The problem of soil moisture retrieval by means of a bistatic radar system, for the purpose of investigating a candidate bistatic mission, is addressed in this paper. The optimal geometric configuration of measurement in terms of incidence and observation (scattering) directions is identified. Such a configuration should ensure good sensitivity to soil moisture and good spatial coverage. We use a theoretical scattering model to simulate the bistatic scattering coefficient of bare soil for analyzing the sensitivity to soil moisture. The error variance of a linear regression estimator is employed for this purpose. This index is computed as function of elevation and azimuth scattering angles. Results shows that the best performances in terms of soil moisture retrieval can be achieved by complementing the bistatic measurements with the monostatic ones, which are supposed to be available through already operating spaceborne radars. The problem of the feasibility of the bistatic configuration identified through the sensitivity study is also addressed focusing on the duty cycle and the spatial coverage.
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