The Indian National Satellite System or INSAT, is a series of multipurpose geostationary satellites launched by ISRO to satisfy telecommunications, broadcasting, meteorology, and search and rescue operations. Commissioned in 1983, INSAT is the largest domestic communication system in the Indo-Pacific Region and laid the foundation for India's self-reliant space-based communication infrastructure. It is a joint venture of the Department of Space, Department of Telecommunications, India Meteorological Department, All India Radio and Doordarshan. The overall coordination and management of INSAT system rests with the Secretary-level INSAT Coordination Committee.

INSAT satellites provide transponders in various bands to serve the television and communication needs of India. Some of the satellites also have the Very High Resolution Radiometer (VHRR), CCD cameras for meteorological imaging. The satellites also incorporate transponder(s) for receiving distress alert signals for search and rescue missions in the South Asian and Indian Ocean Region, as ISRO is a member of the Cospas-Sarsat program.

INSAT system

The Indian National Satellite (INSAT) system was commissioned with the launch of INSAT-1B in August 1983 (INSAT-1A, the first satellite was launched in April 1982 but could not fulfil the mission). INSAT system ushered in a revolution in India's television and radio broadcasting, telecommunications and meteorological sectors. It enabled the rapid expansion of TV and modern telecommunication facilities to even the remote areas and off-shore islands. Together, the system provides transponders in C, Extended C and Ku bands for a variety of communication services. Some of the INSATs also carry instruments for meteorological observation and data relay for providing meteorological services. KALPANA-1 is an exclusive meteorological satellite. The satellites are monitored and controlled by Master Control Facilities that exist in Hassan and Bhopal.

INSAT-1 series The first generation of INSAT satellites, developed with NASA assistance, included INSAT-1A, 1B, 1C, and 1D, with all of them being launched in the 1980s. Their success established India's capability to operate a national communications and weather-monitoring satellite fleet. 1B, launched in 1983, became the first fully operational Indian GEO communications satellite.

INSAT-2 series The INSAT-2 series during the 1990s, marked the shift to fully indigenous satellite design. Models included INSAT-2A, 2B, SC, 2D, and 2E, each offering expanded transponder capacity, improved meteorological imaging and enhanced reliability.

INSAT-3 series Launched between 2000 and 2003, the INSAT-3 series introduced larger satellites with advanced payloads. 3B was for business communication, 3C for national telecommunication backbone, 3A and 3D for meteorology and disaster warning, and 3E for and data relay.

INSAT-4 series The INSAT-4 generation launched between 2005 and 2010 focused on high-power Ku-band DTH broadcasting. 4A was India's first dedicated DTH satellite, 4B and 4CR was for communication and replacement missions, and 4E (also known as GSAT-6) had a large S-band antenna for mobile communications. INSAT-4 satellites were eventually supplemented by the newer GSAT series.

Transition into GSAT

Many communication satellites which were originally conceived under the INSAT umbrella were reclassified as GSAT as ISRO shifted to newer satellite bus platforms of I-2K and I-3K. INSAT continues to focus mainly on meteorology and disaster management, while GSAT handles broadband, telecom, and strategic communication.

List of INSAT satellites The following is a list of launched INSAT satellites.

