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The WBSCAT Polarimetric Synthetic Aperture Scatterometer for Retrieval of In-Situ Time-Series of Snow Structure
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  • Charles Werner,
  • Othmar Frey,
  • Urs Wegmüller,
  • Andreas Wiesmann,
  • Martin Suess
Charles Werner
Gamma Remote Sensing AG

Corresponding Author:cw@gamma-rs.ch

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Othmar Frey
Gamma Remote Sensing AG
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Urs Wegmüller
Gamma Remote Sensing AG
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Andreas Wiesmann
Gamma Remote Sensing AG
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Martin Suess
ESA-ESTEC
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Abstract

WBSCAT is a new terrestrial microwave scatterometer supporting polarimetric observations over 1 to 40 GHz. This instrument is being developed for the European Space Agency (ESA) to conduct microwave studies of a wide range of ground covers including snow and ice. This instrument is built upon the heritage of SnowScat , operating over the range of 9.2 to 17.8 GHz, that has been used for generating tomographic time-series of snow pack and is part of the ongoing ESA SnowLab project [2]. WBSCAT, like its predecessor, acquires coherent data and can measure polarimetric scattering matrices, interferometric phase, and coherence. Both instruments will be operated in Winter 2018/2019 in Davos Laret, Switzerland mounted on a 10- meter tower and performing multiple daily observations of the snow pack. Either instrument can be attached to a 2.2-meter linear scanner inclined at 45-degrees permitting tomographic snow profiling [1]. The WBSCAT instrument uses radial-scan aperture synthesis to acquire independent observations of the scattering volume and also to restrict the field of view to the undisturbed test site, despite wide antenna beamwidths at low frequencies. The 6 horn antennas, with overlapping frequency ranges of 1 to 6, 2 to 18, and 10 to 40 GHz, are mounted approximately 60 cm radially from the rotation axis of the pan/tilt scanner. The antennas can be scanned between +35 and -45 degrees in elevation and +/- 90 degrees in azimuth, creating a synthetic aperture. The aperture dimensions are mostly determined by the antenna pattern, but at low frequencies, the antenna beamwidth exceeds 90 degrees. Aperture synthesis substantially increases the number of looks for improved radiometric resolution and is a novel approach for ground-based microwave scatterometry. Combining ranging information along with WBSCAT aperture synthesis perpendicular to the line of sight, has the potential for direct 3D imaging of the snow pack.