|Organization||China National Space Administration (CNSA)|
|Purpose||robotic Moon missions|
|Duration||2003 - present|
|Maiden flight||Chang'e 1, 24 October 2007, 10:05:04.602 UTC|
|Vehicle type||lunar orbiters, landers, rovers and sample return spacecraft|
The Chinese Lunar Exploration Program (CLEP; Chinese: ?; pinyin: ), also known as the Chang'e Project (Chinese: ?; pinyin: ) 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-metre (160-foot) radio antennas in Beijing and 40-metre (130-foot) antennas in Kunming, Shanghai, and Ürümqi to form a 3,000-kilometre (1,900-mile) VLBI antenna. A proprietary ground application system is responsible for downlink data reception.
Ouyang Ziyuan, a geologist and chemical cosmologist, 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. He currently serves as the chief scientist of the Chinese Lunar Exploration Program. Another scientist, Sun Jiadong, was assigned as the general designer, while scientist Sun Zezhou was assigned as the 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, having been delayed from the initial planned date of 17-19 April 2007. A second orbiter, Chang'e 2, was launched on 1 October 2010.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, is scheduled for December 2020.
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 land crew on the Moon's south pole "within the next 10 years," (2029-2030).
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.
The first phase entailed the launch of two lunar orbiters, and is now effectively complete.
The third phase will entail a lunar sample-return mission.
|Chang'e 1||24 Oct 2007||Long March 3A||Lunar orbiter; first Chinese lunar mission.||Success|
|Chang'e 2||1 Oct 2010||Long March 3C||Lunar orbiter; following lunar orbit mission flew extended mission to 4179 Toutatis.||Success|
|Chang'e 3||1 Dec 2013||Long March 3B||Lunar lander and rover; first Chinese lunar landing, landed in Mare Imbrium with Yutu 1.||Success|
|Queqiao 1||20 May 2018||Long March 4C||Relay satellite located at the Earth-Moon L2 point in order to allow communications with Chang'e 4.||Ongoing|
|Chang'e 4||7 Dec 2018||Long March 3B||Lunar lander and rover; first ever soft landing on the Far side of the Moon, landed in Von Karman Crater with Yutu 2.||Ongoing|
|Chang'e 5-T1||23 Oct 2014||Long March 3C||Experimental test flight testing technologies ahead of first Lunar sample return; tested return capsule and lunar orbit autonomous rendezvous techniques and other maneuvers.||Success|
|Chang'e 5||Q4 2020||Long March 5||Lunar, orbiter lander and sample return; scheduled for landing near Mons Rümker, will return a sample to Earth for the first time since the Soviet Luna 24 mission in 1976.||Planned|
|Chang'e 6||2023-2024||Long March 5||Lunar, orbiter lander and sample return; scheduled for landing in a currently undisclosed landing site near the Lunar south pole, landing site will most likely depend on the outcome of Chang'e 5.||Planned|
|Chang'e 7||Mid 2020s||Long March TBA||Full mission details are currently unknown, will send a may include and orbiter, lander and/or rover and will perform in depth exploration of the Lunar south pole to look for resources.||Planned|
|Chang'e 8||Late 2020s||Long March TBA||Full mission details are currently unknown, may send spacecraft to the Moon to test new technologies including an ISRU system, ahead of future crewed exploration of the Moon.||Planned|
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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. China's standard satellite telemetry had a range of 80,000 km (50,000 mi), but the distance between the Moon and the Earth can exceed 400,000 km (250,000 mi) 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 km (3,100 mi), 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, 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 °C (266 °F) on the side of the spacecraft facing the Sun to -170 °C (-274 °F) 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 4-5 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 metres (330 ft), then at 30 metres (98 ft), 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. The agreement includes six sectors, covering lunar and deep space, joint spacecraft development, space electronics, Earth remote sensing data, and space debris monitoring. Russia may also look to develop closer ties with China in human spaceflight, and even shift its human spaceflight cooperation from the US to China and build a crewed lunar lander.