The ground-based radar system we used is a coherent system; it records a time-domain voltage induced in the receiving antennas, and thus preserves both the phase and the amplitude of the echoes. The transmitted pulse is +/- 2000 volts and the center frequency of the mono-pulse depends on the lengths chosen for the antennas, which are resistively loaded dipoles. Typically waveforms are averaged coherently to reduce system and environmental noise and these stacked echoes are band-pass filtered to eliminate system artifacts and further reduce noise. Conversion of two-way travel time to depth takes into account the geometry of the radar system and the higher wave velocities in near-surface snow.
This season we were able to use the phase-sensitive radar system (pRES) on loan from the British Antarctic Survey.