THE SNOWSCAT GROUND-BASED POLARIMETRIC SCATTEROMETER: CALIBRATION AND INITIAL MEASUREMENTS FROM DAVOS SWITZERLAND Charles Werner 1 , Andreas Wiesmann 1 , Tazio Strozzi 1 , Martin Schneebeli 2 , Christian Mätzler (3) (1) Gamma Remote Sensing, Gümligen, Switzerland; http://www.gamma-rs.ch , cw@gamma-rs.ch (2) WSL Institute for Snow and Avalanche Research Davos, Switzerland (3) University of Bern, Institute of Applied Physics, Switzerland The COld REgions Hydrology High-resolution Observatory (CoReH20) Mission proposes a dual frequency radar operating at 9.6 and 17 GHz utilizing VV and VH polarization [1]. By combining X- and Ku-Band with both co- and cross-polarization diversity it is possible to estimate the Snow Water Equivalent of dry snow. To support this proposed mission, ESA has sponsored the development of a ground-based coherent polarimetric scatterometer operating over the 9-18 GHz frequency range. ESA is supporting campaigns to acquire and process data using SnowScat for validation of Snow Water Equivalent (SWE) retrieval algorithms. The SnowScat scatterometer is a fully polarimetric, coherent stepped-frequency CW radar that operates in the range of 9-18 GHz. Both angular and frequency diversity are used to obtain sufficient independent “looks” to reduce speckle noise and thus the uncertainty in the estimate of the radar backscatter 0 . The instrument is mounted on the computer-controlled alt/azimuth 2-axis pan/tilt mount. The instrument is temperature regulated and fully weather sealed for installation in the alpine environment. SnowScat was deployed in late Winter 2009 on an 11m tower in a dedicated campaign at the Weissfluhjoch, Switzerland (Figure 1)[2][3]. Figure 1: Snowscat showing antennas, electronics enclosure, and pan-tilt scanner.