China's Lunar Exploration Project (CLEP), or "Chang'e" project, has entered the stage of execution. To promote public understanding of the scientific program, leaders from the CLEP Center of the Commission of Science, Technology and Industry for National Defense and related experts discussed with readers on China's lunar probing roadmap, objectives, and risks at the Commission's official website on the morning of August 16.
There will be many "firsts": three-dimensional picture of the moon, lunar earth thickness
Question: What's the difference between China's lunar probing and past activities by other countries?
Li Chunlai (general engineer of earth application system of CLEP): Based on past experiments by other countries, our exploring work contains necessary repetitive parts to confirm conclusions made before but more exclusive, innovative objectives and activities.
We will for the first time have three-dimensional pictures taken for the whole lunar surface, which is of great significance to studies into lunar terrain, geological structure and hit pit; we plan to explore into the amount and distribution of 14 elements on lunar surface so as to lay a foundation for lunar resource utilization; we will also for the first time probe into the thickness of the whole lunar earth so that we can study the history of lunar surface efflorescence and helium-3 resources. This will be the first time that China acquires first-hand data on moon-earth space environment 70,000 kilometers away.
Hao Xifan (deputy director of CLEP Center): The present project is a scientific and engineering objective independently proposed by our scientists and engineers. In its implementation we firstly need to break away from past restrictions of earth orbits and fly to the moon. More concretely, we have solved problems on lunar environment, lunar orbit and long-distance measurement and control. This contains much innovative work by our technicians, and all scientific instruments are independently developed by ourselves.
Lunar exploration a high-risk task
Question: What about the success rate of lunar probing activities?
Hao Xifan: By now man has sent lunar probes for 122 times, 59 succeeded, or 48 percent.
Question: What are major risks in the project?
Sun Zezhou (deputy general designer of the satellite system of CLEP): Space flight is a high-risk undertaking, and lunar probing is particularly so. This can be proved by statistics on foreign lunar exploration programs.
Judging from the satellite system, the major risk is whether the nine or ten orbit changes can be completed precisely and promptly. We have been working in many aspects to reduce the risk, including planning, product quality control and testing.
Hao Xifan: This is the first time that a Chinese satellite flies away from the earth and probes into an extraterritorial body. Our satellite technologies are based on earth satellites and must be tested under lunar environment; our measurement and control technologies have been only applied on tasks within 40,000 kilometers. But to the moon there is a distance of 380,000 kilometers, which contains many elements unknown to us, and this brings technological risks.
The biggest difficulty in our first lunar tour lies in our lack of deep, first-hand understanding of lunar environment. We hope that the successful operation of Chang'e I could bring us first-hand data and lay a foundation for further projects.
Question: What are the major risks regarding the launching of Chang'e I?
Jin Zhiqiang (deputy general designer of Long March A rockets): By now the success rate of Long March A rockets is 100 percent, but it doesn't mean there is no launching risks. From 1994 till now we only launched 14 times, this is not enough. The rockets are designed with a flying reliability index of 0.95. So, in strict scientific terms, we cannot say every launch will be a success.
There are risks in pre-launching preparations, such as weather, which can delay a launch. Long March A rockets require perfectly heat-insulating products, and any leakage can delay a launch. Another launch can only be organized in three days, and would miss the launch window of Chang'e satellite.
There are more than 50 key operations during the 20-minute process from firing, taking off and the separating of satellite and rocket, problem in any link might lead to a launching failure.
Q: What precautions we take to avoid these problems?
Jin Zhiqiang: For some products for these links we use redundancy and for some others we have strengthened testing on the ground. Meanwhile, these operations and links are tested in previous flights. But one success can never mean all, so there is still risks and what we can do is to reduce them to the minimum.
China's lunar probing a peaceful project
Q: Besides China, Japan, India and Germany also announced their lunar probing plans. What do you think of these plans?
Hao Xifan: These plans have both common points and their specific features.
Firstly, all countries chose orbiting as the first step in this new wave of lunar probing enthusiasm.
Secondly, plans of these countries conducting their first ever lunar probing are stunningly similar, almost all following the roadmap of orbiting, landing and returning.
Thirdly, the scientific objectives of China, Japan, India and Germany are similar, all including mapping the whole moon, surveying lunar resources and environment.
Fourthly, moon-probing countries can be divided into two groups according to their ultimate goals. The US, Russia and the European Space Agency aim at manned lunar landing and the establishing of long-term stationed lunar base. The second group includes countries probing the moon for the first time such as Japan, India, Germany and China. They are at an initial stage and chiefly aim at accumulating experience and technologies.
Fifthly, in the second group each country displays distinct features, showing scientists' imagination. Our Chang'e I will be the first one to survey lunar earth with microwaves; Japan's SELENE-1 carries two sub-probes that will be used on the world first surveying of gravitational field on the back side of the moon; while India excels itself in making small-sized probes.
China's lunar probing is a scientific program serving entirely for the peaceful use of space. There is no military purpose or any direct interest clash with other countries.
By People's Daily Online