Maarg Manthan · Topic 12.31

GSAT-17 as ISRO’s Heaviest Communication Satellite

Science & Technology › Space Technology and ISRO · Topic 12.31

GSAT-17 is a communication satellite of ISRO that was launched on 29 June 2017 by an Ariane 5 rocket of Arianespace from Kourou in French Guiana. With a lift-off mass of about 3,477 kilograms, it was at the time among the heaviest communication satellites built by ISRO, and it carries transponders in the normal C-band, the extended C-band and the S-band, together with equipment for meteorological data relay, search and rescue, and a satellite based navigation payload. The satellite strengthened the INSAT/GSAT system in geostationary orbit and replaced older satellites at the end of their lives. Later satellites became even heavier, such as GSAT-11, which weighed about 5.8 tonnes and was launched in 2018.

5 min read · UPSC Prelims · Science & Technology · Space Technology and ISRO

At a Glance

Launched 29 June 2017
Rocket Ariane 5 VA-238
Site Kourou, French Guiana
Mass About 3,477 kg
Bands C, extended C, S
Exam link UPSC Prelims, Science & Technology: Space Technology and ISRO

Where Does It Fit?

This is the last topic of the macro on space technology and ISRO. It ends with a communication satellite that shows the INSAT/GSAT line of satellites and the use of foreign rockets for heavy payloads. Previous topic: NASA-ISRO Synthetic Aperture Radar (NISAR) Mission. Next topic: Nuclear Fission and Nuclear Fusion.

What Are the Key Features of GSAT-17?

Feature	Details
Launch	29 June 2017 from the Guiana Space Centre, Kourou, on Ariane 5 flight VA-238, along with another satellite, Hellas Sat 3-Inmarsat S EAN
Mass	About 3,477 kg at lift-off, built on ISRO’s standard I-3K bus
Orbit	Geostationary orbit at about 93.5 degrees East
Payload	24 normal C-band, 12 extended C-band and 1 S-band transponders
Other payloads	Meteorological data relay and satellite aided search and rescue
Life	Planned for about 15 years
Role	Extends and strengthens the INSAT/GSAT system for communication, broadcasting and weather data relay

Why Did ISRO Use a Foreign Launcher and What Followed?

Launcher limits: GSLV Mk II could carry about 2,500 kg to geosynchronous transfer orbit, less than the mass of GSAT-17
LVM3: the more powerful LVM3 made its first operational launch on 5 June 2017, the same month, with GSAT-19 weighing about 3,136 kg, the heaviest satellite launched from India at that time
Foreign launch services: ISRO bought commercial launches on Ariane 5 for heavier satellites such as GSAT-11 and GSAT-24
GSAT-11: launched in December 2018 on Ariane 5, weighing about 5,854 kg, a high throughput Ka and Ku band satellite
GSAT-N2: launched in January 2025 on a SpaceX Falcon 9, weighing about 4,700 kg, mainly for broadband and in-flight connectivity
Indigenous goal: LVM3 and its upgrades are meant to launch such satellites from India
Commercial route: NSIL now manages demand driven satellites, as in ISRO’s Space Research Programme and ANTRIX Corporation
Revenue: ISRO also sells launch services on PSLV and LVM3 to others

What Else Should You Remember?

Ariane 5: a European heavy launcher that flew from 1996 to 2023, and was succeeded by Ariane 6
Kourou: the European spaceport near the equator, which allows efficient launches to geostationary orbit
Transponder meaning: a relay unit on a satellite that receives, amplifies and re-sends a signal
C-band and extended C-band: radio bands around 4 to 8 GHz, with wider coverage and less rain fade
S-band: around 2 to 4 GHz, used for mobile satellite services and telemetry
Search and rescue: satellite aided alerts from distress beacons are relayed through the Cospas-Sarsat system
Weather data relay: collects data from automatic weather stations and sends to the India Meteorological Department
Heavier trend: communication satellites keep growing in mass and power, with high throughput designs
Life and replacement: older INSAT satellites are replaced by new GSAT satellites as they age
Heavy lift: heavier satellites need heavier rockets, so launch capacity is a determinant
Link: INSAT and GSAT families are described in Satellite Systems: INSAT, GSAT, IRS (Remote Sensing)
Caution: masses and slots quoted in exams should match standard sources
Why bigger satellites: more power and more transponders allow a single satellite to carry more channels and data and lower the cost per unit of capacity
Station keeping: chemical thrusters keep the satellite in its slot, and fuel left at the end of life decides how long it can work
End of life: at retirement the satellite is moved to a graveyard orbit above the geostationary ring, as in Space Junk and Graveyard Orbits
Use by broadcasters: television channels, direct to home operators and VSAT networks lease transponders from ISRO through NSIL and Antrix
Services after floods and cyclones: satellite links often stay working when ground networks fail, making them useful for disaster communication

Why Does It Matter for the Exam?

