On December 17, 2025, the construction of the Cherenkov Telescope Array Observatory (CTAO) southern site was officially launched in the Atacama Desert, Chile. The groundbreaking ceremony brought together representatives from CTAO, the European Southern Observatory (ESO), and government authorities.
This event marks a major milestone for high-energy astronomy and holds special significance for IRFU, which plays a key role in the development of the observatory.
700 Mirrors by 2030, 200 as Early as 2026!
IRFU is contributing to the project by supplying 700 mirrors for 7 of the 14 Medium-Sized Telescopes (MSTs) at CTAO’s southern site.
R&D for these mirrors began in 2009 at IRFU, with prototypes developed in collaboration with the French company Kerdry, based in Brittany. The final design was completed in 2019 to meet the technical specifications. Since then, Kerdry has been producing the mirrors in series. Before shipment, each mirror undergoes final characterization in a dark room at IRFU.
The first two batches of 100 mirrors each, currently undergoing validation at IRFU, will equip the first MSTs by late 2026.
9 NectarCam Cameras by 2030, the first as early as 2026!
The NectarCAM, a camera designed for CTAO’s MSTs, is currently being integrated and verified at IRFU.
NectarCAM is a 3m x 3m x 1.5m instrument weighing approximately 2.3 tons. It features a wide 8-degree field of view and includes 1,855 pixels, grouped into 265 modules of seven photomultiplier tubes (PMTs) each.
IRFU is responsible for the integration and testing of the cameras at the Saclay site, coordinating with CNRS laboratories (IN2P3 and INSU), as well as the design and supply of electronic components for signal sampling.
Camera Exchange Operations Between the Dark Room and Integration Hall
The first NectarCAM will be shipped to the CTAO southern site in 2026.
Its installation will take place once the structure of the first MST is erected, and it will participate in the very first sky observations. Teams from IRFU will be directly involved in installing the camera in Chile and validating its data. By 2030, a total of nine NectarCAM cameras will be integrated and tested at IRFU for delivery to CTAO.
From Cherenkov Light to Celestial Objects: Data Analysis
IRFU is heavily involved in the development of software components. Sky map analyses are performed using Gammapy, an open-source software selected by the Cherenkov Telescope Array Observatory (CTA) in June 2021.
Gammapy has benefited from the contributions of around 70 scientists worldwide, with strong involvement from German and French laboratories, including IRFU’s Department of Astrophysics (IRFU/DAp).
The IRFU team contributes to the development of components for:
- Control and operation of the NectarCAM camera
- Data processing systems for the telescopes
The team is also engaged in prospective studies to define and optimize future observations for scientific topics of interest to the institute, such as dark matter research, tansient sources (GRBs), galactic and extragalactic surveys, studies of the central region of the Milky Way, multi-messenger studies (gamma photons, gravitational waves, neutrinos).
Contacts IRFU
- DPhP: Jean-François Glicenstein, François Brun, Emmanuel Moulin
- DAp : Thierry Stolarczyk
- DEDIP : Eric Delagnes, Jean-Marc Reymond
CTAO Science Book published in 2018
