Indian National Satellite System (INSAT) and Indian Remote Sensing Satellite System (IRS)

INSAT and IRS Satellite Systems for Civil Services Exam

Indian National Satellite System (INSAT)

• Background: INSAT is a series of geostationary satellites by ISRO (Dept. of Space) for India’s communication and meteorology. It was commissioned in 1983 with INSAT‑1B (after INSAT‑1A failed in 1982)en.wikipedia.org. This ushered in a revolution in TV/radio broadcasting, telecommunications and weather monitoring, extending services even to remote and island regionsen.wikipedia.orgisro.gov.in. INSAT (a joint venture of DOS, DOT, IMD, AIR, DD) is the largest domestic communication satellite system in the Asia-Pacific regionisro.gov.in.
• Objectives & roles: INSAT’s multipurpose satellites carry transponders (C/Extended C/Ku bands) to provide telecommunications and broadcasting (e.g. direct TV, All-India Radio), data relay and satellite news gathering, and weather imagingen.wikipedia.orgisro.gov.in. Some INSATs include meteorological sensors (VHRR, CCD) to support round-the-clock weather observationen.wikipedia.orgen.wikipedia.org. INSAT also carries search-and-rescue transponders (COSPAS-SARSAT) for distress alerts and disaster warningen.wikipedia.orgisro.gov.in. In effect, INSAT has bridged the digital divide by enabling national telephone/Internet links (VSAT networks) and bringing television/radio to rural and island areasen.wikipedia.org. It also supports “tele-education” (EduSAT) and telemedicine programs under national schemes.
• Major satellites: INSAT includes several generations of satellites:
  • INSAT‑1 series (1980s): INSAT‑1A (Apr 1982, failed) and INSAT‑1B (Aug 1983, first successful)en.wikipedia.org; INSAT‑1C (1988) and 1D (1990) all for communication and basic meteorology.
  • INSAT‑2 series (1990s): INSAT‑2A (Jul 1992), 2B (1993), 2C (1995) and 2D (1997, failed), 2E (1999) – all primarily telecommunications satellitesisro.gov.in.
  • INSAT‑3 series (2000s): INSAT‑3B (2000, comms), 3A (Apr 2003, meteorology + comms)isro.gov.in, 3C (2002), 3D (July 2013, advanced weather imaging)en.wikipedia.org, 3DR (Sept 2016, weather data relay)en.wikipedia.org and INSAT‑3DS (Feb 2024, meteorology)en.wikipedia.org. Kalpana‑1 (Sep 2002) was India’s first dedicated meteorological satellite, carrying cloud-mapping sensorsen.wikipedia.org.
  • INSAT‑4 series: INSAT‑4A (Sep 2005) and 4B (Mar 2007) – telecom satellitesisro.gov.in; INSAT‑4C (Jul 2006) failed, replaced by INSAT‑4CR (Sept 2007). (Later GSAT satellites continue INSAT’s functions.)
• Applications: INSAT satellites serve national telecom and broadcast networks (phone trunking, VSATs, Direct-to-Home TV, All-India Radio)isro.gov.in. They are vital for meteorology: INSAT-3D/3DR and Kalpana-1 provide visible/infrared cloud imagery and sounding for weather forecasting. INSAT’s Search-and-Rescue payload helps detect distress beacons in the Indian Ocean. The system also aids disaster management by providing real-time communication and early warning (cyclones, floods, etc.). In sum, INSAT underpins mass media, communications infrastructure and weather servicesisro.gov.inen.wikipedia.org.
• Notable milestones: INSAT made India self-reliant in satellite communications and TV broadcasting, reaching remote areas (Andamans, Lakshadweep)en.wikipedia.org. Key milestones include the first INSAT video transmissions in 1988 and full indigenous design of later satellites. INSAT is credited with democratizing TV/radio (over 100 channels) and building India’s largest GEO satellite networkisro.gov.in.
• Recent/future launches: The latest INSAT meteorological satellite INSAT-3DS was successfully launched on 17 Feb 2024en.wikipedia.org. Future plans include GSAT series successors (e.g. GSAT-20/22/23) for expanded communications. (INSAT remains active mainly via the INSAT-3/GSAT line of satellites.)

Indian Remote Sensing Satellite System (IRS)

