At the site of the planned European giant telescope ELT, the foundation is now in place and construction work on the huge dome has begun. The European Southern Observatory ESO made this public with a photo showing the construction work, which is now in full swing again.
The corona pandemic severely delayed the construction of the Extremely Large Telescope (formerly European Extremely Large Telescope), so the construction site was completely closed for almost a year. The ELT is scheduled to take the first scientific pictures in September 2027 and should still be well ahead of the other giant telescopes GMT (Giant Magellan Telescope) and TMT (Thirty Meter Telescope). In the case of the latter, it is not even certain where it will be.
Milestone of technology
The Extremely Large Telescope was originally supposed to start work in 2024, but the pandemic thwarted the schedule here too. By far the most powerful optical telescope in the world is being built on the Cerro Armazones mountain, which is over 3,000 meters high in the Chilean Atacama desert. About 18 meters of rock (220,000 m3) removed to make room for the Giant Telescope.
Like that of the James Webb Space Telescope (JWST), the telescope’s gigantic primary mirror with a diameter of almost 40 meters is composed of hexagonal segments. But while the JWST has 18, the ELT’s primary mirror has 798, each one is 1.5 meters tall and weighs 250 kilograms.
Meanwhile, work on the mirror elements in Europe has continued. The six individual elements of the M4 mirror, the heart of the ELT’s adaptive optics, were already completed in the autumn. It will be able to change its shape quickly and with extreme precision to compensate for disturbances from the atmosphere. Magnets on the back of the mirror are said to be able to carry out up to 1000 fine corrections per second with an accuracy of 50 nanometers.
According to ESO, the M4 mirror will be the largest deformable mirror ever, and it is one of the “most challenging and sophisticated components”. Thanks to the adaptive optics, the ELT will be able to deliver sharper images than even space telescopes like Hubble and James Webb. A special tower is being built on the giant telescope for testing and calibrating the M4 mirror. The pit dug for this purpose can also be seen in the photo that has now been published.
(Image: ESO)
(mho)