DSLWP-B

from Wikipedia, the free encyclopedia
DSLWP-B / Longjiang 2 / OSCAR-94
Type: Research satellite , amateur radio satellite
Country: China People's RepublicPeople's Republic of China People's Republic of China
Operator: Harbin Polytechnic University , CAMSAT (Chinese AMSAT )
COSPAR-ID : 2018-045C
Mission dates
Dimensions: 47 kg
Size: 50 cm × 50 cm × 40 cm
Begin: May 20, 2018, 21:25 UTC
Starting place: Xichang LC-3
Launcher: CZ-4C
Status: crashed on schedule
Orbit data
Orbit inclination : 21 °
Apogee height :  13,700 km
Perigee height :  350 km

DSLWP B , Longjiang-2 , LO-94 or Lunar OSCAR 94 was a Chinese research satellite and amateur radio satellite . It was designed and built by Harbin Polytechnic University (HIT). The satellite was in operation from May 2018 to July 2019.

Purpose and structure

After the Jet Propulsion Laboratory proposed using its "Interplanetary Nano-Spacecraft Pathfinder in Relevant Environment" (INSPIRE) to use microsatellites not only in Earth orbit but also for deep-space missions, similar considerations were made in China. Since there was still room for additional payloads on the Changzheng-4C launcher, which was supposed to carry the relay satellite for the Chang'e-4 mission into space, it was obvious to seize the opportunity for such a microsatellite experiment. The first question was whether it was even possible to manufacture and control deep-space probes with little capital investment.

DSLWP was a lunar flight mission for low-frequency radio astronomy , amateur radio and training, consisting of the microsatellites DSLWP-A and B. DSLWP stands for Discovering the Sky at Longest Wavelengths Pathfinder . It was planned that DSLWP-B would fly in formation with its twin satellite DSLWP-A and serve to validate technologies for low-frequency radio astronomy. In detail, the communication between the two satellites, the measurement of the distance they had from each other and the synchronization of their on-board clocks were to be tested, i.e. things that are of essential importance for the Very Long Baseline Interferometry to be operated by the satellites the holding of a flight formation in the constantly changing force of gravity, which prevails in the earth-moon system depending on the position in the orbit.

The main payload of the satellite was a long-wave detector developed and built by the National Center for Space Science of the Chinese Academy of Sciences with two tripole antennas, similar to the one on the back of the relay satellite , arranged on the top and bottom of the satellite next to the barrel-shaped platform the electronics for the intermediate storage of the data and a small parabolic antenna for the transmission of said data to the assigned ground stations of the Academy of Sciences in Kunming and Miyun near Beijing, which are very simple for reasons of weight saving . The UHF transmitter for the amateur radio operator had a power of 33  dBm (2  W ). Two antennas of linear polarization were offset by 90 ° and mounted perpendicular to the direction of flight. The satellite was stabilized on three axes . The satellite also carried a small optical camera developed by the Saudi Arabian Research Organization King Abdulaziz City for Science and Technology (KACST).

Mission history

The satellite was on 20 May 2018 21:25 UTC with a Long March-4C rocket along with the main payload Queqiao ( Chang'e-4 Relay, Relay CE 4) and its twin satellite DSLWP-A from the Xichang Satellite Launch Center in China started. After the Queqiao relay satellite had first detached itself from the launch vehicle and started its journey to the moon, one by one the two microsatellites also separated from the rocket and swiveled into an elongated transfer orbit. On May 25th, DSLWP-B reached an elliptical moon orbit on its own . DSLWP-B was received by at least 42 radio amateurs worldwide (as of July 29, 2018). It exceeded the planned one-year mission duration and finally crashed on July 31, 2019 at 16:20 GMT on the moon erdabgewandte side, about 300 km north of the place where the Lunar Orbiter 1 of NASA was opened on 29 October 1966th

Since the Xi'an satellite control center and the Beijing space control center had to look after the two microsatellites as well as the Queqiao relay satellite, which had absolute priority, only limited resources were available for the former. During the transfer orbit to the moon, DSLWP-A and DSLWP-B were monitored and controlled from the ground stations in Santiago de Chile , Swakopmund and Qingdao as well as the deep-space stations Kashgar and Giyamusi . After the braking maneuver to swing into lunar orbit at DSLWP-A failed, the remaining microsatellite was looked after for the remainder of the mission by Qingdao, Kashgar and Swakopmund, although given the other tasks that these stations had to do - the People's Liberation Army has a large number of communication and reconnaissance satellites in orbit - with DSLWP-B three to four hours of orbit tracking through two of the three assigned stations was possible per day.

