Shijian 20th

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Shijian 20th
Type: Experimental satellite
Country: China People's RepublicPeople's Republic of China People's Republic of China
Operator: Chinese Academy of Space Technology
COSPAR-ID : 2019-097A
Mission dates
Dimensions: > 8000 kg
Begin: December 27, 2019
12:45 p.m. ( UTC )
Starting place: Wenchang Cosmodrome
Launcher: Long March 5
Status: active
Orbit data
Track height: 35,786 km
Orbit inclination : 0 °

Shijian 20 ( Chinese  實踐 二十 號  /  实践 二十 号 , Pinyin Shíjiàn Èrshí Háo , German: "Exercise 20") is a Chinese technology testing satellite .

history

The satellite, built by the Chinese Academy of Space Technology under the direction of Li Feng (李峰) of the Qian Xuesen Laboratory for Space Technology , is based on the company's newly developed DFH-5 bus and is used to test the key technologies of the new satellite platform. After some problems with the Langer Marsch 5 launcher - the largely identical predecessor satellite Shijian 18 crashed into the Indian Ocean on July 2, 2017, six minutes after take-off - Shijian 20 lifted from the cosmodrome on December 27, 2019 at 12:45 pm (UTC) Wenchang on Hainan Island . About 34 minutes after take-off, the 8-ton satellite separated from the rocket's kick stage and entered geostationary orbit .

particularities

Solar panels

The DFH-5 bus has two semi-rigid solar cell wings made of six modules each , which form a “crucifix” and give the satellite a “ wingspan ” of 45 m when fully extended , around 10 m more than the Boeing 737 airliner . This generates an output of 30 kW, of which 18 kW are available for the payloads. The solar panels are China's largest of their kind in terms of both span and area, and the folding mechanism is more complicated than ever. Once unfolded, the solar cell wings, each weighing around 50 kg, can be slowly rotated around their longitudinal axis by a motor in order to align them as possible towards the sun. In April 2008, the NigComSat-1 communications satellite , which was based on the DFH-4 bus , had its rotating mechanism on a solar cell wing failed, which subsequently led to a total loss of the satellite. The drive was then redesigned by the Space Technology Academy.

Broadband data transmission

The Chinese Academy of Space Technology has been working on technologies for a satellite-based Internet shared by military and civilian customers since 2016 , which is of particular interest for streaming services, mobile communications, rescue services and the Internet of Things . One of the problems here is that the well-suited for this purpose in itself K a band (27-40 GHz) is already widely used. Therefore contributes Shijian 20 is now one of the Research Institute 504, the Chinese Academy of space technology , also known as "branch Academy Xi'an" (西安分院), developed "Flexible High-Speed Transponder" (broadband flexible transponder) for the Q / V area , so 33–75 GHz, where the device searches for free frequencies as required. This increases the practically achievable data transmission rate by four to five times and is now 70 Gbit / s with a bandwidth of 5.5 GHz. A first system test took place on January 4, 2020, and the frequency change was successfully tested from March 10 to 14, 2020.

The next step is to test the data transmission under different weather conditions, with a focus on the investigation of the absorption losses due to raindrops , which are a certain problem in countries with monsoon climates. In China, several companies are currently working on communication satellites based on the DFH-5 bus with transmission rates of 100 Gbit / s to 1 Tbit / s, which want to make high-quality Internet available to the countries involved in the New Silk Road projects and their neighboring states without that complex fiber optic networks have to be built.

Communication laser

In bad space weather , when the solar wind disrupts radio traffic, the People's Liberation Army already routinely uses the so-called " optoelectronic message transmission " by means of laser , a high-speed variant of the old blinking signals. Also find communication lasers on the Beidou - navigation satellites use to their flight in a net-shaped constellation of satellites to coordinate. In contrast to these applications, where there is always only one laser on the satellite, Shijian 20 has an infrared laser terminal developed by the research institute 504 over a period of 15 years with three different systems that are to be tested over a longer period of time in order to be able to use the Development of future communication lasers, especially for the modular space station , which is expected to go into operation in 2022 , to collect data from practical orbital operation. The laser terminal currently installed on Shijian 20 achieved a transmission rate of 10 Gbit / s with quadrature phase shift keying in a test at the beginning of April 2020 in two-channel operation, which compared to a single laser also offers better immunity to interference . Template: future / in 2 years

Hybrid drive

Shijian 20 has a hybrid drive. On the one hand, it has a liquid thruster that delivers a high vacuum thrust and was used to quickly bring the satellite into its geostationary orbit after separation from the launcher. The control nozzles for aligning the satellite are also chemical thrusters. The satellite is also equipped with an ion thruster for fine orbit corrections during its expected 16-year lifespan . This generates only a small amount of thrust, but it can be regulated very precisely, which means that the satellite is highly efficient in using fuel.

