Satellite Communication Important Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. The transmitter-receiver combination in the satellite is known as

1. Duplexer
2. Repeater
3. Transponder
4. Relay

Ans. The correct answer is c. Transponder

Explanation: A transponder is the transmitter-receiver combination in the satellite. The main functions of a transponder are amplification and frequency translation. The transponder cannot broadcast and receive on the same frequency, hence requires frequency translation.

Ques. What is the reason for carrying multiple transponders in a satellite?

1. Better reception
2. More number of operating channels
3. Redundancy
4. More gain

Ans. The correct answer is b. More number of operating channels

Explanation: A satellite must be capable of handling several channels in order to be economically feasible. As a result, most satellites have many transponders, each with its own frequency. Every transponder represents a separate communication channel.

Ques. Internet services are provided by

1. Military satellite
2. Agriculture satellite
3. Weathering satellite
4. Broadcasting satellite

Ans. The correct answer is d. Broadcasting satellite

Explanation: Internet services are provided through the use of broadcasting satellites.

Ques. The transmission of the signal from an earth station to the satellite through a channel is known as

1. Uplink
2. Downlink
3. No link
4. None of the above

Ans. The correct answer is a. Uplink

Explanation: The transfer of a signal from an earth station to a satellite through a channel is referred to as uplink.

Ques. Electromagnetic waves can carry

1. Audio signal
2. Video signal
3. None of the above
4. Both audio and video signal

Ans. The correct answer is d. Both audio and video signals

Explanation: Electromagnetic waves are a form of energy that can travel through space at the speed of light. They can carry a wide range of information, including audio and video signals.

Ques. Which type of satellite amplifies the transmitted signals before re-transmitting them to Earth?

1. Active satellite
2. Passive satellite

Ans. The correct answer is a. Active satellite

Explanation: Passive satellites were used in the early days, however, in recent years, active satellites have been used.

Ques. Direct To Home (DTH) television broadcasting is possible because of satellite communication.

1. True
2. False

Ans. The correct answer is a. True

Explanation: Direct To Home (DTH) television broadcasting results from satellite communication.

Ques. GSAT-30 satellite launched by India is a

1. Military satellite
2. Communication satellite
3. Agriculture satellite
4. Weathering satellite

Ans. The correct answer is b. Communication satellite

Explanation: GSAT-30 is a communications satellite developed by the Indian Space Research Organisation (ISRO).

Ques. Ohsumi satellite belongs to which country?

1. The United States of America
2. Japan
3. India
4. China

Ans. The correct answer is b. Japan

Explanation: The Ohsumi satellite was the first Japanese satellite to be put into orbit. It was launched on February 11, 1970, from the Uchinoura Space Center in Kagoshima, Japan.

Ques. The downlink frequency is lower than the uplink frequency.

1. True
2. False

Ans. The correct answer is a. True

Explanation: The original signal from the earth station to the satellite is referred to as the uplink, and the re-transmitted signal from the satellite to the receiving stations is referred to as the downlink. The downlink frequency is usually lower than the uplink frequency. The most frequent uplink frequency is 6 GHz, whereas the most common downlink frequency is 4 GHz.

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Short Answers Questions [2 Marks Questions]

Ques. What is a satellite?

Ans. An object in orbit around a larger object in space is called a satellite. Satellites can be classified as either artificial (like the International Space Station revolving around the Earth) or natural (like the moon orbiting the Earth).

Ques. What is a space station?

Ans. A space station is a spaceship that maintains a human crew in orbit for an extended period of time and hence serves as a space home.

Ques. What is satellite communication?

Ans. Satellite communication is the transmission of data from one location to another using a communication satellite in orbit around the Earth. A communication satellite is a man-made spacecraft that sends a signal using a transponder by establishing a channel between the transmitter and the receiver at separate Earth locations.

Ques. List the factors on which the carrier-to-noise ratio of a satellite depends.

Ans. The three factors that affect a satellite's carrier-to-noise ratio are as follows:

• Bandwidth
• Free space for path losses
• Effective power radiated from the isotropic

Ques. How are the artificial satellites used in satellite communication classified?

Ans. Artificial satellites used in satellite communication are classified as

• Passive satellites
• Active satellites

Ques. How are satellite communication services classified?

Ans. Satellite communication services are classified as

• One-way satellite communication
• Two-way satellite communication

Ques. Name the countries that have their own satellites.

Ans. There are 12 countries in all that have their own satellites. Among them are the following:

• India – Rohini D1
• Japan – Ohsumi
• China – Dong Fang Hong I

Ques. What is One-way Satellite Communication?

