Source: People's Daily Overseas Edition
This is an imposition photo: the first reflective panel assembled by the "China Sky Eye" (top left, taken August 2, 2015), nearly half of the "China Sky Eye" reflective panel installed (top right, taken December 16, 2015), nearly eighty percent of the "China Sky Eye" reflective panel installed (bottom left, March 9, 2016), and "China Sky Eye" during maintenance (bottom right, taken July 21, 2022). Photo by Xinhua News Agency reporter Ou Dongqu
Jiang Peng inspects the equipment at the "China Sky Eye". Profile picture
Introduction to the popular science of "China's Sky Eye". Profile picture
The picture shows the "Eye of China Sky" from the air. Photo by Xinhua News Agency reporter Ou Dongqu
What secrets are hidden in the vast starry sky above us? Does deep space give birth to new opportunities for human development?
The mountains are stacked, and the green forest is like the sea. Between the mountains of Pingtang County, Guizhou Province, a magnificent single-aperture spherical radio telescope stands quietly, gazing at the starry sky, with human curiosity and expectation, exploring radio signals tens of billions of light years away.
The full name of "China Sky Eye" is the 500-meter aperture spherical radio telescope, abbreviated as FAST. With a new design concept, FAST is the world's largest and most sensitive single-aperture spherical radio telescope, capable of searching for faint signals from tens of billions of light-years away in the radio band.
Recently, our reporter interviewed Jiang Peng, chief engineer of "China Sky Eye" FAST. As a "starchaser" who guards the "Chinese Sky Eye", Jiang Peng's main research direction is radio astronomy technology and methods, and he is currently fully responsible for the operation and development planning of the "China Sky Eye". Let's listen to the story of Jiang Peng looking up at the starry sky with the "Chinese Sky Eye".
Make a "retina" for FAST
In 2009, 31-year-old Jiang Peng had just graduated with a doctorate and was in good spirits.
At this time, he stood at a crossroads in his life: one choice was to continue to engage in in-depth research in the direction of doctoral studies; The other is to choose a new and challenging scientific work.
When he hesitated, Jiang Peng saw the recruitment information of "China Sky Eye" and instantly became interested.
"At that time, in my opinion, the construction of the 'Eye of China's Sky' was very bold and extremely challenging." Jiang Peng told this reporter that the FAST telescope has almost met all his expectations and ideas for a legendary project - the largest engineering volume, ultra-high accuracy requirements, and extremely special working methods, which constitute unprecedented technical challenges in the engineering field.
"I really wanted to know how this project was going to come to fruition, so I wanted to join this innovative team." Jiang Peng said.
After submitting his resume without hesitation, Jiang Peng successfully became a member of the team. After that, he plunged headlong into the mountains of Guizhou and began a 14-year life with FAST.
How hard is FAST to build?
It not only involves dozens of different professional fields such as astronomy, mechanics, mechanical engineering, structural engineering, electronics and even geotechnical engineering, but also has no precedent for key technologies, key materials are urgently needed, and the on-site construction environment is also very complex.
For the FAST team, the construction of FAST is "crossing the river by feeling the stones", how to design, how to achieve, how to debug and use after completion... All problems can only be solved by the construction team itself.
"It's much more difficult than the engineering projects we normally know, and a lot of things are not certain." Jiang Peng said.
In the early days of FAST construction, the first task Jiang Peng received made him feel pressure.
"At that time, Mr. Nan Rendong, the chief scientist and chief engineer of FAST Engineering, asked me if I dared to undertake the key task of FAST construction - cable network engineering." Jiang Peng said, "Simply put, it is to equip FAST, the 'eye of heaven', with a 'retina'. Since my major is structural mechanics, this responsibility is in my hands. ”
Unlike the world's existing single-aperture radio telescopes, FAST's "retina", the spherical reflective surface, is a cable net of 6670 steel cables, which needs to change frequently between the spherical surface and the parabolic surface to collect and observe astronomical signals. This places very high demands on the steel cable net that supports the bottom of the FAST "cauldron". The cable network engineering is the core component of the FAST reflective surface to realize the displacement function, and it is also the core technical difficulty of construction.
