Tianlian

Tianlian (Simplified Chinese: 天链, Traditional Chinese: 天鏈, English: Sky Link) also known as CTDRS, is a Chinese data relay communication satellite constellation. The constellation serves to relay data from ground stations to spacecraft and rockets, most significantly China's crewed spaceflight program. The system currently consists of twelve satellites of three generations, with the first satellite being launched in 2008.

Mission Tianlian is used to provide real-time communications between orbiting satellites and ground control stations. The Chinese tracking and data relay satellites were developed by the China Academy of Space Technology (CAST) and it is similar to the American Tracking and Data Relay Satellite System (TDRSS) in concept. The system is designed to support near-real-time communications between orbiting spacecraft and ground control, as well as complement the ground-based space tracking and telemetry stations and ships in tracking spacecraft. This is necessary because ground stations can only maintain contact with a satellite while it is overhead. Positioning multiple satellites in geostationary orbit ensures that the ground station and satellite are both always in view of at least one relay satellite, allowing for constant communication between the ground station and target satellite. The system provides data relay services for crewed Shenzhou missions, from Shenzhou 7 onwards, the Tiangong space station, and interplanetary missions. All satellites were launched from the Xichang Satellite Launch Center and operate in geostationary orbit.

Tianlian I Tianlian I consists of five satellites, all based on the DFH-3 satellite bus. The first satellite of the series, Tianlian I-01, was launched on the maiden flight of the Long March 3C launch vehicle on 25 April 2008. With the launch of Tianlian I-03, a spacecraft could be tracked for 70% of its orbit, compared to only 15% without the constellation.

Tianlian II Tianlian II is the second generation of the constellation and currently consists of 6 satellites based on the DFH-4 satellite bus. The second generation system greatly improves data transmission rates and its multi-targeting ability. This in turn improves spacecraft operational safety and flexibility.

Tianlian III Tianlian III is the third generation of the constellation and launched its first satellite on 29 July 2026 from the Wenchang Space Launch Site with the Long March 7A rocket. It is based on the enhanced platform of DFH-4 satellite bus, DFH-4E which provides further improvements to the satellite platform's carrying capacity. Equipped with a new generation of payload products, the satellite's multi-user parallel data transmission capability has been significantly enhanced.

Satellites +SatelliteSimplified Chinese NameLaunch (UTC)Carrier RocketLaunch siteBusLongitudeStatusCOSPAR IDSATCAT no.First GenerationTianlian I-01天链一号01星25 April 2008, 15:35Long March 3CXSLC LC-2DFH-377.0° EastInactive2008-019A32779Tianlian I-02天链一号02星11 July 2011, 15:41Long March 3CXSLC LC-2DFH-3176.72° EastInactive2011-032A37737Tianlian I-03天链一号03星25 July 2012, 15:43Long March 3CXSLC LC-2DFH-316.86° EastInactive2012-040A38730Tianlian I-04天链一号04星22 November 2016, 15:24Long March 3CXSLC LC-2DFH-376.95° EastActive2016-072A41869Tianlian I-05天链一号05星6 July 2021, 15:53Long March 3CXSLC LC-2DFH-3106.2653° EastActive2021-063A49011Second GenerationTianlian II-01天链二号01星31 March 2019, 15:51Long March 3BXSLC LC-2DFH-479.9° EastActive2019-017A44076Tianlian II-02天链二号02星13 December 2021, 16:09Long March 3BXSLC LC-3DFH-4171.04° EastActive2021-124A50005Tianlian II-03天链二号03星12 July 2022, 16:30Long March 3BXSLC LC-2DFH-410.5° EastActive2022-078A53100Tianlian II-04天链二号04星26 March 2025, 15:55Long March 3BXSLC LC-2DFH-480.0° EastActive2025-062A63361Tianlian II-05天链二号05星27 April 2025, 15:54Long March 3BXSLC LC-2DFH-4Active2025-084A 63662Tianlian II-06天链二号06星23 July 2026, 12:00Long March 3BXSLC LC-2DFH-4Active2026-168A 100140Third GenerationTianlian III-01天链三号01星29 July 2026, 11:50Long March 7AWSLS LC-201DFH-4EActive2026-172A 100172

Tianlian

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