Towards a unified Heliophysics Archive: A Multi-mission strategy for long-term data preservation and scientific synergy

The ESAC Science Data Center (ESDC) develops and operates the science archives for ESA missions. Within the ESDC, each archive provides scientists with access to the data of every ESA Heliophysics mission: Ulysses, SOHO, Cluster/DoubleStar, Proba-2, ISS-SOLACES, and Solar Orbiter. Most of ESA’s heliophysics archives are approaching the legacy phase, with fewer active missions (Solar Orbiter, SMILE, Proba-3) and new missions typically having reduced budgets for archiving activities. More widely, across the whole of the ESDC, we will soon reach a key turning point at which there will be more missions in the legacy phase than active ones. Thus, there is a need to streamline and reduce archive development, operations, and maintenance costs. Maintaining numerous independent archives is resource-intensive and unsustainable in the long term, and leads to significant challenges, including software obsolescence, lack of standardization and interoperability, loss of institutional knowledge, and a fragmented, divergent archive evolution. The long-term preservation and scientific exploitation of heliophysics data are essential to maximizing the legacy and value of ESA missions. To achieve this, we propose a strategic integration of currently stand-alone mission archives into a unified, scalable platform: The ESDC Multi-Missions Data Services (EMDS). The EMDS will allow cross-disciplinary, unified data access through the homogenization of interoperability mechanisms like the IVOA TAP protocol and HAPI, standardizing interfaces across scientific domains and enhancing scalability, maintainability, and usability. This strategy will be the de facto standard for new heliophysics missions like SMILE and Proba-3, while existing archives will be migrated to EMDS, ensuring their data is accessible and preserved for long-term scientific use. Finally, building on the EMDS infrastructure, a common user interface - The Heliophysics Archive (HPA) is being developed to provide unified access to all ESA Heliophysics data. The first version of the HPA was made available in April 2025, initially limited in scope and offering access to a new Solar Orbiter Field of View tool and the SOAR TreeView. Over time, the HPA will become the overarching front-end to access data from all ESA Science Heliophysics missions. This presentation outlines the vision, architecture, and implementation strategy for evolving ESA’s heliophysics archives into a single, cohesive system.