Facts: date, rocket, mass
Bands: C, extended C, S
Context: LVM3 and GSAT-19, GSAT-11 later
Current affairs link: heavy satellite launches on foreign and Indian vehicles
Common errors: calling GSAT-17 the heaviest ISRO satellite today, or saying it was launched by GSLV

As an analytical point, GSAT-17 shows the importance of heavy launch capability. India built capacity with LVM3 so that it need not depend on foreign rockets for heavy satellites.

Why Is This Topic Important?

Facts Launch details
Bands Payload
Trend Heavier satellites

What Came Next?

The next macro covers nuclear technology and energy. Next topic: Nuclear Fission and Nuclear Fusion.

Key People and Terms

Ariane 5 European heavy rocket
Kourou French Guiana spaceport
I-3K ISRO satellite bus
Extended C-band Wider part of C band
SAR Search and rescue
HTS High throughput satellite

Exam Corner

Points to Remember

GSAT-17 launched: 29 June 2017 on Ariane 5.
Mass: about 3,477 kg.
GSAT-11 (2018): about 5,854 kg.
LVM3 first operational launch: June 2017, GSAT-19.
Spaceport: Kourou.

Do Not Confuse With

GSAT-17 and GSAT-19 Ariane-launched versus LVM3-launched
GSAT-17 and GSAT-11 3.5 tonnes versus 5.8 tonnes
Ariane 5 and GSLV European versus Indian rocket

Memory Hook

Seventeen on Ariane from Kourou in June, three-and-a-half tonnes; then eleven grew to five-and-a-half.

Mains Angle

Questions ask for facts and the context of launches. These points help.

Heavier satellites Trend
Launchers Foreign versus own
Services Broadband

A Question You May Face

An original practice question, not a past paper question.

“Discuss the evolution of ISRO’s communication satellites from GSAT-17 to the later high throughput satellites and the importance of heavy launch capability.”

How to Answer

GSAT-17 Facts.
Trend Heavier, HTS.
Launchers Foreign to LVM3.
Way Own heavy lift.

GS Relevance

Prelims: GSAT-17 launch date, rocket, bands, mass, later heavier satellites. GS Paper 3: science and technology, space communication.

Frequently Asked Questions

What is GSAT-17?

GSAT-17 is an Indian communication satellite weighing about 3,477 kilograms, launched on 29 June 2017 by an Ariane 5 rocket from Kourou in French Guiana. It carries C-band, extended C-band and S-band transponders and also meteorological data relay and search and rescue payloads, working from geostationary orbit.

Why was GSAT-17 launched from French Guiana?

GSAT-17 was heavier than the 2,500 kilograms that India's GSLV Mk II could lift to geosynchronous transfer orbit at that time, so ISRO bought a commercial launch on the European Ariane 5 rocket. The more powerful LVM3, which can lift about 4,000 kilograms, had only just made its first operational launch in June 2017.

What bands does GSAT-17 use?

GSAT-17 carries 24 transponders in the normal C-band, 12 in the extended C-band and 1 in the S-band. C-band and extended C-band are used for wide-area communication and broadcasting with good resistance to rain, and the S-band supports mobile satellite services and telemetry.

Which ISRO satellites are heavier than GSAT-17?

Later satellites are heavier than GSAT-17, including GSAT-11, a high throughput communication satellite of about 5,854 kilograms launched on Ariane 5 in December 2018, and GSAT-N2, about 4,700 kilograms, launched on a SpaceX Falcon 9 in January 2025 for broadband and in-flight connectivity.

What is a transponder?

A transponder is the unit on a communication satellite that receives a signal from the ground, amplifies it, shifts its frequency and sends it back to Earth. A satellite has many transponders working in different bands, and their number and bandwidth decide how much communication traffic the satellite can carry.

PYQ Practice — Statement Analysis

1 GSAT-17 was launched by an Ariane 5 rocket from Kourou.

True

On 29 June 2017.

2 GSAT-17 carries transponders in the C, extended C and S bands.

True

For communication and relay.

3 GSAT-17 was launched by GSLV Mk II from Sriharikota.

False

It was launched by Ariane 5.

4 GSAT-17 is heavier than GSAT-11.