DETERMINATION OF THE ICE DIELECTRIC PERMITTIVITY USING THE DATA OF THE TEST IN ANTARCTICA OF THE GROUND-PENETRATING RADAR FOR MARS98 MISSION

A ground-penetrating radar will be integrated inside the guiderope bal last of the Mars'98 balloon mission, A prototype of this impulse syste m working in the 5-15 MHz band was tested close to Dumont d'Urville, t he French Antarctic Station, in February 1993, We obtained a large set of profiles in cold ice with a glacier thickness from 200 to about 90 0 m, For each depth, the measured echoes are very clear with a good si gnal-to-noise ratio (SNR). In this paper, nle firstly describe the per formances of the radar and we study the electromagnetic propagation in the Antarctica glacier, This knowledge allows us to use the frequency wavenumber migration to focus the signal, to increase the SNR and to rebuild an image of the subsurface. The migration process gives a good estimation of the real part of the permittivity (i.e., the velocity), The fact that the signal comes from different depths is used to measu re the imaginary part of the permittivity which defines the ice attenu ation. The spectral analysis gives its frequency dependence.