China Targets Far Side for Sample Return

In the new age of lunar exploration, China is by no means a newcomer. The Chinese Lunar Exploration Program, also known as Chang’e, has seen the launch of eight missions and three successful Moon landings since 2007. Chang’e-6 launched on May 3rd at 5:27 p.m. local time, and is China’s most ambitious lunar mission yet.

While Chang’e-6 is broadly a repeat of the Chang’e-5 mission completed over three years ago, a successful mission would present its fair share of unprecedented science. Building off the success of Chang’e-5’s sample return and Chang’e-4’s successful landing on the lunar farside, Chang’e-6 aims to become the first mission to return samples from the farside of the Moon. 

Chang’e-6 is expected to land in Apollo Crater which is itself part of a larger region of the Moon, the South Pole–Aitken basin. The South Pole-Aitken basin is an ancient impact basin, and the largest impact basin on the Moon. Its study yields insights into the dramatic and turbulent early life of the Moon, during the time of its formation over four billion years ago. Because of this, the SPA basin is a tantalizing scientific target, even for the scientific community of the United States. As part of the 2022 Planetary Science Decadal Survey, scientists recommended NASA investigate the feasibility of a rover-based mission to gather samples from the SPA basin to be returned to Earth by Artemis Astronauts.

Chang’e is no stranger to the region, with Chang’e-4 performing the first landing in the SPA basin back in January of 2019, delivering the Yutu-2 rover which continues to operate as of May 2024, over five years since its arrival. Chang’e-6 also marks the beginning of the ambitious fourth phase of the Chinese Lunar Exploration Program. The ultimate aim of the Chang’e program going forward will be to establish a robotic science station at the lunar South Pole. The so-called “Lunar Research Station Prototype” will be formed by Chang’e-7 and Chang’e-8 (planned to launch in 2026 and 2028 respectively) and will investigate the resource distribution of the lunar South Pole and demonstrate how different robotic elements can cooperate to form a working research outpost on the Moon. This is being done in preparation of China’s ambitions to send taikonauts to the Moon by 2030, and establish their own international crewed outpost, known as the ILRS, at the lunar South Pole in the early 2030s.

Chang’e-6 does not directly contribute to this research station itself, but does take advantage of pre-placed architecture, the Queqiao-2 relay satellite which launched on March 20th 2024. Queqiao-2, a successor to the still-active Queqiao relay, hangs at the Earth-Moon L2 point where it can hang over the lunar farside while remaining in view of the Earth. This positioning allows the spacecraft to act as a relay to missions operating in lunar regions where the Earth is never above the horizon. The recent launch of Queqiao-2 also means there will be no gap in capability once its aging predecessor goes offline, allowing missions like Yutu-2 to continue and providing relay support to future Chang’e missions.

As reported by SpaceNews, in an interview with Chinese Central Television, the deputy director of the Center of Lunar Exploration and Space Engineering of China, Ge Ping stated “China’s lunar exploration program has always valued international cooperation and has always been open to international cooperation.” This statement was made in regard to the idea of using Queqiao-2 to support Moon missions launched by other nations, however Chang’e-6 will be realizing this value in its own way.

Chang’e-6 will be carrying a range of international payloads. This includes Pakistan’s first lunar science mission, the ICECUBE-Q (sometimes shortened to iCUBE-Q) orbiter, a cubesat which will be joining the search for water resources on the Moon. Pakistan is a member of the International Lunar Research Station (ILRS) project, an international endeavor originally organized by China and Russia in 2021 to establish the ILRS at the lunar South Pole. The ILRS today comprises 13 members, with Nicaragua who joined on April 24th, 2024 being the latest signatory. ILRS are considered a peer competitor to the US-led Artemis Accords, both being groups of nations acting in support of parallel but ultimately similar goals of exploring the Moon. In this respect, ICECUBE-Q is Pakistan’s first contribution to a program that some speculate could eventually land a Pakistani astronaut on the Moon, though no such intention has been formally declared.

