Integrated Multi-Technique Precise Orbit Determination Using GNSS, DORIS and SLR: A Real-Data-Based Assessment for Future Co-location in Space Missions

Future ‘space-tie’ satellite missions such as Genesis aim at co-locating multiple space-geodetic techniques on a single satellite platform to improve the consistency and long-term stability of the Terrestrial Reference Frame (TRF). However, quantifying the benefits of such satellite-based co-location requires not only advanced simulation capabilities, but also a robust validation of real observation data using consistent multi-technique processing strategies. Already today, missions such as the Sentinel satellites provide an opportunity to realise satellite-based co-location by carrying multiple space-geodetic observation techniques onboard.

To date, most multi-technique Precise Orbit Determination (POD) approaches rely on orbit determination approaches in which the TRF is fixed and, in the case of Global Navigation Satellite Systems (GNSS) Low Earth Orbit (LEO) POD, GNSS constellation orbits and clocks are typically held fixed as well. Consequently, cross-technique interactions and their impact on GNSS constellation orbits and clocks, LEO orbits, Earth Rotation Parameters (ERPs), and the TRF have so far not been comprehensively assessed for all space-geodetic techniques. Investigating these effects using real observations is therefore a crucial step that can already be performed prior to Genesis.

In this study, we investigate an integrated multi-technique POD approach using real GNSS, Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and Satellite Laser Ranging (SLR) tracking data. The analysis covers the multi-technique LEO satellites Sentinel-3A, Sentinel-3B, and Sentinel-6A (MF), together with the GPS and Galileo constellations over a two-year period. Using GFZ’s in-house software EPOS-OC, LEO and GNSS constellation orbits and clocks, the TRF, and ERPs are estimated simultaneously within a single adjustment, fully consistent with respect to dynamic and geometric modelling.

A stepwise integration is performed, starting from single-technique LEO POD solutions and proceeding to the integration into a combined GNSS constellation solution using GNSS observations only. DORIS and SLR observations are incrementally added to assess their impact on LEO orbits, GNSS constellation orbits and clocks, ERPs, and ground station coordinates.

The results provide a real-data-driven assessment of integrated multi-technique POD for satellite-based co-location and form a basis for subsequent Genesis end-to-end simulation studies and future Genesis real-data processing.