  We present an in-depth characterization of the polarimetric channel of the
Large-Angle Spectrometric COronagraph LASCO-C2 onboard the Solar and
Heliospheric Observatory (SoHO). The polarimetric analysis of the white-light
images makes use of polarized sequences composed of three images obtained
though three polarizers oriented at +60{\deg}, 0{\deg} and -60{\deg},
complemented by a neighboring unpolarized image, and relies on the formalism of
Mueller. The Mueller matrix characterizing the C2 instrument was obtained
through extensive ground-based calibrations of the optical components and
global laboratory tests. Additional critical corrections were derived from
in-flight tests relying prominently on roll sequences and on consistency
criteria, mainly the tangential direction of polarization. Our final results
encompass the characterization of the polarization of the white-light corona,
of its polarized radiance, of the two-dimensional electron density, and of the
K-corona over two solar cycles. They are in excellent agreement with
measurements obtained at several solar eclipses except for slight discrepancies
affecting the innermost part of the C2 field-of-view, probably resulting from
an imperfect removal of the bright diffraction fringe surrounding the occulter.
