C. Baufays

Synergic inversion technique for active and passive microwave remote sensing of the ocean

A unified approach for combining active and passive microwave measurements for remote sensing applications is described. A synergic inversion technique has been developed and applied to the retrieval of geophysical parameters of the ocean surface and of the atmosphere. It is based on the combination of radiometric and radar measurements at the electromagnetic and cell level and not only on the correction of radar measurements by radiometric measurements, or conversely. Such a combination is performed through a common quantity: the bistatic scattering coefficient of the observed surface. This is used in a direct model to simulate combined measurements from active and passive sensors. It requires a rather complete and accurate calculation of the scattering of microwaves by the rough sea surface. >

Fully and nonfully developed sea models for microwave remote sensing applications

A new statistical description of the ocean surface is proposed and described. Classically it is assumed that the spectrum of the surface vertical displacements depends only on one external, or forcing parameter-the wind speed (or the wind friction velocity); this is, true for fully developed sea states only. In the more general case of nonfully developed sea states, the spectrum should depend as well on internal parameters describing the characteristic features of the surface. Such a representation is discussed in this article for applications to active and passive microwave remote sensing of the oceans.

Sea surface scattering calculations in maritime satellite communications

A method extending the Kirchhoff classical approach for mobile maritime satellite communications is presented. Carrier to specular and carrier to multipath ratios are evaluated from scattering by the rough sea surface calculations using the boundary perturbation method. They are compared with experimental results and with other experimental models. The results illustrate the limited effects of the wind speed and significant wave height, the important dependence on the elevation angle and the very large effects of the ship motions. >

Comparison of microwave signatures for fully and nonfully developed sea models

The boundary perturbation method is applied to a numerical comparison of active and passive microwave signatures for fully developed sea conditions described by a classical sea surface displacement spectrum with one degree of freedom, and for nonfully developed sea conditions described by a new displacement spectrum, with three degrees of freedom. It is shown that altimeters and scatterometers at low incidences are rather sensitive to the sea state development, and in particular to the significant slope, while scatterometers at high incidences and radiometers are much las, except for wave tank conditions.