Altimetry waveforms inversion over Antarctica

Denis BLUMSTEIN (CNES, France)


Fernando Niño (CTOH / LEGOS, France); Frederique Remy (LEGOS, France); Etienne Berthier (LEGOS, France); Nathalie Steunou (CNES, France); Nicolas Picot (CNES, France)

Event: 2014 SARAL/AltiKa workshop

Session: Land ice and Sea ice

Presentation type: Type Poster

Measurement provided by radar altimeters is much richer than the few parameters traditionnally used in the applications (mainly ground altitudeand backscatter). Indeed, the whole history of the radar return is available, this is called radar waveforms.

By a careful analysis of sequences of consecutive waveforms, it is possible to retrieve crucial information about the nature of the soil backscatter as well as details about the topography at a resolution much better than the footprint
of the altimeter. In particular the shape of the waveforms allows us to discriminate the power return by the surface from the return by the subsurface.
These parameters can then be used to provide information about geophysical characteristics of the terrain (snow grain size, etc) and its temporal evolution through the analysis of the penetration of the radar wave in the snow.

This poster will describe the technics we have developped to perform waveforms inversions through the use of an accurate waveform simulation model that is able to handle the Envisat mission (Ku band, 13.6 GHz) as well as the
new AltiKa mission from CNES/ISRO that provides measurements in Ka band (35.75 GHz) on the same orbit.

We will also show how we can use good high resolution DEM, e.g. from the Spirit projet (CNES/SPOT IMAGE), in order to improve the retrievals in regions which are notoriously difficult for radar altimetry (near the coast).
Finally we will show results obtained on a few places of the Antarctica icesheet.