History of the project
Tracing the origins of a visionary observatory
The WST was conceived to transform our understanding of the Universe through large-scale spectroscopy.
Rooted in a European–Australian partnership and supported by Horizon Europe, the WST builds on years of preliminary design studies and international collaboration to create the next-generation facility that will expand the frontiers of astrophysical discovery.
The idea
Origins and Scientific Motivation
References
- The Astronet Science Reference, 2023, Astronet website, URL (accessed 03/04/2026).
- Mérand, A. et al. 2020, Report on the Scientific Prioritisation Community Poll (2020), The Messenger, vol. 184, 14. URL.
- US Decadal Survey, 2023, Pathways to Discovery in Astronomy and Astrophysics for the 2020s, National Academies of Sciences, Engineering, and Medicine website, URL (accessed 03/04/2026).
- Australia in the era of global astronomy: the decadal plan for Australian astronomy 2016–2025, 2015, Australia Academy of Science website, URL (accessed 03/04/2026).
- Discovery at the Cosmic Frontier: Canadian Astronomy Long Range Plan 2020-2030”, 2021, Casca website, URL (accessed 03/04/2026).
The idea of a fully dedicated spectroscopic telescope took shape in the mid-2010s, when astronomers worldwide recognised the growing need for a large-aperture facility optimised for wide-field spectroscopy.
With the advent of powerful observatories such as the Vera Rubin Observatory, the Square Kilometre Array (SKA), and the Cherenkov Telescope Array (CTA), together with space missions including James Webb, Gaia, Euclid and the planned Nancy Grace Roman, and NewAthena, it became clear that astronomy was entering a new era of data abundance.
The unprecedented number of galaxies and stars that are expected to be observed by these facilities — for example, up to 20 billion galaxies and 17 billion stars down to R~27.5 from the Vera Rubin Observatory alone — make it essential to complement imaging with spectroscopic follow-up. Only a dedicated facility could collect the vast number of spectra required to understand the nature, composition, and evolution of these sources.
Across continents, this need was echoed in strategic documents such as the Astronet Science Vision and Infrastructure Roadmap 2022-2035, the US Decadal Survey 2020, and the Australian and Canadian Decadal Plans for Astronomy (2016–2030). Within Europe, a 2021 ESO community poll confirmed that 75% of respondents viewed a wide-field spectroscopic telescope as the most crucial facility for the coming decades.
Spectel
From concept to collaboration
Between 2016 and 2020, the idea was first explored under the name SpecTel, a design study conducted at ESO.
Led by Luca Pasquini and Bernard Delabre, the study proposed two innovative concepts for a 10-metre-class wide-field spectroscopic telescope:
- a five-mirror design optimised for gravity-invariant instruments, and
- a wide-field Cassegrain telescope designed for fibre-fed spectrographs.
At the same time, ESO established a Working Group chaired by Richard Ellis, which developed the first comprehensive scientific case for a large-aperture spectroscopic survey telescope.
The group’s report highlighted two key requirements: the largest possible field of view and the use of optical fibres feeding intermediate- and high-resolution spectrographs.
In 2018, Pasquini et al. presented an updated design that also considered a large Integral Field Unit (IFU) at a separate focal station, enhancing the telescope’s versatility and scientific reach.
Further bibliography
- Hall et al., 2016. Ground-based and Airborne Telescopes VI. Proceedings of the SPIE, Volume 9906 (2016), DOI: 10.1117/12.2254876
References
- Pasquini L. et al., 2016. New telescope designs suitable for massively multiplexed spectroscopy, Proceedings of the SPIE, Volume 9906, id 99063C, DOI: 10.1117/12.2232289
- Ellis, R. et al. 2017. The Future of Multi-Object Spectroscopy, a ESO Working Group report, eprint arXiv:1701.01976, DOI:https://doi.org/10.48550/arXiv.1701.01976
- Pasquini L. et al. 2018. A concept for a new spectroscopic facility, Proceedings of the SPIE, Volume 10700, id. 107004E, DOI: 10.1117/12.2313076
Exploring a new design
The birth of the wide-field spectroscopic telescope
In 2021, building on these foundations, a European–Australian consortium led by Roland Bacon was formed to advance the concept and explore a new design — the Wide-field Spectroscopic Telescope (WST).
The WST inherited the SpecTel vision and introduced a major innovation: the parallel operation of two powerful instruments —
- a multi-object spectrograph (MOS) offering both low- and high-resolution modes, and
- a giant panoramic Integral Field Spectrograph (IFS).
This dual capability combines statistical power with detailed spatial information, maximising the scientific return and enabling the telescope to conduct transformational surveys of galaxies, stars, and transients.
Foundations
The conceptual design phase
Between 2021 and 2024 the Consortium carried out a preliminary design study. At the same time, the Science Team, led by the Project Scientist Vincenzo Mainieri, was formed and developed the initial science drivers, which were published in a first version of the WST White Paper.
The WST project was funded by the European Commission under the Horizon Europe infrastructure programme in mid-2024 and entered its detailed Conceptual Design Phase (CDP) in 2024.
During this phase, the consortium is further developing and strengthening the scientific case, technical architecture, and operational model for the facility, ensuring that it meets the highest standards of scientific excellence, sustainability, and inclusivity.
The CDP represents the basis for the WST’s candidacy as ESO’s post-ELT facility, defining the long-term path toward its construction in Chile, one of the world’s most productive astronomical regions.
References
- Mainieri V. et al. 2024. The Wide-field Spectroscopic Telescope (WST) Science White Paper, eprint arXiv2403.05398, DOI: https://arxiv.org/abs/2403.05398
- Pasquini L. et al. 2018. A concept for a new spectroscopic facility, Proceedings of the SPIE, Volume 10700, id. 107004E, DOI: 10.1117/12.2313076
PERSPECTIVE
A shared vision for the future
The WST is more than an astronomical facility — it is a collaborative vision for the future of astrophysics. By bringing together scientists, engineers, and institutions from across Europe, Australia, and beyond, the project reflects a collective commitment to open science, technological innovation, and responsible research infrastructure.
Through this partnership, the WST will complement major facilities such as ESO’s Extremely Large Telescope, Vera Rubin Observatory, Euclid, Gaia, and the Square Kilometre Array, the Einstein Telescope, unlocking the full scientific potential of the 2040s and beyond.
Milestones
More than a decade of collaboration, gazing toward the Universe
Initiated by Luca Pasquini & Bernard Delabre; two 10m-class telescope concepts proposed.
Chaired by Richard Ellis; defined key scientific and technical requirements.
Inclusion of a large Integral Field Unit (IFU) option (Pasquini et al. 2018).
European–Australian collaboration led by Roland Bacon; dual MOS + IFS concept introduced.
Development of design, science case, and governance.
Science drivers developed and published. Synergies with other facilities highlighted.
All the expertise required to perform the concept study of a facility as ambitious as the WST.
Next section
The three-year WST concept study
The project follows two concurrent timelines, each with its own milestones and deliverables.
