New funding for the CTAO project over the next three years

The Cherenkov Telescope Array Observatory (CTAO) is a new observatory for studying gamma rays. It is currently under construction and is expected to be fully operational by 2031. It is being built at two sites, CTAO-North on the Canary Island of La Palma and CTAO-South in Chile’s Atacama Desert, and will be ten times more sensitive than previous detectors.

Construction on La Palma is already well advanced. CTAO-North will consist of four Large-Sized Telescopes (LSTs), each with a mirror diameter of about 23 meters, and nine Medium-Sized Telescopes (MSTs). The first LST has already been completed and is currently in the commissioning phase. During this phase, the different systems of the telescope are tested and optimized to prepare it for reliable scientific operation. The other three LSTs are also almost complete, while the MSTs are still under construction. CTAO-South is at an earlier stage of construction. Work at the site began in December 2025, and currently mainly roads and foundations for the telescopes are being built. A total of 14 MSTs and 37 Small-Sized Telescopes (SSTs) are planned.

Gamma rays are produced in some of the most energetic processes in the Universe, for example in the explosions of massive stars or in jets from active galaxies. Unlike charged particles such as electrons and protons, gamma rays are not deflected by magnetic fields as they travel through the Universe. Their direction can therefore provide information about where they came from. However, the gamma rays themselves do not reach the telescopes. When they enter Earth’s atmosphere, they produce a shower of secondary particles which produce so-called Cherenkov light when they travel faster than the speed of light in the atmosphere. The telescopes record this light and use it to reconstruct properties such as the energy and direction of the original gamma ray. With CTAO, researchers will study the sources of cosmic rays and other extreme astrophysical phenomena and search for signs of dark matter.

Over the coming years, CTAO will enter an important phase as construction continues and the telescopes are put into operation. A German consortium consisting of two Max Planck Institutes, one Helmholtz Center, and seven German universities, including TU Dortmund University, is involved in this work. The German Federal Ministry of Research, Technology and Space (BMFTR) is providing the participating universities with a total of €4.1 million over the next three years. Of this funding, €300,000 will go to the Dortmund subproject.

One focus of Dortmund’s involvement is the commissioning of the four LSTs on La Palma. Before the telescopes can be used for scientific observations, their different components need to be tested, calibrated, and adjusted. Early-career researchers, including members of our group, regularly travel to La Palma and work there in shifts for several weeks. The first LST is already in operation. Although data taking still has to be interrupted occasionally because of technical problems, it already works quite reliably. Most observations are carried out together with the neighboring MAGIC telescopes. Earlier this year, a major storm caused damage to the telescope, but most of it has now been repaired. Calibrations of the different subsystems and software updates are still being carried out to further improve the quality of the data, but most of the larger tests have already been completed. Some of the data can already be used for scientific analyses.

TU Dortmund University and Ruhr University Bochum are also developing a system to monitor vibrations of the LSTs. This can help detect possible damage to the drive system or the supporting structure at an early stage. Dortmund also contributes to software development for the observatory.

The research groups at TU Dortmund University and Ruhr University Bochum already work closely together as part of the Ruhr Innovation Lab and the DFG Collaborative Research Center 1491. Together, they study different topics in astrophysics, astroparticle physics, and plasma astrophysics. Multi-messenger astronomy plays an important role in this research. It combines information from different cosmic messengers, such as electromagnetic radiation, neutrinos, and gravitational waves. In the coming years, CTAO will greatly improve the possibilities for observing gamma rays and open up new opportunities for studying astrophysical phenomena together.