Reporter Lin Jie, reporter of China Youth Daily.
In early February, red lanterns were hung on the campus of Sun Yat-sen University's Zhuhai campus, and most teachers and students had returned to their hometowns for the Spring Festival. In the laboratory of the Tianqin Center of Sun Yat-sen University, there is such a group of young people, who are busy spending the Spring Festival of the Year of the Dragon.
Engineer Liu Linxia in the experiment. Photo courtesy of the interviewee.
Engineer Liu Linxia is one of them, and the optical platform lens bonding experiment she is responsible for is in full swing. "The lenses and components that need to be bonded to the optical table are divided into dozens of steps, each of which needs to be carried out in a cleanroom. In particular, the bonding of lenses is to accurately position and bond the glass pieces with a height difference of no more than one hundredth of a human hair on the surface of the concave and convex surfaces in tens of seconds, so it takes several days to adjust the assembly work before each step of bonding. The bonding accuracy of any step in the experimental process is not up to the requirements, and all the previous work is wasted. She said that in order to complete the experimental tasks according to the specified time node, the teachers and students in the laboratory gave up their weekends and holidays. As the core component of space gravitational wave detection, the development of optical platform is one of the key technologies that need to be overcome.
There are many teachers and students like Liu Linxia who stick to the front line of scientific research, and it is their adherence to ideals and beliefs and their enthusiasm for serving the country through scientific research that make the Tianqin Project smoothly promoted.
One of our team's recent research focuses on how to improve the real-time nature of Lyra gravitational wave data analysis. Hu Yiming, an associate professor at the Tianqin Center of Sun Yat-sen University, said that an important observation object of Tianqin is the merger of massive black holes. In recent years, many international peer studies have shown that when the "giants" in these universes merge, they may emit fleeting electromagnetic signals. By combining the gravitational wave detection of Tianqin with electromagnetic wave observation, it is possible to perceive the moment of the merger of black holes in an all-round and three-dimensional way, which is expected to answer many core scientific questions such as the origin and gravitational nature of large black holes. And all this depends on the real-time nature of gravitational wave data analysis.
Hu Yiming said that the selection of Tianqin's orbit around the earth allows gravitational wave data to be transmitted to the ground quickly and in real time, and the bottleneck lies in how to complete the analysis of the data quickly and in real time. With traditional methods, this process takes a long time, often requiring days on a supercomputer. But thanks to the combined efforts of the Tianqin team, they have been able to update the results of the analysis in the order of hours. "Now we are continuing to work on further improving our analytics to enable real-time analysis. ”
It is understood that Tianqin is expected to provide a large amount of information that cannot be obtained by other means of detection, especially information about high-redshift massive black hole binary stars, the dynamics of galaxies or star clusters in the nucleus, and the dense binary star system in the Milky Way, which is of great significance for revealing the origin and growth history of massive black holes, the dynamics of the nuclear region of galaxies or star clusters, the astrophysics of stellar compact stars, the origin and evolution of double compact stars in the Milky Way, the expansion of the universe, gravity and the nature of black holes, the early universe and high-energy label physics, etc. It is also possible to discover new physics that cannot be predicted at present, which will have a significant role in promoting the study of astronomy and physics.
The development of the Tianqin program needs to overcome a series of key core technologies, including the establishment of high-precision inertial datums, inter-satellite laser interferometry, the realization of ultra-static and ultra-stable satellite platforms and large-scale formation flights, and the realization of gravitational wave detection signal identification and measurement, etc., which will be able to promote the leapfrog development of China's high-precision space exploration payload and satellite technology, and its technological progress has important applications in the measurement of the earth's gravity field, which has great strategic value.
At present, the teachers and students of the Satellite Platform Technology Laboratory of Tianqin Center are still continuing to promote the project. Liu Jianping, a distinguished associate researcher at the Tianqin Center of Sun Yat-sen University, told the reporter of China Youth Daily and China Youth Network that during the winter vacation, the team still maintained uninterrupted scientific research, insisted on experimental testing and group discussions, and ensured the steady progress of the project. Space gravitational wave detection missions have put forward unprecedented requirements for ultra-static and ultra-stable satellite platforms. The members of the research group have made important progress in many aspects, such as space environment analysis and the integrated design of gravitational wave detection satellites. "We will continue to work hard to promote the research, testing and verification of satellite platform related technologies, so as to help Tianqin play the movement of gravitational waves in space as soon as possible. ”
The Tianqin Project is a space gravitational wave detection plan proposed by Luo Jun, an academician of the Chinese Academy of Sciences, in 2014, and is known as the "Chinese plan" for space gravitational wave detection. The plan is expected to deploy three identical satellites in an equilateral triangular constellation with a side length of about 170,000 kilometers in the Earth's orbit at an altitude of about 100,000 kilometers around 2035The 1MHz 1Hz gravitational wave detection window answers major scientific questions such as the origin of massive black holes in the universe, and unveils more mysteries of the universe for mankind.
Tianqin plans to promote the progress of key technologies and ensure the realization of gravitational wave detection tasks in accordance with the "0123" technology roadmap. The numbers for each phase represent the number of satellites that need to be launched.
The "0" step is to carry out lunar laser ranging experiments, develop a new generation of laser ranging reflectors, and build a new laser ranging station. In April 2019, the Tianqin Ranging Station completed the civil engineering completion acceptance and began operation, realized the Apollo 15 cooperation target ranging in May, and achieved high-precision ranging of all five cooperation targets on the lunar surface in November of the same year, which was the first time in China, making China the third country in the world to complete the test.
The main purpose of the Tianqin ranging station is to obtain the precision ranging capability of high-orbit satellites and provide technical support for the high-precision orbit determination of Tianqin satellites. In order to realize the high-precision laser ranging task of ultra-long-distance satellites, the Tianqin ranging station took the lead in carrying out 380,000 kilometers of Earth-Moon ranging work. Han Xida, an engineer of the Tianqin Project, said, "Every preparation must be meticulous in order to have an extremely weak lunar signal."
Han Xida explained that the difficulty of this work lies in the ultra-high pointing accuracy and tracking accuracy requirements for ranging telescopes at an ultra-long distance of 380,000 kilometers, and there are still a few stations that can achieve Earth-Moon laser ranging. In October 2023, through the unremitting efforts of the teachers and students of the station, they obtained the 1064nm band full moon measurement signal, which is the first measurement of the Tianqin ranging station to obtain the full moon measurement signal, which plays a supporting role in daytime ranging.
In the first step, the "Tianqin-1" technical test satellite was successfully launched on December 20, 2019, and all the six key technologies were tested in orbit, and the key indicators reached the highest level in China, realizing the improvement of the core technology of China's space gravitational wave detection, and using domestic satellite data to obtain the global gravity field model for the first time in China.
In the second step, the Tianqin-2 technical test satellite has completed the ground verification of key technologies, and it is expected to launch two satellites for in-orbit tests around 2026.
In the third step, the work related to the Tianqin-3 gravitational wave detection satellite project was smoothly advanced, the first round of evaluation of the main scientific objectives of Tianqin was completed, and the potential impact of the Earth-Moon gravitational field was solved.
During the interview, the reporter learned that the basic research facilities of the Tianqin Project have all been completed, and the layout has formed "one center + three stations", which provides a strong guarantee for the implementation of the Tianqin Plan. At present, facing the national strategic needs, the laboratory plays a leading role in carrying out basic research, promoting the development of disciplines, and promoting technological progress.
*: China Youth Daily client).