The GEO600 project will end on 31 December 2026
More than three decades of cutting-edge research at the German-British detector have shaped the international field of gravitational-wave astronomy.
To the point
- End of operations: The gravitational-wave detector GEO600 south of Hanover, Germany, will cease operation at the end of 2026. The last Open Day will take place this summer. Group tours will be offered until the end of the year. In early 2027, dismantling of the facility will begin.
- Retirement: Max Planck director Karsten Danzmann will retire on 31 March 2026. As a consequence, funding for the GEO600 project will terminate at the end of the year.
- Cutting-edge research: GEO600 is a beacon of international research. Technologies developed and tested in the GEO project are now used in all major gravitational-wave detectors around the world. The findings and experience gained also play a role in preparing future observatories such as the Einstein Telescope and the Cosmic Explorer.
GEO600 has advanced gravitational-wave astronomy worldwide
Karsten Danzmann, director at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Professor at Leibniz University Hannover says: “As a beacon of German-British gravitational-wave research, GEO600 has fostered international cooperation, shaped generations of scientists, and enabled key technological advances. GEO600 has made lasting contributions to gravitational-wave astronomy that will have an impact far into the future.”
GEO600 is part of an international network of five detectors today (alongside the two LIGO instruments in the US, Virgo in Italy, and KAGRA in Japan). These instruments use extremely pure laser light that travels through two perpendicular vacuum tubes, which are several hundred meters or several kilometers long, as well as highly sensitive measurement and control technology, to observe gravitational waves. In September 2002, GEO600 and the LIGO detectors conducted their first coordinated observing run, forming the first international network of gravitational-wave detectors.
These space-time ripples, predicted by Albert Einstein in 1916, are like the sound of the cosmos. They are created in extreme cosmic events and have revolutionized our understanding of the dark side of the Universe since their first direct detection in 2015. Since then, the network has observed and analyzed more than 200 mergers of black holes or neutron stars.
GEO600 – technology incubator and test bench
The larger the instrument, the more sensitive it is to tiny length changes caused by passing gravitational waves. The fact that GEO600 is the smallest detector in the network was an incentive for its German-British scientists from the very beginning. They made GEO600 a technology incubator and test bed for innovative methods in optics, mechanics, and control engineering.
GEO600 researchers developed and tested much of the technology now standard in all large gravitational-wave detectors. Thanks to this and other technology, large detectors have regularly observed distant mergers of black holes or neutron stars during their most recent observing run.
An astronomical watch service
Whenever the larger detectors in the network are unable to collect scientific measurement data during their months- or years-long upgrade phases, GEO600 takes over. In the “Astrowatch” program, the detector listens to the Universe while continuing its daily experiments. When other telescopes observe exceptional astronomical events, such as supernova explosions, GEO600 can record the resulting gravitational waves.
Research for the Einstein Telescope
GEO600 also makes vital contributions to the Einstein Telescope, Europe’s planned third-generation gravitational-wave observatory. Only GEO600, with its unique design, can investigate the very high laser power expected at the beam splitter of the Einstein Telescope under realistic conditions. The beam splitter is the semi-transparent mirror that splits the laser light into two measurement beams running perpendicular to one another.
The high laser power causes changes in the temperature of the beam splitter, thereby altering its optical properties. At GEO600, an innovative system compensates for this. This system not only improves the measurement sensitivity of GEO600, but also provides valuable experience for future detectors, such as the Einstein Telescope.
Breaking new ground
Research at GEO600 will continue until the end of 2026, as scientists are once again breaking new ground with the detector. They are working to make a previously little-explored part of the gravitational-wave spectrum accessible. GEO600 will search for gravitational waves at very high frequencies of up to 2 MHz. That is more than a hundred times higher than the highest frequencies observed by the other instruments in the international network.
This way, the detector is expected to deepen our understanding of dark matter and the early Universe. With this goal in mind, the researchers have been upgrading the facility since the summer of 2024. They have already reached important milestones and recorded first measurement data in the extremely high-frequency part of the gravitational-wave spectrum.
Visiting GEO600
In the summer of 2026, the 11th and final Open Day will take place at the detector site in Ruthe near Sarstedt, about 20 kilometers south of Hanover, Germany. Planning for this day is currently underway and the date will be announced soon. Until the end of 2026, the Max Planck Institute for Gravitational Physics will continue to offer group tours of GEO600. Further information is available at https://www.geo600.org/visits.
Background information
GEO600
GEO600 is an interferometric gravitational-wave detector near Hanover, Germany. It is being developed and operated by scientists from the Max Planck Institute for Gravitational Physics and Leibniz University Hannover, together with partners in the United Kingdom, and is funded by the German Federal Ministry of Research, Technology and Space, the State of Lower Saxony, the Max Planck Society, the Science and Technology Facilities Council (STFC), and the Volkswagen Foundation.
The GEO Collaboration
The GEO Collaboration comprises scientists at 23 European research institutions. The GEO Collaboration and its members are part of the LIGO Scientific Collaboration. A full list of the about 300 members of the GEO Collaboration is available in the LIGO Roster.
Technological firsts and lasting contributions
Much of the technology that makes today’s gravitational-wave detectors successful astronomical observatories was first explored and validated at GEO600. The detector serves as a proving ground for bold, sometimes uncertain, and ultimately transformative ideas.
