Robotic probe launched to the far side of the Moon

The robotic Chang’e 6 probe, tasked with the world’s first attempt to recover samples from the far side of the Moon, embarked on its historic journey on Friday from Hainan province in far southern China.

A Long March 5 heavy-lift carrier rocket, China’s largest and most powerful space vehicle, with 20 floors and weighing 870 tons, lifted off from its launch pad at 5:27 p.m. with the Chang’e 6 spacecraft of 8.35 tons. aboard and soared into the sky, leaving hundreds of thousands of spectators in awe at and around the coastal Wenchang Space Launch Center.

The liftoff marked the beginning of the country’s second lunar sample return expedition after the successful Chang’e 5 mission in winter 2020.

However, the mission in progress will be much more difficult, challenging and fascinating than Chang’e 5, which landed on the near side of the Moon, and will definitely go on record (regardless of whether it is a great success or an unfortunate failure ) as a symbol. of a bold and pioneering work in the history of lunar exploration by humanity.

Previously, the United States, the former Soviet Union and China carried out 10 lunar sample return missions, but all of these samples were collected from the near side of the Moon.

As one of the most important space voyages in China, and also in the world, this year, the important steps of the Chang’e 6 mission have made headlines around the world and attracted much attention from the Chinese people.

The local tourism authority in Wenchang estimated that at least 200,000 travelers arrived in Longlou, a township home to the launch complex, on Friday to witness the takeoff.

According to the China National Space Administration, after flying for about 37 minutes, the Long March 5 rocket successfully placed the robotic lunar probe on an Earth-Moon transfer trajectory, the gateway to our celestial neighbor.

Complex operation

In the coming days, the Chang’e 6 probe is scheduled to fly along its trajectory toward the Moon and perform some correction operations before performing a key braking maneuver to avoid accidentally passing by the Moon. Thereafter, the spacecraft will be captured by the moon’s gravity and enter a lunar orbit.

Like its predecessor, the Chang’e 6 spacecraft is designed and built by the Beijing-based China Academy of Space Technology, a subsidiary of China Aerospace Science and Technology Corp, and also consists of four components: an orbiter, an lander and an ascender. and a reentry capsule.

Its operating process will basically mimic that of the Chang’e 5 spacecraft. After the probe reaches lunar orbit, its components will separate into two parts: the orbiter and reentry capsule will remain in orbit, while the lander and the ascender will begin to approach the lunar surface.

When everything is ready, the combination lander and ascent will make a soft landing in the South Pole’s Aitken Basin, a gigantic crater on the far side of the Moon and also the largest, oldest and deepest basin recognized on the Moon. You will then begin using a drill and mechanical arm to collect surface and underground samples.

If all goes well, up to 2 kilograms of stones and soil will be collected and packed in a vacuum-sealed metal container inside the ascender.

Once the collection operation is complete, the elevator motors will lift it into lunar orbit to dock with the reentry capsule. The vacuum sealed container containing the samples will be transferred to the module before the ascender is disengaged.

The combination orbiter and reentry capsule will leave lunar orbit and return to Earth orbit, where the pair will separate and the reentry capsule will perform a series of complicated maneuvers to return to the Siziwang Banner landing site in the Mongolian autonomous region. Inside. region.

The main difference between the Chang’e 5 and Chang’e 6 probes lies in their landing destination on the Moon and the corresponding technical problems, the most crucial of which are communication difficulties between the far side of the Moon and the Land.

To establish a data link for the Chang’e 6 probe, China deployed a new relay satellite into lunar orbit in March.

Wang Qiong, deputy chief designer of the Chang’e 6 mission, said there will be a number of challenges and uncertainties during the 53-day expedition, adding that Chinese scientists and engineers have made efforts to find the best available solutions.

“During the Chang’e 5 mission, the probe worked on the near side, so we could monitor its work processes and send control signals to it at any time. But in the case of Chang’e 6, we will have to rely solely on “The Queqiao 2 relay satellite for transmitting data and signals has limited coverage over the landing site, which will consequently restrict our communication with the Chang’e 6 probe,” he said.

Wang said engineers have applied some new advanced technologies on the mission, such as rapid sampling system and intelligent data analysis mechanism, to ensure that sample collection tasks are completed effectively and efficiently on the lunar surface. in a shorter operating time.

In the event of a communications outage, the Chang’e 6 probe is capable of performing some key maneuvers according to pre-established programs, he added.

