Chang'e-4

Chang'e-4
NSSDC ID	2018-103A
Mission goal	Earth moon
Client	CNSA
Launcher	Changzheng 3B / E
construction
Takeoff mass	Lander: 1,200 kg Rover: 140 kg
Course of the mission
Start date	7th December 2018
launch pad	Xichang Cosmodrome
20th May 2018 Start from Queqiao 7th Dec 2018 Start of Chang'e-4 Dec 12, 2018 Reaching the lunar orbit 3rd Jan 2019 Landing on the moon, Von Kármán / South Pole Aitken Basin ? Mission end

Chang'e-4 ( Chinese  嫦娥 四號  /  嫦娥 四号 , Pinyin Cháng'é Sìhào ) is a space probe of the China National Space Administration (CNSA) that was launched on December 7, 2018 and consists of a lander with a rover . Chang'e-4 is China's second lunar lander and rover. After the successful landing of Chang'e-3 , Chang'e-4, originally an identical reserve probe for the previous mission, was adapted to new scientific objectives. Like its predecessors, the spacecraft is named after Chang'e , the Chinese goddess of the moon .

The probe landed successfully on January 3, 2019 at 3:26 a.m. CET in the Von Kármán lunar crater in the South Pole Aitken Basin on the far side of the moon .

Overview

The Chinese lunar exploration program has three phases. The first phase consisted of reaching the lunar orbit - accomplished through the Chang'e-1 missions in 2007 and Chang'e-2 in 2010. The second was the landing and launching of a rover on the Moon, as was done by Chang'e-3 in 2013 and now by Chang'e-4 in January 2019. In the third phase, moon samples are to be collected from the side facing the earth and sent to earth - a task for the future Chang'e-5 and Chang'e-6 missions . The program is designed to enable manned moon landings in the 2030s with the aim of establishing an outpost near the South Pole.

The Chang'e 4 mission was launched on November 30, 2015 as part of the second phase of China's lunar exploration program. Xu Dazhe , director of the China National Space Administration , said in the opening speech that the Chang'e-4 mission should be a platform for international cooperation and joint new developments on many levels.

The Chinese lunar exploration program approved private investment by individuals and companies for the first time in Chang'e-4. The aim is to accelerate innovations in the aerospace industry , reduce production costs and promote military-civil relationships. In order to integrate the payloads of foreign partners, the objectives of the mission had to be adjusted. This contributed to the fact that the mission became more complicated and delayed. The aim of the mission is to research the age and composition of the rock in an unexplored region of the moon. Another goal is to develop and test the technologies required for the following phases of the program. After Chang'e-4, a number of other robot-based moon missions will follow. These are supposed to prepare a manned moon landing , among other things with the testing of techniques for the construction of buildings .

aims

The scientific goals include:

• Measurement of the lunar surface temperature over the duration of the mission
• Measurement of the chemical composition of lunar rocks and soils
• low-frequency radio astronomical observations and investigations
• Study of cosmic rays
• Observation of the solar corona , investigation of its radiation properties and mechanisms and investigation of the development and transport of coronal mass ejections (CME) between the sun and earth

Components

Queqiao Relay Satellite

Communication with Chang'e-4

→ Main article : Elsternbrücke (relay satellite)

Since a direct radio connection with the back of the moon is not possible, the relay satellite Elsternbrücke ( Queqiao ) was launched from the Xichang cosmodrome on May 21, 2018 at 05:28 local time and in the halo orbit around the Earth-Moon Lagrange point L ₂ behind stationed on the moon. The name of the satellite is derived from the Chinese story of the cowherd and the weaver . Queqiao can relay radio signals between the earth and the back of the moon, enabling communication and control during the mission.

Microsatellites

As part of the Chang'e 4 mission, two microsatellites were launched together with Queqiao . The two microsatellites each measure 50 × 50 × 40 cm and weigh 45 kg and were called Longjiang-1 and Longjiang-2 ( 龙江  - "Dragon River"). Longjiang-1 was unable to enter lunar orbit, however, while Longjiang-2 was successful and operated in lunar orbit for 14 months until it was brought to a controlled crash on the back of the moon on July 31, 2019 at 10:20 pm Beijing time. These microsatellites had the task of observing the sky in the frequencies from 1 MHz to 30 MHz, corresponding to wavelengths from 300 m to 10 m, in order to investigate energetic phenomena of cosmic origin. This was a long-cherished goal of science, because due to the earth's ionosphere, no observations can be made in this frequency range in earth orbit. A group flight of the two probes was planned in order to be able to operate interferometry.