Ans. One-way satellite communication is commonly used between one or more Earth stations through the use of a satellite. Communication takes place between the first earth satellite's transmitter and the second earth satellite's receiver. The signal is only sent in one direction.

Ques. What is Two-Way Satellite Communication?

Ans. Information is transmitted between any two earth stations in two-way satellite communication. The signal gets transmitted from the first to the second earth station, resulting in two uplinks and two downlinks between the earth stations and the satellite.

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Long Answers Questions [3 Marks Questions]

Ques. What are the applications of satellite communication?

Ans. The following are the applications of satellite communication

• In TV broadcasting, for example, DTH. 
• In Radio telecom. 
• Internet applications, for example, give Internet connection for transferring data, GPS applications, Internet surfing, and so on. 
• In military applications and routes.
• For voice correspondence. 
• For innovative work, in numerous regions. 

Ques. Why are uplink and downlink frequencies different?

Ans. The uplink and downlink signal transmission processes only use frequency ranges selected by the International Telecommunication Union (ITU). In satellite communication, each band has an uplink frequency band and a downlink frequency bandwidth. Because most satellites use the same antenna for both uplink and downlink, it is important to use different uplink and downlink frequencies to keep the satellite receiver from jamming. The bandwidth difference between uplink and downlink frequencies allows for the use of a single antenna in satellite communication, minimizing the amount of related infrastructure required.

Ques. Explain the role of transponders in satellite communication.

Ans. The transponder of a communications satellite is a set of related components that act as a communication path between the receiving and sending antennas. It is mostly used in satellite communication to transmit received signals. Some latest satellites use on-board processing, which demodulates, decodes, re-encodes, and modulates the signal on the satellite. This type, known as a "regenerative" transponder, is more advanced but offers several advantages, including an improved signal-to-noise ratio when the signal is regenerated from the digital domain, as well as the ability to select and manage data in the digital domain.

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Very Long Answers Questions [5 Marks Questions]

Ques. What are the advantages of satellite communication?

Ans. The advantages of satellite communication are

• Satellite communication provides extensive geographical coverage, particularly in less inhabited areas.
• Satellite communication allows for the easy establishment of wireless and mobile communication applications regardless of location.
• High bandwidth and broadcast possibilities.
• It is used in a wide range of applications including global mobile communication, private business networks, long-distance telephone transmission, weather forecasting, radio/TV signal broadcasting, military intelligence gathering, ship and aircraft navigation, connecting remote areas, television distribution, and so on.
• The coding and decoding technology normally provides security in satellite communication.
• It is simple to receive service from a single supplier, and uniform service is available.
• Satellite communication is the best alternative because installation and maintenance are simple and inexpensive.
• During an extreme situation, each Earth Station may be immediately relocated from one site and put in another.

Ques. What are the disadvantages of satellite communication?

Ans. The following are the disadvantages of satellite communication

• The cost of satellite design, development, investment, and insurance is higher.
• Frequency congestion is possible.
• Propagation and interference issues may appear.
• Satellite launch into space is a costly operation.
• The time it takes to reach the satellite from Earth can range between 270 and 320 milliseconds. This propagation delay might result in an echo across telephone lines.
• Satellites are difficult to repair and keep in good working order.
• Some factors, such as weather or sunspots, impact the satellite's signal, causing interference and making optimal satellite functioning difficult.
• Once launched, it must be monitored and managed on a regular basis to ensure that it remains in orbit.
• Satellite systems have a longer propagation delay than ordinary terrestrial systems.

Ques. What are the different types of artificial satellites used in satellite communication?

Ans. The different types of artificial satellites used in satellite communication are

• Navigation satellites: The GPS (Global Positioning System) is a satellite navigation system that uses a network of satellites to pinpoint your exact location on Earth.
• Communication satellites: These satellites are used for television, phone, or internet signals and are placed in geostationary orbits, allowing them to provide coverage for entire countries or continents.
• Weather satellites: Weather satellites are like giant cameras in space that take pictures of clouds and measure the temperature and rainfall on Earth. These satellites can be in different orbits depending on their purpose, but they all help us understand the weather better and make more accurate forecasts.
• Earth observation satellites: Earth observation satellites are like giant cameras in space that take pictures of our planet. These satellites orbit very close to Earth, allowing them to capture incredibly detailed images of the land, oceans, and atmosphere.
• Astronomical satellites: Astronomical satellites are like giant telescopes in space that study the universe. They can take pictures of stars, planets, and galaxies, and they can also study the properties of light and matter. Some astronomical satellites, like the James Webb Space Telescope, are in special orbits that allow them to see very faint objects.
• International Space Station (ISS): This is a habitable space laboratory. The ISS travels at a speed of 28,000 km/h at a height of 400 km and circles the Earth every 92 minutes.

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