Einstein Telescope
General Info

European Gravitational Observatory (EGO)

Via E. Amaldi 56021 Cascina (Pisa) Italy

legal status




Einstein Telescope (ET) will be an Observatory of Gravitational Waves (GW) of future generation. It builds on the success of current, second-generation detectors Advanced Virgo and Advanced LIGO, whose breakthrough discoveries of merging black holes (BHs) and neutron stars over the past decade have ushered scientists into the new era of GW astronomy. ET consists of a set of multi-km arm optical interferometers with suspended optics. Each ET detector is composed by two interferometers: ET-LF devoted to the detection of the GW in the Hertz frequency regime, and ET-HF aiming to detect the GW signal up to few kHz. ET will achieve a greatly improved sensitivity by increasing the size of the interferometer from the 3km arm length of the Virgo detector to 10-15km, and by implementing a series of new technologies. These include a cryogenic system to cool some of the main optics to 10 – 20K, new quantum technologies to reduce the fluctuations of the light, and a set of infrastructural and active noise-mitigation measures to reduce environmental perturbations. The expected improvement of the sensitivity with respect to the current detectors is about one order of magnitude at high frequency and several orders at low frequency. ET will make it possible, for the first time, to explore the Universe through GW along its cosmic history up to the cosmological dark ages, shedding light on open questions of fundamental physics and cosmology. It will probe the physics near black-hole horizons, help understanding the nature of dark matter, and the nature of dark energy and possible modifications of general relativity at cosmological scales. Exploiting the ET sensitivity and frequency band, the entire population of stellar and intermediate mass black holes will be accessible over the entire history of the Universe, enabling to understand their origin (stellar versus primordial), evolution, and demography. ET will observe the neutron-star inspiral phase and the onset of tidal effects with high SNR providing an unprecedented insight into the interior structure of neutron stars and probing fundamental properties of matter in a completely unexplored regime (QCD at ultra-high densities and possible exotic states of matter). The excellent sensitivity extending to kHz frequencies will also allow us to probe details of the merger and post-merger phase. ET will operate together with a new innovative generation of electromagnetic observatories covering the band from radio to gamma rays (such as the SKA, the Vera Rubin Observatory, E-ELT, CTA). Two candidate sites, one in Sardinia and one in the Euregio Meuse-Rhine, and two geometries, triangular and 2L shaped, are under investigation. The science potential and the feasibility of a single-site solution, located either in the Sardina candidate site or in the Euregio Meuse-Rhine site is compared with respect to the possibility to realize a 2L geometry distributed in the two candidate sites.
Total Investment 1912 M€ Design 5 M€ Preparation 171 M€ Implementation 1736 M€ Operation 37 M€/year Project 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 2026 2028 2030 2032 2034 2036 2038 RM06 RM08 RM10 RM16 RM18 RM21 LA24
Roadmap Entry
as project: 2021
Total investment
1912 M€
Design Phase
5 M€
Preparation Phase
171 M€
Implementation Phase
1736 M€
Operation start
37 M€/year
The idea of a 3rd generation GW observatory has been conceived in the FP6 I3 activity ILIAS (2004-2008) and in an exploratory workshop funded by ESF (2005); a pivotal step has been the realization of the ET Conceptual Design in FP7 design study (2008-2011), followed by the development of some of the enabling technologies in collaboration with the Japanese project KAGRA through an IRSES-FP7 project, ELiTES (2012-2017) and currently through the Interreg ETpathfinder and E-TEST projects, the SarGrav facility funded by the Sardina Region and the ETIC IR0000004 PNRR project of the Italian Ministry of research. The ET scientific collaboration has been formalised in 2022 and now counts more than 1600 members. The next steps will be the definition of the observatory geometry and layout, the selection of the hosting site and beginning of the land acquisition process (2025-2026), acquisition of legal status, creation of governance structure (2025+) followed by the main call for tender and the beginning of the excavation works. The aim is to start the operations about in 2035.
The Einstein Telescope Research Infrastructure will provide two main “outputs”: astronomical event triggers online and scientific data. The set of offered services described hereafter is built around these two main outputs. OPA (Open Public Alerts): ET will be a unique instrument to provide online triggers to the multimessenger astronomy partners (optical telescopes and other ground based detectors and satellites). In fact its capability to accumulate enough signal to noise ratio (SNR) before the merging phase of a coalescence will be a unique breakthrough characteristic that will transform this part of Astronomy Event Database: Integrated with the previous service, there will be a repository that contains and describes the events detected by ET and by the other GW partners. This online database will be the starting point for the scientists collaborating with and using ET for multimessenger astronomy. High Latency Scientific Data: On a defined timescale all of the gravitational wave strain data for Advanced LIGO and Advanced Virgo are released to the public. The data release will be fully compliant to the FAIR requirements; for this reason, the open data platform service will be completed by a Public Analysis Software service, where the code needed to read the Einstein Telescope data will be provided together with the fundamental tools for analysing Einstein Telescope data streams. This platform will integrate contributions coming from the wide scientific community, once validated. The service will be addressed to all the communities interested in Einstein Telescope data, from astronomers to geologists. For this reason, it will be integrated with analogous systems developed by other communities.
S S H D I G I T E N E E N V H & F
In the preparatory and construction phases ET is cooperating with the European and Global Ris for a number of aspects including technical and scientific items like civil and mechanical engineering, computing and energy. Contacted Ris are CERN, ESO, ESS, CTAO, SKAO. In the operating phase ET will collaborate with all the actors of the multimessenger astronomy and then with Ris like ESO optical telescopes (ELT, …), Neutrino detectors (Km3NET, Icecube), CTA, SKA, … Considering the multidisciplinary nature of Einstein Telescope, collaborations with Ris devoted to geophysical studies like EPOS are expected.