Exploring space ties between GNSS and SLR in the realization of terrestrial reference system– validation, enhancement and integration

• Applicant: Dr.-Ing. Bingbing Duan
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 568370903

An accurate Terrestrial Reference Frame (TRF) is fundamental for a wide range of metric observations collected by both ground instruments and artificial satellites. Achieving a reference frame that permits 1 mm accuracy and 0.1 mm/year stability over decades remains a challenge (Pearlman et al. 2019a). The latest determination, the International Terrestrial Reference Frame (ITRF2020 and ITRF2020-u2023), still falls short due to systematic technique-specific errors and limitations in geodetic infrastructure. Space ties, which co-locate multiple geodetic techniques on the same satellite, provide a significant advantage over local ties by directly linking geodetic techniques in space. Unlike local ties, space ties help to mitigate the uneven spatial distribution of co-location sites, as a single satellite can be observed by multiple techniques from diverse locations. Additionally, space ties remain stable over time and are unaffected by changes in ground-based geodetic infrastructure. Despite numerous Global Navigation Satellite System (GNSS) and Low Earth Orbiting (LEO) satellites being equipped with both GNSS antennas and Satellite Laser Ranging (SLR) Laser Retroreflector Arrays (LRAs), these space ties are not yet incorporated into ITRF2020, primarily due to the lack of precise pre-flight antenna calibrations and the need for advanced orbit models. This study aims to address these challenges by: (1) Validating space ties between GNSS and SLR for satellites including Galileo, GRACE, GRACE-FO, Jason-2/3, Sentinel-3A/B, Sentinel-6A, and Swarm-A/B/C. (2) Enhancing TRF parameter solutions through advanced orbit macro models and simultaneous GNSS+LEO processing. (3) Integrate space ties into TRF determination by leveraging local ties, space ties, and their combination. Using data from GNSS (including LEO) and SLR (including LAGEOS-1/2) over a 15-year period (2010-2025), this study will assess TRF parameter consistency across different processing scenarios. The outcomes will provide practical insights for the upcoming Genesis mission, scheduled for launch in 2028, and contribute to the next generation ITRF determination.

• DFG Programme: Research Grants
• International Connection: Switzerland
• Co-Investigators: Professor Dr. Urs Hugentobler; Professor Dr. Oliver Montenbruck; Privatdozent Dr. Peter Steigenberger
• Cooperation Partner: Professor Dr.-Ing. Rolf Dach