Determination of an SLR terrestrial reference frame and Earth Rotation Parameters from SLR observations to altimetry and spherical geodetic satellites

The contribution of the International Laser Ranging Service (ILRS) to the latest International Terrestrial Reference System (ITRS) realizations is based on Satellite Laser Ranging (SLR) observations of just four spherical satellites (LAGEOS-1/2 and Etalon-1/2). Since 2025, one more spherical satellite (LARES-2) is used by the ILRS to determine global geodetic parameters such as coordinates and velocities of globally distributed SLR stations and Earth Rotation Parameters (ERP), namely x- and y-pole coordinates and length of day (LOD). However, SLR observations to eight more spherical satellites (Starlette, Ajisaj, Stella, GFZ-1, WESTPAC, Larets, BLITS, LARES) and several altimetry satellites are available over an overall time span from 1976 with the total number of their SLR observations exceeding the number of SLR observations of the five presently used satellites by a factor of about five. Orbits of these satellites have various altitudes and inclinations and can be determined at the 1-2 centimeter level of accuracy. The long observational time series and the differing orbital characteristics of the satellites lead to an improved SLR observation geometry.

In this study, we investigate the potential of using SLR observations of seven altimetry satellites (TOPEX/Poseidon, Jason-1/-2/-3, Sentinel-3A/-3B/6A) for the determination of global geodetic parameters mentioned above, as compared to using SLR observations of five and 13 spherical satellites and in combination with them.