CoAuthors

Christian Schwatke (Deutsches Geodätisches Forschungsinstitut (DGFI-TUM), Germany); Marcello Passaro (Deutsches Geodätisches Forschungsinstitut (DGFI-TUM), Germany)

A consistent long-term sea level data record is a fundamental requirement for many applications, especially for climate studies. However, combining satellite altimetry missions with different instruments and different sampling capabilities requires a careful pre-processing and calibration of all altimeter systems. This can be done by means of a global cross-calibration of all missions. In addition, this technique is able to provide information on the quality of single missions and to reveal e.g. instrument drifts or differences in the center-of-origin realization of satellite’s orbits.
The project conducts inter-calibrations of contemporaneous altimeter systems based on extended crossover analyses on a global scale. For the period from 1992 up to the present, the study performs calibration and validation of all available altimeter missions. Within the past four years, the focus lay on the new missions Jason-3 and Sentinel-3. However, all other missions were also included: past missions such as TOPEX as well as ice-dedicated missions such as Cryosat-2.
The project uses an extended multi-mission crossover analysis approach in order to assess the performance of each mission. The cross-calibration is realized globally by adjusting an extremely large set of single- and dual-satellite sea surface height (SSH) crossover differences. Iterative variance component estimation is applied to obtain an objective relative weighting between altimeter systems with different performance. The analysis yields time series of radial errors of each mission and can be used to derive inter-mission biases, to identify potential altimeter drifts, as well as to extract information on the quality of precise orbit determination (POD) and geophysical corrections.
This contribution summarizes the results of this project from the past 4 years.