Image mosaic of the back of the moon, taken by LRO . At the top left the Mare Moscoviense , at the bottom left the dark Tsiolkovskiy crater , in the lower third of the image the spotty large basin region of Mare Ingenii , Leibnitz, Apollo and Poincaré.

Lander and Rover

The lander and rover were launched into space by a Changzheng 3B / E launcher from the Xichang Cosmodrome six months after the relay satellite launched on December 8, 2018 at 02:23 am local time . It was the first ever landing on the far side of the moon. It took place in an unexplored region of the moon called the South Pole Aitken Basin .

The total landing mass of the unit was 1340 kg, of which 1200 kg was accounted for by the lander and 140 kg by the rover. After landing, the lander extended a ramp to bring the rover Jadehase 2 to the surface of the moon. The rover measures 1.5 m × 1.0 m × 1.0 m and has a mass of 140 kg.

Scientific payloads

Both the lander and the rover, as well as Queqiao and the microsatellites orbiting the moon, carry scientific payloads. The relay satellite ensures communication, while the lander and rover investigate the geophysics of the landing zone. Some of these payloads are supplied by international partners in Sweden, Germany, the Netherlands and Saudi Arabia.

Countries

The lander and rover carry scientific payloads to study the geophysics of the landing zone with very limited chemical analysis capability.

The lander is equipped with the following instruments:

• Landing camera (LCAM)
• Terrain camera (TCAM)
• Low frequency spectrometer (VLFRS) for researching sunbursts etc.
• Neutron and radiation dose detector ( Lunar Neutron and Radiation Dose Detector ; LND), one of scientists of the Institute of Experimental and Applied Physics at the University of Kiel developed under the direction of Robert Wimmer-Schweingruber neutron dosimeter that the particularly dangerous in addition to measuring for people Neutron radiation, for which there are so far only very different model calculations, also serves to determine the water content of the soil. The first results were presented to Sönke Burmeister from the institute on April 18, 2019 at a festive ceremony in Beijing. When the resources of the Chinese deep space network had to be partially withdrawn from the lunar program in May / June 2020 as part of the preparation for the Mars mission Tianwen-1 , the neutron and radiation dose detector was the only device on the Chang'e-4 -Mission that continued to operate.
• The lander also carries a 2.6 kg container of seeds and insect eggs to test whether plants and insects can hatch in synergy and grow together. The experiment included seeds from potatoes, rapeseed, cotton and Arabidopsis thaliana , plus yeast and fruit fly eggs . On January 7, 2019, cotton sprouted first. When the larvae hatched, they would have produced carbon dioxide , while the germinated plants released oxygen through photosynthesis . The scientists led by Xie Gengxin and Liu Hanlong from Chongqing University hoped that the plants and animals together could create a simple synergy within the container. A miniature camera made every growth visible. However, when the moonlit night fell on January 13 at the Chang'e-4 landing site, the temperature in the container dropped to −52 ° C and the creatures died 212.75 hours after being awakened from the hibernation by irrigation shortly after landing . In 1982 the crew of the Soviet space station Salyut 7 bred some Arabidopsis ; they were the first plants to flower and produce seeds in space. They had a lifespan of 40 days.

rover

→ Main article : Jade Bunny 2

• Panorama camera (PCAM)
• Lunar Penetrating Radar (LPR) is a ground penetrating radar
• Visible and Near-Infrared Imaging Spectrometer (VNIS) for imaging spectroscopy
• Advanced Small Analyzer for Neutrals (ASAN) is an energetic analyzer for neutral atoms from the Swedish Institute for Space Physics (IRF). It will show how solar wind interacts with the lunar surface and maybe even the process of making moon water.

Queqiao

• Evaluation experiment Netherlands-China Low-Frequency Explorer (NCLE) for the preparation of possible, later, radio astronomical research in the low-frequency radio wave range below 30 MHz, especially with regard to the research of strongly red-shifted radiation of neutral hydrogen from the dark age . Under the earth's ionosphere such experiments are futile because of their shielding effect and in the lower earth orbit too much electromagnetic pollution disturbs .

