INSAT

Also called: Indian National Satellite System · Topic: Transport and Communication in India · NCERT: Class 11, Ch 6 "Introduction to Remote Sensing"; Class 12, Ch 7 "Transport and Communication"; Class 12, Ch 7 "Transport and Communication"

Meaning

INSAT (Indian National Satellite System) is India's multipurpose satellite system, set up in 1983. Its satellites sit in geostationary orbit and handle telecommunication, television broadcasting, meteorology (weather observation) and disaster warning.

• It matters because one system serves both the economy (telecom, TV, weather data for farmers and fishers) and security.
• It is one of the largest domestic communication satellite systems in the Asia-Pacific region [3].

Explanation

How satellite communication works

• Basic idea: a satellite receives a signal from one place on Earth, makes it stronger, and sends it back to many places at once.
• Transponder: the part of the satellite that does this work. It receives a signal, makes it stronger and sends it back down.
• Synoptic view: a satellite sees a very large area at one time and watches it without a break.
• It helps weather forecasting.
• It helps disaster monitoring of cyclones, floods and droughts.

• It helps border surveillance.

• Two roles:

• Satellites are a mode of communication themselves. They carry phone calls, TV and radio signals and data.
• Satellites also support other modes, such as phone networks, TV broadcasting, aircraft and ship navigation, and banking networks.

Why geostationary orbit

• Geostationary orbit: an orbit high above the Equator.
• A satellite here goes round Earth once a day.
• Earth also takes one day to spin once.

• So from the ground, the satellite seems to stay over one fixed spot.

• Result: dish antennas can point at one place in the sky and never need to move.

• At its peak, INSAT had nine operational communication satellites in geostationary orbit, with more than 200 transponders [3].
• These transponders worked in the C, Extended C and Ku bands (different ranges of radio frequency) [3].
• The Ku-band works well with small dish antennas, as in DTH TV.

What INSAT does

• Services [3]:
• telecommunications
• TV broadcasting
• satellite newsgathering
• societal applications, such as education and health
• weather forecasting
• disaster warning

• Search and Rescue (picking up distress signals from ships, aircraft and people)

• TV reach (around 2000): INSAT took satellite TV to over 65% of India's land area and over 80% of its population [4].

• Weather role [4]:
• INSAT was the only source of repeated, wide-area weather observations over the Indian Ocean from geostationary orbit.
• Its instruments measure cloud motion vectors, which means wind speed and direction worked out from how clouds move.
• They also measure cloud-top temperature, water vapour, and vertical profiles of temperature and humidity (how these change with height).
• Result: better forecasts, early detection of the genesis (birth) of cyclones, and prediction of each cyclone's track.

How the system began

• SITE (1975-76) used NASA's ATS-6 satellite to bring educational TV to about 2,400 villages [5].

• It showed that satellites could meet the education needs of rural India. This idea led to INSAT.

• APPLE (19 June 1981) was ISRO's first home-built experimental communication satellite. It was placed in geosynchronous orbit at 102° E [2].

• It was a test run for India's own communication satellites.

• INSAT-1A (1982) failed early.

• INSAT-1B (1983) got the INSAT system working.
• Later: the GSAT series grew from what India learnt through APPLE and INSAT.

Where it occurs

• Orbit: geostationary orbit above the Equator. Each satellite stays over one fixed spot.
• Who runs it: ISRO (Indian Space Research Organisation, founded 1969), India's national space agency.
• Year: the system began working in 1983 with INSAT-1B.
• Coverage on the ground:
• all of India for telecom and TV

• around 2000, satellite TV covered over 65% of the land area and over 80% of the population [4]

• Weather watch: over the Indian Ocean, including the cyclones that form there [4].

• Remote areas: villages, hills, islands and border areas where land networks are weak.

Don't confuse with

• IRS (Indian Remote Sensing satellites): IRS studies Earth's surface from a polar orbit, which passes over or near both poles. Its data is processed at NRSC, Hyderabad. INSAT is geostationary and is used for communication and weather.
• SITE (1975-76): SITE used NASA's ATS-6, a foreign satellite lent to India for one year [5]. INSAT is India's own satellite system.
• APPLE (1981): APPLE was a single experimental communication satellite, launched on Ariane-1 from Kourou, French Guiana [2]. INSAT is a full working system of many satellites.
• NavIC (earlier IRNSS): NavIC is India's navigation system, with 7 satellites (3 geostationary + 4 inclined geosynchronous) [6]. INSAT is used for communication and weather, not positioning.

Prelims Hooks

• INSAT: set up in 1983, in geostationary orbit. It is used for telecom, TV broadcasting, meteorology and disaster warning.
• Trap: INSAT-1A (1982) failed. INSAT-1B (1983) was the satellite that got the system working.
• INSAT had nine operational communication satellites with more than 200 transponders in the C, Extended C and Ku bands [3].
• INSAT services include Search and Rescue and satellite newsgathering, not only TV and weather [3].
• INSAT was the only geostationary source of repeated, wide-area weather observations over the Indian Ocean [4].
• Order of milestones: ISRO (1969) → Aryabhata (1975) → SITE (1975-76) → Rohini RS-1 (1980) → APPLE (1981) → INSAT-1B (1983) → IRS-1A (1988).

Mains Points

• INSAT is strategic infrastructure (GS-III).
• Its continuous, wide view supports weather forecasts, cyclone tracking and disaster warning.

• Because it was the only geostationary weather source over the Indian Ocean, India could not depend on others for cyclone warnings [4].

• INSAT helped close India's development gap.

• SITE showed that TV could reach villages. INSAT then took TV, education and health services to remote areas with weak land networks.

• By about 2000, satellite TV reached over 80% of India's people [4].

• A step towards self-reliance.

• India moved from SITE, which used a foreign satellite, to INSAT, its own system, and then to the GSAT series and NavIC.
• Together, these support Digital India, disaster management and secure communication for the armed forces.

Related concepts

• Satellite communication
• Aryabhata
• Rohini satellites
• APPLE satellite

Read more

• Satellite communication and India's early satellites