Contract signed for construction of CTAO-South roads and telescope foundations

This week, a major contract, worth several million Euros, has been signed between ESO and a consortium of Chilean companies for the construction of telescope foundations for the Cherenkov Telescope Array Observatory’s (CTAO’s) southern hemisphere array (CTAO-South) at ESO’s Paranal Observatory in Chile. The contract includes more than 50 foundations for CTAO-South telescopes, as well as approximately 17 km of roads connecting these foundations to the support facilities. ESO, a founding member of the CTAO European Research Infrastructure Consortium and host of its southern array, signed the contract on behalf of this international organisation. The construction of this important civil infrastructure is expected to take one year, paving the way for the first telescopes to be erected on site. Therefore, this milestone marks the beginning of the array’s construction in the southern hemisphere. 

The CTAO will be the largest and most powerful ground-based observatory for gamma-ray astronomy. It is composed of two telescope arrays—CTAO-South, and CTAO-North in La Palma, Spain. One located in the southern hemisphere and the other in the northern hemisphere, both will keep a watchful eye out for an elusive form of radiation called Cherenkov radiation. When cosmic gamma rays reach the atmosphere and interact with it, they generate a cascade of ultra-energetic particles; as they move through the air, these particles create a faint blue flash of “Cherenkov light”. By analysing this faint light, astronomers can infer much about the cosmic sources, like supermassive black holes and supernova remnants, that emitted the original gamma rays. 

To capture Cherenkov radiation, the CTAO-South site will consist of 51 individual telescopes of different sizes to detect both bright and faint events. The site will cover an area of about 3 square kilometres and is located about 10 kilometres away from Cerro Paranal, the home of ESO’s Very Large Telescope. Once built, the CTAO will make data and analysis software publicly available for the entire global scientific community to share, strengthening worldwide collaboration and helping to answer questions across both astronomy and particle physics, like the hunt for dark matter, the mechanics of supernovae, and how dense neutron stars collide. 

The CTAO will be the first observatory of its kind, able to observe the high-energy Universe with unparalleled sensitivity. Its location near Cerro Paranal, far from light pollution sources and under one of the world’s darkest and most pristine night skies, is key to detecting the extremely faint Cherenkov blue light. 

More information 

In January 2025, the CTAO was established as a European Research Infrastructure Consortium (ERIC) by the European Commission. The Founding Members of the CTAO ERIC are Austria, the Czech Republic, the European Southern Observatory (ESO), France, Germany, Italy, Poland, Slovenia, and Spain. Additionally, Japan is a Strategic Partner, and the accession of Switzerland and Croatia as Founding Members is being processed.

Courtesy of European Southern Observatory