Landing zone

The landing site is the Von Kármán crater (180 km diameter) in the South Pole Aitken Basin on the far side of the moon. The Von Kármán crater is surrounded by mountains up to 10 km high, and the landing site is at an "altitude of 5935 m". The area on which a landing was possible was only 1/8 of the target area that the previous probe Chang'e-3 had available in December 2013. Therefore, Chang'e-4 had to land practically vertically, a rather risky maneuver. As with the previous probe, Chang'e-4 interrupted the descent for about 13 seconds a minute before landing to ascend 99 m above the ground with the help of a device from the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences (中国科学院 上海 技术 物理 研究所) developed and built a laser rangefinder and a three-dimensional imaging laser scanner from the same institute to independently search for a flat place free of boulders, onto which it then slowly lowered itself. One of the main problems with this was that the electrostatically charged moondust raised by the engine during the final phase of the descent could endanger the probe's systems. For this reason, the Space Mechanics group (空间 力学 des) of the Institute of Mechanical Engineering at Tianjin University , headed by Cui Yuhong (崔玉红) and Wang Jianshan (王建 山), developed the smoothest possible landing procedure in extensive computer simulations and practical experiments. The touchdown on January 3, 2019 at 02:26 UTC then took place without any problems.

As recently as January 2019, China applied to the International Astronomical Union to name the landing site 天河 Pin (Pinyin Tiānhé Jīdì ), or "Base Milky Way", a reference to the legend of the cowherd and the weaver , where the Milky Way separates the two lovers and only is bridged once a year by a swarm of magpies forming a bridge (today's relay satellite Elsternbrücke ). On February 4, 2019, the application was approved by the IAU, the Latin name of the landing site is "Statio Tianhe".

In the following months, researchers from the Laboratory for Lunar and Deep Space Exploration of the National Astronomical Observatories , the Faculty of Astronomy and Space Science at the University of the Chinese Academy of Sciences, and the Chinese Academy of Space Technology, the manufacturer of the probe, the landing camera and terrain camera Landers and the panoramic camera of the rover photos taken and they sat in relation to the of Chang'e-2 and the lunar Reconnaissance Orbiter of NASA created lunar maps. After photogrammetric evaluation of the images, the landing site was determined to be 177.5991 ° east longitude and 45.4446 ° south latitude, which is a deviation of 348 m in length and 226 m in width, i.e. a total of 415 m compared to the LRO -Data means. This can be explained by measurement errors when determining the orbit of the NASA probe, with the irregular gravitational field of the moon on its back and factors that are justified in the camera. Therefore, the Chang'e-4 lander is now to be used as a geodetic reference point for the navigation of Jade Hare 2 and for future landings on the back of the moon.

Results

Schematic structure of the moon (left: front facing the earth, right: back)

Already during the Chang'e 3 mission the landing site near a crater had been chosen with care, in such a way that the lander could land safely on level ground, while the rover already had access to ejecta from 40 without further drilling -50 m depth, which had been thrown to the surface by the meteorite impact producing the crater. Chang'e-4 has now gone one step further. The South Pole Aitken Basin , the largest crater in the solar system with a diameter of 2500 km, was formed about 4 billion years ago when a very large impact body largely eroded the lunar crust (i.e. the top layer of the moon). Later impacts created the Von Kármán Crater and the Finsen Crater northeast of it . The advantage of this location for the engineers was that the level floor of the Von Kármán crater ensured a safe landing, while it was hoped that the impact producing the neighboring Finsen crater had thrown material upwards from great depths.

Jacket material

That hope was fulfilled. When a group of scientists from the National Astronomical Observatories of the Chinese Academy of Sciences and the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, the maker of the Rover Jadehase 2 mounted infrared spectrometer ( Visible and Near-infrared Imaging Spectrometer or VNIS) The first thing that struck them when looking at data that he had collected at two locations 30 m apart was the extraordinary amount of low-calcium orthopyroxenes (pyroxenes with orthorhombic symmetry). A further analysis revealed that the most abundant mineral group in the regolith at those two locations were olivines , followed by the low-calcium pyroxenes, and very few calcium-rich pyroxenes. Moon rocks with this composition had never been found before, and the researchers led by Li Chunlai came to the conclusion that it is very likely to be mantle material that had been ejected when the Finsen crater was formed, i.e. material from the layer below the crust 150 km thick on the back of the moon .

On May 15, 2019, Li Chunlai and his colleagues published their report in the British journal Nature . In a comment published in the same issue, Patrick Pinet, deputy director of the Institut de Recherches en Astrophysique et Planétologie at the Paul Sabatier University in Toulouse and one of the supervisors of the OMEGA Visible and Infrared Mineralogical Mapping Spectrometer on board the European Mars Express, similar to the Chinese VNIS, agreed Probe , based on the results of the Chinese researchers in principle, suggested that Jade Hare 2 should not only examine the fine-grained soil, but also the reflected light from larger boulders.

