Scientists regularly visit the volcanoes to make all kinds of scientific observations using sophisticated instruments. However a pair of eyes is often a very useful tool. By making visual observations volcanologists can note things such as the amount of steam coming out of the ground at a particular spot, any rockfalls, changes in areas of warm ground, and the development of new fumaroles and hot springs, all of which may indicate changes in the state of the volcano.
Often it is not possible for a scientist to visit a volcano every day so we now use remotely operated cameras to supplement those observations. Our remote cameras are a mixture of standard digital cameras and newer 'netcams' - digital cameras that are specifically designed for remote operation. The controlling computer asks them to take a photo at regular intervals and downloads the file to our data centres and made available to the website.
Several of the cameras are some distance from the volcano, based at locations where we have power and communications. Some of the cameras in remote locations such as White Island are solar powered. At White Island the pictures are telemetered 50 km to Whakatane using spread spectrum radios where they are stored on the acquisition server. The images are then transferred to our data centres and onto the website across internet data links. Our newest cameras are infrared-capable, allowing pictures to be taken at night when there is enough ambient light such as from a full moon. During the course of an eruption the download rate from the cameras can be increased to capture the eruption sequence in more detail.