Combining GNSS and SLR Measurements Using the Space Tie: Effects on Terrestrial Reference Frame Origin and Scale

Abstract:

The reliable and accurate definition of the International Terrestrial Reference Frame (ITRF) is of prominent importance for the current and future development of Earth Sciences, as such a frame provides the basis for all the relevant measurements, both from terrestrial and satellite techniques. As a consequence, a precise and stable ITRF is a fundamental condition required to monitor global phenomena and the complicated interactions existing between the different spheres of the System Earth. In order to compensate for technique-specific weaknesses, four different space-geodetic observing systems are currently exploited for the realization of the ITRF. The connection between the different technique networks is provided by local ties measured at co-located ground sites.

This work addresses the potential of combining two of the currently used techniques, namely theGlobal Navigation Satellite Systems (GNSS) and the Satellite Laser Ranging (SLR), exploiting their space tie. This approach is based on the SLR tracking of GNSS satellites equipped withretroreflector arrays, as it allows determining the spacecraft orbit by means of both the optical and the microwave signals. Time series of SLR observations to GNSS satellites have been combined together with GNSS data from a network of about one hundred IGS permanent stations and SLR observations to the two LAGEOS satellites. The resulting time series have been analysed with theCombination and Analysis of Terrestrial Reference Frames (CATREF) software in order to evaluate their relevance, quality and the accuracy of their associated physical frame parameters, namely the origin and the scale. Finally, the proposed combination allows evaluating the level of agreement between terrestrial ties and space geodesy estimates at co-located sites and may contribute in understanding the reasons of possible tie discrepancies detected in the current realization of the ITRF.