One in Ten Million—Exclusive Interview with Ye Peijian, Chief Scientist with China’s Lunar Exploration Program

Every time before a satellite launch, Ye Peijian feels the pride swell. “Everybody in the country will know we succeed when the satellite goes into space.”

Ye has been devoted to China’s lunar probing for two decades. In 2001, he accepted the role of the chief scientist of the Chang’e-1 project and led his team to trailblaze the Chinese path to the moon. From the demonstration of lunar exploration plans to team organization and relevant design and research and then to the implementation of the lunar-probing missions, Ye has witnessed every thrilling moment of the Chang’e project and knows all about the hardship behind the success. Currently, he serves as chief scientist of deep space exploration at the China Academy of Space Technology (CAST). As a consultant to chief designer and chief commander of the Chang’e probe project, Ye continues to steer China’s journey of lunar exploration.

Just two days before the launch of the Chang’e-4 probe, Ye said at a motivational conference: “After living for more than 70 years, I have seen many ups and downs. But I feel excited now because I am so proud. Humans will finally land a spacecraft on the moon’s far side, and Chang’e-4 is ready. I have had such great luck. Among the 7.5 billion people on Earth, the core team of the Chang’e-4 project consists of only a few hundred. This opportunity is only one in ten million. And we got it.”

China Pictorial (CP): Were there any setbacks in the three-year feasibility study of China’s lunar exploration program conducted from 2001 to 2004? What foundation did the discussion lay for the program?

Ye Peijian: It was quite a complicated process. Due to limited funding, we had to achieve scientific goals and progress in space technology with a limited number of launches. So, we planned to complete all unmanned lunar probe processes in three steps—orbiting, landing and returning. There was no divergence in the design of the three-step plan, but there was disagreement on how to perform the first step. Several options were presented, and the CAST’s plan was ultimately chosen for two main reasons. First, we could not adopt too many new technologies concerning risk control so we mainly inherited the technologies of two previous satellites, Dongfanghong-3 and China Earth Resource Satellite-2. Second, China is a latecomer in lunar exploration, so we needed some innovative ways to accelerate the project and ensure it continues moving even after completion. In all, we achieved quite a good balance of inheritance and innovation.

One critical lesson China has learned from both manned spaceflights and lunar exploration program is the importance of sound top-level design. Throughout the three steps for our lunar probes, we will stick to the plan and keep the team stable. We have all adopted this philosophy: When working on one step, we consider how to utilize the technology used in the former step as well as how to serve the next step. This ensures we continue striding forward no matter how hard it is.

CP: After the Chang’e-1 project was first launched in 2004, it took your team three years to finish building the Chang’e-1 satellite. What was the biggest challenge of that period?

Ye: When I accepted the role of the chief designer of Chang’e-1, I was shouldering enormous responsibility because I also served as the chief designer and commander of another satellite, China Earth Resources Satellite-2, China’s first transmission satellite for Earth observation.

Chang’e-1 was China’s first lunar-probing satellite, and we confronted many unprecedented technical challenges that were sources of hardship and pressure. For instance, how did the satellite approach the moon without getting sucked to its surface by gravity? We could not experiment on Earth to answer this question. And how should we tackle communications with the moon nearly 400,000 kilometers away from Earth? Moon-based positioning requires ultraviolet radiation sensors but there was none in China at that time, so we had to start research on it from scratch. An Earth satellite requires two-body positioning while a moon satellite requires three-body positioning including Earth, the sun and the moon, so its antenna must spin. How could we make it happen? The temperature gap along the moon orbit can exceed 300 degrees Celsius, so how could the satellite survive both extremes while circling the moon? There were many more questions. Ultimately we summarized seven key technical problems and solved them one by one.

CP: What was your tensest moment working on the lunar exploration program?

Ye: I kept thinking that we deserved to succeed after all the efforts we made. If we didn’t succeed, there might have been something we missed. Our work on the Chang’e project has been meticulous. You should see the hundreds of malfunction emergency response plans we made for the Chang’e-4 mission. We took everything we could imagine into consideration and drilled procedures, even including who makes decisions when problems emerge and how to report to authorities. However, there is no guarantee for success in any scientific experiment.

I have witnessed the launch of each Chang’e spacecraft personally. As a key member, I always stay calm so nobody else panics. If I appear anxious, people may expect huge trouble. The best scenario for flight control experts is when they’re drinking coffee and chatting, with nothing else left to do.

CP: How do you monitor the progress of the lunar exploration program and prevent potential risk?

Ye: Despite the success of Chang’e-1, opposition to the launch of Chang’e-2 was strong. But should Chang’e-1 be China’s one-off lunar exploration? A backup satellite had already been completed, and there was little reason not to launch it to accumulate more experience for the future. Chang’e-2 successfully reached the Earth-Sun L2 point, which is 1.5 million kilometers from Earth, and achieved a flyby of the asteroid 4179 Toutatis. Before the latest lunar mission, some objected to the idea of Chang’e-4 landing on the moon’s far side. As long as China’s lunar exploration continues, the far side was always going to remain key to innovation. If the chance emerges, why skip it and spend more time and money in the future to do the same thing? Chang’e-4 faced many challenges as it worked to land on the far side of the moon. Communications problems became a major issue, so we launched a relay satellite. The geographic environment of the far side of the moon is quite complicated, so landing required multiple sensors to determine the surrounding landform, something we also successfully accomplished.

CP: The Chang’e-4 mission included international cooperation on its scientific payloads, which were supplied by four international partners. What is your opinion on the collaboration?

Ye: Only a limited number of visits have been made to the moon, and scientists all over the world jump at the opportunity to conduct research there. International cooperation contributes to mankind, demonstrating China’s inclusiveness and openness. Some international lunar exploration projects exclude China, but we aren’t looking to exclude anyone. All countries are welcome to participate in our space station construction and our lunar exploration. American scientists have suggested extending the operational time of Queqiao (Magpie Bridge), China’s lunar relay satellite, to five years. They hope to use the satellite, and we also welcome that.

CP: What is the value of exploring the moon?

Ye: Was the moon part of Earth? Or did it come into being simultaneously with Earth? There are still no promising clues. Research of the moon can enhance our understanding on the formation of the universe. Better understanding of the moon can facilitate the renovation and exploration of Earth. There is also a wealth of resources on the moon. For example, Helium-3 from the moon can be used to generate nuclear power. Its supply of Helium-3 is enough for 10,000 years of human use. It is a kind of clean energy. The difficulty is how to exploit it on the moon and take it back to Earth. It may seem hard now, but what about in a century or two? It is not available now, but it is not necessarily unavailable in the future.

CP: What do you think of the ability and momentum of China’s deep space exploration compared to other countries?

Ye: Moon exploration has regained popularity in the 21st century. But we cannot expect China to make remarkable achievements overnight. Our efforts have paid off, but in general we are still lagging behind the global forerunners in this field.

We aim to take samples from the moon back to Earth this year. We are also conducting research on sending astronauts to the moon and planning to visit the South and North Poles of the moon. In the foreseeable future, we will be in a leading position in lunar exploration. According to our plan, the Mars-1 probe will be launched in 2020. It will not only orbit Mars, but also land and rove on the Red Planet. If the plan succeeds, China will be a step ahead on exploring Mars. We also plan to explore asteroids and reach Jupiter by the 100th anniversary of the founding of the People’s Republic of China. Only when those steps are completed will China take a leading position in deep space exploration.