Reflected GPS L1/L2 Observations used for Sea Ice Remote Sensing and Altimetry

GPS signals are reflected from the ocean and sea ice surface. The reflections can be recorded in a costal setup. The GPS transmitter on the satellite and the GPS receiver on the coast form a bistatic radar. A large number of reflections can be detected with a small passive device over a long period. Diffuse and coherent reflection emerge. In a collaboration with ESA and IEEC a Sea Ice campaign was conducted. In the winter period 2008/2009 an experiment was set up on a cliff above Disko Bay (69.27°N, 53.54°W). At the experimental site two independent GNSS-R equipments were deployed: the GORS receiver (GFZ, JAVAD JNSS), and the GOLD-RTR receiver (IEEC). The GOLD-RTR setup recorded reflected waveforms with different polarisations. Polarimetric observations are used to characterize the ice type. The GORS setup, on the other hand, uses reflected C/A and L2C signals in the L1 and L2 band for interferometry. Those signals are recorded for both frequencies at a sampling rate of 200 Hz autonomously. Daily recurring GPS reflections from upto 50 satellites were recorded in the GORS setup. The reflections covered an area of 40 km^2. Phase coherence for the interferometric observations is determined. An increase in coherence is detected for the period of sea ice formation in January. For this period, observations are used for altimetry. The comparison with the arctic tide model (AODTM-5) shows an agreement of altimetric results with semidiurnal tides. Sea surface height (WGS84) derived from L1 and L2 observations and validated using the tide model