Currently, however, the priority of the researchers working with Li Chunlai is to steer the rover about 2 km to the southwest. Chang'e-4's landing site is right on the edge of the zone where the ejecta from the Finsen crater, which at the time was hurled in all directions in a radial pattern, lies on the surface of the moon. According to the photos and spectrograms taken by the orbiters Chang'e-1 and Chang'e-2, if the rover succeeds in driving the rover 2 km radially away from the Finsen Crater, it should come across basalt regolith that the scientists have not contaminated by mantle material want to examine for comparison purposes. However, due to the uneven terrain, this is not easy. On November 4, 2019, at the end of the 11th lunar day, the rover was 218 m north west of the lander. Only on February 18, 2020, at the beginning of the 15th lunar day, could a gradual change of direction to the south-west be initiated, but in March 2020 it was then necessary to drive to the north-west again.

Regolith layers

In addition to the infrared spectrometer, Jadehase 2 has a ground penetrating radar with which he can access two 1.15 m long 60 MHz rod antennas on the back and three 500 MHz dipoles, each 33.6 × 12 cm in size, on the underside of his housing, for example 30 cm above the ground, can look deep into the regolith . The radar is constantly in operation during the lunar day, when electricity is available from the rover's solar modules , and sends an impulse into the ground every 0.66 seconds via the 500 MHz antenna. Since the rover moves between the measuring points, where it stops for detailed investigations, at a speed of about 5.5 cm / s, this results in a radar measurement every 3.6 cm.

The landing site of Chang'e-4 (star) with ejecta from Finsen (yellow) and Von Kármán L (green).

After Chang'e-4 landed on January 3, 2019 and the rover had rolled off the ramp, a few calibrations had to be carried out first, then Jadehase 2 began with the measurements from the so-called "point A". By the end of his second working day on the moon on February 11, 2019, he made radar measurements at 106 m over a total distance of 120 m. After Li Chunlai and his colleague Su Yan (苏 彦) from the National Astronomical Observatories had evaluated the data, which took almost a year, they were able to determine an astonishingly diverse soil structure that was completely different from what the previous rover Jadehase had in January Found on the front of the moon in 2014 . At the landing site of Chang'e-4 in the South Pole Aitken Basin, the researchers found three different layers near the surface:

• Up to a depth of 12 m, relatively fine-grained sand, with only a few boulders embedded in it.
• From a depth of 12 to 24 m initially an upper layer with large quantities of largely evenly distributed boulders with a diameter of 20 cm to 1 m, then a much more inhomogeneous layer with three zones along the route of the rover, initially with boulders from 1 to 3 m Diameter, then 30 cm to 1 m, and finally 1 m large boulder.
• From a depth of 24 to 40 m, the rock density decreased sharply, with the few rocks mostly in the upper part of this layer, including very fine sand.

In an article published on February 26, 2020 in the American journal Science Advances , Li Chunlai and his colleagues came to the conclusion that after an initial impact formed the Von Kármán crater, multiple impacts with the Finsen crater in the following period northeast of the landing site and the Von Kármán L crater, a secondary crater south of the landing site, produced additional ejecta that ground and mixed the existing boulders, while more regolith formed between the impact events due to regular space weathering. Using the ground penetrating radar, this process, which was previously only tangible through model calculations, can be verified in detail through direct observation on site.

Impact breccia

At the beginning of the eighth working day on the moon (July 25 to August 7, 2019), Jade Hare 2 discovered and photographed a dark green, viscous mass in a fresh impact crater. As a result, the engineers responsible for controlling the rover designed a new course to determine the depth of the crater and the distribution of the ejecta. Jadehase 2 approached the crater carefully and examined the substance and the surrounding material with his infrared spectrometer, the same instrument with which he had already found the mantle material from the depths of the moon at the beginning of the mission . An evaluation of the photos and spectrograms taken by experts from the National Laboratory for Remote Sensing (遥感 科学 国家 重点 实验室) at the Institute for Aerospace Information Gathering (空 天 信息 创新 研究院) of the Chinese Academy of Sciences showed that the crater with a diameter of around 2 m was about 30 cm deep, the unknown mass in the pit formed an elongated spot of 52 × 16 cm. Many of the gray-brown lumps in the vicinity of the crater, which were initially thought to be rock debris, were crushed by the wheels of the 140 kg rover during the course of the investigation. It was therefore caked regolith, which, as a spectrographic analysis showed, consisted to a considerable extent of feldspar , plus olivine and pyroxene in roughly equal proportions. The material was initially classified as "weathered norite ". The shiny mass inside the crater was identified as impact breccia , also by comparison with soil samples taken by the astronauts on the Apollo missions . However, it has not yet been clarified whether this is material that was hurled into the investigated crater from a nearby crater, or whether it was formed during the impact event that caused the latter crater. The results will be presented in detail in the Earth and Planetary Science Letters on August 15, 2020 .

