Improved Ionospheric Delay Correction for Satellite Altimetry (IDA)

• Applicants: Dr.-Ing. Denise Dettmering; Professor Dr.-Ing. Michael Schmidt
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 536704090

Sea level is an important indicator of global change. Satellite altimetry has been providing essential measurements of sea level rise for 30 years. In order to derive highly accurate and long-term stable information from the data, the measurements must be corrected to account for ionospheric delay. The aim of this project is to investigate, evaluate, and combine different existing ionospheric corrections for satellite altimetry measurements, with the overall objective of developing an innovative improved ionospheric delay correction that is not only of the best possible quality but also consistent over all surface types (open ocean, coastal and polar areas, inland) and for the entire altimetry era (1992 to present). The project will develop a methodology to derive DORIS-based ionospheric corrections for along-track satellite altimetry. In addition, two different combination approaches will be developed to couple ionospheric data from the altimeter and from the DORIS receiver with GNSS-based model information: (1) a modern machine learning-based method and (2) an innovative analytical solution based on localized B-spline functions. Both methods will be compared with respect to accuracy, long-term stability and efficiency. Based on the developed innovative methods, the project will answer the following research questions: (1) How do the existing ionospheric corrections differ in terms of accuracy and applicability for specific studies (e.g. sea level trend studies, ocean tide estimation)? (2) What is the benefit of using DORIS observations to correct satellite altimetry measurements for ionospheric effects? (3) How can machine learning help to improve ionospheric corrections for satellite altimetry? (4) How can an optimal ionospheric correction for satellite altimetry be derived, and what is its impact on scientific sea level studies, e.g. on global mean sea level trend and ocean tide estimates? The project will focus on algorithm development, validation and first impact assessments. It will therefore only process selected altimetry missions (mainly Jason-3, Envisat, and Sentinel-3A) and only shorter time periods, which will, however, cover all phases of solar activity. This lays the foundation for later processing of the entire 30 years of data available from all satellite altimeter missions. This is planned as a follow-up to the project and the resulting corrections will then be made available for scientific applications.

• DFG Programme: Research Grants