+ Launched INSAT satellites INSAT series GSAT Series Other name(s) COSPAR ID Launch date and time,UTC Launch vehicle Lift-off mass Orbital parameters Outcome Purpose Longitude Inclination INSAT-1A rowspan=2 colspan=2 scope="row" 1982-031A , 06:47:00 Delta 3910 / PAM-D 74° East 14.59° Communication First Satellite in INSAT Series and First Satellite of INSAT-1 Series. Built by Ford Aerospace, operated for only five months out of seven years planned. Abandoned on 6 September 1982 after a series of failures. INSAT-1B rowspan=2 colspan=2 scope="row" 1983-089B , 06:32:00 Space Shuttle Challenger STS-8 / PAM-D 93° East (1992-93) 14.69° Communication First successful INSAT satellite. At the end of its seven-year design life it was replaced by the newly launched INSAT-1D, dropping to backup status. Decommissioned in August 1993. INSAT-1C rowspan=2 colspan=2 scope="row" 1988-063A , 06:32:00 Ariane 3 93.5° East 11.6° Communication and meteorology Decommissioned in 2001 after thirteen years of service. INSAT-1D rowspan=2 colspan=2 scope="row" 1988-063A , 05:52:00 Delta 4000 4925-8 83° East 14.30° Telecom Last satellite of INSAT-1 series. Aided in setting up national computer networks. Decommissioned on 14 May 2002. INSAT-2A rowspan=2 colspan=2 scope="row" 1992-041A , 22:42:00 Ariane 4 44L V-51/423 74° East 14.5° Meteorology and Search and rescue INSAT-2A has an advanced power amplifiers for catering communication terminals and was the first series-2 satellite to replace the INSAT-1. INSAT-2B rowspan=2 colspan=2 scope="row" 1993-048B , 22:58:00 Ariane 4 44L V-58/429 93.5° East 14.4° Multipurpose Primarily for telecommunication and meteorological observations, also carried a search and rescue transponder. Decommissioned on 1 July 2004. INSAT-2C rowspan=2 colspan=2 scope="row" 1995-067B , 23:23:00 Ariane 4 44L V-81/453 93.5° East 14.2° Communication It had capabilities of business communication, mobile satellite service and could make television outreach beyond boundaries of India. In January 2013, its communication C-band transponder collapsed. It also improved communication facilities in Northeast India and Andaman and Nicobar Islands. INSAT-2D rowspan=2 colspan=2 scope="row" 1997-027B , 23:23:00 Ariane 4 44L V-97/468 93.5° East 12.8° Communication Became inoperable just four months later on 4 October 1997, due to a power bus anomaly and associated problems, most likely a short circuit. INSAT-2DT rowspan=2 scope="row" Arabsat-1C (formerly) 1992-010 , 23:58:10 Ariane 4 44L V-49/421 82.5° East 14.2° Communication In November 1997, Arabsat-1C was sold to India as INSAT-2DT. Decommissioned in October 2004. INSAT-2E rowspan=2 scope="row" APR-1 1999-016A , 22:03:00 Ariane 4 42P V-117/486 83° East 11° Communication and weather INSAT-2E is using ultra-light Magnesium-lithium alloys developed by DMRL. It also carries two meteorological instruments; the Very High Resolution Radiometer (VHRR), and a CCD camera capable of returning images with a resolution of one kilometre. INSAT-3A rowspan=2 colspan=2 scope="row" 2003-013A , 22:52:00 Ariane 5 42P V-117/486 93.5° East 8.3° Multipurpose Third satellite launched in INSAT-3 series after INSAT-3B & INSAT-3C. INSAT-3B rowspan=2 colspan=2 scope="row" 2000-016B , 23:28:00 Ariane 5 G 505 83° East 10.4° Communication First Geostationary satellite of India. INSAT-3C rowspan=2 colspan=2 scope="row" 2002-002A , 23:46:57 Ariane 4 42L-3 4108 74° East 7.9° Multipurpose Provides voice, video and digital data services to India and neighboring countries. INSAT-3D rowspan=2 colspan=2 scope="row" 2013-038B , 19:54:07 Ariane 5 ECA 569 82° East 1.4° Meteorology The satellite had many new technology elements like star sensor, micro stepping Solar Array Drive Assembly (SADA) to reduce the spacecraft disturbances and Bus Management Unit (BMU) for control and telecom and telemetry function. INSAT-3DR rowspan=2 colspan=2 scope="row" 2016-054A , 11:20:00 GSLV MkII F09 74° East 0.1° Meteorology Uses a 6-channel imager and a 19-channel sounder, as well as search and rescue information and message relay for terrestrial data collection platforms. INSAT-3DS rowspan=2 colspan=2 scope="row" 2024-033A , 12:05:00 GSLV MkII F14 74° East 0.0° Meteorology Follow on of INSAT-3DR mission. INSAT-3E rowspan=2 colspan=2 scope="row" 2003-047E , 23:14:46 Ariane 5G V162 55° East 9.2° Communication Ran out of oxidizer after seven years of operation, moved to Graveyard orbit in April 2014. INSAT-4A rowspan=2 colspan=2 scope="row" 2005-049A , 22:33:00 Ariane 5GS 525 83° East 5.9° Telecom At the time of launch, it was the heaviest satellite India had built. Decommissioned on 21 October 2019. INSAT-4B rowspan=2 colspan=2 scope="row" 2007-007A , 22:03:00 Ariane 5ECA 535 93.48° East 5.6° Communication Suffered a disruption in power supply from one of the two solar panels, rendering half of its transponder capacity useless. Decommissioned on 24 January 2022. INSAT-4C rowspan=2 colspan=2 scope="row" , 12:08:00 GSLV MKI F02 colspan=2 Communication Both rocket and satellite had to be destroyed over the Bay of Bengal after the rocket's trajectory veered outside permitted limits. INSAT-4CR rowspan=2 colspan=2 scope="row" 2007-037A , 12:51:00 GSLV MKI F04 74° East 6.3° Communication Due to an error in the guidance subsystem , rocket achieved orbit had lower apogee and inclination higher than expected. Orbit corrected through satellite, eventually the INSAT-4CR was placed in its slot. Decommissioned on 24 November 2020. INSAT-4E GSAT-6 rowspan=2 scope="row" 2015-041A , 11:22:00 GSLV MKII D6 83° East 6.3° Multimedia Offers a Satellite Digital Multimedia Broadcasting (S-DMB) service across several digital multimedia terminals or consoles which can be used to provide information services to vehicles on the fly and to the mobile phones. INSAT-4F GSAT-7 rowspan=2 scope="row" 2013-044B , 20:30:00 Ariane 5 ECA 570 74° East 0.1° Military According to defense experts, the satellite will enable the navy to extend its blue water capabilities and stop relying on foreign satellites like Inmarsat, which provide communication services to its ships. INSAT-4G GSAT-8 rowspan=2 scope="row" 2011-022A , 20:38:00 Ariane 5 ECA VA202 55° East 1.6° Communication First satellite to carry GAGAN payload.

See also List of Indian satellites Indian Remote Sensing Programme (IRSP) Indian Regional Navigation Satellite System (IRNSS) GSAT

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