The contributions are not limited to ILRS members however, for instance France’s first lunar science payload will also be riding aboard the Chang’e-6 lander. The Detection of Outgassing RadoN (DORN) instrument, integrated with the Chang’e-6 lander, was developed by Institut de Recherche en Astrophysique et Planétologie based in Toulouse, France. DORN will study the amount of radon present in the Moon’s exosphere to provide clues into the decay rate of radioactive uranium on the Moon, a geologic heat source which played a major role in the evolution of the Moon. Sweden provided the Negative Ions at the Lunar Surface (NILS) instrument, the first Swedish hardware to fly to the vicinity of the Moon since ESA’s SMART-1 mission which orbited the Moon in 2003, and first instrument intended to land. It will investigate the quantity of negative ions in the lunar exosphere, to “estimate the importance of negative ions for space-surface interactions and environments of planetary bodies with surface-bound exospheres” according to a paper published by the European Planetary Science Congress in 2022. Italy provided a laser-retroreflector called INstrument for landing-Roving laser Retroreflector Investigations (INRRI), which will provide measurements of lunar topography from orbit. INRRI is the latest in a line of instruments which previously flew on the InSight and Schiaparelli Mars missions.

Chang’e-6 also carries a payload with a little less clarity, China’s third lunar rover, though dramatically smaller and simpler than the Yutu rovers which came before it. The exact purpose of the small rover is unclear, but there is suspicion it may act as an external camera, capturing images of the Chang’e-6 lander’s operations on the lunar surface. The Chinese National Space Agency used remote cameras on Tianwen-1, providing fascinating images of their spacecraft in orbit and on the surface of Mars, although they were static cameras. It remains to be seen if Chang’e-6’s rover will be used to similar effect.

From launch to landing, Chang’e-5 took 23 days to return its samples from Oceanus Procellarum. The Chang’e-5 lander landed in Oceanus Procellarum at local sunrise, and the ascent element loaded with samples departed just ahead of local sunset, a timeframe of 14 days on the surface. The ascent element then rendezvoused with the orbital element and transferred samples into a return capsule. The orbital element then left lunar orbit to return the sample capsule to Earth during an Earth swing-by. Chang’e-6 started life as a back up for Chang’e-5, and thus broadly uses the same system, however the landing for Chang’e-6 is not expected until early June, the mission having an extended orbital phase expected to begin within 4 to 5 days of launch. This extended orbital phase may be needed to verify Chang’e-6’s connection with Queqiao-2 relay satellite. The Chang’e-6 mission is expected to last a total of 53 days, meaning samples won’t come home until late June.

Some of Chang’e-5’s most significant scientific findings were in regards to lunar volcanism, as the mission landed near the suspected volcanic complex, Mons Rümker. Chang’e-5 samples contained a record of ancient volcanic eruptions, and the youngest volcanic rock returned from the Moon to date, at 2 billion years old. If successful, Chang’e-6 will deliver insights into a geologically older part of the Moon’s history, with Apollo Crater and its frozen lava deposits believed to be around 3.9 billion years old. Chang’e-5’s samples contained hydrate materials, raising questions about the distributions of water resources on the Moon, but only providing clues, not ice itself. If Chang’e-6 returns similar materials, its own clues could further enhance our understanding of global ice deposits on the Moon.

More recently, in December of 2023, applications to access the lunar samples returned Chang’e-5 were opened to the international community. Three years after Chang’e samples were returned to Earth, the samples finally became available to US-researchers, including those backed by NASA. If Chang’e-6 samples see a similar length of time out of reach of US scientists, that would see them becoming available after the Artemis Program’s first scheduled astronauts on the lunar surface.

Chang’e-5’s orbiter went on to have an extended mission, wherein it visited the Earth-Sun L1 point, before returning to the Moon’s sphere of influence by entering a Distant Retrograde Orbit (DRO). DRO is the same type of orbit that was utilized by the Artemis I spacecraft, but Chang’e-5 arrived there first, and continues to operate in DRO to this day, performing technology verifications. Whether or not Chang’e-6 will have its own extended mission and what that mission could look like will not be known until it happens.

This latest Chang’e mission to the Moon, running alongside the first flights of NASA’s CLPS initiative can in some ways be likened to the height of the space race, where robotic explorers from two nations flew to the Moon regularly in support of their own respective crewed lunar programs. Today however, these ambitions aren’t just being undertaken by two nations, but international cooperatives of dozens of different governments. While the present flightrate may not be as explosive as it was in the age of Apollo, the modern era of lunar exploration is shaping up to be far larger in scope and capability.

Edited by Nik Alexander