Abstract's details

Inter-pulse complex coherency of Sentinel-6, Sentinel-3, and CryoSat2 radar altimeter pulse echoes backscattered from the ocean surface

Walter Smith (NOAA Lab for Satellite Altimetry, United States)

Event: 2022 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Measurement and Retracking

Presentation type: Type Oral

Serial correlation in sequences of radar pulse echoes backscattered from the ocean surface is an important factor in the design of satellite altimeters and in the exploitation of their measurements. Previous investigations considered serial correlation in the random fluctuations in echo power called speckle noise [Egido and Smith 2018]. This study takes a new and different approach, examining the complex degree of coherence. If ocean echoes behave statistically as expected of backscatter from a homogeneously very rough surface, then the squared magnitude of this complex degree of coherence should describe the correlation in speckle noise.
The classical Berger-Brown model for the expected power in ocean pulse echoes treats the sea surface as frozen and ignores Doppler effects. However, Doppler shifts produced by the motions of the satellite and the sea surface affect the phase of the complex coherence. Therefore, this study extends the Berger-Brown model to explicitly account for Doppler and sea surface motion [Buchhaupt et al 2020], and obtains a more complete treatment of inter-pulse coherency than the classical Berger-Walsh decorrelation estimated with the Van Cittert-Zernike model.
Level-1A data from Sentinel-6, Sentinel-3, and CryoSat2 are processed to obtain empirical estimates of the two-dimensional (fast and slow time dimensions, corresponding to range and inter-pulse time lag) complex degree of coherence, and, independently, the speckle noise correlation. These compare well with the theory as extended in this study. This approach may elucidate the role that ocean surface motion plays in decorrelation of echoes, broadening of Doppler bandwidth, and limiting the precision and accuracy of derived geophysical parameters such as wave height.


Oral presentation show times:

Room Start Date End Date
Sala Grande Tue, Nov 01 2022,09:20 Tue, Nov 01 2022,09:35
Walter Smith
NOAA Lab for Satellite Altimetry
United States