Delay/Doppler altimeter data processing

The ESA Cryosat-2 mission will mount a de- lay/Doppler radar altimeter (DDA), named SIRAL, for the study of the trends in Earth´s continental and marine ice fields. A DDA has many advantages over a conventional altimeter, retrieving a better resolution in the along track direction as a result of coherent processing of the backscattering energy. This permits the extension of applications to ice sheet monitoring as well as coastal studies, maintaining necessary precision for the open ocean. Operational SIRAL data processing for the Cryosat-2 mission is based on the precise wavenumber domain approach, following the strategy developed and verified for the Cryosat-1 mission [1]. A novel way of processing, supported by the chirp zeta transform (CZT) is here presented. Basically the CZT allows the Doppler beam formation to be directed toward the output surface samples in a single stage, increasing the computational efficiency of the processing at the expense of a slightly lower accuracy. The more precise wavenumber domain approach can be used to validate the method. The SIRAL sensor parameters and simulated scenarios will be taken as models to derive experimental results.