Chinese scientists proposed a design plan: to build a near-moon space navigation constellation consisting of 21 satellites

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2024-07-14 21:01Posted on the official account of Shanghai Observer.com

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01 Chinese scientists proposed a design plan to build a communication and navigation constellation similar to the Beidou navigation system that can serve the whole lunar surface, consisting of 21 satellites.

02The research team comprehensively considered various indicators in three aspects: relay communication, lunar navigation, constellation construction and maintenance costs.

03 To this end, the study proposes a near-moon space constellation construction route, which is divided into three stages to gradually achieve 100% quadruple coverage of the whole month.

04At present, China has launched the "Queqiao-1" and "Queqiao-2" relay satellites to provide relay communication support for a number of lunar exploration missions.

05 At the same time, United States, Europe and Japan have also put forward plans to build a lunar communication and navigation constellation.

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According to a report by Hong Kong's English-language media "South China Morning Post" on July 14, Chinese scientists recently proposed a design plan to build a communication and navigation constellation similar to the Beidou navigation system that can serve the entire lunar surface.

The report cites a paper published in June in China Space Science and Technology, titled "Orbit Design Methods for Near-Moon Space Constellations," written by Chen Shiyu and Ni Yanshuo from the Beijing Space Vehicle Design Department, and Peng Jing, chief designer of the Chang'e-8 probe system of the Fifth Academy of China Aerospace Science and Technology Corporation.

The Chinese research team has proposed a near-moon space navigation constellation consisting of 21 satellites, which aims to provide long-term high-precision navigation for long-term, high-density human exploration activities on the moon in a sustainable and cost-effective manner.

The South China Morning Post mentioned that although the paper does not give a specific construction timetable, the preliminary plan of China's lunar exploration program and the plan for the international lunar research station have been announced: China plans to send astronauts to the moon by 2030, and by 2035, with the south pole of the moon as the core, an international lunar scientific research station with basically complete functions and basic supporting elements will be built, and an expanded type will be built by 2045.

Screenshot of the paper

According to the paper, the elevation angle of the moon's south pole to the earth is extremely small, and it is easy to be obscured by the lunar crater, which is difficult to ensure a direct TT&C communication link to the earth. However, because the far side of the moon is occluded by the moon, it is impossible to achieve measurement and control communication through the ground-based tracking and control system. Therefore, it is necessary to deploy relay satellites in near-moon space, including the translational points of the Earth-Moon L1 and L2, to assist in the South Pole of the Moon and the Earth-Earth TT&C communication on the far side.

At the Earth-Moon Lagrange point, the Queqiao-1 relay satellite is in the halo orbit at L2, while the Queqiao-2 is in orbit around the moon

"The near-moon space navigation constellation can provide real-time high-precision navigation and positioning for missions such as lunar surface movement, landing and take-off, which is the necessary basic guarantee to support human long-term and high-density exploration activities on the moon." The article reads.

The South China Morning Post mentioned that at present, global navigation satellite systems are being widely used on the earth's surface or in near-Earth space, such as United States's Global Positioning System (GPS) and China's Beidou Satellite Navigation System (BDS), which are widely used to provide users with all-weather, high-precision positioning, navigation and other services.

According to the report, GNSS usually consists of 20-35 satellites, with an accuracy of several meters, and users can use the signal combination of at least four satellites to locate and obtain time information. The lunar navigation scheme of the research team of the Beijing Spacecraft General Design Department is similar, requiring at least four satellites to be visible to the target at the same time.

On June 25, 2024, the Chang'e-6 returner accurately landed in the predetermined area of the Siziwang Banner in Inner Mongolia, working normally, and achieved the world's first sample return on the far side of the moon. Visual China

This study proposes a near-moon space constellation construction route, which gradually achieves 100% quadruple coverage of the whole moon in three stages (quadruple coverage refers to the proportion of time that at least four stars in the constellation are visible to the target at the same time), and the three stages are as follows:

In the first stage, two elliptical frozen orbit satellites will be deployed to provide full-time ground relay communication for the lunar south pole and achieve 100% one-heavy coverage of the lunar south pole region.

In the second stage, 6 elliptical frozen orbit satellites, 2 near-linear halo orbit satellites, and 1 L2 halo orbit satellite will be deployed, which can provide full-time navigation and positioning for the south polar region of the moon, and at the same time achieve 100% one-time coverage of the lunar polar region and the far side of the moon, so that probes or humans at any position in the moon can communicate with the ground at any time;

In the third stage, 4 elliptical frozen orbit satellites, 2 near-linear halo orbit satellites, 1 L1 halo orbit satellite, and 3 long-distance retrograde orbit satellites will be deployed to achieve 100% quadruple coverage of the whole month, which can provide full-time navigation and positioning for probes or humans at any location in the whole month.

According to the research team, a more systematic constellation optimization method in near-moon space will be formed in the follow-up research by combining orbit parameter optimization technology, and global optimization will be carried out on discrete variables such as orbit type and continuous variables such as orbit parameters, so as to obtain the theoretically optimal constellation configuration.

In recent years, the construction of near-moon space constellation is becoming a hot direction of aerospace research. China launched the Queqiao-1 and Queqiao-2 relay satellites in 2018 and 2024 respectively to provide relay communication support for a number of lunar exploration missions.

According to the WeChat public account "China's Aerospace", the "Queqiao-2" relay satellite uses a large elliptical frozen orbit around the moon as the mission orbit. Due to the irregular shape and structure of the moon, spacecraft flying close to the moon are affected by the gravitational pull of the moon, and the flight trajectory is prone to deviation. The circumlunar large elliptical frozen orbit is a circumlunar orbit in a stable state, in which the spacecraft flies, which is able to minimize the deviation of the flight trajectory.

On March 20, 2024, in Wenchang, Hainan Province, the Long March 8 Yao-3 carrier rocket carrying the Queqiao-2 relay satellite of the fourth phase of the lunar exploration project was ignited at the Wenchang Space Launch Site. Visual China

At the same time, United States, Europe and Japan have also put forward plans to build a lunar communication and navigation constellation.

In 2020, United States the National Aeronautics and Space Administration (NASA) proposed the "LunaNet" architecture to support the Artemis program, which is used to meet the communication needs of lunar south pole exploration and lunar far exploration in the short term, with 2-3 relay satellites in elliptical frozen orbit and Gateway space station in near-linear halo orbit providing relay communication services.

On November 16, 2022 local time, the Artemis 1 space launch system rocket, along with the Orion capsule, was launched from NASA's Kennedy Space Center in Cape Canaveral, Florida, United States United States. The Artemis 1 mission will launch an unmanned spacecraft around the moon to test the spacecraft's propulsion, navigation and propulsion systems in preparation for a manned mission to the lunar surface. Visual China

Europe is also pushing the Lunar Communications Service program in full swing. In 2021, the European Space Agency (ESA) released the "Moonlight" plan, proposing to build a sustainable Lunar Shared Communication and Navigation System (LCNS) around 2027, and plans to launch the first "Lunar Pathfinder" satellite in 2025 to carry out technical verification in an elliptical frozen orbit.

In 2022, the Japan Aerospace Exploration Agency (JAXA) proposed the Lunar Navigation Satellite System (LNSS), which plans to deploy eight satellites in elliptical orbit to provide relay communications and navigation and positioning services for lunar south pole probes.

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