The more forcefully lava rises from the Earth's interior toward the surface, the more gases are released. Carbon and sulfur compounds are good indicators of current activity in a volcanic field. In particular, the ratio of carbon dioxide to sulfur dioxide provides insight into what is happening beneath the Earth's surface.

Until now, these measurements had to be taken from ground level. The drawback is that the gases measured there do not originate solely from volcanic activity but are also emitted by surrounding vegetation and soil.

To minimize these background signals, drones are now being used to fly above the gas clouds. "This is more precise and safer," says Achim Lilienthal, deputy director of the TUM MIRMI Robotics Institute and head of the Chair of Perception for Intelligent Systems at the TUM School of Computation, Information, and Technology.

Autonomous measurement of gases over a volcanic field

As part of the DFG research project "Measurement Technology on Flying Platforms," his research team has developed a system capable of determining gas concentrations over an active volcanic field with high precision. TUM researcher Marius Schaab deployed the system autonomously for the first time on the Aeolian island of Vulcano, off the coast of Sicily.

Schaab mounted a laser on a small cart that automatically locates an airborne drone and aligns itself with a reflector on the drone. The reflected beam is slightly weakened as it passes through the gas cloud because it is absorbed by the gas being measured—in this case, carbon dioxide.