Polarimetric Portraits

Abstract

 "Fully polarimetric" re: electromagnetic measuring systems has conflicting meanings; to disambiguate, "polarimetric portraits" is proposed  A physical optics-based calculation proves the equivalence of polarimetric portraits from dual-and quadrature-polarized radars  GPS/GNSS reflectometry data are sufficient to support polarimetric portraits, enabling new science opportunities

The first polarimetric GNSS-Reflectometer instrument in space improves the SMAP mission’s sensitivity over densely vegetated areas

“…Our approach is tested by performing SM retrievals using the radiometer T B and the T B enhanced with SMAP-Reflectometer data and then comparing them to ground stations from core validation sites (CVS) 23 . This contribution not only returns some of the original SMAP radar capability to contribute to the mission's science products but also demonstrates the scientific value of SMAP-Reflectometer as the first fully polarimetric GNSS-R instrument in space, establishing SMAP as the first fully polarimetric GNSS-R mission 24 .…”

“…The SMAP-Reflectometer unconventionally measures, at linear polarizations (H and V), a signal transmitted at right-hand circular polarization (RHCP) and then scattered from the Earth's surface at a mix of polarization, depending on the scattering surface itself. This is known in the SAR field as hybrid compact polarimetry (HCP) 4,[14][15][16][17][18] , but for the specific case of reflectometry, this is a full polarimetric GNSS reflectometer 19,24 . Hence, SMAP-R is the first-ever full-polarimetric GNSS reflectometer in space, as it is able to receive the full polarimetric portrait of the scene 24 .…”

“…This is known in the SAR field as hybrid compact polarimetry (HCP) 4,[14][15][16][17][18] , but for the specific case of reflectometry, this is a full polarimetric GNSS reflectometer 19,24 . Hence, SMAP-R is the first-ever full-polarimetric GNSS reflectometer in space, as it is able to receive the full polarimetric portrait of the scene 24 . It offers the unique capability to retrieve the Stokes parameters of the reflected wave, giving an unprecedented view of the Earth.…”

Radar Polarimetry: Classical Versus Quad-Pol Methodologies

“…In the special case of a circularly-polarized transmission Stokes vector 1 driving the Mueller matrix, the output Stokes vector is the polarimetric portrait [13] of the observed scene, exactly the result desired by users. This result is reached by a well-defined objective closed-form methodology founded on well-established classical physical optics principles.…”

“…For an active system, the observed field's polarization properties depend on the polarization of the transmitted field [12]. When the objective is to capture a scene's polarimetric portrait [13], the transmitted field must be balanced so that all linearly polarized backscatter constituents have equal opportunity to shine. Circularly polarized transmissions from a radar (or a navigation satellite) satisfy that requirement with only one transmitted polarization.…”