On 7 October 2026, the Einstein Telescope Geometry Comparison Report was submitted to the project’s Board of Governmental Representatives, marking an important milestone in the development of Europe’s future third-generation gravitational-wave observatory.

Coordinated by the Einstein Telescope Organisation (ETO), the report brings together the work of more than 200 experts from over 20 research institutions. It assesses the scientific potential, technical risks, costs, governance requirements and socio-economic impact of the different geometrical configurations under consideration.

Comparing two possible configurations

The Einstein Telescope will detect gravitational waves with unprecedented sensitivity, opening new opportunities to study black holes, neutron stars and the evolution of the Universe.

Two configurations are being considered: a triangular observatory with three 10-km arms, and a network of two L-shaped detectors, each with 15-km arms, located approximately 1,200 km apart.

The report concludes that both configurations can meet the scientific requirements of the Einstein Telescope, although they offer different advantages. The double-L configuration performs better across the broadest range of scientific objectives, while the triangular design presents lower organisational complexity.

The report does not recommend a final configuration but provides a common framework to inform future decisions, considering scientific performance alongside technical, financial and organisational factors.

IFAE’s contribution to the Einstein Telescope

IFAE plays a leading role in the development of the Einstein Telescope, contributing to its scientific coordination and organisational foundations.

Mario Martínez, ICREA Research Professor at IFAE and a member of the ET Directorate, led the Spanish scientific community’s efforts that resulted in Spain’s support for the project’s inclusion in the ESFRI Roadmap in 2021.

From 2022 to 2026, Martínez also coordinated the Horizon Europe Einstein Telescope Preparatory Phase (ET-PP), a €3.45 million European project led by IFAE that established key scientific, technical, governance and organisational foundations for the future observatory.

Eugenio Coccia, Director of IFAE, serves as Chair of the Einstein Telescope Collaboration Board.

The Geometry Comparison Report will now inform discussions within the Einstein Telescope Board of Governmental Representatives on the observatory’s future configuration.

Read the original announcement on the Einstein Telescope website .