In a UHF passive RFID system, a reader transmits an unmodulated continuous wave (CW) to tags, which not only provides energy to tags but also serves as the carrier of tag backscatter signals.
The deflection of the signals in this backscatter gives a picture of how particular snow conditions might be changing the way the satellite's radar is returned.
The amount of X-ray radiation you're exposed to in a backscatter scan is extremely low, a tiny fraction of the amount you're about to be exposed to by flying on a plane.