SANTIAGO A telescope that will be the world's largest when completed could face a delay to start-up as its European backers wait for Brazil to commit to the funding needed for it to be fully operational.
The European Extremely Large Telescope (E-ELT) will have a primary mirror 39 meters (43 yards) in diameter, allowing it to gather around 15 times more light than the largest optical telescopes now functioning.
The tip of a mountain high in the Chilean desert was removed in June so site clearance could get under way, with the telescope slated to reach "first light" in 2024.
But that could now be delayed until 2026, said its operators the European Southern Observatory (ESO) on Thursday.
Full funding of construction is dependent on Brazil becoming the first non-European country to join the ESO, but that has not yet happened. The process is under way but still needs to gain congressional approval in Brazil, where support for it has been patchy.
"It became clear by mid-2014 that the ongoing day-to-day delay was posing an increasing risk to the project and to the scientific aspirations of the ESO community," said the ESO in a report of a meeting its council held this week.
The organization has responded by dividing the construction into two phases. It gave the green-light this week to the first phase, which implies spending of around 1 billion euros ($1.2 billion) and does not require Brazil's participation.
That will mean it can begin building, with contracts for the dome, main structure and some instruments due to be awarded next year.
However, unless additional funds can be identified, the two-step phase means completion could be delayed to 2026, it said.
Should Brazil finish its ratification - and start paying its 130 million-euro accession fee - by early 2017, then the ESO said it should be able to stick to its original plan.
(Reporting by Rosalba O'Brien; Editing by Jonathan Oatis)