Radiation exposure

The dosimeter of the University of Kiel on the Chang'e-4 lander measures the radiation exposure just above the lunar surface in continuous operation. This fluctuates greatly, both in terms of the intensity and the composition of the radiation ( neutron radiation and gamma radiation ). Since there is also a radionuclide battery with an output of 5 W and several radionuclide heating elements on the lander , the results were initially difficult to interpret despite prior calibration . In an initial estimate in February 2020, the scientists in Kiel were able to say that the background radiation on the lunar surface is more intense than on Mars - the radiation exposure during a six-month stay on the moon corresponds roughly to that of a one-year stay on Mars. After a more detailed analysis, it turned out that the neutron radiation exposure at about a man's height above the surface of the moon is two to three times as high as inside the Tiangong 1 and Tiangong 2 space stations , which are located in a near-earth orbit of almost 400 km in the shelter of the Van Allen belts moved, the exposure to gamma rays was still twice as high.

As the scientists led by Robert Wimmer-Schweingruber had already suspected on the basis of measurements from the American Lunar Reconnaissance Orbiter in 2019, there is not only the solar wind but also a “reflected” secondary radiation from protons generated by the impact of cosmic rays on the lunar floor. This effect, which represents a considerable safety risk for space travelers, has now been clearly demonstrated by in-situ measurements with the dosimeter. During the first year, the dosimeter measured an average radiation exposure of 1.4 mSv / day. This corresponds roughly to the effective radiation dose per year on a terrestrial mountain at an altitude of 3500 m. Even though a real astronaut would only spend a few hours a day outdoors (where the dosimeter is attached to the lander) and the rest of the time in a better sheltered shelter, this represents a not insignificant health hazard.

See also

• List of space probes
• Chronology of the moon missions
• Space of the People's Republic of China
• List of man-made objects on the moon

Web links

• Lunar morning and evening status reports from Lander and Rover (Chinese)
• Detailed description of the mission, always updated (English)

