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 or ...
: 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 (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
A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...
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
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 Sputn ...
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-d ...
. The first satellite of the series, Tianlian I-01, was launched on the maiden flight of the
Long March 3C
The Long March 3C (), also known as the Changzheng 3C, CZ-3C and LM-3C, is a Chinese orbital launch vehicle. It is launched from Launch Complex 2 and 3 at the Xichang Satellite Launch Center (XSLC). A three-stage rocket with two strapon liquid ...
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 pad, launch pads, supported by a missile launch contro ...
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 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-d ...
. The second generation system greatly improves data transmission rates and its multi-targeting ability. This in turn improves spacecraft operational safety and flexibility.
Satellites
See also
*
Queqiao
''Queqiao'' relay satellite (), also known as the Chang'e 4 Relay, is a communications relay and radio astronomy satellite for the Chang'e 4 lunar farside mission. As part of the Chinese Lunar Exploration Program, the China National Space Admi ...
- Chinese Data Relay satellite for lunar communication
*
Chinese Deep Space Network - Mission control for deep space missions
*
Tracking and Data Relay Satellite System - US equivalent
*
Luch - Russian equivalent
*
Indian Data Relay Satellite System
Indian Data Relay Satellite System or IDRSS is a planned Indian constellation of Inter-satellite communications satellites. It is planned to initially comprise two satellites, CMS-04 (formerly IDRSS-1) & IDRSS-2 in geostationary orbit. It will fac ...
- Indian equivalent
*
European Data Relay System
The European Data Relay System (EDRS) system is a European constellation of GEO satellites that relay information and data between satellites, spacecraft, UAVs, and ground stations. The first components (a payload and dedicated GEO satellite) we ...
- ESA equivalent
*
Inter-satellite service
Inter-satellite service (also: inter-satellite radiocommunication service) is – according to ''Article 1.22'' of the International Telecommunication Union's (ITU) Radio Regulations (RR)ITU Radio Regulations, Section IV. Radio Stations and Sys ...
*
Shenzhou spacecraft
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