• Background: The IRS programme applies space technology to natural resource development. It began experimentally with Bhaskara‑1 (1979) and Bhaskara‑2 (1981) satellites (optical/microwave sensors)en.wikipedia.org. The first dedicated IRS satellite, IRS‑1A, was launched on 17 March 1988 (Sun-synchronous orbit from Baikonur)en.wikipedia.org. IRS is managed by ISRO (Dept. of Space) under the National Natural Resources Management System (NNRMS).
• Objectives & roles: IRS aims to support India’s economy in agriculture, water, forestry, ecology, geology, and coastal/marine managementen.wikipedia.org. Its goals include mapping land use/land cover, assessing crop yields, monitoring water resources (reservoir levels, irrigation), forest cover and biodiversity, mineral exploration, and coastal zone changes. Remote-sensed data (optical, radar, microwave) are processed by NRSC and shared via the Bhuvan geoportal. Since 1988, IRS has demonstrated real-world utility (e.g. detecting coconut disease from aerial data in 1970en.wikipedia.org). Today the IRS constellation (11+ operational satellites) is the world’s largest civilian remote-sensing fleeten.wikipedia.org.
• Major satellites: Key IRS satellites include:
  • IRS‑1 series: IRS‑1A (Mar 1988, 72.5m multispectral) and IRS‑1B (Aug 1991) – established India’s resource monitoring capabilityen.wikipedia.org. IRS‑1C (Dec 1995) and IRS‑1D (Sept 1997) carried improved LISS multispectral cameras.
  • OceanSat: Oceansat-1 (IRS-P4, May 1999) carried ocean color and wind scatterometer instrumentsen.wikipedia.org; Oceansat-2 (Sept 2009) continued oceanographic studies.
  • ResourceSat: Resourcesat-1 (IRS-P6, Oct 2003) and Resourcesat-2 (Apr 2011) with AWiFS/LISS sensors for large-area agriculture and watershed surveys.
  • CartoSat: Cartosat-1 (IRS-P5, May 2005) and Cartosat-2 (IRS-P7, Jan 2007) series – high-resolution stereo imagers for urban and rural mappingen.wikipedia.org. Cartosat-2A/2B (2008–10) and Cartosat-2C/2D/2E/2F (2016–18) further enhanced mapping. Cartosat-3 (Nov 2019) offers very high (sub-meter) resolution for precision mapping.
  • RISAT (RadarSat): RISAT-2 (Apr 2009, mini-satellite radar), RISAT-1 (Apr 2012, C-band SAR) and later RISAT-2B/2BR series – radar imaging satellites for all-weather reconnaissance.
  • Other EO satellites: Megha-Tropiques (Oct 2011, climate research) and SARAL (Feb 2013, ocean altimetry, Indo-French) contributed to weather/climate data. ScatSat-1 (Sept 2016) carried a scatterometer for ocean wind monitoring. Oceansat-3 (Nov 2022) continues the series.
• Applications: IRS data are used in agriculture (crop acreage, yield and health monitoring), water resources (irrigation planning, watershed analysis), forestry (forest cover mapping, wildlife habitat studies), geology and minerals (mapping rock types, exploring deposits), soil and land-use surveys, and coastal/marine (shoreline change, fishery forecasting)en.wikipedia.org. Urban planners use Cartosat images for infrastructure and sprawl mappingen.wikipedia.org. IRS also plays a key role in disaster management (flood mapping, drought monitoring, cyclone/flood damage assessment) via the ISRO Disaster Management Support Programme. The free Bhuvan portal provides users access to IRS imagery and maps.
• Notable achievements: The IRS constellation (over two dozen satellites launched to date) has made India a leader in remote sensing applications. The system reached 25 years of operation by 2013en.wikipedia.org. It provides unique capabilities such as nationwide thematic maps (crop patterns, groundwater prospects), and rapid post-disaster imagery. IRS satellites have been shared internationally (data dissemination to many countries). India’s demonstration of multispectral sensing in the 1980s laid the groundwork for later meteorological and environmental satellitesen.wikipedia.orgen.wikipedia.org.
• Recent/future launches: Recent IRS missions include Cartosat-3 (Nov 2019) for high-res mapping and Oceansat-3 (Nov 2022) for oceanographyen.wikipedia.org. The geosynchronous imaging satellite GISAT-1 (Aug 2021) failed at launchen.wikipedia.org, but its follow-ups are planned (GISAT-2/EOS-5 scheduled 2024). RISAT-1A (Feb 2022) and ScatSat-1 (2016) expanded radar/ocean wind capabilitiesen.wikipedia.org. Planned satellites include Cartosat-3A/3B (2024), Oceansat-3A (2025), Resourcesat-3 (2025), and NISAR (NASA-ISRO L-band radar in ~2024). These will continue IRS’s support for agriculture, resources and disaster managementen.wikipedia.org.

Differences between INSAT and IRS

• Orbit & Purpose: INSAT satellites are geostationary (fixed longitude) and serve primarily communication, broadcasting and meteorology (TV/radio, telecom networks, weather imaging, SAR)en.wikipedia.orgisro.gov.in. IRS satellites are in sun-synchronous polar orbit and are dedicated to Earth observation (natural resources, environment, mapping)en.wikipedia.orgen.wikipedia.org.
• Payload & Applications: INSAT carries many transponders for data relay and a few weather imagers, focusing on telecom services and weather forecasting. In contrast, IRS satellites carry optical and radar sensors for multi-spectral imaging, serving agriculture surveys, land/water resource management, forestry, mineral exploration, and disaster mapping.
• Management: INSAT is a multi-agency program (Dept. of Telecom, IMD, AIR, Doordarshan and ISRO) supporting national communications infrastructureen.wikipedia.org. IRS is managed by ISRO (Dept. of Space) under NNRMS for civilian remote-sensing needs.
• Coverage: INSAT provides continuous coverage over India and surrounding ocean from GEO (enabling real-time services). IRS gives repeated whole-Earth coverage (revisit cycle days) from polar orbit, building up global datasets.

Mindmap-style Summary (Quick Revision)

• INSAT: Geo-stationary satellites (since 1983) → Telecommunications & broadcasting backbone, meteorology and SARen.wikipedia.orgisro.gov.in (e.g. INSAT‑1B 1983, INSAT‑3A 2003, INSAT‑3DR 2016).
• IRS: Sun-synchronous remote-sensing satellites (since 1988) → Natural resource and environmental monitoringen.wikipedia.org (e.g. IRS‑1A 1988, Oceansat-1 1999, Cartosat-3 2019).
• INSAT vs IRS: INSAT = GEO comms/weather system; IRS = polar-orbit Earth-observation systemen.wikipedia.orgen.wikipedia.org. INSAT serves telecommunication/TV and weather forecasting, whereas IRS serves agriculture, water/forestry/resource mapping and disaster management.