"How can a telescope with a span of 500 meters achieve a control accuracy of 2 millimeters?" With the topic assigned by Nan Rendong, Jiang Peng pondered repeatedly and decided to do a good job in this construction project without precedent.
Not long after the start of the project, the team encountered a big difficulty - cable net fatigue.
The strength of the steel cables on common cable-stayed bridges is 200 MPa and 2 million bends. Because the steel cable of the "Chinese Sky Eye" is equipped with reflective panels, it needs to be repeatedly deformed and constantly stretched; The telescope needs to be used for at least 30 years, which puts forward higher requirements for steel cables. After repeated thinking and calculation, the designer proposed a solution for installing steel cables with a strength of 500 MPa and a bending number of 2 million.
"At that time, the excavation of the site had already begun, and the superstructure could not be finalized due to cable network fatigue, and the implementation of the project was imminent." Jiang Peng said that at that time, they bought dozens of steel cables from the market for experiments, but none of them could meet the requirements. "What to do? If the problem is not solved, the entire telescope construction will have to be stalled. After discussion, we decided to conduct a large-scale experimental study of the fatigue properties of steel cables. ”
Under the guidance of Nan Rendong, Jiang Peng led the team to start a two-year large-scale steel cable fatigue experiment. After nearly 100 failures, they finally developed ultra-high fatigue resistant steel cables and completed the construction project of cable network structure.
As the main supporting structure of the active reflective surface, the cable network structure of FAST is regarded as the cable network structure with the largest span and highest accuracy in the world today.
6670 main cables, 2225 main cable nodes and the same number of pull-down cables complete the cable network of FAST. After the assembly is completed, the huge reflective surface of FAST looks like a "super cauldron", 6 support towers are erected high, the grid gradually climbs the bottom of the "pot", extends upward to "bite" the ring beam, and the reflective surface panel is covered with gaps in the cable net one by one, weaving the giant net.
This cable network structure is the world's first cable network system that adopts the variable position working mode. In other words, according to the mechanical model information, the actuator controls the cable to change the shape of the cable net, and according to the orientation of the observed celestial body, the actuator is activated to control the cable to form an instantaneous paraboloid with a diameter of 300 meters in different areas of the FAST reflective surface to achieve accurate observation.
"China's Heavenly Eye" is the pride left by Nan Rendong to the motherland
In 1993, the General Assembly of the International Union of Radio Science was held in Kyoto, Japan, and Minami Hitoshito also attended the conference.
At the scene, some scientists proposed that before the global radio environment continues to deteriorate, humans should build a new generation of radio astronomy telescopes to receive more information from outer space.
Hearing the news, Nan Rendong, who was nearly 50 years old at the time, was excited: "If we can seize this opportunity, China's astronomical research may be decades ahead of the world." The bold idea of building a new generation of radio astronomy telescopes was born. Nan Rendong, who has always been low-key, couldn't sit still, ran to find Wu Shengyin, a Chinese delegate, and said excitedly: "Let's build one in China!" ”
However, for China in the early 90s, the construction plan for a large radio telescope was almost crazy. Regardless of geological conditions, technical conditions, or engineering costs, it is difficult to achieve. As a result, almost all industry experts are not optimistic about the project.
Despite this, Nam In-dong, who is naturally stubborn and loves to meet challenges, decides to stick to this plan.
For Nan Rendong, the most difficult thing was the period when he applied for the project, he knew that the previous site selection and demonstration process had consumed years of time and energy, and the next project must be successful. Otherwise, it means that all previous work is in vain.
Therefore, Nan Rendong began to pay for his own travel, from the northeast to the southeast to the northwest, unit by unit to talk. In the end, with his efforts, the names of more than 20 cooperative units appeared on the thick project approval application. In order to find a suitable site, Nan Rendong spent more than 10 years traveling all over the mountains and rivers of Guizhou and inspecting dozens of nests.
