Testing the Polarization Model for TANSO-FTS on GOSAT Against Clear-Sky Observations of Sun Glint Over the Ocean

A model is developed to relate the polarized signals measured by the thermal and near infrared sensor for carbon observations-Fourier transform spectrometer (TANSO-FTS) on Japan's Greenhouse Gases Observing Satellite to Stokes' vector for radiation leaving the target. The model requires the position and velocity of the satellite, the yaw angle between TANSO-FTS and the satellite bus, the reflectance and phase shift properties of the pointing mirror of TANSO-FTS, and the radiometric calibration coefficients. The accuracy of the polarization model is tested by comparing the degree of polarization observed in clear sky over sun glint on the ocean against the value predicted by Fresnel reflection from a rough sea surface. Observations from April 2009 to December 2011 suggest that the polarization characteristics of TANSO-FTS have remained stable.