India’S Communication Satellite Programmes and Key Missions

Communication satellites constitute the backbone of India’s space-based telecommunications, direct-to-home (DTH) broadcasting, search and rescue services, and strategic defense communications. Placed primarily in the Geostationary Earth Orbit (GEO) at an altitude of approximately 35,786 km, these systems operate via high-power transponders across diverse frequency spectrums including C-band, Extended C-band, Ku-band, and Ka-band. The Department of Space (DoS) manages the operation and deployment of these assets, which are transitioned commercially under NewSpace India Limited (NSIL).

Evolution of Satellite Series

India’s communication satellite ecosystem transitioned through three major technological generations:

• APPLE (Ariane Passenger Payload Experiment): Launched in June 1981 via Ariane-1, APPLE was India’s first experimental three-axis stabilized communication satellite. It provided foundational experience in station-keeping, thermal control, and payload management in geostationary orbit.
• INSAT (Indian National Satellite) System: Established in 1983 with INSAT-1B, this multi-purpose system combined telecommunication, television broadcasting, and meteorological services. It grew into one of the largest domestic communication satellite networks in the Asia-Pacific region.
• GSAT (Geosynchronous Satellite) Series: Introduced to augment INSAT capacity, the GSAT series exclusively focuses on high-capacity digital communication, broad-band internet connectivity, mobile telephony, and specialized military networks.
• CMS (Communication Satellite) Naming Convention: Beginning with CMS-01 in December 2020, ISRO simplified satellite nomenclature, unifying domestic telecommunication payloads under the CMS tag.

Major Institutional Programmes and Frameworks

The INSAT Coordination Committee (ICC)

The INSAT system operates as a joint venture involving the Department of Space, Department of Telecommunications, India Meteorological Department, All India Radio, and Doordarshan. Inter-agency operational management rests with the Secretary-level INSAT Coordination Committee. Transponders onboard support remote education (Tele-education), remote health facilities (Tele-medicine), and Village Resource Centres (VRCs).

Transponder Frequency Bands

Indian communication payloads rely on distinct radio frequency bands designed for specific applications:

• C-Band and Extended C-Band: Operates at 4 to 8 GHz. Provides wide geographical coverage with resistance to rain attenuation, making it ideal for TV distribution and long-distance telephone links.
• Ku-Band: Operates at 12 to 18 GHz. Utilized for Direct-to-Home (DTH) television services, Very Small Aperture Terminals (VSATs), and high-density broadcast networks.
• Ka-Band: Operates at 26.5 to 40 GHz. Offers high bandwidth for High Throughput Satellites (HTS), enabling high-speed internet connectivity in remote areas.
• S-Band: Operates at 2 to 4 GHz. Primarily used for mobile satellite services, direct audio broadcasting, and strategic applications.

Key Satellite Missions

GSAT-11 (Heavyweight High Throughput Satellite)

Launched in December 2018 via Ariane-5 from Kourou, French Guiana, GSAT-11 weighs 5,854 kg, making it ISRO’s heaviest communication satellite. It features 32 spot beams in the Ka-band and 8 spot beams in the Ku-band, providing a throughput rate of 16 Gbps to support broadband connectivity under the Digital India initiative.

GSAT-7 Series (Rukmini and Angry Fox)

• GSAT-7 (Rukmini): Launched in August 2013, GSAT-7 is India’s dedicated military communication satellite developed for the Indian Navy. It operates in UHF, S, C, and Ku bands to connect naval ships, submarines, aircraft, and land stations.
• GSAT-7A (Angry Fox): Launched in December 2018 using the GSLV-F11 launch vehicle, this satellite caters to the Indian Air Force and Indian Army. It interlinks ground radar stations, airbases, and Airborne Early Warning and Control (AEW&C) platforms.

GSAT-9 (South Asia Satellite)

Launched in May 2017 using a GSLV Mk II, GSAT-9 is a Ku-band communication satellite gifted by India to SAARC member nations (excluding Pakistan). It supports tele-education, tele-medicine, disaster management support, and inter-governmental communication across South Asia.

GSAT-24 (Demand-Driven Commercial Mission)

Launched in June 2022 via Ariane-5, GSAT-24 was the first “demand-driven” communication satellite mission undertaken by NewSpace India Limited (NSIL). The entire satellite capacity was leased to Tata Play to meet DTH broadcasting requirements.

Key Features of Communication Satellites

Key Facts and Trivia

• India’s first experimental communication satellite, APPLE, was transported on a bullock cart for antenna range testing in 1981 due to non-magnetic testing requirements.
• INSAT-1B, launched in 1983, established the foundation for modern direct-to-home broadcasting and nationwide telephony in India.
• GSAT-11 is the heaviest satellite built by ISRO, weighing 5,854 kg at launch.
• GSAT-19 was the first satellite carrying an indigenous electric propulsion system for station-keeping maneuvers.
• GSAT-7 (Rukmini) was India’s first dedicated military satellite deployed exclusively for naval operational communication.
• The GSAT-20 (GSAT-N2) mission was configured to deliver high-capacity Ka-band spot-beam coverage across the Indian mainland and island regions.
• Transponders operate on frequency conversion principle: they receive uplinks from ground stations, amplify signals, and translate them to downlinks for receiver stations.
• High Throughput Satellites (HTS) achieve higher capacity using frequency reuse across multiple narrow spot beams, unlike traditional broad coverage beams.