Supporting Volcano Monitoring From Radar and Optical Satellite Imagery

Satellite remote sensing has become an essential tool for monitoring volcanic activity and responding to crises in near real time. Recent developments in imaging techniques, combined with an increasing number of space missions – operated by public agencies or commercial companies – today provide a wealth of satellite images. During the course of an eruption, the synergy between high-resolution radar (SAR) and optical imagery enables a rapid assessment of volcanic deformation and topographic changes (including lava flows, ash deposition, or lava dome growth/destruction). These data bring invaluable information on eruption dynamics, and contribute to improving volcanic hazard assessment.

VSO interactive services for Volcano Observatories

Delivering satellite observations to end-users, especially scientific teams working in volcano observatories, is a long-term goal that the « Volcano Space Observatory » (VSO) is aiming to address. Interactive interfaces have been developed in the VSO to reconstruct gas and particle emissions and track the evolution of volcanic plumes. New developments will include the upcoming « Volcano Ground Deformation » web platform using Sentinel-1 InSAR. One of the core services is the « InSAR on-demand chain » for the interactive processing of Sentinel-1 InSAR data, which has been recently developed (Grandin et al. 2025) and is accessible via the VSO API.

Grandin, R., Boichu, M., Mathurin, T., Pascal, N., Akiki, R., Anger, J., de Franchis, C., On-demand Sentinel-1 Interferogram Generation Service for Monitoring of Volcano Deformation, ESA Living Planet Symposium, Vienna, June 2025

Emergency acquisitions by high-resolution imaging satellites

Upon alert by volcano monitoring agencies, Pléiades satellites can be tasked in emergency mode to acquire optical imagery through the FormaTerre – CNES « CIEST2 » protocol. These data are automatically ingested into FormaTerre’s processing service DSM-Opt, allowing for a rapid assessment of topographic changes. Access here to the VSO-OPT database.

In parallel, high-resolution SAR images delivered by Capella Space bring complementary coverage at high spatial and temporalresolutions. SAR sensors have the ability to see through clouds or volcanic plumes, a key asset for providing visually-interpretable images of rapidly-changing volcanic landforms, such as explosive craters, fissures or ash/lava deposits. A detailed discussion on these collaborations, highlighting the real-time potential of high-resolution SAR imaging for volcano surveillance, is available in the blog post by Raphaël Grandin entitled « Remote Sensing Brings Volcano Monitoring Toward Real-Time Capability »

Case Studies

The cases presented here demonstrate how these recent advances contribute to scientific research, hazard assessment, and disaster response.

Nyiragongo Volcano, Democratic Republic of the Congo (2021 Eruption)

This study showcases the contribution of satellite-based SAR imagery to understanding the progressive crater collapse associated with the drainage of the Nyiragongo lava lake, feeding lava flows that propagated toward populated areas.

Reference: Smitarello, Grandin & al. (2023).

Piton de la Fournaise, La Réunion

Monitoring lava flows at Piton de la Fournaise, one of the world’s most active volcanoes, using SAR and optical data.
Reference: Chevrel, Villeneuve, Grandin & al. (2023).
Towards near real-time monitoring of volcanic deformation and lava flow eruption using Capella Space SAR images: application to Piton de la Fournaise. Reference: Hauck, Grandin et al. (2026).

Soufrière St. Vincent Eruption (2021)

Multi-sensor monitoring of the Soufrière St. Vincent eruption allowed for capturing the destruction of a lava dome on 9 April 2021, mapping topographic changes, tracking the eruption dynamics and assessing the extent of pyroclastic flow deposits.

References:

Cumbre Vieja (La Palma) Eruption (2021)

This study highlights how the synergy between high-resolution SAR (Capella) and optical (Pléiades) imagery allows for mapping lava flows and ash deposition, as well as monitoring the formation of new cones.