Radioglaciology is the study of glaciers and ice sheets using radar. It employs a geophysical method similar to ground-penetrating radar that operates at frequencies in the MF, HF and VHF portions of the radio spectrum. Radioglaciology is sometimes referred to as "ice-penetrating radar" or "radio-echo sounding".
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Glaciers are well suited to investigation by radar because the imaginary part of the permittivity of ice is small relative to its real part; this ratio is called the loss tangent. The conductivity of ice is small at radio frequencies, so its dielectric absorption is also small.
Principle
The primary goal of many radioglaciological surveys is to measure the thickness of a body of ice, which is an important boundary condition for ice-flow models. Ice thicknesses greater than 4 km have been measured in East Antarctica. Internal reflections have also been detected in many alpine glaciers and all modern ice sheets. These layers represent the internal stratigraphy and can also be used to constrain ice-flow models. The shapes of these internal reflections generally follow the bedrock topography and they are often assumed to be isochronous. Disturbances in these reflections that are unrelated to bedrock topography can be used to understand past ice flow, for example the anticlines arising from the Raymond Effect.
The cause of the observed internal reflections partly depends on the frequency of the radar system used to detect them. There are three primary types of reflections:
Ice-penetrating radar systems, particularly the antennae, are often homemade systems made of commercially available components. However, commercial ground-penetrating radar systems are sometimes used.
Planetary exploration
There are currently two ice-penetrating radars orbiting Mars: MARSIS and SHARAD. An ice-penetrating radar system is planned for the 2022 Jupiter Icy Moons Orbiter, and such systems were also proposed for two orbiters that were part of the cancelled Europa Jupiter System Mission.