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CTAO News: New Array Layouts for the Upcoming New Legal Entity

In summer 2022, the Cherenkov Telescope Array Observatory (CTAO) released the layouts that define the geographical position of the elements that will compose the two CTAO arrays, including the telescopes, calibration systems and atmospheric characterization devices. The distribution considers the approved number of telescopes within the so-called Alpha Configuration: 13 telescopes (four Large-Sized Telescopes, LST, and nine Medium-Sized Telescopes, MST) distributed over an area of ~0.5 km2 for the CTAO Northern Array at La Palma, Spain; and 51 telescopes (14 MSTs and 37 Small-Sized Telescopes, SSTs) over a ~3 km2 surface for the CTAO Southern Array in the Atacama Desert, Chile.

These coordinates are the result of a meticulous optimization to reach the most outstanding scientific performance. The optimization was led by the CTAO Project Scientist, Roberta Zanin, in close collaboration with the Cherenkov Telescope Array Consortium (CTAC) Physics Groups that supported the process.

“The defined layout ensures that the CTAO will have 5 to 10 times better sensitivity than any current instrument. Small modifications may occur based on local geophysical constraints and other factors, but any shift would be limited to prevent a significant difference in terms of performance,” says Roberta Zanin. “With such unprecedented sensitivity, we will guarantee transformational science.”

Layout of the CTAO Northern Array on La Palma, Spain (left) and the CTAO Southern Array in the Atacama Desert, Chile (right). Credits: CTAO and CTAC.

The Alpha Configuration and its geographical positions will be used in the coming Construction Phase of the Observatory, which will initiate once the CTAO transitions its legal status from the current gGmbH (under German law) to a European Research Infrastructure Consortium or ERIC (under European law).

In May 2022, the CTAO’s Board of Governmental Representatives (BGR) submitted the formal request to the European Commission to establish the CTAO ERIC. This request, known as the “Step 2” application, included the final version of all the required documentation with the approval of the future CTAO ERIC member countries, as their formal commitment to build and support the Observatory throughout its lifetime.

“The CTAO gGmbH was charged with two main goals: On the one hand, preparing for construction and, on the other hand, achieving the formation of the ERIC. With this submission, the preparatory phase has concluded. Our hope is that the European Commission ratifies the ERIC before the end of 2023,” explains Federico Ferrini, Managing Director of the CTAO gGmbH, who also comments: “Everything is in order from the managerial point of view to start the construction as soon as the formal conditions are satisfied.”

The European Commission is currently revising the documentation to prepare its final decision. The establishment of the CTAO ERIC, one of biggest milestones in the lifetime of the Observatory, is expected to take place in the first half of 2023. The launch of the CTAO ERIC marks the official start of the construction of the CTAO, the first ground-based gamma-ray observatory and the world’s most powerful instrument to detect this high-energy radiation. And with the data open to all, for the first time, exciting advances in the way we see the Universe are just around the corner!

Cherenkov Telescope Array Observatory