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Satellite Communication in India - Science & Technology Notes

SATELLITE COMMUNICATION IN INDIA

 
 
 
What is a Satellite?
 
A satellite is a man-made object placed into orbit around a celestial body, typically a planet. In the context of space exploration, a satellite specifically refers to an object designed and launched into space to perform various functions.
Here are some key points about satellites:
  • Satellites are propelled into space by rockets and are placed into specific orbits around a celestial body, such as the Earth, Moon, or other planets. They continuously orbit due to the balance between their speed and the gravitational pull of the celestial body
  • There are different types of satellites serving various purposes, including communication satellites for transmitting signals, Earth observation satellites for monitoring the planet\'s surface, navigation satellites for providing positioning information, scientific satellites for conducting experiments and research, and weather satellites for observing and forecasting weather patterns
  • Satellites are equipped with various components such as antennas, sensors, communication devices, power systems (solar panels or batteries), propulsion systems for orbit adjustments, and instruments specific to their intended functions
What is Satellite Communication?
 
Satellite communication, often abbreviated as SATCOM, refers to the use of artificial satellites in Earth\'s orbit to facilitate communication between two or more points on the planet\'s surface or between a ground station and orbiting satellites.
Here\'s an overview of satellite communication:
  • SATCOM involves transmitting signals (voice, data, video, or internet) from an Earth-based transmitter to a satellite in space, which then relays the signals back down to one or more ground stations or other satellites
  • SATCOM networks consist of multiple satellites working together in constellations or in geostationary orbits. These satellites are equipped with antennas and transponders that receive, amplify, and retransmit signals back to Earth
  • Satellite communication serves various purposes, including long-distance telecommunications (such as phone calls, television broadcasts, and internet services), remote sensing, military and defence communications, emergency communication during disasters, and global positioning systems (GPS)
  • SATCOM offers global coverage, enabling communication in remote or rural areas where traditional terrestrial networks might be limited or unavailable. It also provides reliable communication for maritime, aviation, and military operations in areas without ground-based infrastructure
  • Some SATCOM systems employ constellations of smaller satellites in low Earth orbit (LEO) or medium Earth orbit (MEO). These constellations offer advantages like lower latency, increased data speed, and better coverage compared to traditional geostationary satellites
  • Geostationary satellites, placed in high orbits above the equator, remain stationary relative to Earth\'s surface. They\'re commonly used for television broadcasting, broadband internet, and long-distance communication due to their fixed positions
  • Users access satellite communication through ground stations equipped with antennas and transceivers. Terminals like satellite phones, VSATs (Very Small Aperture Terminals), and satellite internet dishes enable communication by sending and receiving signals to and from satellites
Working of Satellite Communication

Satellite communication involves a complex process that enables the transmission of signals between ground stations, terminals, and satellites in orbit. Here\'s an overview of how satellite communication works:

Ground Stations and Terminals: Communication begins at ground-based terminals equipped with antennas and transceivers. These terminals can be satellite phones, VSATs (Very Small Aperture Terminals), satellite television receivers, or other devices that send and receive signals.

Up-linking Signals: The ground-based terminal sends signals to a satellite via radio frequencies. This process, known as up-linking, involves transmitting the signals to the satellite in space.

Satellite Reception and Processing: Satellites equipped with transponders receive the incoming signals from ground stations. Transponders on the satellite then amplify and retransmit these signals back to Earth.

Down-linking Signals: The retransmitted signals are directed toward specific receiving stations or ground terminals on Earth. This process, known as down-linking, enables users to receive the transmitted data, which could include phone calls, internet data, television broadcasts, or other communication services.

Orbital Mechanics: Satellites orbiting the Earth follow predetermined paths, ensuring coverage across designated areas. Geostationary satellites remain stationary relative to Earth\'s surface, positioned in high orbits above the equator, while other satellites in lower orbits travel at higher speeds, providing different types of coverage and advantages.

Multiple Satellites and Networks: Some satellite communication systems involve multiple satellites working together in constellations. These constellations, whether in low Earth orbit (LEO), medium Earth orbit (MEO), or geostationary orbit (GEO), ensure global coverage, reduce latency, and enhance communication capabilities.

Data Transmission and Reception: Users equipped with appropriate terminals receive the transmitted data or communication signals through their devices. Satellite phones, internet modems, TV receivers, and other devices decode and process the received signals for human use.