Finally, in July 2007, FAST was officially approved by the state as a major scientific and technological infrastructure in the Eleventh Five-Year Plan. From that day on, FAST embarked on a rapid construction journey, just as its acronym (fast).
"Professor Nan told me at the time that radio astronomy research in China started many years later than other countries in the world. If you start later than others, you must spend a little more time and go faster than others, otherwise you will never catch up. Recalling Nan Rendong, Jiang Peng told this reporter such a story. Once, Jiang Peng's project team encountered a relatively big change, and Nan Rendong called him to the office and asked: "Jiang Peng, you said that you are a young man who has just graduated for two years, can I fully trust you?" Jiang Peng was silent for a long time, and replied word by word: "Teacher Nan, I think you can trust me." ”
After the start of FAST construction, Nan Rendong gradually handed over the task of commissioning and operating the "China Sky Eye" to the new generation of young scientists and engineers of FAST. On September 25, 2016, the "Eye of China" was officially completed. One year later, Nam In-dong died of illness at the age of 72. Jiang Peng said that "China's heavenly eye" is the pride left by Nan Rendong's teacher to the motherland.
Nan Rendong also wrote a few poems to himself and his favorite motherland:
"Beautiful cosmic space,
With its mystery and brilliance,
Calling us to step through mediocrity,
Enter its boundless vastness..."
After the completion of FAST, it soon entered the debugging stage, and Jiang Peng succeeded Nan Rendong as the second chief engineer, continuing to lead the team to overcome one difficulty after another.
In his opinion, this is a battlefield without gunsmoke. FAST's new design concept meant that the team could not have any successful experience to draw on, and they had to establish a measurement and control methodology system adapted to the special working style of FAST. To this end, Jiang Peng led the team to fight at the project site for three consecutive Spring Festivals.
In the Spring Festival of 2019, when the lights of others' homes were on, the FAST team had to work until three or four o'clock in the morning almost every day. In order to ensure the progress of the project, one core member did not have time to return home, and even took his pregnant wife to the scene to take care of him.
In August 2017, FAST achieved tracking of fixed target sources for the first time; In April 2019, it passed the process acceptance and opened to Chinese domestic astronomers; In January 2020, it passed the national acceptance and officially opened for operation.
The rapid success of FAST construction and commissioning is inseparable from the persistence and enthusiasm of the scientific research team and construction team behind it who have been working hard in the front line of scientific research for ten years.
Speaking of his team members, Jiang Peng joked: "We are a group of 'silly boys' who only know how to work and don't know other things." There is a saying that best reflects our team spirit, that is, a group of 'silly boys' rely on their own 'silly' strength to do things! ”
Jiang Peng believes that scientific research work has three characteristics, the first is not necessarily successful, but "unsuccessful" scientific research is not necessarily good scientific research, scientific research is to explore all possibilities, continuous trial and error. Secondly, the working time and cycle are very long, can not rush to achieve quick results, need to calm down, patient, excellence, polishing in order to make progress. "We can't always amplify the effect of 1 day and ignore the power accumulated in 1 year." Jiang Peng said, "Only if you choose the right direction and continue to persevere, over time, you will quickly find that those who persevere will throw those who follow the trend and those who are eager to achieve quick results far away." "The third characteristic of scientific research is that scientific research workers must adhere to the front line, and the front line is the position and battlefield of scientific research workers, and it is the place where they should reside."
"As a researcher, I think the most important qualities are truth-seeking and pragmatism. Many scientific research work can not see results immediately, which requires us scientific researchers to endure long-term loneliness and sit on a cold bench, which are the good qualities that scientific and technological workers, especially those who are on the front line, need to have. Jiang Peng told this reporter, "The front line of scientific research is the forefront of generating scientific value, and I think it is very important to ensure the enthusiasm of front-line researchers." What I am trying to do now is to make better scientific and technological talents feel at ease and willing to stay on the front line of scientific research. ”
Stay awake to stay ahead of the curve
Some astronomy enthusiasts once asked curiously, where is FAST "fast"?
