China has accomplished¹ its first successful Lunar Laser Ranging (LLR), with a 1.2-meter telescope laser ranging system.

 

中国利用一架1.2米的激光望远镜测距系统成功完成月球激光测距。
 

 

Based on the signals of laser pulses reflected by the lunar retro-reflector planted by the U.S. manned mission Apollo 15, the applied² astronomy group from the Yunnan Observatories³ measured the distance between the Apollo 15 retro-reflector and the Yunnan Observatories ground station to be 385823.433 kilometers to 387119.600 kilometers, from 9:25 p.m. to 10:31 p.m. Beijing Time, on Jan. 22, 2018.

 

Theoretically, LLR measures the distance between the Earth and the moon by calculating the time a laser pulse takes to travel from a ground station on Earth to a retro-reflector on the moon and back again. 

 

LLR technology traverses fields such as laser and photoelectric⁴ detection, automatic control and space orbiting. Compared to other methods, LLR can achieve the highest accuracy of distance measurement between the Earth and the moon. 

 

"Although LLR in China has not achieved the same level as pioneering countries like the U.S., our initial success still means the progress, which started from scratch," said Li Yuqiang, an associate researcher with Yunnan Observatories. 

 

Results of LLR are vital to advanced research in astro-geodynamics, Earth-moon system dynamics⁵ and lunar physics. Until China made its first LLR, only the United States, France and Italy had successfully harnessed the technology. 

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