AVTIS has two operational modes to see through the weather: active radar and passive radiometer. In the active radar mode, AVTIS measures the distance to the volcano surface, using a 94GHz frequency modulated continuous wave (FMCW) millimetre wave radar. In passive radiometric mode, the instrument records naturally emitted and reflected radiation at the same frequency to construct an image of the surface brightness temperature.



The instrument is lightweight and portable, so that it can easily be deployed at multiple viewpoints around the volcano and build up a 3D thermospatial model of the dome.