## 1 Introduction  
It is well known that some of the most scenic landscapes and islands of Greece are due to the intense volcanic activity that occurred centuries to millennia ago [1; 2]. While Santorini is the most famous and a worldwide renowned touristic site, there are other active volcanic systems (i.e., Milos and Nisyros) within the south Aegean volcanic arc, which were formed from the subduction of the African tectonic plate beneath the Eurasian plate. Of this arc, the Methana peninsula is the westernmost dormant but geodynamically and hydrothermally active volcanic system [3]. The peninsula is connected with the north-eastern coast of Peloponnesus by a narrow gooseneck-shaped isthmus and stretches for approximately 44 km\({}^{2}\) northward into the Saronic Gulf. Of the around 32 andesitic and dacitic lava domes scattered across the peninsula, the Methana volcano is the largest and is the subject of the present study. The volcanic hazard in Methana is considered \"low\" [4]: given that the last historic eruption was registered in approximately 230 BC, volcanic products derived from highly explosive eruptions were not found [3] and no alarming signs were observed in recent times. However, several aspects provide sufficient motivation for a dedicated investigation into the Methana volcano. From a hazard point of view, the neotectonic basin constituting the Saronic Gulf area is considered seismically active [5], and the active fault systems therein were considered preferential paths for present-day geothermal fluid leakage and, as such, potential sites for magma uprising [3]. Thermal springs are indeed clear manifestations of volcanic geothermal energy in Methana, and gas exhalations suggest a mixture between a dominant hydrothermal component and mantle-derived fluids [3]. Additionally, from a risk point of view, the volcano is not far from Athens (less than 50 km south-west) and any activity at the volcano would impact the local population (about 2500 inhabitants over the year, increasing during summer due to tourism). Further proof that monitoring the Methana volcano has recently been given higher priority on the agenda of Greek institutions is provided by the installations of six seismological stations by the Greek Institute of Geodynamics of the National Observatory of Athens (NOA) [6] alongside a new NOANET Global Navigation Satellite System (GNSS) station [7]. This recent development significantly updates what was stated by [4], i.e., of the whole Greek volcanic arc of Methana-Milos-Santorini (Thera)-Nisyros, Methana is among the volcanic fields not efficiently monitored. In this context, the present study aims to investigate and characterize the ground motions observed at the surface of Methana volcano based on the results achieved by means of multi-interferogram processing of Synthetic Aperture Radar (SAR) images collected by the Copernicus Programme Sentinel-1 satellite constellation in the period from March 2015 to August 2019. Interferometric SAR (InSAR) approaches have been largely exploited to study and monitor surface deformation at different locations across the volcanic arc (e.g., [8; 9; 10; 11; 12; 13; 14; 15; 16; 17]) and have proved their effectiveness to provide a spatially distributed estimation of volcanic activity due to magma chamber processes as well as shallow deformation associated with hydrothermal activity (e.g., low temperature venting). Despite this abundant literature, to the best of our knowledge, no InSAR study has previously focused on Methana. Given the varied land cover and presence of vegetation at Methana, we intentionally selected a Multi-Temporal InSAR (MT-InSAR) processing approach providing both Persistent Scatterers (PS) and Distributed Scatterers (DS) in order to augment the monitoring capability and the number of measurement points.