In telecommunication, the use of artificial satellites to provide communication links between various points on the earth is known as satellite communication. Today, we have approximately 2,000 artificial satellites orbiting the earth carrying voice, video, and data to and from one or many locations worldwide.
Development of Satellite Communication
The idea of satellite communication first appeared in the short story “The Brick Moon.” The story describes the construction and launch of a satellite made of bricks into the earth’s orbit. The satellite aided mariners in navigation, as people sent Morse code signals back to earth by jumping up and down on the satellite’s surface.
The emergence of the First Practical Concept of Satellite Communication
In 1945, Arthur C. Clarke, a Royal Air Force officer, proposed the first practical concept of satellite communication. Clarke suggested that a satellite at an altitude of 35,786 km above the earth’s surface would be moving at the same speed as earth’s rotation. At this altitude, the satellite would remain in a fixed position relative to a point on earth. This orbit is now known as the “geostationary orbit.” It is ideal for satellite communication because an antenna on the ground can be pointed to a satellite 24 hours a day without having to track its position. Clarke theorised that three satellites spaced equidistantly in geostationary orbit would provide radio coverage to the entire world except for some of the polar regions.
Launch of the first artificial Satellite
Sputnik 1, was the first satellite to be successfully launched by the Soviet Union on October 4, 1957. It followed an elliptical orbit around the earth, taking about 96 minutes to complete a revolution. The satellite was 58 cm in diameters with four antennas sending low-frequency radio signals at regular intervals. It transmitted signals for only 22 days until its battery ran out and was in orbit for only three months.
Other Major Milestones in Satellite Communications
- Pioneer 1, an intended lunar probe, was the first satellite to relay communications. The satellite flew high enough to carry out the proof of concept relay of telemetry across the world.
- In 1958, NASA’s project SCORE was the first satellite that was built for relay communication. It made use of a tape recorder to store and forward voice messages.
- Syncom 3 was the first geostationary communication in geosynchronous orbit making it appear as a stationary object in the sky from the ground.
Communication satellites have one of three primary types of orbit, and they are classified as:
- Geostationary orbit – In this orbit, the apparent position of the satellite in the sky when viewed by a ground observer doesn’t change. This is because the satellite’s orbital period is the same as the rotation rate of the earth.
- Medium Earth Orbit – In this region, the satellites are closer to the earth. Orbital altitudes range from 2,000 to 36,000 kilometres above the earth.
- Low Earth Orbit – The region below the medium earth orbit is referred to as low earth orbit. They are about 160 to 2,000 kilometres (99 to 1,243 mi) above the earth.
Satellites in MEO and LEO orbit the earth faster, and they do not remain fixed to a point in the sky continually like a geostationary satellite. Hence, to provide continuous communications capability with these lower orbits requires a larger number of satellites, so one will always be in the sky for transmission of communication signals.
Remarkable advances have been made in the use of satellites for communication. Satellite communication has helped very much in quicker and cheaper international communication. We hope to see more of these advancements being made in communication in the coming few years.
Did you know that the speed of sound in space is zero meters per second? This is because sound cannot travel in a vacuum. The sound wave is a wave which spreads through the vibration of particles in a medium. Since a vacuum is an empty space there is no medium for the sound to travel through in the outer space. Learn many more such fascinating facts about the fantastic space @ BYJU’S.