China finished its first Lunar Laser Ranging (LLR) experiment on Jan. 22, with a 1.2-meter telescope laser ranging system, said the country’s news site huanqiu.com.

A 532-nanometer laser wave with a pulse width of 10 nanoseconds and energy of 3.3 Joule was sent to the lunar retro-reflector left by the U.S. manned mission Apollo 15 from the Yunnan Observatory.

Based on the signal reflected, the distance measured between the Apollo 15 retro-reflector and the ground station of Yunnan Observatory was 385823.433 kilometers to 387119.600 kilometers, from 9:25 p.m. to 10:31 p.m. Beijing Time, on January 22, 2018. The error was within 1 meter.

LLR is a comprehensive technology that covers multiple areas such as laser and photoelectric detection, automatic control, and space orbiting. Compared with other methods, it is the most accurate way to measure the distance between the earth and moon.

It was a major breakthrough for China to complete the first LLR detection.

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