An analytical closed-form model is derived for the average power echo
received by a bistatic altimeter from an oceanic surface at a frequenc
y high enough for the Kirchhoff scattering mechanism to be dominant ov
er the Bragg resonance one. The asymmetric behavior of the sea waves i
s taken into account, modeling the surface height as a non-Gaussian di
stributed random process and an explicit expression of the so-called '
'electromagnetic bias'' is obtained as a function of the skewness coef
ficient of the distribution, Results obtained applying such model to a
monostatic geometry are shown to be in good agreement with those repo
rted in literature as well as with those obtained by numerical simulat
ions. It is also shown that, letting the ''non-Gaussianity'' term tend
to zero, our model correctly reduces to the well-known Brown model fo
r Gaussian surfaces. This work has been conceived in the frame of the
feasibility study of a bistatic remote sensing system, consisting of a
constellation of satellites flying at the same altitude with an opera
ting geometry such that the incidence and scattering angles are equal.