Combination of ground- and space-based GNSS observations: GFZ

Combined Orbit Determination of GNSS and LEO

Geodetic observations of Global Navigation Satellite Systems (GNSS) including today GPS, GLONASS, Galileo, and BeiDou have been used for more than 20 years to monitor the Earth system, to realize the International Terrestrial Reference System (ITRS) and to determine the orbital positions of Low Earth Orbiters in space. So far, space-based GNSS observations (tracked onboard LEOs) are not considered for the realization of the ITRS, despite their high quality, the absence of tropospheric delays, and the associate geometrical information provided by the LEO orbit dynamics. Space-based GNSS observations improve geodetic products by reducing correlations between parameters and by reducing systematic biases. The main objective of this project is to evaluate systematically the long-term impact of the combination of ground and space-based GNSS observations on station coordinates, satellite orbits, and the terrestrial reference frame. The DFG-funded project INGE aims to incorporate space-based GNSS observations of as many low Earth orbits as possible. This includes GNSS observations of missions dedicated to the gravity field (e.g., GRACE, GRACE-FO), altimetry (e.g., Jason-2, Jason-3), magnetic field (i.e., Swarm) but also the recently launched European Sentinel satellites and other missions. Consequently, the main output will be a long-term, fully consistent GNSS solution including station coordinates, reference frame parameters (Huang et al., 2021b, 2022a, 2022b), GNSS and LEO satellite orbits (Huang et al. 2021a), and Earth rotation parameters. Within the project we contributed to the GENESIS whitepaper (Delva et al., 2023).

[Translate to English:] Kombination boden- und raumgestützter GNSS-Beobachtungen — Phase center offset (PCO) correction, terrestrial scale and correlation between estimated from GPS ground-only (G), GPS+Galileo ground (G+E), GPS+Swarm (G+L), fully combined solution (G+E+L), colors reflect the fixed PCO information; all solutions without no-net-scale condition (Huang et al., 2021b) *(GFZ)*

References

Huang, W., Männel, B., Brack, A., Ge, M., Schuh, H. (2022a): Estimation of GPS transmitter antenna phase center offsets by integrating space-based GPS observations. - Advances in Space Research, 69, 7, 2682-2696. doi.org/10.1016/j.asr.2022.01.004

Huang, W. (2022b): Enhancing GNSS by integrating Low Earth Orbiters, PhD Thesis, Berlin : Technische Universität, xiv, 133 p. https://doi.org/10.14279/depositonce-15101

Huang, W., Männel, B., Brack, A., Schuh, H. (2021b): Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check. - GPS Solutions, 25, 4. https://doi.org/10.1007/s10291-020-01035-5

Huang, W., Männel, B., Sakic, P., Ge, M., Schuh, H. (2021a): Correction to: Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse ground networks. - Journal of Geodesy, 95, 104. https://doi.org/10.1007/s00190-021-01557-x

Delva, P., Altamimi, Z., Blazquez, A., Blossfeld, M., Böhm, J., Bonnefond, P., Boy, J.-P., Bruinsma, S., Bury, G., Chatzinikos, M., Couhert, A., Courde, C., Dach, R., Dehant, V., Dell’Agnello, S., Elgered, G., Enderle, W., Exertier, P., Glaser, S., Haas, R., Huang, W., Hugentobler, U., Jäggi, A., Karatekin, O., Lemoine, F. G., Le Poncin-Lafitte, C., Lunz, S., Männel, B., Mercier, F., Métivier, L., Meyssignac, B., Müller, J., Nothnagel, A., Perosanz, F., Rietbroek, R., Rothacher, M., Schuh, H., Sert, H., Sosnica, K., Testani, P., Ventura-Traveset, J., Wautelet, G., Zajdel, R. (2023): GENESIS: co-location of geodetic techniques in space. - Earth Planets and Space, 75, 5. https://doi.org/10.1186/s40623-022-01752-w

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