Long Term Stability of the SLR and VLBI Geodetic Networks

The International Laser Ranging Service (Carabajal et al. AGU2024) includes a number of multi-technique Core Sites which can be used to inter-compare different instruments and space technologies. Core stations which have each been occupied by more than one SLR system, as well as co-located VLBI systems provide a robust basis for monitoring advances in instrument development. The vertical resolution of SLR and VLBI systems has been established by Altamimi et al, AGU2024, who show scale agreement at the 1 mm level. The vertical agreement between SLR and VLBI systems at McDonald Geodetic Observatory, Wettzell Geodetic Observatory and the Matera Center for Space Geodesy is presented. The heights of these stations are seen to show no significant motion over periods which can extend for over 30 years. This stable behavior allows the combination of the strength of independent space techniques in a rigorous definition of the Reference Frame.