Individual evidence

1. ↑ ^{a b} 雷丽娜: 我国 嫦娥 四号 任务 将 实现 世界 首次 月球 背面 软着陆. In: http://www.gov.cn . December 2, 2015, accessed May 7, 2019 (Chinese). 
2. ↑ Successful first landing on the back of the moon , Tagesschau.de of January 3, 2019; accessed on January 3, 2019
3. ↑ Sputnik: China Prepares for Breakthrough Chang'e 4 Moon Landing in 2018. Accessed December 10, 2018 . 
4. ↑ Echo Huang, Echo Huang: China lays out its ambitions to colonize the moon and build a “lunar palace”. Retrieved December 10, 2018 . 
5. ↑ Stuart Clark: China's moon mission to boldly go a step further . In: The Guardian . December 31, 2017, ISSN  0261-3077 ( theguardian.com [accessed December 10, 2018]).
6. ^ Leonard David, Space com's Space Insider Columnist | March 17, 2015 8:00 am ET: China Outlines New Rockets, Space Station and Moon Plans. Retrieved December 10, 2018 . 
7. ↑ Paul D. Spudis: China's Moon Missions Are Anything But Pointless. Retrieved December 10, 2018 . 
8. ^ Leonard David, Space com's Space Insider Columnist | June 9, 2016 04:14 pm ET: To the Far Side of the Moon: China's Lunar Science Goals. Retrieved December 10, 2018 . 
9. ↑ 付毅飞: 嫦娥 四号 中继 星 发射 成功 人类 迈出 航天 器 月 背 登陆 第一步. In: http://news.china.com.cn . May 22, 2018, accessed January 3, 2019 (Chinese). 
10. ↑ ^{a b} Luyuan Xu: How China's lunar relay satellite arrived in its final orbit. In: The Planetary Society. June 25, 2018, archived from the original on October 17, 2018 ; accessed on December 10, 2018 . 
11. ↑ “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 8, 2019 (Chinese). 
12. ↑ ^{a b} Pioneering astronomy. Retrieved December 10, 2018 . 
13. ↑ ^{a b c d} The scientific objectives and payloads of Chang'E −4 mission . In: Planetary and Space Science . tape 162 , November 1, 2018, ISSN  0032-0633 , p. 207–215 , doi : 10.1016 / j.pss.2018.02.011 ( sciencedirect.com [accessed December 10, 2018]).
14. ↑ Chang'e-4 lunar far side satellite named 'magpie bridge' from folklore tale of lovers crossing the Milky Way. Retrieved December 10, 2018 . 
15. ↑ 赵磊: 探 月 工程 嫦娥 四号 探测器 成功 发射 ， 开启 人类 首次 月球 背面 软着陆 探测 之 旅. In: http://cn.chinadaily.com.cn . December 8, 2018, accessed January 6, 2019 (Chinese). 
16. ↑ Chang'e 3, 4 (CE 3, 4) / Yutu. Retrieved December 10, 2018 . 
17. ↑ Robots on board the "Chang'e 4": China's moon rover starts rolling - spiegel.de
18. ↑ 倪伟: “嫦娥 四号” 月球 车 首 亮相 面向 全球 征 名 年底 奔 月. In: http://www.xinhuanet.com . August 16, 2018, accessed January 6, 2019 (Chinese). 
19. ↑ 祝 梅: 浙江 大学 光电 科学 与 工程 学院 教授 徐 之 海 - 我 向 宇宙 奔跑 不 停步. In: zjnews.zjol.com.cn. February 8, 2019, Retrieved April 29, 2019 (Chinese). 
20. ↑ 光电 科学 与 工程 学院 2018 年度 “我 为 学科 添 光彩” 突出 案例 出炉. In: zju.edu.cn. March 22, 2019, Retrieved April 29, 2019 (Chinese). 
21. ↑ 纪 奕 才 、吴伟仁 et al .: 在 月球 背面 进行 低频 射 电 天文 观测 的 关键 技术 研究. In: jdse.bit.edu.cn. March 28, 2017, Retrieved July 30, 2019 (Chinese). 
22. ↑ ^{a b} 侯东辉, Robert Wimmer-Schweingruber, Sönke Burmeister et al .: 月球 粒子 辐射 环境 探测 现状. In: jdse.bit.edu.cn. February 26, 2019, accessed August 28, 2020 (Chinese). 
23. ↑ Denis Schimmelpfennig: Rocket launch successful: Chinese probe with Kiel experiment on the way to the moon. In: uni-kiel.de. December 7, 2018, accessed May 12, 2019 . 
24. ↑ Robert Wimmer-Schweingruber et al .: The Lunar Lander Neutron & Dosimetry (LND) Experiment on Chang'E4. In: hou.usra.edu. Retrieved May 12, 2019 . 
25. ↑ 国家 航天 局 交接 嫦娥 四号 国际 载荷 科学 数据 发布 月球 与 深 空 探测 合作 机会. In: clep.org.cn. April 18, 2019, accessed May 12, 2019 (Chinese). 
26. ↑ 郭超凯: 嫦娥 四号 、 玉兔 二号 进入 第十八 月夜 科学 成果 揭示 月 背着 陆 区 月 壤 成分. In: chinanews.com. May 29, 2020, accessed May 29, 2020 (Chinese). 
