A miniaturised ultraviolet spectrometer for remote sensing of SO2 fluxes: a new tool for volcano surveillance

For 30 years, the correlation spectrometer (COSPEC) has been the principal tool for remote monitoring of volcanic SO2 fluxes. During this time, the instrument has played a prominent role in volcanic hazard assessment. COSPEC data also underpin estimates of the global volcanic SO2 flux to the atmosphere. Though innovative for its time, COSPEC is now outdated in several respects. Here we report the first measurements with a potential replacement, using a low cost, miniature, ultraviolet fibre-optic differential optical absorption spectrometer (mini-DOAS). Field experiments were conducted at Masaya Volcano (Nicaragua) and Soufrière Hills Volcano (Montserrat). The mini-DOAS was operated from a road vehicle and helicopter, and from a fixed position on the ground, indicating fluxes of ∼4 and 1 kg s−1 at Masaya Volcano and Soufrière Hills Volcano, respectively. Side-by-side observations with a COSPEC on Montserrat indicate a comparable sensitivity but the mini-DOAS offers several advantages, including the collection of broadband ultraviolet spectra. It has immense potential for geochemical surveillance at volcanoes worldwide.