Relay and Routing: Satellites act as relays, receiving signals from one location and transmitting them to another, allowing communication between distant points on Earth.

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Indian National Satellite (INSAT)

The Indian National Satellite (INSAT) system is a series of multipurpose geostationary satellites developed and operated by the Indian Space Research Organisation (ISRO). The INSAT program aims to provide a range of communication, broadcasting, meteorological, and search and rescue services for India and neighboring regions.

Here\'s an overview:

  • INSAT satellites facilitate a wide range of communication services, including television broadcasting, telecommunication, broadband internet connectivity, and emergency communication across India
  • INSAT satellites play a crucial role in weather monitoring and forecasting. They carry meteorological instruments that gather data on weather patterns, cloud cover, temperature, and humidity, aiding meteorologists in analyzing and predicting weather conditions
  • INSAT satellites are equipped with payloads for search and rescue operations. They detect distress signals from emergency beacons, helping in locating and rescuing ships, aircraft, or individuals in distress
  • Some INSAT satellites have imaging capabilities for Earth observation. They capture images of the Earth\'s surface, supporting applications in agriculture, forestry, environmental monitoring, and disaster management
  • The INSAT system comprises multiple satellites positioned in geostationary orbits, ensuring continuous coverage over the Indian subcontinent and nearby regions. These satellites are strategically placed to maintain a constant position relative to Earth\'s surface, providing uninterrupted services
 
 

 

Previous Year Questions
 

1.Who amongst the following was the Chairman of I.S.R.O. when INSAT-3B was launched? (UPSC CSE  2001)

(a) Anil Kakodkar

(b) Abdul Kalam

(c) K. Kasturirangan

(d) U.R.Rao

Answer: (c)

2.INSAT–3E, India’s communication satellite, was launched in 2003 from: (UPSC CSE 2004)

(a) French Guiana

(b) Seychelles

(c) Mauritius

(d) Mauritania

Answer: (a) 

3.Consider the following statements in respect of India advanced satellite INSAT–4A: (UPSC CSE  2006)

1) INSAT-4A was launched in December, 2005 from New Mexico.

2) The European Commercial Launch Service Provider Arianespace was associated with the launch of INSA T-4A.

3) Tata-Sky; a digital cable service provider; is associated with DTH television broadcasting service from INSA T 4A.

Which of the statements given above are correct?

(a) 1, 2 and 3

(b) 1 and 2 only

(c) 2 and 3 only

(d) 1 and 3 only

Answer: (c)
 
Frequently Asked Questions on Satellite Communication
 

What is satellite communication?

    • Satellite communication involves transmitting data, signals, or information via satellites orbiting the Earth to facilitate various forms of communication, including TV broadcasting, internet connectivity, telephony, and data transmission.

How does satellite communication work?

    • Signals are sent from ground stations to satellites in orbit, which then relay these signals back to other ground stations or terminals. This process allows communication over long distances and across remote or inaccessible areas.

What are the main components of satellite communication?

    • The key components include ground stations (uplink and downlink), satellites in orbit, transponders onboard the satellites, and user terminals or receivers.

What are the advantages of satellite communication?

    • Satellite communication offers global coverage, even in remote areas where terrestrial networks might be unavailable. It provides reliable communication, wide area coverage, and supports various services simultaneously.

What are the types of satellite orbits used in communication?

    • Geostationary Orbit (GEO): Satellites in this orbit remain fixed relative to a point on the Earth\'s surface, ideal for continuous coverage (commonly used for TV broadcasting and telecommunications).
    • Medium Earth Orbit (MEO) and Low Earth Orbit (LEO): These orbits are used for satellite constellations providing global coverage (commonly used for internet services).

What services utilize satellite communication?

    • Satellite communication supports a wide range of services including broadcasting (TV and radio), internet connectivity (satellite internet), telephony (satellite phones), navigation (GPS), and data transmission for various industries.

What is the role of transponders in satellite communication?

    • Transponders on satellites receive signals from the ground, amplify them, change their frequencies, and retransmit them back to Earth, enabling communication between different points on the globe.

Are there any limitations to satellite communication?

    • While offering global coverage, satellite communication can face issues such as signal latency due to the distance signals travel, susceptibility to weather interference, and higher initial setup costs.

How is satellite communication evolving?

    • Advancements in technology are leading to the development of high-throughput satellites, smaller satellite constellations, and improved signal processing techniques, enhancing data rates and coverage