Tianlian Relay Satellite

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The Tianlian relay satellite ( Chinese  天鏈系列中繼衛星  /  天链系列中继卫星 , Pinyin Tianlian Xìliè Zhongji Weixing , literally "sky chain") are a system of roughly distributed around the equator relay satellites in geostationary orbits , which by the National Space Agency and the Office for Manned Spaceflight of the People's Republic of China is operated jointly and serves to communicate with spacecraft in near-earth space.

history

As early as 1970, as part of the Shuguang project , under the impression of NASA's Spacecraft Tracking and Data Acquisition Network, which at the time consisted solely of ground stations, Chinese scientists proposed launching relay satellites for communication with the planned spacecraft. The Shuguang spaceship never got beyond a model made of wood and cardboard, and the concept of geostationary relay satellites was far beyond the technical possibilities of China at the time - the experimental satellite Dong Fang Hong I had just been brought into an orbit of 439 × 2384 kilometers . However, in the years that followed, Chinese space travel made progress. On April 8, 1984, Dong Fang Hong 2-2 successfully put a communications satellite into geostationary orbit for the first time, and after the People's Republic of China's manned space program was approved on September 21, 1992 , the Chinese Academy of Space Technology began during the 9. Five-year plan (1996-2000) with the first studies for relay satellites. In January 2003 the development of the system consisting of several satellites of the type "Tianlian 1" was officially started.

The satellites developed under the direction of Wang Jiasheng (王家胜, * 1943) were based on the company's slightly modified DFH-3 bus , now called "DFH-3A", as it was with the Chang'e-1 and Chang lunar probes 'e-2 was used. They were not only intended as relay satellites for the Shenzhou spaceships, but also for data transmission, orbit tracking, and control of satellites in medium and low orbits . Since these spacecraft move at a relatively high speed, while the relay satellite remains static relative to Earth, and also required high data transmission rates, the development work was not easy. On April 25, 2008, Tianlian 1A, the first satellite in the series, was launched and placed in a geostationary orbit at 77 ° east longitude. The payload weight of the 2100 kg satellite was 306 kg, which was a new record for this bus.

While the space travelers in the Shenzhou 5 (2003) and Shenzhou 6 (2005) missions were only able to communicate with the Beijing Space Control Center via the ground stations and track tracking vessels of the Chinese deep space network for about 12% of the time , the challenging Shenzhou 7 -Mission that was planned to be an spacecraft now covered more than half of a 90-minute orbit, an increase from 10 to 50 minutes. In September 2008, the Shenzhou 7 spacecraft, which circled the earth at a height of a little over 300 km, radioed the images of Zhai Zhigang's space walk etc. to the satellite at an altitude of almost 36,000 km, which forwarded them to the Beijing space control center. The next satellite in the system, Tianlian 1B , was launched on July 11, 2011 and placed at 171.1 ° east longitude. A good three months later, on September 29, 2011, the Tiangong 1 space laboratory was launched, followed by the unmanned Shenzhou 8 spacecraft on October 31, 2011 , with which docking maneuvers were practiced. During the manual docking maneuver carried out by Liu Wang on June 24, 2012 with Shenzhou 9 , the two satellites also played a key role in position determination and data transmission.

With the start of Tianlian 1C on July 25, 2012 with a position at 20.4 ° east, the construction of the system was initially completed. The DFH-3A satellite bus itself has a service life of 12 years, but the Tianlian satellites are only certified for a service life of six years. Therefore, on November 22, 2016, more than eight years after Tianlian 1A, the Tianlian 1D satellite was launched to replace the former. At first, however, the four satellites still operated together. In the meantime, Tianlian 1D has taken over the position of Tianlian 1A at 77 ° east longitude, Tianlian 1A was parked at 79.7 ° east longitude (as of 2020).

Meanwhile, based on the DFH-4 bus of the Chinese Academy of Space Technology , which has a service life of 15 years and a payload weight of up to 600 kg, the next generation of relay satellites - Tianlian 2. The first satellite in the series, Tianlian 2A, was launched on March 31, 2019 and positioned at 80.5 ° East Longitude. It has twice as high a data transmission speed as the satellites of the previous series and can also service significantly more spacecraft at the same time. These spacecraft are not just about manned spaceships, but above all about the Ziyuan (资源) earth observation satellites , such as those used in the China-Brazil Earth Resources Satellite Program . In addition to data transmission - the relay satellites can also communicate with each other - the Tianlian satellites are also used to determine the position of spacecraft. Especially when they are aiming for high orbits, missiles can get into a "blind area" that is not visible to the ground stations of the Xi'an satellite control center . During this time, the relay satellites can take over the transmission of the telemetry data. Since in this case there is no need for tracking ships, the preparation time for a mission is shortened. Since nothing was left to chance when the Mars probe Tianwen-1 was launched on July 23, 2020, the relay satellites Tianlian 1B and Tianlian 2A were used in addition to the track tracking ship Yuan Wang 5.

