Analysis of Grazing GNSS Reflections Observed at the Zeppelin Mountain Station, Spitsbergen

A reflectometry station has been set up in 2013 near Ny-angstrom lesund, Svalbard, at 78.9082 degrees N, 11.9031 degrees E. The main goal of the setup is to resolve the spatial and temporal variations in snow and ice cover, based on reflection power observations at grazing elevations. In this study, we develop a method to map the recorded signal power to the main reflection contributions while also discussing the spatial characteristics of the observations. A spectral analysis resolving differential Doppler between direct and reflected signals is presented to identify reflection contributions for a complete year (2014). Strong water reflections are identified with power ratios higher than 70dB/Hz and constant Doppler shifts of 0.5-0.6Hz for all elevations. Contributions with ratios higher than 40dB/Hz can be related to specular land or glacier reflections, for which Doppler shift usually increases with the elevation angle and the distance between reflection point and receiver. Reflections nearby, around 3-5km, show differential Doppler of 0.4-0.5Hz, while for reflections farther than 16km away, Doppler shift is usually larger than 0.8Hz. Azimuth variations cause cross-track drift of up to 4 degrees during the observation year. Topography-induced shadowing of very low lying satellites limits the extent of the monitoring area. However, the amount of satellites tracked daily, up to 30, allows the reflectometry station to constantly record reflections over areas with thick snow cover and glaciers. This offers the possibility to compare the derived reflected power with local meteorological data to resolve snow and ice variations on the area.