One of the problems with stabilizing the position of satellites using reaction wheels is that they have to be desaturated - in the case of DSLWP-B every one or two days - in order to reduce the stored angular momentum back to zero. Since the moon no longer has a magnetic field, the satellite had to be "held" by means of its four control nozzles, each with a thrust force of 0.2 N, in order to accomplish this, which on the other hand gave it additional speed. Together with other factors such as the radiation pressure of the sunlight on the 0.33 m² solar panel of the satellite when it was outside the moon's shadow, this made the orbit calculation and control difficult. Unlike the regular probes of the lunar program , no VLBI monitoring was approved for DSLWP-B by the Chinese deep space network and only the unified S-band technology was available for measuring the distance and speed of the satellite. Using sophisticated mathematical methods , such as those to be used in the Mars 2020 mission , where real-time orbit monitoring is not possible anyway due to the long signal propagation time, it was possible to keep the DSLWP-B correctly in orbit during the entire mission.

Operation and Impact

Micro camera

The optical lunar exploration device of the King Abdulaziz City for science and technology, in principle a small digital camera, brought about a great political success according to those responsible for the lunar program of the People's Republic of China . A total of 30 pictures were taken with the camera, and in particular the photos of the Mare Imbrium with the earth with the Persian Gulf, the Red Sea and the Arabian Peninsula in the background - " Hilal watches over the kingdom" - took care of the middle East caused a stir. On the one hand, this provided media support for the Chinese naval base in Djibouti and the various construction projects within the framework of the New Silk Road , and on the other hand, the basis for further joint space projects with Saudi Arabia, a very financially strong state that has so far primarily worked with the American in this sector, was created Stanford University collaborates. On June 12, 2019, the Human Space Agency at the Central Military Commission's Weapons Development Division and the United Nations Office for Outer Space announced that one of the National Center for Nanotechnology and the National Center for Materials Science - both working under the umbrella of the King -Abdulaziz City for Science and Technology - jointly submitted project to develop gallium arsenide solar cells for space applications has been tentatively accepted for use on the planned modular space station in China.

Data reception and international understanding

Below the government level, the development group from the Institute of Satellite Technology at the Faculty of Space Technology at Harbin Polytechnic University (哈尔滨 工业 大学 航天 学院 卫星 技术 研究所) under the direction of Wei Mingchuan (魏明川, * 1991) had contacts with around 40 university ground stations all over the world, for example to Wakayama in Japan and to the Dwingeloo radio telescope in the Netherlands to receive payload data. For comparison: the official deep space network of the People's Liberation Army gets by in regular operation with three stations spread across the planet.

In addition, the students in Harbin had mounted a simple camera on the satellite, which could be controlled by amateur radio operators in order to take photos of the moon and earth. One of these photos was published on February 15, 2019 in the American magazine " Science ". During the periods when the satellite was not visible from China, radio stations in other parts of the world maintained radio contact. The German amateur radio operator Reinhard Kühn from Sörup was also involved in this. When Reinhard Kühn sent commands to DSLWP during the solar eclipse of July 2, 2019 , he added a sequence for downloading a photo that shows the eclipse over the Pacific off Chile. The resulting picture was u. a. received by the radio telescope in Dwingeloo , the Netherlands .

Official rating

Measured against the original objectives, the DSLWP mission was only a partial success. Only one of two low-cost satellites could be brought into orbit and the techniques necessary for long-base interferometry could not be tested. Nevertheless, those responsible for the People's Republic of China's lunar program rated the experiment positively. DSLWP-B was the world's first microsatellite that swiveled independently into an earth-moon transfer orbit, carried out orbit correction maneuvers near the moon and thus reached an orbit around the moon. This was at least one approach to low-capitalization deep space issues.

