The European Space Sciences Committee (ESSC) mourns the profound loss of Professor Hermann Opgenoorth, who passed away on 19 May 2025. Hermann was not only a distinguished member of our scientific community but a driving force whose passion for space weather science and unwavering commitment to scientific excellence left an indelible mark on European and international space research.

Born in Germany in 1951, Hermann embarked on his scientific journey at Uppsala University, where he earned his PhD in Geophysics in 1981. This marked the beginning of a remarkable four-decade career that would see him become one of Europe’s most respected voices in space science.

Hermann’s research centred on the intricate interactions between the solar wind, magnetosphere, and ionosphere of Earth and Mars. His work seamlessly integrated space-based and ground-based observations, reflecting his comprehensive approach to understanding our solar system’s complex dynamics.

He served as Head of the Solar System Missions Division at the European Space Agency, and as co-chair of the United Nations’ Committee on the Peaceful Uses of Outer Space (UN COPUOS) Expert Group on Space Weather, where he worked tirelessly to ensure space weather research served the global community.

Hermann was a member of the ESSC from 2012 to 2021. As chair of the ESSC’s Solar System Exploration Panel from 2016 to 2021, he guided critical discussions that shaped European space science priorities. Perhaps most notably, he was the driving force behind the ESF/ESSC Space Weather Assessment and Consolidation Working Group, which produced the comprehensive Assessment and Recommendations for a Consolidated European Approach to Space Weather — a foundational document that continues to influence European space weather strategy.

The scientific community recognised Hermann’s extraordinary contributions through several prestigious awards. In 2018, he received the International Marcel Nicolet Award at European Space Weather Week, and in 2023, the European Geosciences Union honoured him with the Julius Bartels Medal — acknowledgements that reflected not only his scientific achievements but his role as a mentor and leader in the field.

Beyond his scientific accomplishments, Hermann will be remembered for his remarkable personality that enriched every interaction. Colleagues knew him as a man of great humour and tireless energy, whose appetite for lively scientific debates was matched only by his gift for telling hilarious stories. His towering presence and booming voice commanded attention in any room, yet his approachable demeanour and genuine warmth made him beloved by students, colleagues, and collaborators across the globe.

Hermann was, above all, a fierce defender of scientific integrity — a champion who never wavered in his commitment to rigorous research and honest scientific discourse.

The ESSC extends its deepest condolences to Hermann’s family, friends, and the countless colleagues whose lives he touched throughout his remarkable career. While we mourn his passing, we celebrate a life devoted to advancing human knowledge and fostering international scientific collaboration. Hermann’s legacy lives on in the research he conducted, the institutions he helped build, and the many scientists he inspired along the way.

The ESSC is honoured to have counted Professor Hermann Opgenoorth among our members. He has definitely made an impact for science in his life that will last much longer than a life can be. This may comfort his family and all who appreciated knowing him.