Chinese Lunar Exploration Program – Wikipedia

Chinese lunar research program (2004 present)

The Chinese Lunar Exploration Program (CLEP; Chinese: ; pinyin: Zhnggu Tnyu), also known as the Chang'e Project (Chinese: ; pinyin: Chng' Gngchng) after the Chinese moon goddess Chang'e, is an ongoing series of robotic Moon missions by the China National Space Administration (CNSA). The program incorporates lunar orbiters, landers, rovers and sample return spacecraft, launched using Long March rockets. Launches and flights are monitored by a telemetry, tracking, and command (TT&C) system, which uses 50-meter (160-foot) radio antennas in Beijing and 40-meter (130-foot) antennas in Kunming, Shanghai, and rmqi to form a 3,000-kilometer (1,900-mile) VLBI antenna.[1][2] A proprietary ground application system is responsible for downlink data reception.

Ouyang Ziyuan, a geologist, chemical cosmologist, and the program's chief scientist, was among the first to advocate the exploitation not only of known lunar reserves of metals such as titanium, but also of helium-3, an ideal fuel for future nuclear fusion power plants. Ye Peijian serves as the program's chief commander and chief designer.[3] Scientist Sun Jiadong is the program's general designer and Sun Zezhou is deputy general designer. The leading program manager is Luan Enjie.

The first spacecraft of the program, the Chang'e 1 lunar orbiter, was launched from Xichang Satellite Launch Center on 24 October 2007,[4] having been delayed from the initial planned date of 1719 April 2007.[5] A second orbiter, Chang'e 2, was launched on 1 October 2010.[6][7] Chang'e 3, which includes a lander and rover, was launched on 1 December 2013 and successfully soft-landed on the Moon on 14 December 2013. Chang'e 4, which includes a lander and rover, was launched on 7 December 2018 and landed on 3 January 2019 on the South Pole-Aitken Basin, on the far side of the Moon. A sample return mission, Chang'e 5, which launched on 23 November 2020 and returned on 16 December in the same year, brought 1,731 g (61.1oz) of lunar samples back to earth.[8]

As indicated by the official insignia, the shape of a calligraphic nascent lunar crescent with two human footprints at its center reminiscent of the Chinese character , the Chinese character for "Moon", the ultimate objective of the program is to pave the way for a crewed mission to the Moon. China National Space Administration head Zhang Kejian announced that China is planning to build a scientific research station on the Moon's south pole "within the next 10 years," (20192029).[9]

The Chinese Lunar Exploration Program is divided into four main operational phases, with each mission serving as a technology demonstrator in preparation for future missions. International cooperation in the form of various payloads and a robotic station is invited by China.[10]

The first phase entailed the launch of two lunar orbiters, and is now effectively complete.

Before Chang-e 5, no lunar sample-return was conducted in over four decades.

The second phase is ongoing, and incorporates spacecraft capable of soft-landing on the Moon and deploying lunar rovers.

The third phase included a lunar sample-return mission.

After the "3 steps" phase is done, the phase for the development of an autonomous lunar research station near the Moon's south pole will commence.[10][14][15]

As of 2019[update], China was reviewing preliminary studies for a crewed lunar landing mission in the 2030s,[23][24] and possibly building an outpost near the lunar south pole with international cooperation.[10][23]

In 2021, China and Russia announced they will be building a moon base together, also formally invited more countries and international organizations to join their International Lunar Research Station (ILRS) project being developed by the two nations,[25] as a competitor to the American Artemis Program.[26]

Planned hard landing Planned soft landing

The biggest challenge in Phase I of the program was the operation of the TT&C system, because its transmission capability needed sufficient range to communicate with the probes in lunar orbit.[28] China's standard satellite telemetry had a range of 80,000 kilometers (50,000 miles), but the distance between the Moon and the Earth can exceed 400,000 kilometers (250,000 miles) when the Moon is at apogee. In addition, the Chang'e probes had to carry out many attitude maneuvers during their flights to the Moon and during operations in lunar orbit. The distance across China from east to west is 5,000 kilometers (3,100 miles),[29] forming another challenge to TT&C continuity. At present, the combination of the TT&C system and the Chinese astronomical observation network has met the needs of the Chang'e program,[30] but only by a small margin.

The complexity of the space environment encountered during the Chang'e missions imposed strict requirements for environmental adaptability and reliability of the probes and their instruments. The high-radiation environment in Earth-Moon space required hardened electronics to prevent electromagnetic damage to spacecraft instruments. The extreme temperature range, from 130 degrees Celsius (266 degrees Fahrenheit) on the side of the spacecraft facing the Sun to 170 degrees Celsius (274 degrees Fahrenheit) on the side facing away from the Sun, imposed strict requirements for temperature control in the design of the detectors.

Given the conditions of the three-body system of the Earth, Moon and a space probe, the orbit design of lunar orbiters is more complicated than that of Earth-orbiting satellites, which only deal with a two-body system. The Chang'e 1 and Chang'e 2 probes were first sent into highly elliptical Earth orbits. After separating from their launch vehicles, they entered an Earth-Moon transfer orbit through three accelerations in the phase-modulated orbit. These accelerations were conducted 16, 24, and 48 hours into the missions, during which several orbit adjustments and attitude maneuvers were carried out so as to ensure the probes' capture by lunar gravity. After operating in the Earth-Moon orbit for 45 days, each probe entered a lunar acquisition orbit. After entering their target orbits, conducting three braking maneuvers and experiencing three different orbit phases, Chang'e 1 and Chang'e 2 carried out their missions.

Lunar orbiters have to remain properly oriented with respect to the Earth, Moon and Sun. All onboard detectors must be kept facing the lunar surface in order to complete their scientific missions, communication antennas have to face the Earth in order to receive commands and transfer scientific data, and solar panels must be oriented toward the Sun in order to acquire power. During lunar orbit, the Earth, the Moon and the Sun also move, so attitude control is a complex three-vector control process. The Chang'e satellites need to adjust their attitude very carefully to maintain an optimal angle towards all three bodies.

During the second phase of the program, in which the spacecraft were required to soft-land on the lunar surface, it was necessary to devise a system of automatic hazard avoidance in order that the landers would not attempt to touch down on unsuitable terrain. Chang'e 3 utilized a computer vision system in which the data from a down-facing camera, as well as 2 ranging devices, were processed using specialized software. The software controlled the final stages of descent, adjusting the attitude of the spacecraft and the throttle of its main engine. The spacecraft hovered first at 100 meters (330 feet), then at 30 meters (98 feet), as it searched for a suitable spot to set down. The Yutu rover is also equipped with front-facing stereo cameras and hazard avoidance technology.

In November 2017, China and Russia signed an agreement on cooperative lunar and deep space exploration.[31] The agreement includes six sectors, covering lunar and deep space, joint spacecraft development, space electronics, Earth remote sensing data, and space debris monitoring.[31][32][33] Russia may also look to develop closer ties with China in human spaceflight,[31] and even shift its human spaceflight cooperation from the US to China and build a crewed lunar lander.[34]

Chang'e 4 lander on the Moon

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Chinese Lunar Exploration Program - Wikipedia