Scientific benefits

The far side of the Moon is the hemisphere of the Moon that is permanently away from the Earth due to tidal forces on the planet. Since it is never visible from Earth, that region was once nicknamed the “dark side of the Moon,” even though it receives as much sunlight as the near side.

The far side of the Moon has been photographed extensively by various spacecraft, beginning with a Soviet probe in 1959. However, no probe had landed on its surface until the Chinese Chang’e 4 mission, which landed in the Pole’s Aitken Basin. South in January 2019. .

Due to its many mysteries, the Other Side has been the subject of scientific speculation and popular science fiction culture since the Apollo era.

As a landing destination, the South Pole’s Aitken Basin is believed to hold clues to important and intriguing scientific questions.

There has been a popular hypothesis that the basin was formed by the impact of a massive asteroid, about 200 kilometers in diameter. The collision was so powerful that it excavated part of the lunar mantle (material between the lunar core and the crust) and brought it to the surface. The physical characteristics of the gigantic crater therefore seem different from those of other lunar regions.

Chinese researchers have found that the soil layer on the far side is much thicker than that on the near side, but they have yet to find out why the crust on the two sides differs drastically in terms of thickness.

Scientists around the world have called for a sample return mission to the far side, stressing that the advantage of going there is the possibility of learning more about the interior composition of the Moon.

According to mission planners from the China National Space Administration, many domestic and foreign scientists have said they are eagerly waiting for the Chang’e 6 probe to bring back samples from the far side, because such materials will have high scientific value.

For example, samples brought back by the Chang’e 5 probe have helped scientists discover that there were volcanic activities on the near side of the Moon about 2 billion years ago. The samples from the other side will allow them to verify the hypothesis that the volcanoes became inactive in that hemisphere about 4 billion years ago.

Professor Martin Sweeting, a Fellow of the Royal Society of the United Kingdom and distinguished professor of space engineering at the University of Surrey, told China Daily before Friday’s launch that he was “looking forward to the launch of Chang’e 6 which, by for the first time, bringing unique samples from the far side of the Moon.

Sweeting said landing and retrieving samples on the far side, out of sight and direct communication from Earth, is a “very complex and demanding engineering activity” that will depend on advanced control systems and robotics on the surface and communications over of the Queqiao 2 relay. Satellite in lunar orbit.

“The surface of the far side is very different from that of the near side… with a multitude of impact craters and relatively few flat, dark areas, so comparing the composition of samples from the far side of Chang’e 6 with those previously collected from the near side will be of great scientific value for the international community,” he stated.

Giuseppe Reibaldi, president and founder of the Moon Village Association, a Vienna-based NGO, and executive secretary of the Global Expert Group on Sustainable Lunar Activities, said the Chang’e 6 mission will combine the challenges of the two previous Chinese lunar expeditions: the Chang’e 4 probe that made the first lunar landing on the far side and the Chang’e 5 that recovered samples from the visible side of the Moon.

The formation and composition of the Moon are not well understood to this day, and analysis of the far-side samples will make an important contribution to understanding them, said Reibaldi, who worked for the European Space Agency for 35 years.

“It is expected that some materials recovered from the other side will be made available to the international scientific community, to give more scientists access to these samples, as was done in the case of Chang’e 4,” he added.

International cooperation

In addition to the unprecedented attempt to collect samples from the far side of the Moon, the Chang’e 6 probe is also important because it is expected to carry three European scientific payloads to the far side.

According to the space administration, there is a radon measuring instrument from France’s national space agency on the Chang’e 6 lander, which will help study the movement of lunar dust and some volatile chemicals between the lunar regolith, a layer of unconsolidated rock material, and the lunar exosphere.

The second payload is a passive laser retroreflector from Italy’s National Institute of Nuclear Physics, which will be used as a laser rangefinder for the Chang’e 6 lander.

The third payload, developed by the Swedish Institute of Space Physics with support from the European Space Agency, will be the first dedicated negative ion instrument to fly beyond Earth. It will seek to detect negative ions emitted from the lunar surface as a result of interaction with solar winds.

More than 20 proposals from foreign space agencies and research organizations competed for the golden opportunity to join the Chang’e 6 mission to reach the other side. The three from Europe were winners.

This is not the first time China has offered opportunities to foreign scientists to deploy their scientific equipment to the moon. During the Chang’e 4 mission, the Chinese probe had carried German and Swedish sensor devices to the other side.

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