At 5:28 on the 1st, the Chang'e 4 relay satellite "Bengqiao" was launched and will provide relay communication services for the Chang'e 4th back landing detector launched at the end of this year. In addition, the "Bridge Bridge" also carries a laser corner reflector, which will carry out the laser pointer ranging test of the Earth and Moon, and undertake the pilot research work of the "Tianqin Plan".
It is understood that after entering the mission track, "Bengqiao" will try to carry out the laser ranging test that is the farthest in human history. The laser ranging test is a scientific measurement of the distance between the stars and the ground by laser. The principle is that a highly isotropic pulsed laser beam is directed toward a corner mirror placed on the surface of the satellite, and the distance between the stars and the ground is calculated by the time difference between transmission and reception. The longest distance laser pointer ranging test in human history is the lunar laser ranging. In 1969, Apollo 11 placed a laser ranging mirror array on the moon, and the United States, France, Japan, and China successively completed the test. There are not many countries that master this technology. After all, if you want to find and aim at a small laser mirror on the moon surface 380,000 kilometers away, it is difficult to find a needle in a haystack. If the "Yanqiao" satellite laser ranging test is successful, it will be a big leap in the spacecraft's measuring rail technology.
It is reported that the team of Academician Luo Jun of Huazhong University of Science and Technology began to develop laser angle reflectors in 2015. The device carried by the "Bengqiao" will be the pioneering research work for the "Tianqin Plan" for detecting gravitational waves in space in the future.
According to reports, the project will achieve the world's first purely reflective laser pointer ranging beyond the Earth's Moon distance, which is the first step in the “0123 Plan” of the “Tianqin Plan” implementation roadmap, namely the “0” plan. In part, the purpose is to develop lunar and deep-space satellite laser ranging technology to provide technical verification and reserve for the precise orbit determination of the later "Tianqin" satellite.