f Modelling of an alpin glacier from ground penetrating radar sounding

In order to explain and interprete the received signal from radar sounding of a temperate glacier, we propose an electromagnetic modelleng of a multilayered medium. The experimental site is the Mont-de-Lans glaceer in the french Alps, previously studied by drilling and seismic experiments . Numerous radar profiles have been collected on the glaceer witli two Ground Penetrating Radar instruments . The one is a discharge radar with a single antenna for transmission and reception; when the antenna is laid at the interface between free space and ground, the central frequency of the generated pulse is at about 7 MHz . The received signal contains rather long oscillating wave-trains and is processed by deconvolution techniques. The other radar uses two resistively loaded dipole antennas, and the phase of the transmitted signal is modulated by codeel sequences; a compression of the received echoes is performed by applying the matched filter . If using complementary codes of 100 ns elementary step duration to modulate the phase of a 40 MHz carrier frequency, a range-resolution of about 8 meters in ice is obtained .