CTA: Cherenkov Telescope Array

Manel Martínez

The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for gamma-ray astronomy at very-high energies. With more than 100 telescopes located in the northern (ORM Observatory, La Palma) and southern (ESO Paranal Observatory, Chile) hemispheres, CTA will be the world’s largest and most sensitive high-energy gamma-ray observatory.

Introduction

CTA will observe the sky at an unprecedented very high energy. In fact, the cosmic particle accelerators CTA will probe can reach energies inaccessible to man-made accelerators like the Large Hadron Collider. CTA’s unique capabilities will help us to address some of the most perplexing questions in astrophysics. CTA will seek to understand the impact of high-energy particles in the evolution of cosmic systems and to gain insight into the most extreme and unusual phenomena in the Universe. CTA will search for annihilating dark matter particles and deviations from Einstein’s theory of relativity and even conduct a census of particle accelerators in the Universe.

Progress of the CTA project in 2019

In 2019 the main progress in the CTA project in what concerns politics has been the agreement of setting as soon as possible a ERIC (European Research Infrastructure Consortium) structure for the CTA Observatory, substituting the current GmbH temporary solution and, in what concerns construction, the commissioning and first Crab Nebula detection recorded by the LST1 prototype in November 24th 2019.

During 2019 the gamma ray group at IFAE was composed by about 15 physicists with similar proportion of senior scientists, postdocs and PhD students and shared its time between the CTA project and the MAGIC Telescopes. In addition about 10 engineers and technicians (software, mechanics and electronics) invested a good fraction of their time for the CTA project at IFAE.

Along 2019 IFAE has continued participating with high impact and visibly in CTA. A. Moralejo has served as CTA’s Coordinator of the Analysis and Simulations working group, and IFAE has held important responsibilities also at the highest management level of the LST Collaboration: M. Martinez has served as the Chair of its Steering Committee and O. Ballester has been the LST Systems Engineer, O. Blanch the Camera Coordinator, A. Moralejo the Software Coordinator. All them have been members of the Executive Board of the LST project.

In addition, until end of spring 2019 M. Martinez continued as well as the leader of the 13 Spanish groups that presently constitute the CTA-Spain consortium.

For the IFAE/UAB Raman LIDAR project, during the year 2019 the LIDAR has been commissioned and upgraded to strict safety and reliability requirements, and a “CTA Pathfinder” status has been granted by CTAO, allowing a deployment at the ORM observatory for a period of about one year under the umbrella of CTA-North for on-site performance and endurance tests.

In what concerns mechanics, during 2019 the final Azimuth Locking System (ALS), a mechanical system designed by IFAE to lock automatically the LST in the parking position and hold it in the worst meteorological condition expected, was build with FEDER funds administrated by IAC under the supervision of IFAE engineers. It was successfully installed by the IFAE engineering team in the LST in November 2019 (see fig 1)

During the last few years, IFAE has played an important role in the CTA Analysis and Simulations working group, with the development of an independent analysis chain within the framework of the MAGIC reconstruction software (MARS). The results from the simulations have been instrumental in the evaluation of the proposed locations for CTA north and south, and in the definition of the so-called “baseline designs” for the two arrays. The CTA Consortium acknowledged this role by appointing A.Moralejo as the Coordinator of the Analysis and Simulations working group during 2019. In addition, IFAE has coordinated the development of the data analysis software used in the commissioning of the first LST.

In what concerns Data, after the end of the European Commission H2020 project ASTERICS, IFAE has kept actively contributing to the development of the first open, high-level data format for Atmospheric Cherenkov telescopes data, now within the EU Project ESCAPE.

Figure 1: The ALS (Azimuth Locking System) designed, installed and commissioned by the IFAE mechanical team, in the open position.

The commissioning of the first LST camera at the ORM

IFAE experts had a key role in the commissioning of the first LST camera at the ORM

The most important IFAE activity in 2019 has been the commissioning of the first LST camera at ORM, in which the experts from IFAE have played a key role.

During the whole year, the IFAE team, composed by O.Blanch, E.Moretti, L.Jouvin and D.Kerszberg, together with the IFAE engineering team, have been taking a leading participation in the technical shifts at ORM for the commissioning of the LST1 camera.

As a consequence, the camera could record gamma ray events from the Crab Nebula and detect it with high significance in a very short time immediately after pointing in its direction (see figure 2), a real highlight in the progress of the LST1 commissioning.

Thanks to its leading role in the construction, integration and commissioning of the LST1 camera, a UTE (Union Temporal de Empresas) lead by IFAE and including ICC-UB, was awarded the 3 M€ tendering of FEDER funds administrated by the IAC, for the delivery of the cameras for the three remaining LSTs.

Figure 2: Gamma ray signal from the first pointing to the Crab Nebula, recorded by the LST1 Telescope in Nov 24th 2019.