## 5 Discussion
### Benefits of MOUNTS  
The benefits of the developed system are the following:  
* Automated processing of free multisensor dataset which provide key parameters for volcano monitoring: surface deformation and reflectivity changes (Sentinel-1), heat anomalies (Sentinel-2), SO2 gas emission (Sentinel-5P), and seismic activity (USGS and GEOFON earthquake catalogues). This interdisciplinary approach allows for assessment of a variety of volcanic phenomena in various volcanological contexts. Moreover, exploiting multiple sensors spanning across the electromagnetic spectrum reduces the dependency to sensing conditions (e.g., night, clouds). * Flexible design allowing fast implementation of new targets to monitor, with freedom regarding the size and shape of the region of interest. This allows to rapidly respond to new eruptive crisis, and adapt to the specific scenarios (e.g., monitoring of summit activity on small \(\sim\)1-2 km spatial extent, and/or monitoring of effusive activity on large \(>\)50 km extent). The system currently monitors 17 volcanoes in various volcanological and climatic settings across the globe, many of which recently experienced large eruptive crisis. Figure 10: Multiparametric dataset combining space-based and ground-based sensors, which help decipher the recent eruptive dynamics of Ambrym (Vanuatu). The eruption onset on 15 December 2018 is indicated by a red vertical line across the plots. Time series of: (**a**) decorrelation score COH (pixels with coherence \(<\)0.5) in blue indicating surface reflectivity change, and deformation score DEF in red; (**b**) thermal anomalies from S2 SWIR analysis in orange (N hot pixels \(\times\)10\({}^{6}\)) and MODIS MIR analysis in black (VRP), processed by MOUNTS and MIROVA, respectively; (**c**) SO2 gas mass in the atmosphere from Sentinel-5P analysis in purple and OMPS analysis in black, processed by MOUNTS and NASA respectively; (**d**) magnitudes of the earthquake recorded in the vicinity of the volcano, recovered from the USGS global earthquake catalog. Images: (a.1) wrapped interferogram computed between SAR images d.1 and d.2, revealing very strong ground deformation (areas with strong phase decorrelation are masked to show only where deformation fringes are visible); (a.2) interferometric coherence, on which a new eruptive vent is identifiable; (b.1) S2 SWIR image prior to eruption onset, showing the persistent lava lakes activity; (b.2) S2 SWIR image after eruption onset, showing the lava flow emplacement from the new eruptive vent; (c.1) SSP image showing SO2 emissions prior to eruption onset; (c.2) SSP image showing strong decrease of SO2 emissions after eruption onset; (d.1,2) S1 intensity images immediately before and after the eruption onset, revealing profound morphological changes. Spatial extent of images a.1,2, b.1,2 and d.1,2 = 10 \(\times\) 10 km, extent of images c.1,2 = 500 \(\times\) 500 km. * Visualization through an open-access website (www.mounts-project.com) of both geocoded images (i.e., DInSAR interferograms wrapped/unwrapped, DInSAR coherence map, SAR VV intensity image, SWIR B12-B11-B8A image, and SO\({}_{2}\) PBL concentration), and time series of parameters extracted from each image type (i.e., deformation score, number of decorrelated pixels, number of hot pixels, and SO\({}_{2}\) mass, respectively). This allows to apprehend the evolution through time of the volcanic activity and eruptive products. Download of full resolution images and time series graphs (PNG format) is readily possible from the website; more specific data download based on user-defined queries is planned, but for the moment possible on-demand only. * Based on the free SNAP toolboxes, providing a unique framework to manipulate data from various satellites, with state-of-the-art processing algorithms (e.g., DInSAR).