Current satellite list

Status: July 22, 2020

Start (UTC) carrier
rocket		 Satellite
name		 bus Position
(east longitude)		 Catalog no.
( AFSC )		 COSPAR
name		 comment
Apr 25, 2008 CZ-3C Tianlian 1A DFH-3A 79.7 ° 32779 2008-019A reserve
July 11, 2011 CZ-3C Tianlian 1B DFH-3A 171.1 ° 37737 2011-032A
July 25, 2012 CZ-3C Tianlian 1C DFH-3A 20.4 ° 38730 2012-040A
Nov 22, 2016 CZ-3C Tianlian 1D DFH-3A 77.2 ° 41869 2016-072A
31 Mar 2019 CZ-3B Tianlian 2A DFH-4 80.5 ° 44076 2019-017A

Future development

In September 2018, the National Center for Space Science proposed to place a system of six relay satellites in an orbit between Earth and Mars around the sun for future deep- space missions - also usable by other countries. The start of the project for this “Universally Usable Interplanetary Relay Satellite Constellation” (通用 的 星际 中继 通信 卫星 星座) or UNICON, also known as “Communication Satellite Constellation for Deep Space Exploration” (深 空 探测 通信 卫星 星座), was specified in 2020, the first satellite should be in 2025 start.Template: future / in 5 years

Individual evidence

  1. ↑ 王家胜: 数据 中继 卫星 系统 的 研制 与 分析. In: cnki.com.cn. Retrieved July 21, 2020 (Chinese).
  2. ↑ 冯 贵 年 、 于 志坚: 跟踪 与 数据 中继 卫星 系统 的 现状 和 发展. In: cnki.com.cn. Retrieved July 21, 2020 (Chinese).
  3. ^ Gunter Dirk Krebs: DFH-3 bus. In: space.skyrocket.de. Retrieved July 21, 2020 (English).
  4. ↑ China sets up first space station for spacecraft data relay. In: en.people.cn. May 2, 2008, accessed July 21, 2020 .
  5. ↑ 王家胜 院士 ： 架设 天地 链路. In: news.sciencenet.cn. December 18, 2016, accessed July 21, 2020 (Chinese).
  6. ↑ China launches relay satellites. In: german.cri.cn. April 26, 2008, accessed July 21, 2020 .
  7. ↑ Stephen Clark: Chinese data relay spacecraft put into orbit. In: spaceflightnow.com. April 25, 2008, accessed July 21, 2020 .
  8. ↑ a b Zhang Han: China launches new data relay satellite. In: globaltimes.cn. April 1, 2019, accessed on July 22, 2020 .
  9. ↑ Tianlian 1-02. In: n2yo.com. Retrieved July 21, 2020 (English).
  10. ↑ Tianlian 1-03. In: n2yo.com. Retrieved July 21, 2020 (English).
  11. ↑ 张利文 、 孙 自 法: 中国 成功 发射 第三 颗 中继 卫星 “天 链 一号 03 星”. In: chinanews.com. July 26, 2012, accessed July 21, 2020 (Chinese).
  12. ↑ Mark Wade: DFH-3 in the Encyclopedia Astronautica (English)
  13. ↑ 李玉坤: 天 链 一号 04 星 发射 成功 我国 中继 卫星 4 星 共轨. In: bjnews.com.cn. November 23, 2016, accessed July 22, 2020 (Chinese).
  14. ↑ Tianlian 1-04. In: n2yo.com. Retrieved July 22, 2020 (English).
  15. ↑ CTDRS. In: n2yo.com. Retrieved July 22, 2020 (English).
  16. ↑ TIANLIAN 2-01. In: n2yo.com. Retrieved July 22, 2020 (English).
  17. ↑ 王家胜: 中国 数据 中继 卫星 系统 及其 应用 拓展. In: cnki.com.cn. Retrieved July 22, 2020 (Chinese).
  18. ↑ 李国利 、 王 然: 我国 天 基 测控 系统 团队 完成 多项 技术 状态 准备 静待 天 问 一号 发射. In: xinhuanet.com. July 21, 2020, accessed July 21, 2020 (Chinese).
  19. ↑ 火星 ， 我们 来 了！ 远望 5 号 船 再次 解缆 起航. In: www.sohu.com. June 14, 2020, accessed July 22, 2020 (Chinese).
  20. ↑ 国家 空间 科学 中心 : 铺 人类 星际 互联网 让 深 空 探测 不 迷航 —— 中国 科学家 提出 深 空 探测 通信 卫星 星座 方案. In: sohu.com. September 18, 2018, accessed July 22, 2020 (Chinese).
  21. ↑ 中国 科学家 提出 深 空 探测 通信 卫星 星座 方案. In: news.sciencenet.cn. September 18, 2018, accessed July 22, 2020 (Chinese).