With the European Southern Observatory’s Extremely Large Telescope (ESO's ELT) construction just a few years away from completion, the science community is preparing to observe with the world’s biggest eye on the sky later this decade. At the same time, we at ESO continue to enable scientists worldwide to discover the secrets of the Universe with our world-class observatories on the ground, including our flagship facility the Very Large Telescope (VLT), the Very Large Telescope Interferometer (VLTI) and, together with our international partners, the Atacama Large Millimeter/submillimeter Array (ALMA) and the future Cherenkov Telescope Array Observatory (CTA). But we are already looking beyond the ELT and setting our sights on the next facility that will revolutionise the global astronomical landscape.

ESO is dedicated to consistently transforming the scientific landscape by designing, building and operating ground-based observatories that push technology to new heights and expand our knowledge of the cosmos. The ELT follows in the footsteps of the 10-year-old collaborative efforts of the Atacama Large Millimeter/submillimeter Array (ALMA), which remains the most powerful facility capable of studying the cold Universe, and ESO’s 25-year-old Very Large Telescope (VLT), which remains at the global forefront of visible-light astronomy. It’s a project made possible thanks to decades of trailblazing technology, work that ESO began at its La Silla Observatory over 50 years ago, and 60 years of bringing communities together. Now ESO is looking to the future: what breakthroughs in astronomy will we make in the 2040s and beyond?

With Expanding Horizons, ESO will search for its next innovative ground-based programme. We aim to identify the next transformational facility that will advance humanity’s understanding of the Universe whilst fostering international collaboration. ESO will accept proposals from the entire astronomical community.

The next ESO Programme should be identified in line with ESO’s Vision. It should deliver a facility that enables scientific benefits in a number of areas and serves a large part of the astronomical community. Examples include (but are not limited to):

• A new telescope facility at an existing or new observatory site;
• A significant upgrade of an existing facility that is (co-)owned by ESO;
• Other combinations. 

Important: ESO does not operate as a funding agency. The design, construction and operation of the new facility will be owned by ESO, either alone or in partnership with other organisations. 

ESO’s next Programme will be selected by ESO’s Council, following the recommendations of a Senior Science Committee (to be announced) and ESO’s Executive. The selection criteria will be:

• Scientific drive: Which fundamental problems in astronomy are expected to be addressed in the 2040s? How broad an impact will the new facility have? What synergies will there be with other ESO facilities?
• Organisational ability: Are the necessary competencies and skillsets available to own the design and development of the new facility? Is the organisation able to fulfil its operational requirements? 
• Sustainability: To what degree could the new facility be designed, built and operated in an environmentally, socially and financially sustainable manner?
• Institutional model: Should the new facility be developed in a partnership with another organisation?
• Risk assessment