  Recently launched high precision Synthetic Aperture Radar (SAR) satellites
such as TerraSAR-X, COSMO-SkyMed, etc. present a high potential for better
observation and characterization of the cryosphere. This study introduces a new
approach using high frequency (X-band) SAR data and an Electromagnetic
Backscattering Model (EBM) to constrain the detailed snowpack model Crocus. A
snowpack EBM based on radiative transfer theory, previously used for C-band
applications, is adapted for the X-band. From measured or simulated snowpack
stratigraphic profiles consisting of snow optical grain radius and density,
this forward model calculates the backscattering coefficient for different
polarimetric channels. The output result is then compared with spaceborne
TerraSAR-X acquisitions to evaluate the forward model. Next, from the EBM, the
adjoint operator is developed and used in a variational analysis scheme in
order to minimize the discrepancies between simulations and SAR observations. A
time series of TerraSAR-X acquisitions and in-situ measurements on the
Argenti\`ere glacier (Mont-Blanc massif, French Alps) are used to evaluate the
EBM and the data assimilation scheme. Results indicate that snow stratigraphic
profiles obtained after the analysis process show a closer agreement with the
measured ones than the initial ones, and therefore demonstrate the high
potential of assimilating SAR data to model of snow evolution.
