microwaves from ice?

ith

I think it works on the idea that microwaves go through ice without too much trouble. The soil below radiates microwaves because it is above absolute zero.

You can also measure the thickness with an AC signal down in the audio band. Soil generally conducts. Ice generally doesn't.

google:

Microwave Radiometer

works on thermal noise from the ice.

requires a very sensitive wide dynamic range receiver and careful antenna design

Steve Roberts

I was trying to remember how it works, and it hit me after some lunch.

The usual suspect is a "Dicke Switch" , it has a horn aimed outside the aircraft, and then a waveguide relay switches a sensitive log amp detector between the ice noise and a known resistive source at a known temperature , or a calibrated noise diode.

Hope that helps,

Steve Roberts