Doppler Ambiguities Masking for Altimeter Waveforms: a Model Based Approach

Delay/Doppler processing for radar altimeters allows to improve the along-track resolution, but it can be affected by Doppler ambiguities depending on the design of the instrument. If not accounted for, Doppler ambiguities can cause a distortion of the multilooked waveforms and a loss of accuracy in retrieved geophysical parameters. This paper presents a waveform model based approach to define a Doppler ambiguity mask to filter out the samples affected by the ambiguous returns before multilooking, assuming a uniform rough scattering surface. The effectiveness of the proposed method for Doppler ambiguities masking has been verified on Sentinel-6 simulated data and on in-orbit data from CryoSat SARin acquisitions over ocean.