To help scientists track volcanic events over the long term and predict future eruptions, an international team has designed a low-cost, low-power sulfur dioxide (SO2) camera for permanent deployment on volcanoes around the world. The camera will allow volcanologists to monitor geochemical changes in volcanoes on a continuous basis during daylight hours. Ultraviolet (UV) SO2 cameras have become valuable tools for measuring volcanic emissions since their introduction in the mid-2000s, due to their ability to provide high spatial- and temporal-resolution data sets. However, unlike differential optical absorption spectroscopy (DOAS) instruments, which operate on a continuous basis at numerous open-vent volcanoes worldwide, SO2 cameras have been permanently installed at only a few volcanoes. “Before now, only three volcanoes have had permanent SO2 cameras installed on them,” said University of Sheffield researcher Thomas Wilkes. “Discrete field campaigns have been carried out, and while they can be invaluable for a range of research questions, it is important to be able to measure volcanic activity continuously, since it can vary substantially from minutes to decades to centuries and beyond.” Kilauea lava lake captured at night, with the relatively substantial gaseous emissions clearly visible. Courtesy of Tom Pering. Building and operating an SO2 camera can cost upward of $20,000, which is one reason why permanent installations of these cameras are so scarce. To reduce costs, the researchers used low-cost sensors from Raspberry Pi cameras that were modified to enhance UV sensitivity. The team then constructed a UV-transmissive optical system and mounted it to the sensor. The instrument ultimately uses a sensor that is similar to smartphone camera sensors, Wilkes said. He said that the team modified its sensor to make it sensitive to UV light, enabling SO2 detection. The researchers used a spectrometer to calibrate the camera’s optical depths. The high thermal stability of the spectrometer eliminated the need for a thermoelectric cooler, which decreased the power consumption of the instrument, further lowered costs, and reduced instrument complexity. The power consumption of the new SO2 camera averages 3.75 W — about half of what was needed to power previous systems. The researchers said that low power requirements are especially useful when there is minimal solar power available at a site. The new camera can run on fewer (or smaller) solar panels or batteries than earlier SO2 cameras, reducing the overall cost further. The new design for the camera comes with a price tag of around $5000 — approximately one-fourth of the cost to build previous models. “Wherever possible, we 3D print parts too, to keep costs as low as we can,” Wilkes said. “We also introduce a user-friendly, freely available software for controlling the instrument and processing the acquired data in a robust manner.” The affordability and user-friendliness of the new camera will make it accessible to more volcanologists, who otherwise might not have access to data sets containing accurate gas emission rates. The SO2 camera installation on Kilauea volcano, Hawaii. The gas plume can be faintly seen rising from the crater at the center of the image and drifting to the left. The flank of Moana Loa can be seen in the background. Courtesy of Tom Pering. Wilkes and his team presented two preliminary data sets from volcanoes where the new SO2 camera is now in continuous operation: Lascar, a stratovolcano in Chile; and Kilauea, a shield volcano in Hawaii. The camera has also been installed on the El Reventador volcano in Ecuador and the Lastarria volcano in Chile. Although SO2 cameras are cost-efficient and easy to use, Wilkes said that they are dependent on meteorological conditions. They also perform best under clear skies when the volcanic gas plume moves in a 90° angle to the viewing direction of the camera, he said. Nevertheless, the new camera could broaden the use of permanently deployed SO2 cameras on volcanoes in different environments around the globe, owing to its low-cost, low-power design and open-source code for processing data sets. Longer-term testing of instrument performance is needed, but the new camera has the potential to provide valuable data sets for comparison with alternative ground-based remote sensing instruments. “The SO2 camera can provide higher time- and spatial-resolution data, which could facilitate new volcanological research when installed permanently,” Wilkes said. The research was published in Frontiers in Earth Science (www.doi.org/10.3389/feart.2023.1088992).