Cooling system

The DFH-5 bus is relatively large, but its surface area is not sufficient to radiate the heat generated by the payloads in normal operation, especially if they are in the center of the housing. For this reason, the satellite has a closed coolant circuit . A liquid is conveyed to all devices via tubes, where it absorbs the excess heat and transports it to a heat sink on the outside of the satellite, which then radiates the heat into space. Said shape memory polymer heat sink lay flat against the wall of the satellite during launch. After Shijian 20 reached correct orbit and began operating, the latch automatically released and the heat sink unfolded. If this cooling system proves itself in the long run, one could elegantly solve the contradiction between the waste heat generation of the increasingly demanding payloads and the inadequate housing surface in future satellite platforms in the 10 kilowatt range. Since the cooling system installed in Shijian 20 keeps the temperature inside the satellite at 35  K , i.e. −238 ° C, it would also be suitable for cooling the sensitive devices in deep space probes in order to reduce their heat noise.

Web links

Individual evidence

  1. ↑ Gunter Dirk Krebs: SJ 20. In: space.skyrocket.de. Retrieved April 8, 2020 .
  2. ↑ 孙 琳 、 樊立辉: 南京大学 田庆 久 教授 、 中国 空间 技术 研究院 李峰 研究员 来 工程 中心 进行 学术 交流. In: software.henu.edu.cn. April 2, 2019, accessed April 8, 2020 (Chinese).
  3. ↑ 胡 喆 、 周旋: 一身 真 功夫 亮点 真不少 —— 盘点 实践 二十 号 卫星 上 的 “黑 科技”. In: xinhuanet.com. December 27, 2019, accessed April 8, 2020 (Chinese).
  4. ↑ a b Chris Gebhardt: Long March 5 conducts critical return to flight mission. In: nasaspaceflight.com. December 27, 2019, accessed April 8, 2020 .
  5. ↑ a b 赵竹青: 实践 二十 号 卫星 成功 发射 掀开 我国 航天 器 升级 换代 新篇章. In: scitech.people.com.cn. December 27, 2019, accessed April 8, 2020 (Chinese).
  6. ↑ a b Mark Wade: DFH-5 in the Encyclopedia Astronautica , accessed on April 8, 2020 (English).
  7. ↑ China Displays Cutting-edge Space Technology at Paris. In: cgwic.com. June 17, 2019, accessed April 8, 2020 .
  8. ↑ 黄 全权 、 鲁慧蓉: 中国 研制 并 交付 的 尼日利亚 通信 卫星 一号 失效. In: chinanews.com. November 12, 2008, accessed April 8, 2020 (Chinese).
  9. ↑ 罗马 廊檐: 实践 -13 / 中 星 -16 卫星 ： 刷新 国内 高 轨 卫星 技术 “新 指标”. In: blog.sina.com.cn. April 18, 2017, accessed April 8, 2020 (Chinese).
  10. ↑ 李 煌: 卫星 宽带 柔性 转发 器 中 交换 系统 的 设计 研究 与 硬件 实现. In: gb.oversea.cnki.net. Retrieved April 8, 2020 (Chinese).
  11. ^ Zhang Fei et al .: Design of a Near Perfect Reconstruction Prototype Filter on Flexible Transponder for Broadband Satellite Communications. In: researchgate.net. Retrieved April 8, 2020 .
  12. ↑ 实践 二十 号 卫星 ： 我国 首 个 Ka 频段 宽带 柔性 转发 器 在 轨 测试 第一 阶段 圆满 成功. In: spaceflightfans.cn. March 20, 2020, accessed April 8, 2020 (Chinese).
  13. ↑ 张睿 奇 、 郭洪英: 航天 科技 五 院 西安 分院 实践 二十 号 卫星 Q / V 载荷 技术 圆满 完成 第一 阶段 在 轨 测试. In: spacechina.com. April 10, 2020, accessed April 10, 2020 (Chinese).
  14. ↑ 张宏洲: 2017 军校 巡礼 第二 十五 站 ： 航天 工程 大学. In: mod.gov.cn. June 15, 2017, Retrieved April 8, 2020 (Chinese).
  15. ↑ 速率 高达 10Gbps！ 实践 二十 号 卫星 激光 通信 通过 在 轨 验证. In: spaceflightfans.cn. April 8, 2020, accessed April 8, 2020 (Chinese).
  16. ↑ 蒋建军 et al .: 形状 记忆 智能 复合 材料 的 发展 与 应用. In: jme.biam.ac.cn. August 17, 2018, accessed April 8, 2020 (Chinese).
  17. ↑ 夏爱兰: 神奇 的 形状 记忆 材料. In: xinhuanet.com. September 27, 2019, accessed April 8, 2020 (Chinese).
  18. ↑ 胡 喆 、 周旋: 一身 真 功夫 亮点 真不少 —— 盘点 实践 二十 号 卫星 上 的 “黑 科技”. In: xinhuanet.com. December 27, 2019, accessed April 8, 2020 (Chinese).