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Radar interferometric phase errors induced by Faraday rotation
  • Simon Zwieback,
  • Franz Meyer
Simon Zwieback
University of Alaska Fairbanks, University of Alaska Fairbanks

Corresponding Author:szwieback@alaska.edu

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Franz Meyer
University of Alaska Fairbanks, University of Alaska Fairbanks
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Ionospheric Faraday rotation distorts satellite radar observations of the Earth's surface. While its impact on radiometric observables is well understood, the errors in repeat-pass interferometric observables and hence in geodetic deformation analysis are largely unknown. Because the Faraday-induced errors cannot rigorously be compensated for in non-quadpol systems, it is imperative to determine their magnitude and nature. Focusing on distributed targets at L-band, we combine theoretical and empirical analyses for a range of land covers using airborne observations with simulated Faraday rotation. We find that the typical deformation error is up to 2 mm in the co-pol channels but may exceed 5 mm for intense solar maxima. The cross-pol channel is more susceptible to severe errors. We identify the leakage of polarimetric phase contributions into the interferometric phase as a dominant error source. The polarimetric scattering characteristics induce a systematic dependence of the Faraday-induced deformation errors on land cover and topography. Also their temporal characteristics, with pronounced seasonal and quasi-decadal variability, predispose these systematic errors to be misinterpreted as deformation. While the relatively small magnitude of 1--2 mm is of limited concern in many applications, the persistence on semi- to multi-annual time scales compels attention when long-term deformation is to be estimated with millimetric accuracy. Phase errors induced by uncompensated Faraday rotation constitute an important and hitherto neglected error in interferometric deformation measurements.
2022Published in IEEE Transactions on Geoscience and Remote Sensing volume 60 on pages 1-11. 10.1109/TGRS.2021.3094996