Abstract:
The lunar laser ranging (LLR) technique is based on the two-way time-of-flight of laser pulses from an earth
station to the retroreflectors that are located on the surface of the moon. We discuss the ranging technique
and contribution of the timing systems and its significance in light of the new LLR station currently under
development by the Hartebeesthoek Radio Astronomy Observatory (HartRAO). Firstly, developing the LLR
station at HartRAO is an initiative that will improve the current geometrical network of the LLR stations
which are presently concentrated in the northern hemisphere. Secondly, data products derived from the
LLR 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 better
understanding the earth–moon system. We highlight factors affecting the measured range such as the effect
of earth tides on station position and delays induced by timing systems, as these must be taken into account
during the development of the LLR analysis software. HartRAO is collocated with other fundamental space
geodetic techniques which makes it a true fiducial geodetic site in the southern hemisphere and a central point
for further development of space-based techniques in Africa. Furthermore, the new LLR will complement the
existing techniques by providing new niche areas of research both in Africa and internationally.
