Figure 6. 400-MHz profile of the metal
utilidor tunnel along line DE in Figure 5.
The distortions in the diffractions are
caused by uneven antenna towing speed.
The time delay to the utilidor roof and the
diffraction itself correspond to a dielectric
constant of 1.57 and a snow density of
about 0.34 g/cm3.
known. The distortions in the diffractions are
Old Clean Air Facility (OCAF)
caused by uneven towing speed. The more uni-
This facility has been abandoned and is known
form left limb of the utilidor diffraction can be
to be under several meters of snow; our purpose
matched with a theoretical curve generated with a
here was to find it. A 100-m survey line (line XZ in
refractive index nm = 1.26 (ε = 1.57), which is close
Fig. 5) that apparently traversed the roof is shown
to the values (1.30, 1.69) corresponding to the ve-
in Figure 7, along with its migration. The data
locity arrived at using the utilidor depth and time
were horizontally filtered and compressed suffi-
delay. These values correspond to snow density of
ciently to allow the maximum migration aperture
0.340.37 g/cm3 (Cumming 1952) and are slightly
(127 scans) permitted by the software to cover an
less than other values obtained at the South Pole
entire diffraction. All the diffractions fit a model
and discussed below.
hyperbola generated by a migration velocity cor-
7
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