Multiplatform TIR remote sensing for monitoring and surveillance of the Campi Flegrei caldera.

Thermal infrared (TIR) remote sensing is an increasingly used technique for studying various natural and anthropogenic processes by evaluating the thermal state of the Earth’s surface. Technological advancements have supported the development of thermal cameras for ground-based, airborne, and satellite platforms. Additionally, Unmanned Aerial Systems (UAS) are increasingly regarded as versatile platforms due to their flexible observation scales.

In a volcanic framework, TIR remote sensing enables the study of ground temperature and the identification of thermal anomalies caused by hot fluid discharge (e.g., gas and lava) or surface heating due to fluid migration in the subsoil during unrest phases, which modify the pressure and temperature conditions of the crust. TIR remote sensing is therefore an essential tool for monitoring and surveillance of active volcanoes, although the spatial coverage and resolution of planned surveys can sometimes be inadequate for emergency management. Indeed, ground-based measurements do not guarantee extensive spatial coverage, while satellite data lack flexibility regarding spatial and temporal resolutions. Finally, airborne measurements are challenging to organize operationally during emergencies and are inherently risky. In this scenario, UAS platforms represent a reasonable trade-off in terms of spatial coverage, resolution, and logistics.

Here, we present a case study of multiplatform (satellite and UAS) TIR remote sensing as part of the monitoring activities at the Campi Flegrei caldera by INGV – OV. This active volcanic system is characterized by complex interactions between magmatic and hydrothermal reservoirs, causing frequent unrest with ground deformation, seismicity, gas emissions, and surface temperature anomalies. Among the latter, we focus on the most significant anomalies located near the Solfatara – Pisciarelli hydrothermal system.

Satellite measurements consist of nighttime images acquired by the Landsat-8 and Landsat-9 satellites from May 2018 to August 2025, with a 100 m spatial resolution, processed to retrieve an approximately monthly distribution of Land Surface Temperature (LST). Conversely, UAS data consist of images acquired monthly by INGV – OV with a 10 cm spatial resolution at flight altitudes ranging from 45 to 70 m. For logistical reasons, the Pisciarelli dataset spans from September 2019 to May 2025, while images of Solfatara were only acquired during the first halves of 2024 and 2025.

The results show that satellite data can detect a single anomaly at the Solfatara – Pisciarelli hydrothermal system without revealing significant temporal variations in temperature. On the other hand, UAS data identify multiple anomalies for both the Solfatara and Pisciarelli sites, highlighting surface heating in Pisciarelli starting around September 2021. This trend is consistent with analyzed seismicity and ground deformation datasets.

This study demonstrates the role of multiplatform TIR data integration in improving monitoring and surveillance activities at active volcanoes.