27. ↑ 李季: 嫦娥 四号 和 玉兔 二号 自主 唤醒 进入 第十 九月 昼 工作 期. In: chinanews.com. June 15, 2020, accessed June 15, 2020 (Chinese). 
28. ↑ Change-4 Probe lands on the moon with “mysterious passenger” of CQU
29. ↑ 李 依 环 、 白 宇: “太空 棉” 长出 嫩芽 嫦娥 四号 完成 人类 首次 月 面 生物 试验. In: scitech.people.com.cn. January 15, 2019, accessed January 17, 2019 (Chinese). 
30. ↑ 蒋云龙: 月球 上 的 第一 片绿叶. In: scitech.people.com.cn. January 16, 2019, accessed January 17, 2019 (Chinese).  Contains a cartoon explaining the biosphere experiment.
31. ↑ Andrew Jones: Lunar nighttime brings end to Chang'e-4 biosphere experiment and cotton sprouts. In: gbtimes.com. January 16, 2019, accessed January 20, 2019 . 
32. ↑ 郭泽华: 月球 上 的 嫩芽 现在 咋样 了？ In: chinanews.com. January 15, 2019, accessed January 20, 2019 (Chinese). 
33. ↑ Lin Honglei, Lin Yangting et al .: In Situ Photometric Experiment of Lunar Regolith With Visible and Near ‐ Infrared Imaging Spectrometer On Board the Yutu ‐ 2 Lunar Rover. In: agupubs.onlinelibrary.wiley.com. February 11, 2020, accessed on May 9, 2020 . 
34. ↑ 林 杨 挺 et al .: 科研 人员 对 玉兔 二号 光谱 的 光照 作 几何 校正. In: spaceflightfans.cn. May 9, 2020, accessed May 9, 2020 (Chinese). 
35. ↑ Huang Jun et al .: Diverse rock types detected in the lunar South Pole – Aitken Basin by the Chang'E-4 lunar mission. In: spaceflightfans.cn. March 12, 2020, accessed on May 9, 2020 . 
36. ↑ Sweden joins China's historic mission to land on the far side of the Moon in 2018. Retrieved December 10, 2018 . 
37. ^ Discovering the Sky at the Longest Wavelengths. In: astron.nl. Retrieved July 30, 2019 . 
38. ^ Heino Falcke , Hong Xiaoyu et al .: DSL: Discovering the Sky at the Longest Wavelengths. In: astron.nl. Retrieved July 30, 2019 . 
39. ↑ Marc Klein Wolt: Netherlands-China Low-Frequency Explorer (NCLE). In: ru.nl. Retrieved July 30, 2019 . 
40. ↑ ^{a b} Paul D. Spudis: China's Journey to the Lunar Far Side: A Missed Opportunity? Retrieved December 10, 2018 . 
41. ↑ 嫦娥 四号 任务 圆满 成功 北京 航天 飞行 控制 中心 致信 空 天 院. In: aircas.cas.cn. January 12, 2019, accessed May 31, 2019 (Chinese). 
42. ↑ 刘 锟: “玉兔 二号” 月球 车 顺利 踏上 月球 背面！ 后续 还将 完成 哪些 使命？ In: jfdaily.com. January 4, 2019, accessed May 7, 2019 (Chinese). 
43. ↑ 嫦娥 四号 成功 实现 人类 探测器 首次 月球 背面 软着陆 上海技物所 3 台 载荷 均 工作 正常. In: sitp.ac.cn. January 7, 2019, accessed May 17, 2019 (Chinese). 
44. ↑ 叶培 建 院士 带 你 看 落月. In: cast.cn. January 3, 2019, accessed May 17, 2019 (Chinese). 
45. ↑ 嫦娥 四号 探测器 实 拍 降落 视频 发布. In: clep.org.cn. January 11, 2019, accessed May 11, 2019 (Chinese).  Contains video recorded by the landing camera of the last 6 minutes of the descent and a diagram explaining the individual phases of the landing.
46. ↑ Helga Rietz: Floating dust on the moon. In: deutschlandfunk.de. August 1, 2012, accessed May 14, 2019 . 
47. ↑ Researchers warn of short circuits on the moon. In: spiegel.de. February 5, 2007, accessed May 14, 2019 . 
48. ↑ 刘晓艳: 天津 大学 空间 力学 团队 助 “力” 国家 空间 探测 工程 多项 科研成果 应用于 “嫦娥” 系列 和 火星 探测 计划. In: tju.edu.cn/. January 30, 2019, accessed May 13, 2019 (Chinese).  The method developed by the Space Mechanics group will also be used at the end of 2019 for Chang'e-5 and in April 2021 for the landing of the Mars probe Yinghuo-2 .
49. ↑ 唐艳飞: 嫦娥 四号 成功 着陆 月 背！ 传 回 世界 首张 近距 拍摄 月 背 影像 图. In: guancha.cn. January 3, 2019, accessed January 6, 2019 (Chinese). 
50. ↑ 陈海波: 月球 上 多 了 5 个 中国 名字. In: xinhuanet.com. February 16, 2019, accessed September 26, 2019 (Chinese). 
51. ↑ Planetary Names: Landing site name: Statio Tianhe on Moon. In: planetarynames.wr.usgs.gov. February 18, 2019, accessed September 26, 2019 . 
52. ↑ Liu Jianjun, Li Chunlai et al .: Descent trajectory reconstruction and landing site positioning of Chang'e-4 on the lunar farside. In: nature.com. September 24, 2019, accessed on September 26, 2019 . 
