Radar altimetry has been instrumental in advancing our understanding of Earth's oceans over the past thirty years, facilitating crucial insights into sea level variations, ocean dynamics, and many more. As we commemorate three decades of progress in radar altimetry, the need for a comprehensive and consistent orbit series spanning this period has become increasingly apparent. This presentation introduces an orbit series, based on consistent models and using Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) observations for Precise Orbit Determination (POD).
Our approach begins with an explanation of the adapted methodology used to compute satellite orbits for all DORIS-equipped altimetry missions, from TOPEX/Poseidon to the most recently launched SWOT mission. In order to assess the quality of the orbits, an internal and external quality control is performed. This is followed by an altimetry analysis, with a focus on the analysis of the crossover points and changes in regional sea level variability and trends.
Quality control measures include the internal comparison with post-fit Satellite Laser Ranging (SLR) residuals and orbit comparisons with internally processed consistent reduced dynamic Global Positioning System (GPS) orbits. Subsequently the orbits are also compared with external combined orbit solutions, which are expected to have reduced minimum residual errors. A key aspect of our analysis involves the identification of geographic patterns in the satellite orbits, providing valuable insights into orbit dynamics and how these can be improved on a global scale. This comprehensive validation process serves to enhance confidence in the accuracy and consistency of the generated orbit series.
Finally, we demonstrate the utility of our orbits in global sea level monitoring, showcasing their effectiveness in key quality parameters such as crossover analysis.
In conclusion, this presentation encapsulates an effort to construct a consistent 30-year orbit series for radar altimetry satellites based on DORIS observations only, a unique opportunity for advancing our understanding of Earth's oceans and their dynamic evolution.