth. It is at an altitude of 35786 km and the orbital period is equivalent to the Earth rotation period. The size of the GEO beam footprint goes from 200 to 3500 km. Earth-based satellite antennas do not have to rotate to track communications satellites; that’s why communications satellites are situated in a geostationary orbit. Communications satellites can be pointed permanently at the position in the sky where the satellites are situated. Weather satellites are also situated in this orbit for real-time observations and information gathering, and navigation satellites improve GPS accuracy.
  • Medium Earth Orbiting (MEO): MEO has a circular orbit around Earth. MEO is situated at an altitude ranging from 7000 to 25000 km. The size of the MEO beam footprint goes from 100 to 1000 km. Communications satellites in MEO incorporate the O3b and O3b mPOWER constellations. These are utilized for communication to maritime and remote locations. 
  • Low Earth Orbiting (LEO): LEO has a circular orbit around Earth. LEO is situated at an altitude ranging from 300 to 1500 km. The size of the LEO beam footprint goes from 100 to 1000 km. 

Applications of satellite communication:

  • Radio broadcasting: Satellite radio provides sound transmission administrations in certain nations. Versatile administrations permit listeners to roam a continent, listening to the same audio programming anywhere. Satellite radio is broadcast by a communications satellite, which covers a lot more extensive geological reach than terrestrial radio signals.
  • Web access: satellite communication innovation has been utilized as a way to interface with the Internet through broadband information associations.
  • Military: Communications satellites are utilized for military communications applications. To convey significant data starting with one site then onto the next.
  • Information assortment: Satellite correspondence is used to gather the climate data. 
  • Communication: It is a significant application for communication satellites in intercontinental significant distance communication. The Public Switched Telephone Network transfers call from landline phones to an earth station, where they are then sent to a geostationary satellite.

Advantages of satellite communication:

  • The area of inclusion is more.
  • Transmission cost is autonomous of inclusion region
  • More data transmission and broadcasting prospects

Disadvantages of satellite communication 

  • It is very expensive to launch the satellites into orbit.
  • The propagation delay of satellite frameworks is more than that of conventional terrestrial frameworks.
  • Hard to give fixing exercises on the off chance that any issue happens in a satellite framework.
  • Free space loss is maximum in satellite communications. 
  • There can be congestion of frequencies.

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