The international space science communities mourn the loss of Professor Hermann Opgenoorth, who passed away on May 19, 2025. Hermann was born in Bottrop, Germany, in 1951 and began his scientific career with a Master’s degree in Geophysics from the University of Münster in 1978. He moved to Sweden in 1981, earning his PhD from Uppsala University in 1983, followed by a Docent qualification in 1990. Hermann’s career spanned over four decades, during which he made seminal contributions to science.

Hermann’s research was pivotal in elucidating the complex interactions between the solar wind, magnetosphere, and ionosphere at both Earth and Mars. He was renowned for pioneering coordinated observations that combined data from both space-based missions and ground-based observatories, and for putting fundamental research to good use, exemplified in his engagement in space weather. His contributions to European Space Agency (ESA) missions, as well as his leadership in establishing ground-based networks like EISCAT, SuperDARN, and the IMAGE magnetometer array, exemplified his commitment to integrated, collaborative science. He had an attitude that was curious, steadfast, tenacious and brilliant. An important element of Hermann’s work over those 40+ years was his support for numerous early career researchers around the globe, many of whom now have successful careers in the field.

Beyond his scientific achievements, Hermann was a fervent advocate for international cooperation in space research. As Head of the Solar System Missions Division at the European Space Agency, he championed missions that bridged scientific inquiry with societal relevance. During this time Hermann was a driving force behind initiatives such as the International Living With a Star (ILWS) program, fostering global partnerships to advance our understanding of space weather and its impacts on Earth. A different, but no less important initiative, was the creation of the Mars Upper Atmosphere Network (MUAN), designed to bring together an international group of scientists working on the plasma environment of Mars. While initially small, MUAN now brings together scientists from around the globe to its meetings, where new results are discussed, new collaborations begun and new mission concepts prepared. Hermann was also a pivotal member of the Expert Group on Space Weather for the United Nations’ Committee on peaceful Use of Outer Space and the co-chair of an ESF/ESSC Space Weather Assessment and Consolidation Working Group.

Hermann’s outstanding contributions have been recognised by his peers and colleagues through several awards. In 2018 Hermann was awarded the International Marcel Nicolet Award at the European Space Weather week and in 2023 Julius Bartels Medal by the European Geosciences Union, honouring his exceptional work in substorm and space weather research, as well as his unwavering commitment to fostering international collaboration. He was also an Honorary Fellow of the Royal Astronomical Society and held Honorary Professorships at the University of Leicester.

In the later years of his career, he joined Umeå University in northern Sweden, where he continued his passionate engagement in research, mentoring, and international collaboration as Professor Emeritus. Although officially retired, he remained deeply involved in the scientific community — contributing to ongoing projects, supporting early-career scientists, and strengthening global research networks. His presence at Umeå was marked by intellectual generosity, enthusiasm for discovery, and a sincere commitment to nurturing the next generation of researchers. He was a deeply valued colleague whose guidance and warmth left a lasting impression on his colleagues.

Hermann’s legacy is one of scientific depth, lasting contributions to space physics, and an unwavering dedication to international collaboration. He will be remembered for shaping key areas of solar-terrestrial research, and his commitment to advancing science through cooperation and mentorship will continue to inspire future generations of researchers. He will also be remembered for his endless and cheerful stories over a beer in cozy pubs.

He is survived by his family, colleagues, and a global community of researchers who were privileged to work alongside him.

With deep respect and remembrance,
Dr. Maria Hamrin, Department of Physics, Umeå University, Sweden
Dr. Audrey Schillings, Department of Physics, Umeå University, Sweden
Prof. Mark Lester, University of Leicester, UK
Dr. Johan Köhler, Swedish National Space Agency
Close collaborators and friends of Professor Hermann Opgenoorth,
on behalf of his many colleagues and friends in the international space science communities