Frequencies

  • 435.4 MHz downlink - 250/500 bps - GMSK / JT4G
  • 436.4 MHz downlink - 250/500 bps - GMSK / JT4G (amateur radio frequencies in the 70 cm band coordinated by IARU .)
  • 2.27522 GHz downlink - 250/500 bps - GMSK / JT4G
  • VHF Uplink (exact frequency (s) not published)

Web links

Individual evidence

  1. ↑ Jonathan McDowell: Twitter message. May 27, 2018, accessed September 14, 2018 .
  2. ↑ Joe Spier: ANS-232 AMSAT News Service Special Bulletin - Harbin Institute of Technology Lunar Satellites Designated as Lunar-, OSCAR 93 (LO-93) and as Lunar-OSCAR 94 (LO-94). August 20, 2018, accessed September 14, 2018 .
  3. ^ Jon Nelson: Interplanetary Nano-Spacecraft Pathfinder in Relevant Environment (INSPIRE). In: jpl.nasa.gov. Retrieved September 14, 2019 .
  4. ↑ 欧阳 琦 、 陈明 et al .: “龙江 2 号” 月球 轨道 微 卫星 定 轨 分析. In: jdse.bit.edu.cn. February 22, 2019, accessed September 14, 2019 (Chinese).
  5. ↑ 张 锦绣 、 陈 学 雷 et al .: 月球 轨道 编队 超长 波 天文 观测 微 卫星 任务. In: jdse.bit.edu.cn. March 27, 2017, Retrieved September 14, 2019 (Chinese).
  6. ↑ BG2BHC, HIT Research Center of Satellite Technology: Successful Configurations. July 29, 2018, accessed September 14, 2018 .
  7. ↑ China's micro lunar orbiter crashes into Moon under control. Xinhua , August 2, 2019; accessed August 2, 2019 .
  8. ↑ Andrew Jones: Lunar Orbiter Longjiang-2 Smashes into Moon. In: planetary.org. August 5, 2019, accessed December 3, 2019 .
  9. ↑ Xu Luyuan: How China's lunar satellite relay arrived in its final orbit. In: planetary.org. June 15, 2018, accessed September 14, 2019 .
  10. ↑ However , there were VLBI experiments with the university ground stations mentioned below. Wei Mingchuan: VLBI. July 29, 2018, accessed September 14, 2019 .
  11. ↑ 欧阳 琦 、 陈明 et al .: “龙江 2 号” 月球 轨道 微 卫星 定 轨 分析. In: jdse.bit.edu.cn. February 22, 2019, accessed September 14, 2019 (Chinese).
  12. ↑ “龙江 二号” 微 卫星 圆满 完成 环 月 探测 任务, 受控 撞 月. In: clep.org.cn. August 2, 2019, accessed August 15, 2019 (Chinese). The upper photo was taken with the Saudi camera, the lower one with the student camera by German and Dutch amateur radio operators.
  13. ^ Space and Aeronautics. In: kacst.edu.sa. Retrieved August 15, 2019 .
  14. ↑ مركز تميز الفضاء والطيران. In: kacst.edu.sa. Retrieved August 15, 2019 (Arabic).
  15. ^ Leonard David: Experiments Selected for China's Space Station. In: leonarddavid.com. June 12, 2019, accessed October 12, 2019 .
  16. ^ Nanotechnology. In: kacst.edu.sa. Retrieved October 12, 2019 .
  17. ↑ Advanced Materials Technology. In: kacst.edu.sa. Retrieved October 12, 2019 .
  18. ↑ 卫星 技术 研究所. In: sa.hit.edu.cn. January 7, 2015, accessed August 15, 2019 (Chinese).
  19. ↑ Hong Yu: Chinese students behind photo published in Science. In: en.people.cn. February 21, 2019, accessed August 15, 2019 .
  20. ^ Cees Bassa and Tammo Jan Dijkema: Imaging the Earth from Lunar orbit. In: planetary.org. October 15, 2018, accessed August 15, 2019 .
  21. ↑ “龙江 二号” 微 卫星 圆满 完成 环 月 探测 任务, 受控 撞 月. In: clep.org.cn. August 2, 2019, accessed August 15, 2019 (Chinese).
  22. ↑ German amateur radio operator photographs solar eclipse - from the moon. In: Der Spiegel . August 16, 2019, accessed August 27, 2019 .
  23. ↑ “龙江 二号” 微 卫星 圆满 完成 环 月 探测 任务, 受控 撞 月. In: clep.org.cn. August 2, 2019, accessed September 15, 2019 (Chinese).
  24. ^ IARU: IARU Amateur Satellite Frequency Coordination. May 19, 2018, accessed on September 14, 2018 .