Comparison of remote sensing ground based systems for volcanic emission monitoring

Ground-based remote sensing systems provide safe, real-time, continuous and reliable measurements of parameters of volcanological interest and have become indispensable tools for monitoring volcanic activity and potentially mitigating its effects on the environment and local communities. Ground-based systems, where installed, offer continuous spatial and temporal coverage, providing data of high resolution and sensitivity, which are essential for validating satellite data The latter are characterised by much greater density and larger spatial coverage, and for this reason have now become irreplaceable for volcanic monitoring on a global scale.     This work presents the preliminary comparison results of simultaneous measurements from ground-based systems, consisting of different types of instruments operated by several international research groups. Among these, the most relevant systems we used were (1) a new portable and low-cost TIR system consisting of three collimated cameras, one in the visible, a panchromatic TIR in the 8-14 μm window and an identical TIR camera filtered with a bandpass centred at 8.7 μm, for the detection of SO2 emission height, columnar content, and flux, (2) two high-performance SO2 dual UV imaging systems (EnviCam3) with synchronous acquisition of images (on- and off-band wavelength channels for SO2 detection), and an integrated spectrometer (co-aligned with cameras to provide calibration of SO2 retrievals), (3) a MAX-DOAS, and (4) an IR camera continuously looking at Popocatépetl thermal anomalies.   The described ground-based systems were used for simultaneous volcanic emission monitoring measurements of Sabancaya Volcano, Perú, and Popocatépetl Volcano, Mexico, in dedicated field campaigns organized in November 2022, and February 2024 respectively, partly funded by the INGV ATTEMPT and DYNAMO projects, and the KAIROS project (SESAR 3 Joint Undertaking).The SO2 fluxes time series obtained from the different ground based systems were cross-compared with each other and with the flux retrieved by the TROPOMI instrument on board the S5p satellite.These types of comparative measurements represent a significant step forward in understanding the relationships between the various ground-based measurements carried out, their use for validating space-based measurements and, in particular, the estimation of SO2 flux using remote sensing optical methods.