A review of the lunar laser ranging technique and contribution of timing systems

摘要

The lunar laser ranging (LLR) technique is based on the two-way time-of-flight of laser pulses from an earthstation to the retroreflectors that are located on the surface of the moon. We discuss the ranging techniqueand contribution of the timing systems and its significance in light of the new LLR station currently underdevelopment by the Hartebeesthoek Radio Astronomy Observatory (HartRAO). Firstly, developing the LLRstation at HartRAO is an initiative that will improve the current geometrical network of the LLR stationswhich are presently concentrated in the northern hemisphere. Secondly, data products derived from theLLR experiments – such as accurate lunar orbit, tests of the general relativity theory, earth–moon dynamics,interior structure of the moon, reference frames, and station position and velocities – are important in betterunderstanding the earth–moon system. We highlight factors affecting the measured range such as the effectof earth tides on station position and delays induced by timing systems, as these must be taken into accountduring the development of the LLR analysis software. HartRAO is collocated with other fundamental spacegeodetic techniques which makes it a true fiducial geodetic site in the southern hemisphere and a central pointfor further development of space-based techniques in Africa. Furthermore, the new LLR will complement theexisting techniques by providing new niche areas of research both in Africa and internationally.