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 "slug": "i-3k",
 "title": "I-3K",
 "updated": "2026-10-25",
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 "excerpt": "The I-3K, also known as INSAT-3000, is a geostationary satellite bus developed by ISRO's U R Rao Satellite Centre for 3,000 to 3,500 kg communication satellites.",
 "snippet": "The I-3K, also known as INSAT-3000, is a geostationary satellite bus developed by ISRO's U R Rao Satellite Centre for 3,000 to 3,500 kg communication satellites.",
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 "markdown": "# I-3K\n\n**I-3K** (INSAT-3000) is a geostationary satellite bus developed by the U R Rao Satellite Centre (URSC) of the Indian Space Research Organisation (ISRO) for spacecraft in the 3,000 to 3,500 kg launch-mass class, used primarily for communication and advanced payload missions.<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> The \"I\" in the name stands for INSAT, ISRO's communication satellite series, and the bus is marketed commercially by Antrix Corporation and New Space India Ltd. It is compatible with ISRO's GSLV and with commercially available launch vehicles, and most I-3K satellites have in fact flown on [Ariane 5](https://www.edgepedia.org/ariane-5) from Kourou.<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup><sup> • </sup><sup>[2](https://space.skyrocket.de/doc_sat/isro_i3k.htm)</sup>\n\n| Key fact | Detail |\n|---|---|\n| Developer | U R Rao Satellite Centre (URSC), ISRO; marketed by Antrix Corporation and New Space India Ltd<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> |\n| Class | Standard bus for 3,000–3,500 kg satellites; bus dimensions 2.0 m × 1.8 m × 3.2 m<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> |\n| Power | Spacecraft power 6.5–12 kW; payload power 6–8.5 kW<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> |\n| Payload and propellant | Payload mass 300–400 kg; propellant capacity 1,600–2,600 kg<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> |\n| Mission life | More than 15 years<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> |\n| Launch vehicles | Compatible with ISRO's GSLV and commercial launch vehicles; Ariane 5 has carried most I-3K satellites<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup><sup> • </sup><sup>[2](https://space.skyrocket.de/doc_sat/isro_i3k.htm)</sup> |\n| Commercial first | First Indian-built satellite bus sold commercially to a foreign customer, Eutelsat W2M<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> |\n\n## Design and specifications\n\nThe I-3K is one of a family of ISRO buses scaled by mass class, alongside the I-1K (1,000–1,700 kg), [I-2K](https://www.edgepedia.org/i-2k) (2,000–2,500 kg), I-4K (4,000–5,000 kg), and I-6K (up to about 6,500 kg) platforms.<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> Within that family it occupies the mid-large slot: it carries roughly twice the spacecraft power of the I-2K (6.5–12 kW versus 3–5 kW) and about twice the propellant (1,600–2,600 kg versus 850–1,420 kg), which supports the long station-keeping life expected of a heavy geostationary communications satellite.<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup>\n\nA satellite bus is the standardized service platform that houses the subsystems a payload needs: power generation and distribution, attitude control, propulsion, and thermal control.<sup>[3](https://www.esa.int/Applications/Connectivity_and_Secure_Communications/Hylas/Platform)</sup> On I-3K spacecraft this platform supports payloads of 300 to 400 kg drawing 6 to 8.5 kW, and the design life exceeds 15 years.