Impact of terrestrial reference frame on the SLR validation results of GNSS and LEO orbits

The Satellite Laser Ranging (SLR) technique is used to independently validate the microwave-based satellite orbit products. In the so-called SLR validation, the orbit quality is assessed based on the analysis of the SLR residuals, which are the discrepancies between the direct SLR range measurements and the station-satellite vector calculated based on the SLR station positions and the evaluated orbits in Earth-fixed reference frame. Therefore the results of SLR validation are strongly related to the SLR station coordinates. In 2022, the new realization of the International Terrestrial Reference Frame – ITRF2020 – has been released, which considers a few innovations, mainly, an extended model of post-seismic deformations, and the seasonal station coordinate variations in form of annual and semi-annual terms.  In this study, we investigate the impact of recent advancements in ITRF into the SLR-based orbit validation of LEO and GNSS satellites.      

We perform the SLR validation of LEO orbit (Swarm-ABC, Sentinel-3A/B, Jason-3) products provided by European Space Agency (ESA) Copernicus Service and Technical University of Graz for one year. Also, we validate Galileo and BeiDou-3 orbit products delivered by ESA and Center for Orbit Determination in Europe in 2023. 

We incorporate the latest ITRF2020 realization into the SLR validation processing, contrasting the outcomes with solutions that involve the previous ITRF2014 release to illustrate the impact of TRF aging on validation results. Additionally, we examine the influence of including seasonal station motions on SLR validation outcomes. Furthermore, a comparison is made between SLR validation results when utilizing the most recent alternative TRF realizations, namely DTRF2020 and JTRF2020. We discuss the dependency of residuals on different measurement conditions, such as elevation angle and azimuth angle, and their time variability.