Automatic Determination of the SLR Reference Point at Côte d’Azur Multi-Technique Geodetic Observatory

Abstract The Satellite Laser Ranging (SLR) station known as GRSM-7845 in the International Laser Ranging Service (ILRS) is hosted by the Observatoire de la Côte d’Azur (OCA) located in Caussols, France. Its reference point is the intersection of the telescope axes, which is supposed to be static. Measuring devices and a data processing chain were set up to automatically determine this point, more quickly and accurately than traditional local survey. In order to use an indirect approach (circular fitting), circular and motorized prisms were fixed on the station to be always visible during the telescope rotation. A software package was developed to control the telescope, the dome and the total station motions for fully automatic measurements. In addition to providing an easy determination of the cross-axis for local ties, this system will allow to study the potential motion of the telescope’s axes intersection throughout the year.