Brightness temperature spatial correlations in SMOS antenna

The European Space Agency mission Soil Moisture and Ocean Salinity (SMOS) is devoted, since its launch in 2009, to provide global soil moisture and sea surface salinity values. SMOS uses an L band 2-D interferometric radiometer by aperture synthesis to obtain polarimetric brightness temperature images. This work is devoted to compute the spatial correlations in the measured antenna brightness temperature. Those correlations can be characterized in terms of effective point spread functions (PSFs). Thus, the PSFs for SMOS are also computed for each point of the antenna. Departing from SMOS data, it is found that two-point correlations, as well as point spread functions, can be assumed as translational invariants. Therefore, PSFs can be described in terms of a convolution kernel. Although computing two-point correlation needs about one month of data, the PSF convolution kernel can be computed using a single orbit. This fact, allows us to use it as a metric to assess the effect of changes in processing procedures or calibration methods.