<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup> A representative spacecraft, GSAT-17, measures 3.1 m in length with a diameter of 1.7 m and a span of 20 m with arrays deployed, has a dry mass of 1,400 kg against a launch mass of 3,477 kg, and uses an ISRO LAM motor.<sup>[4](https://keeptrack.space/satellite/42815)</sup>\n\n## Missions\n\nThe bus has flown across ISRO's INSAT-4 and GSAT communication fleets. Gunter's Space Page lists Insat 4A (launched 21 December 2005, 3,081 kg), Insat 4B (11 March 2007, 3,100 kg), GSAT-8 (20 May 2011, 3,150 kg), GSAT-10 (28 September 2012, 3,435 kg), GSAT-15 (10 November 2015, 3,164 kg), GSAT-16 (6 December 2014, 3,180 kg), GSAT-17 (28 June 2017, 3,477 kg), GSAT-18 (5 October 2016, 3,404 kg), GSAT-19 (5 June 2017, 3,136 kg, on GSLV Mk.3), GSAT-29 (14 November 2018, 3,423 kg), GSAT-30 (16 January 2020, 3,357 kg), and GSAT-24 (22 June 2022, 4,180 kg), all on Ariane 5 or GSLV Mk.3 vehicles.<sup>[2](https://space.skyrocket.de/doc_sat/isro_i3k.htm)</sup> ISRO's own bus documentation lists the missions as GSAT-8/10/14/15/16/17/18, Eutelsat W2M, GSAT-30, and GSAT-24.<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup>\n\n**Enhanced variant.** Several later satellites use an enhanced I-3K configuration. GSAT-29, a multi-beam, multi-band communication satellite with a lift-off mass of 3,423 kg, is configured around the enhanced I-3K bus and carries Ka and Ku high-throughput transponders plus Q/V-band and optical communication technology demonstrators; it was the heaviest satellite launched from India at the time.<sup>[5](https://www.isro.gov.in/DataCommunication.html)</sup> GSAT-30 is likewise configured on the enhanced I-3K bus structure, weighing 3,357 kg and providing C and [Ku band](https://www.edgepedia.org/ku-band) services with a designed in-orbit life of more than 15 years.<sup>[5](https://www.isro.gov.in/DataCommunication.html)</sup> ISRO's annual report also described GSAT-20 as configured on the standard I-3K bus with a Ka × Ka high-throughput payload and an estimated lift-off mass of 3,650 kg.<sup>[6](https://www.isro.gov.in/media_isro/pdf/AnnualReport/annual_report_2017-18.pdf)</sup>\n\n**Payload examples.** GSAT-10, built on the I-3K bus, carried 12 Ku, 12 Normal C and 6 Lower Extended C transponders plus the GAGAN navigation augmentation payload and a Ku beacon, with a mass of 3,425 kg, 6 kW of power and a 15-year mission life, launched by Ariane 5 to 83 degrees east.<sup>[7](https://www.drsvsharma.com/wp-content/uploads/2023/09/ISAC-Presentation-January-2014.pdf)</sup> The bus is not limited to communications: the NASA-ISRO Synthetic Aperture Radar mission NISAR is built around ISRO's I-3K bus and carries an L-band SAR (1,260 MHz) delivered by NASA and an S-band SAR (3,200 MHz) developed by ISRO's Space Applications Centre.<sup>[8](https://www.isro.gov.in/media_isro/pdf/AnnualReport/annual_report_2018-19.pdf)</sup>\n\n## Commercial sale: Eutelsat W2M\n\nIn February 2006 Eutelsat selected a partnership of EADS Astrium and Antrix, ISRO's commercial arm, to build the W2M communications satellite, the first order resulting from that alliance.<sup>[9](https://spaceflightnow.com/news/n0602/01w2m/)</sup> EADS Astrium was prime contractor and built the communications payload of typically 26 Ku-band transponders (up to 32 depending on operating modes); ANTRIX/ISRO supplied the satellite bus based on the flight-proven I3K model and integrated and tested the spacecraft, which had a launch mass of about 3 tons and payload power of about 4 kW for a 15-year design life.<sup>[9](https://spaceflightnow.com/news/n0602/01w2m/)</sup> W2M launched on 20 December 2008 on an Ariane 5 with a lift-off mass of 3,460 kg.