—This paper presents a detailed characterization of5 sea/ocean clutter returns at X-band, imaged by TerraSAR-X6 (TSX) mission from the radiometric, statistical, and polarimet-7 ric standpoints. Different TSX data takes, covering the typical8 spaceborne incidence angle region (20◦ –45◦ ), are analyzed: dual-9 polarized and experimental quad-polarized (quad-pol) data have10 been used. The thermal noise of the receiver for quad-pol data11 turns out to be an important limitation in the sea characterization12 from TSX, particularly at high incidence angles (above 36◦ ), where13 low signal-to-noise ratios (SNRs) can impair the proper data14 distribution fitting and the polarimetric backscattering descrip-15 tion. Statistical analysis shows large deviation from Gaussianity,16 indicating presence of texture, mainly in the small incidence region17 (20◦ –36◦ ), with favorable SNR conditions. The different polari-18 metric features revealed contribution of nonpolarized scattering...