  The work which we present takes place within the framework of mission SMOS of
the ESA which will consist to send a radiometer (1.4 GHz) in space. The goal of
the research which we propose is the improvement of the comprehension of the
effects of structure soil and litter. The effects of the litter and
heterogeneities of the ground are probably important but still ignored. Its
effect can be corrected via a simple radiative model. It is thus necessary to
set up an analytical model which would make it possible to correct the effect
of this additional layer. The objective of this article is to present the
analytical models which we retained to correct the effect of the vegetation and
the litter in order to know the emissivity of the bare soil. We developed a
numerical model (with software HFSS) of calculation of the emissivity of
multi-layer systems in order to validate the results of the forward inversion
models. Ranges of permittivity are introduced with the model in order to take
account of the disturbances related to measurement and the variation of the
water content of the layers.
