While the construction of ESO's Extremely Large Telescope (ELT) in Chile's Atacama Desert is on hold due to the COVID-19 pandemic, important progress on the project is being made elsewhere. In the past few months, design activities for the telescope’s dome have been completed (in a process called final design review) and manufacturing of the dome components is currently ongoing.
The extensive design review solved several complex problems inherent to building a top-performing science machine, with strict scientific requirements, in the extreme environment of the Atacama Desert. Engineers also had to ensure the operational requirements were met: high reliability, low maintenance, and resistance to earthquake and strong winds, for example. The latest renderings show what the dome will look like, and how subtle but important changes were made from the older designs.
The ELT dome and telescope structure contract was placed with the Italian consortium ACe (Cimolai, Astaldi). It covers not only the design, but also the manufacture, transport, construction, on-site assembly and verification of the dome and telescope structure. The company is currently working on finalising the design for the telescope structure, with the final design review anticipated to happen in the first quarter of 2021.
ACe is also manufacturing key hardware components for the dome that will protect the ELT. As part of the design process, ACe manufactured and extensively tested several critical components to qualify the design as well as the manufacturing and assembly procedures. This included prototyping and manufacturing the seismic isolation systems and testing a full-scale dome ventilation louver. It also involved testing the performance of the dome cladding panels, including a trial installation on a 10m-high partial dome structure, manufacturing the full set of dome rotation trolleys (36 units in total, each weighting 27 tons) and manufacturing the structural components for the first bottom ring of the dome lattice structure. Some of those components have already been shipped to Chile.
ESO's ELT, with a main mirror 39.3 metres in diameter, will be by far the largest optical/near-infrared telescope in the world once it sees first light later this decade. When completed, the ELT dome and telescope structure will dwarf other similar constructions around the world. The telescope structure, weighing some 3700 tonnes, will be equipped with the five telescope mirrors, which will collect and direct the light from astronomical targets to the various instruments. The instruments themselves will be placed in two platforms, about the size of a tennis court each, located on either side of the telescope structure. The giant ELT dome will house all of these structures, protecting them from the desert elements. The dome will be about 80 metres high and have a diameter of about 88 metres, giving it a footprint roughly equivalent to a football pitch. The upper part of the dome structure, out of steel and weighing about 6100 tonnes, will rotate on top of the concrete cylindrical base of the dome, to allow the telescope to point in any direction through its large observing slit.
ESO’s ELT will apply its unique angular resolution to answer the biggest astronomical questions of our time, exploring the past and present of the universe, the locations and compositions of exoplanets, and the nature of dark matter and dark energy.