<sup>[2](https://space.skyrocket.de/doc_sat/isro_i3k.htm)</sup><sup> • </sup><sup>[10](https://satmagazine.com/wp-content/uploads/2026/02/SatMag_Nov08-1.pdf)</sup>\n\nThe mission ended in failure. W2M suffered a sudden failure of its electric-power subsystem on 22 January 2009 while being moved from its in-orbit test location toward its final geostationary slot at 16 degrees east, after four weeks of trouble-free in-orbit testing.<sup>[11](https://www.unoosa.org/pdf/publications/st_space_46.pdf)</sup> The failure was not due to operator error and was traced to a system on the I3K platform provided by Antrix; Antrix was in charge of the spacecraft bus, including much of the suspect power system, and had overseen integration and testing in India.<sup>[11](https://www.unoosa.org/pdf/publications/st_space_46.pdf)</sup><sup> • </sup><sup>[12](https://spaceflightnow.com/news/n0901/28w2m/)</sup> Eutelsat decided not to integrate the satellite into its fleet, and the spacecraft later passed through the designations Eutelsat 48B, Eutelsat 28B, Eutelsat 48D, and Afghansat 1.<sup>[2](https://space.skyrocket.de/doc_sat/isro_i3k.htm)</sup>\n\n## Technology transfer\n\nURSC-ISRO offers to transfer the I-3K bus technology to Indian industries with adequate experience and facilities; enterprises register and submit proposals through IN-SPACe in [Ahmedabad](https://www.edgepedia.org/ahmedabad).<sup>[1](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)</sup>\n\n## References\n\n1. [Spacecraft Bus Details: I-3K Bus, IN-SPACe](https://www.inspace.gov.in/sys_attachment.do?sys_id=1c3939e12b2c0750e95ef17b6e91bfb6)\n2. [ISRO: I-3K (I-3000) Bus, Gunter's Space Page](https://space.skyrocket.de/doc_sat/isro_i3k.htm)\n3. [Platform (Hylas-1), ESA](https://www.esa.int/Applications/Connectivity_and_Secure_Communications/Hylas/Platform)\n4. [Track GSAT-17 Live, NORAD 42815, KeepTrack](https://keeptrack.space/satellite/42815)\n5. [Data Communication Satellites: GSAT-29, GSAT-30, ISRO](https://www.isro.gov.in/DataCommunication.html)\n6. [ISRO Annual Report 2017-18](https://www.isro.gov.in/media_isro/pdf/AnnualReport/annual_report_2017-18.pdf)\n7. [ISAC Presentation, January 2014 (GSAT-10 salient features)](https://www.drsvsharma.com/wp-content/uploads/2023/09/ISAC-Presentation-January-2014.pdf)\n8. [ISRO Annual Report 2018-2019 (NISAR)](https://www.isro.gov.in/media_isro/pdf/AnnualReport/annual_report_2018-19.pdf)\n9. [Eutelsat selects alliance for new W2M satellite, Spaceflight Now (1 February 2006)](https://spaceflightnow.com/news/n0602/01w2m/)\n10. [SatMagazine November 2008 (W2M based on I-3K, 3,460 kg)](https://satmagazine.com/wp-content/uploads/2026/02/SatMag_Nov08-1.pdf)\n11. [United Nations, st_space_46 (W2M power subsystem failure traced to I3K platform)](https://www.unoosa.org/pdf/publications/st_space_46.pdf)\n12. [New European TV satellite fails quickly in space, Spaceflight Now (28 January 2009)](https://spaceflightnow.com/news/n0901/28w2m/)\n\n---\n*Topic: Encyclopedia › Technology and the built world › Transport and spaceflight › Spaceflight › Satellites › Satellites by country, orbit, and bus › Soviet/Russian and other non-Western bus families*\n\n*Initially written Oct 15, 2026 · Edited: Oct 25, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n",
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 "credit": "\"I-3K\", Edgepedia (EdgeChat), https://www.edgepedia.org/i-3k. Edgepedia Community License 1.0.",
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 "speakable": "The I-3K, also known as INSAT-3000, is a geostationary satellite bus developed by ISRO's U R Rao Satellite Centre for 3,000 to 3,500 kg communication satellites."
}