Tianlian (

Simplified Chinese Simplification, Simplify, or Simplified may refer to: Mathematics Simplification is the process of replacing a mathematical expression by an equivalent one, that is simpler (usually shorter), for example * Simplification of algebraic expressions, ...

: 天链,

Traditional Chinese A tradition is a belief or behavior (folk custom) passed down within a group or society with symbolic meaning or special significance with origins in the past. A component of cultural expressions and folklore, common examples include holidays ...

: 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 seven satellites in two 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 The China Academy of Space Technology (CAST) () is a Chinese space agency and subordinate of China Aerospace Science and Technology Corporation (CASC). The agency was founded on 20 February 1968, and is the main spacecraft development and prod ...

(CAST) and it is similar to the American

Tracking and Data Relay Satellite System The U.S. Tracking and Data Relay Satellite System (TDRSS) is a network of American communications satellites (each called a tracking and data relay satellite, TDRS) and ground stations used by NASA for space communications. The system was desig ...

(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 Shenzhou 7 () was the third human spaceflight mission of the Chinese space program. The mission, which included the first Chinese extra-vehicular activity (EVA) carried out by crew members Zhai Zhigang and Liu Boming, marked the commencement o ...

onwards, the Tiangong space station, and interplanetary missions. All satellites were launched from the

Xichang Satellite Launch Center The Xichang Satellite Launch Center (XSLC), also known as the Xichang Space Center, is a spaceport of China. It is located in Zeyuan Town (), approximately northwest of Xichang, Liangshan Yi Autonomous Prefecture in Sichuan. The facility bec ...

and operate in geostationary orbit.

Tianlian I

Tianlian I consists of five satellites, all based on the DFH-3

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are opposed to specially produced satellites. Bus- ...

. The first satellite of the series, Tianlian I-01, was launched on the maiden flight of the Long March 3C

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload ( spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pads, supported by a launch control center and ...

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 2 satellites based on the

DFH-4 Dongfanghong () was a satellite program of the People's Republic of China. The program started in August 1965 as Project 651—a less ambitious successor to the earlier Project 581—with the goal of launching a satellite heavier than both Sputni ...

. The second generation system greatly improves data transmission rates and its multi-targeting ability. This in turn improves spacecraft operational safety and flexibility.

Satellites

References

{{Orbital launches in 2008 Satellites orbiting Earth 2008 in spaceflight 2019 in spaceflight Shenzhou 7 Shenzhou program Communications satellites in geostationary orbit Communications satellite constellations Communications satellites of China Spacecraft launched in 2008 Spacecraft launched in 2019 Inter-satellite communications satellites Spacecraft launched by Long March rockets

Mission

Tianlian I

Tianlian II

Satellites

See also

References