Estimates of Faraday rotation with passive microwave polarimetry for microwave remote sensing of earth surfaces

A technique based on microwave passive polarimetry for the estimates of ion ospheric Faraday rotation for microwave remote sensing of Earth surfaces is described. Under the assumption of azimuth symmetry for the surfaces under investigation, it is possible to estimate the ionospheric Faraday rotation from the third Stokes parameter of microwave radiation. An error analysis shows that the Faraday rotation can be estimated with an accuracy of better than 10 with a space-based L-Band system, and the residual correction erro rs of linearly polarized brightness temperatures can be less than 0.1 K. it is suggested that the estimated Faraday rotation angle can be further util ized to derive the ionospheric total electron content (TEC) with an accurac y of about 1 TECU = 10(16) electrons-m(-2), which will yield 1 mm accuracy for the estimate of an ionospheric differential delay at Ku-band. Therefore , this technique can potentially provide accurate estimates of ionospheric Faraday rotation, TEC, and differential path delay far applications includi ng microwave radiometry and scatterometry of ocean salinity and soil moistu re as well as satellite altimetry of sea surface height. A conceptual desig n applicable to real aperture and aperture synthesis radiometers is describ ed for the measurements of the third Stokes parameter.