Mt Ruapehu will soon be one of a handful of volcanoes around the world watched around the clock by a ``radar eye'' aimed at saving lives.
The new high speed Doppler radar system will mean volcanologists from Massey University and the University of Hamburg in Germany will be able to record every explosive burst from the active volcano.
It is the first monitoring system of its kind in the country and one of only a few in the world.
The instrument, installed over the past month, has a 1.2-metre diameter radar dish that focuses its narrow beam precisely over the crater lake.
The experimental radar would be an important addition to the existing range of warning instruments installed at Mt Ruapehu, Volcanic Risk Solutions director Shane Cronin said.
``Once this instrument is calibrated, it can be used for the regular monitoring and warning activities carried out by the Department of Conservation, GeoNet and GNS Science.''
The radar should directly detect the volcanic particles thrown out of the crater lake, often at several hundred metres per second. Vulcanologist Gert Lube said the radar penetrated through darkness, clouds and mist and could give reliable and rapid eruption warnings even the summit could not be seen.
Last week, GNS Science upgraded the aviation alert to yellow following a sustained rise in the temperature of the crater lake.
Mt Ruapehu last erupted in 2007.