The Applied Astronomy Group of Yunnan Observatories, Chinese Academy of Sciences, has long been working on Lunar Laser Ranging (LLR), and recently has made great progress after multiple major technological breakthroughs. On the night of Jan.22, using the 1.2-meter Telescope Laser Ranging System, the group detected the laser echo signal from the lunar-surface reflector Apollo15 for several times, which is the first successful LLR experiment nationwide in China.

LLR is to calculate the distance between the Earth and the Moon precisely, by measuring the time of the laser pulse travelling from ground station to the lunar reflector. It is a comprehensive technology covering a number of areas from laser, photoelectric detection, automatic control to space orbit, which is also currently the most accurate technique in Earth-Moon distance measurement. The observational data has significant value for many areas such as astronomical geodynamics, Earth-Moon dynamics, lunar physics and the verification of gravitational theory. Previously, there were only three countries, including the USA, France and Italy, which succeeded in LLR experiment. This time the lunar ranging carried out by Yunnan Observatories fills the gap in Chinese LLR area.

The 1.2m Telescope Laser Ranging System uses common optical path mode. The laser wavelength is 532nm with pulse-width 10ns and frequency 10Hz. Laser energy during the experiment is 3.3J. Average Earth-Moon distance is 384403.0km. From 21:25 to 22:31, as shown by the experimental data, the distance between the observatory and the lunar reflector Apollo15 is 385823.433km~387119.600km, with ranging accuracy within 1m.

The 1.2-meter Telescope during the LLR (Image by Tang Rufeng)

Acknowledgement：The LLR experiment was supported by the National Natural Science Foundation of China(NSFC) and Bureau of Infrastructure,Logistics&Finance,CAS

Contact:

LI Yuqiang
Applied Astronomy Research Group
Yunnan Observatories, Chinese Academy of Sciences
TEL: 0871-63920402
Email: lyq@ynao.ac.cn