Study of multi-polarization C-band backscatter signatures for Arctic sea ice mapping with future satellite SAR

The Advanced Synthetic Aperture Radar (ASAR) is scheduled for launch on the ENVISAT satellite in 2001. ASAR will be operated at C band with multiple polarizations and multiple incidence angles. To evaluate the use of future ASAR data for Arctic sea ice mapping, we carry out a study of multiple polarization C-band SAR signatures of various sea ice types. We present polarimetric SAR data acquired over sea ice acquired by the Jet Propulsion Laboratory (JPL) polarimetric AIRSAR system on the NASA DC-8 aircraft over sea ice regions in the Beaufort Sea and the Bering Sea. We use a physical sea ice model to obtain and study polarimetric scattering signatures of sea ice under various conditions. We also compare sea ice signatures with backscatter of ocean surface at different wind speeds using an empirical C-band ocean wind geophysical model function. We present backscatter signatures for ENVISAT ASAR single polarization modes and alternating polarization modes over all swaths. Me find that different polarization combinations in various ENVISAT ASAR image modes at different incidence angle ranges need to be selected to obtain more accurate or more robust results for sea ice mapping. In the wide swath mode, ENVISAT ASAR polarization can be chosen to measure either horizontal or vertical backscatter exclusively. For light wind conditions near a sea ice edge, horizontal backscatter is better to distinguish between first year ice (excluding young ice) and open ocean surface at large incidence angles. For high winds, vertical back-scatter is better in identifying most sea ice types (except multi-year ice at large incidence angles) from open water over a large range of incidence angles. We also investigate diurnal effects to determine the impact on sea ice backscatter acquired at different times of the day. Results show that diurnal effects on first year ice are significant so that SAR data collected over sun-synchronous ascending orbits and descending orbits in daytimes and nighttimes need to be analyzed separately to obtain consistent sea ice mapping results. This study also provides useful information for the application of the future RADARSAT-2 multi polarization SAR to sea ice mapping.