Radar altimeter signals in Ku band are known to be affected by penetration and subsurface scattering into snow and ice. The mechanisms for radar-altimeter scattering are still poorly known, and this is a major issue when attempting to measure the surface elevation over ice sheets and sea-ice floes. As a result, the backscattered altimeter signal is a complex combination of energy backscattered from the surface and the subsurface, with contributions that may vary significantly in space and time depending on the density, the temperature, the stratification and the grain size of the snowpack. [Partington et al., 1989; Legresy and Remy, 1998]
With respect to Ku-band, Ka-band radar altimeter is more reliable for providing consistent measurements of the snow surface. Indeed Ka-band waveforms are weakly impacted on their leading edge by volume scattering, because of a penetration depth lower than in Ku-band, which is not well known in theory.
This study aimed at providing some answers about the potential benefits of a dual Ku/Ka band instrument for snow measurements. For that purpose, the first objective was to develop a dedicated numerical simulator, able to generate synthetic Ku/Ka waveforms (accounting for the instrumental configuration of CRISTAL), in both Low Resolution Mode (LRM) and SAR modes, and over different types of snowpack. The second objective was to use the simulator to study radar altimetry over ice sheets and sea ice surfaces, using the CRISTAL dual bands altimeter configuration.
The simulator was developed in synergy between IGE and CLS. IGE provided their expertise in glaciology, along with the Snow Model Radiative Transfer (SMRT) [Picard et al., 2018]. CLS provided their expertise in altimetry, along with its altimetry simulator (named AltiDop).
The technical note written at the and of this task is available here: PMM_Task3_report_TN3_v2