FAST is safe and efficient, with no extension of a day. The project construction lasted 2011 days from the date of approval of the start report on March 5, 2011 to the completion of the project on September 25, 2016, and there were no major safety accidents throughout the process.
FAST is less than two years in commissioning. "You know, even a traditional telescope commissioning cycle is rarely less than 4 years in the world, and we only took about 2 years to complete the commissioning of this extremely complex system." Jiang Peng said.
Early scientific research is already underway as early as the commissioning phase. In the process of constantly calibrating the "vision" of the "Chinese Sky Eye", Chinese astronomers are racing against time to carry out scientific observations. When the telescope could not move, they used drift scanning to let the earth rotate with the "Chinese sky eye" to survey the sky. Less than a year after its completion, FAST achieved an accurate tracking observation mode, verifying its ultra-high sensitivity and telescope efficiency.
FAST begins the systematic discovery of new pulsars as soon as the commissioning phase. This is thanks to the scientific team's advance preparation, corresponding observation and data processing training for team members, development of data processing software and databases...
What is FAST strong about?
The key technical achievements of FAST can be applied to many related fields, such as large-scale structural engineering, high-precision dynamic measurement in the kilometer range, large-scale industrial robot development, and multi-beam receiver devices.
FAST extends China's space measurement and control capabilities from geosynchronous orbit to the outer edge of the solar system, increasing the downlink rate of deep space communication data by dozens of times. FAST improves the accuracy of pulsar timing by several times, and can observe and form the world's most accurate pulsar timing array and build pulsar clocks, laying the foundation for the forward-looking research of autonomous navigation.
As a multidisciplinary basic research platform, with its super sensitivity, FAST has the ability to extend neutral hydrogen observation to the edge of the universe, observe dark matter and dark energy, and study the structure and physical laws of matter in extreme states; It is hoped to discover strange and quark material and discover neutron stars and black hole binary stars without relying on models to accurately determine the mass of black holes; It can be used to search for possible interstellar communication signals, find extraterrestrial civilizations...
In recent years, there have been more than 150 high-level papers based on FAST open data, and the total number of pulsars discovered has exceeded 780, which is more than 3 times the total number of pulsars discovered by all other telescopes in the same period in the world, and a series of scientific achievements with international influence have been produced in the fields of pulsar physics, the origin of fast radio bursts, the formation and evolution of galaxies, and many papers have been published in the journal Nature, and 2 papers have been published in the journal Science, one of which is a result on fast radio bursts selected in the The world's top ten scientific discoveries and breakthroughs in 2020 selected by Nature and Science.
In Jiang Peng's view, astronomy is romantic, but the competition in the field of astronomical instruments is cruel. Jiang Peng told this reporter: "The competition in astronomy is still relatively fierce, and we must have a sense of crisis." If we turn our gaze to the future, we must remain sober enough, solve key problems solidly, and continuously improve the performance of the telescope, only in this way can we maintain FAST's hard-won lead in the context of increasingly fierce international competition. ”
Talking about how to continue the glory of FAST, Jiang Peng said that first of all, we must continue to improve the performance of FAST. For telescopes such as FAST, improving performance includes several aspects, on the one hand, its field of view coverage, which requires a breakthrough in receiver technology, and is currently working hard to tackle key problems. At the same time, from the perspective of single-aperture telescopes, there are still its limitations in resolving ability, so the advancement of array telescopes may be a good solution, and you need to find an array scheme with high cost performance and excellent performance. It is estimated that some tests of the pilot array will be launched in 2023 or 2024 to verify the feasibility of the pilot array scheme, including some technical reserves, imaging capabilities, and comprehensive aperture imaging tests.
Speaking of the feelings of the struggle of the "China Sky Eye" team, Jiang Peng said in an interview with the second "delegates' channel" of the first session of the 14th National People's Congress: "As far as our eyes can see is the sea of stars, but every step we have taken is down-to-earth. (Reporter Yang Junfeng)
People's Daily Overseas Edition (Version 05, July 11, 2023)