BBC.com. A contract has been signed that will lead to the construction of one of this century’s key astronomical facilities.

The European Extremely Large Telescope (E-ELT) will be the biggest optical and infrared observatory ever built, with a primary mirror nearly 40m across.

The Italian-led ACe Consortium will manufacture, transport, and assemble the E-ELT’s major structural elements – its support frame and protective dome.

It should enable the Chile-based telescope to see ”first light” in 2024.

At €400m (£305m; $445m), the contract is the largest ever awarded by the European Southern Observatory – an intergovernmental organisation that runs some of the world’s largest and most advanced telescopes.

It has already had the top of the Armazones mountain in Chile’s Atacama Desert levelled to receive the observatory.

Development on the mirrors – in particular, a very complex quaternary mirror – continues apace.

And commissioning steps have been made on the three initial instruments and adaptive optics system (the technology used to overcome atmospheric disturbance when looking at stars).

The support structure and dome were seen as significant outstanding items.

The signatures put to their construction contract in Garching bei München, Germany, on Wednesday mean the E-ELT project can now move to full implementation. Read the full article here.