  We measure the coherent scattering of low-intensity, near-resonant light by a
cloud of laser-cooled two-level rubidium atoms with a size comparable to the
wavelength of light. We isolate a two-level atomic structure by applying a 300G
magnetic field. We measure both the temporal and the steady-state coherent
optical response of the cloud for various detunings of the laser and for atom
numbers ranging from 5 to 100. We compare our results to a microscopic
coupled-dipole model and to a multi-mode, paraxial Maxwell-Bloch model. In the
low-intensity regime, both models are in excellent agreement, thus validating
the Maxwell-Bloch model. Comparing to the data, the models are found in very
good agreement for relatively low densities ($n/k^3\lesssim 0.1$), while
significant deviations start to occur at higher density. This disagreement
indicates that light scattering in dense, cold atomic ensembles is still not
quantitatively understood, even in pristine experimental conditions.