53. ↑ Dirk Eidemüller: The moon shows its coat. In: pro-physik.de. May 15, 2019, accessed May 16, 2019 . 
54. ↑ 月 背 探测 预选 着陆 区 科学 目标 分析. In: jdse.bit.edu.cn. Retrieved May 18, 2019 (Chinese). 
55. ↑ 嫦娥 四号 成功 实现 人类 探测器 首次 月球 背面 软着陆 上海技物所 3 台 载荷 均 工作 正常. In: sitp.ac.cn. January 7, 2019, accessed May 16, 2019 (Chinese). 
56. ↑ 嫦娥 四号 月球 背面 重大 成果 ： 发现 月 幔 源 物质 初步 证据. In: news.kedo.gov.cn. May 16, 2019, accessed May 16, 2019 (Chinese). 
57. ↑ 国家 天文台 基于 嫦娥 四号 探测 数据 发现 月球 背面 幔 源 物质 初步 证据. In: nao.cas.cn. May 16, 2019, accessed May 16, 2019 (Chinese). 
58. ↑ China's Chang'E 4 mission discovered new "secrets" from far side of the moon. In: english.nao.cas.cn. May 15, 2019, accessed on May 16, 2019 . 
59. ↑ Li Chunlai et al .: Chang'E-4 initial spectroscopic identification of lunar far-side mantle-derived materials. In: nature.com. May 15, 2019, accessed on May 16, 2019 . 
60. ↑ Patrick Pinet. In: sci.esa.int. November 4, 2011, accessed May 16, 2019 . 
61. ↑ Patrick Pinet: The Moon's mantle unveiled. In: nature.com. May 15, 2019, accessed on May 16, 2019 . 
62. ↑ Daniela Albat: View of the mantle of the moon - moon rover "Jadehase 2" identifies lunar mantle material in large crater basins. In: scinexx.de. May 16, 2019, accessed May 16, 2019 . 
63. ↑ 嫦娥 四号 首批 科学 成果 发表 玉兔 二号 揭示 月球 深 部 物质. In: clep.org.cn. May 16, 2019, accessed May 18, 2019 (Chinese). 
64. ↑ 嫦娥 四号 着陆 器 和 巡视 器 完成 第 十一月 昼 工作 ， 进入 第十一 月夜. In: clep.org.cn. November 4, 2019, Retrieved November 6, 2019 (Chinese). 
65. ↑ 嫦娥 四号 着陆 器 和 “玉兔 二号” 月球 车 顺利 唤醒 ， 进入 第十 五月 昼 工作 期. In: clep.org.cn. February 18, 2020, accessed February 19, 2020 (Chinese). 
66. ↑ “玉兔 二号” 醒来 ， 进入 第十 六月 昼 工作 期！ In: cnsa.gov.cn. March 20, 2020, accessed March 21, 2020 (Chinese). 
67. ↑ Fang Guangyou et al .: Lunar Penetrating Radar onboard the Chang'e-3 mission. In: iopscience.iop.org. September 29, 2014, accessed March 15, 2020 .  P. 1615 ff.
68. ↑ 月球 背面 拓荒者 —— 嫦娥 四号 着陆 月球 背面 一 周年. In: clep.org.cn. January 3, 2020, accessed March 16, 2020 (Chinese). 
69. ↑ 嫦娥 四号 再次 月夜 休眠 第二 月 昼 工作 正常. In: clep.org.cn. February 13, 2019, accessed March 16, 2020 (Chinese). 
70. ↑ 国家 天文台 人才 库. In: sourcedb.naoc.cas.cn. September 9, 2013, accessed March 16, 2020 (Chinese). 
71. ↑ Li Chunlai, Su Yan et al .: The Moon's farside shallow subsurface structure unveiled by Chang'E-4 Lunar Penetrating Radar. In: advances.sciencemag.org. February 26, 2020, accessed on March 15, 2020 . 
72. ↑ 嫦娥 四号 着陆 器 和 “玉兔 二号” 巡视 器 完成 自主 唤醒 ， 开始 第 十月 昼 工作. In: clep.org.cn. September 24, 2019, accessed September 26, 2019 (Chinese). 
73. ^ Andrew Jones: China's Lunar Rover Has Found Something Weird on the Far Side of the Moon. In: space.com. August 30, 2019, accessed December 12, 2019 . 
74. ↑ “玉兔 二号” 揭示 月球 背面 “不明 胶状 物质” 可能 成因. In: clep.org.cn. June 23, 2020, accessed June 24, 2020 (Chinese). 
75. ↑ Gou Sheng et al .: Impact melt breccia and surrounding regolith measured by Chang'e-4 rover. In: sciencedirect.com. Retrieved July 9, 2020 (Chinese). 
76. ↑ Robert F. Wimmer-Schweingruber et al .: The Lunar Lander Neutron and Dosimetry (LND) Experiment on Chang'E 4. In: arxiv.org. January 29, 2020, accessed on August 8, 2020 . 
77. ^ Johan von Forstner: Lunar Lander Neutrons & Dosimetry on Chang'E 4. In: physik.uni-kiel.de. February 8, 2020, accessed August 8, 2020 . 
78. ↑ 嫦娥 四号 600 天 科学 成果 归纳. In: clep.org.cn. August 26, 2020, accessed August 28, 2020 (Chinese). 
79. ^ Robert Wimmer-Schweingruber: Chinese moon mission Chang'e 4. In: youtube.com. January 26, 2020, accessed August 30, 2020 .