The ASTRI Project in the Framework of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) will be the next generation facility to investigate the very high-energy gamma-ray emission from a large variety of celestial sources. The full array, installed at two sites, one in the northern and one in the southern hemisphere, will start to operate at the beginning of the next decade. In the meantime, a few telescope prototypes have been developed and some pre-production CTA telescopes have been planned. Within this framework, the Italian National Institute for Astrophysics (INAF) is leading the ASTRI project, whose aim is two-fold. The ASTRI Collaboration has successfully developed and installed in Sicily a prototype of the CTA small-sized telescopes (SST), according to an innovative dual-mirror (2M) optical solution and equipped with a silicon-based photo-detector Cherenkov camera. Moreover, INAF is leading the development of one of the mini-arrays of pre-production CTA telescopes composed of at least nine dual-mirror telescopes and proposed to be installed at the CTA southern site in 2018. The ASTRI mini-array of SST pre-production CTA telescopes will be able to both verify some of the adopted innovative solutions, such as the wide field of view, and to investigate sources emitting at energies from a few TeV up to hundreds of TeV. We discuss the preliminary results obtained by the ASTRI SST-2M prototype during its ongoing commissioning phase, the expected Monte Carlo performance of the ASTRI mini-array of SST pre-production CTA telescopes, and provide an overview of the scientific topics that can be addressed both, as a stand-alone mini-array and in synergy with other pre-production CTA telescopes

Science with the ASTRI mini-array for the Cherenkov Telescope Array: Blazars and fundamental physics

ASTRI ("Astronomia a Specchi con Tecnologia Replicante Italiana") is a flagship project of the Italian Ministry of Research (MIUR), devoted to the realization, operation and scientific validation of an end-to-end prototype for the Small Size Telescope (SST) envisaged to become part of the Cherenkov Telescope Array (CTA). The ASTRI SST-2M telescope prototype is characterized by a dual mirror, Schwarzschild-Couder optical design and a compact camera based on silicon photo-multipliers. It will be sensitive to multi-TeV very high energy (VHE) gamma rays up to 100 TeV, with a PSF ∼ 6′ and a wide (9.6°) unaberrated optical field of view. Right after validation of the design in single-dish observations at the Serra La Nave site (Sicily, Italy) during 2015, the ASTRI collaboration will be able to start deployment, at the final CTA southern site, of the ASTRI mini-array, proposed to constitute the very first CTA precursor. Counting 9 ASTRI SST-2M telescopes, the ASTRI mini-array will overtake current IACT systems in differential sensitivity above 5 TeV, thus allowing unprecedented observations of known and predicted bright TeV emitters in this band, including some extragalactic sources such as extreme high-peaked BL Lacs with hard spectra. We exploited the ASTRI scientific simulator ASTRIsim in order to understand the feasibility of observations tackling blazar and cosmic ray physics, including discrimination of hadronic and leptonic scenarios for the VHE emission from BL Lac relativistic jets and indirect measurements of the intergalactic magnetic field and of the extragalactic background light. We selected favorable targets, outlining observation modes, exposure times, multi-wavelength coverage needed and the results expected. Moreover, the perspectives for observation of effects due to the existence of axion-like particles or to Lorentz invariance violations have been investigated

Expected performance of the ASTRI mini-array in the framework of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) Observatory is a world-wide project for the ground-based study of the sources of the highest energy photons. By adopting telescopes of three different size categories it will cover the wide energy range from tens of GeV up to hundreds of TeV, limited only by the source physical properties and the gamma absorption by the extragalactic background light. The full sky coverage will be assured by two arrays, one in each hemisphere. An array of small size telescopes (SSTs), covering the highest energy region (3-100 TeV), the region most flux limited for current imaging atmospheric Cherenkov telescopes, is planned to be deployed at the southern CTA site in the first phase of the CTA project. The ASTRI collaboration has developed a prototype of a dual mirror SST equipped with a SiPM-based focal plane (ASTRI SST-2M) and has proposed to install a mini-array of nine of such telescopes at the CTA southern site (the ASTRI mini-array). In order to study the expected performance and the scientific capabilities of different telescope configurations, full Monte Carlo (MC) simulations of the shower development in the atmosphere for both gammas and hadronic background have been performed, followed by detailed simulations of the telescopes. In this work the expected performance of the ASTRI mini-array in terms of sensitivity, angular and energy resolution are presented and discussed

Simulation of the ASTRI two-mirrors small-size telescope prototype for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is a world-wide project to build a new generation ground-based gamma-ray instrument operating in the energy range from some tens of GeV to above 100 TeV. To ensure full sky coverage CTA will consist of two arrays of Imaging Atmospheric Cherenkov Telescopes (IACTs), one in the southern hemisphere and another one in the northern hemisphere. CTA has just completed the design phase and it is entering in the pre-production one that includes the development of telescope precursor mini-arrays. ASTRI is an ongoing project, to develop and install at the southern CTA site one of such mini-arrays composed by nine dual-mirror small size telescopes equipped with an innovative camera based on silicon photomultiplier sensors. The end-to-end telescope prototype, named ASTRI SST-2M, has been recently inaugurated at the Serra La Nave observing station, on Mount Etna, Italy. ASTRI SST-2M expected performance has been carefully studied using a full Monte Carlo simulation of the shower development in the atmosphere and detector response. Simulated data have been analyzed using the traditional Hillas moment analysis to obtain the expected angular and energy resolution. Simulation results, together with the comparison with the available experimental measurements, are shown

The High-Level Interface Definitions in the ASTRI/CTA Mini Array Software System (MASS)

ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is a Flagship Project funded by the Italian Ministry of Education, University and Research, and led by INAF, the Italian National Institute of Astrophysics. Within this framework, INAF is currently developing an end-to-end prototype, named ASTRI SST-2M, of a Small Size Dual-Mirror Telescope for the Cherenkov Telescope Array, CTA. A second goal of the project is the realization of the ASTRI/CTA mini-array, which will be composed of seven SST-2M telescopes placed at the CTA Southern Site. The ASTRI Mini Array Software System (MASS) is designed to support the ASTRI/CTA mini-array operations. MASS is being built on top of the ALMA Common Software (ACS) framework, which provides support for the implementation of distributed data acquisition and control systems, and functionality for log and alarm management, message driven communication and hardware devices management. The first version of the MASS system, which will comply with the CTA requirements and guidelines, will be tested on the ASTRI SST-2M prototype. In this contribution we present the interface definitions of the MASS high level components in charge of the ASTRI SST-2M observation scheduling, telescope control and monitoring, and data taking. Particular emphasis is given to their potential reuse for the ASTRI/CTA mini-array

ASTRI for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) will be the largest ground-based observatory operating in the very-high-energy gamma-ray (20 GeV - 300 TeV) range. It will be based on more than one hundred telescopes, located at two sites (northern and southern hemispheres). The energy coverage, in the southern CTA array, will extend up to hundreds of TeV thanks to 70 small size telescopes (SST), with primary mirrors of about 4 meters in diameter and large field of view of the order of 9 degrees. It is proposed that one of the first sets of precursors for the CTA SSTs array will be represented by nine ASTRI telescopes. Their prototype, named ASTRI SST-2M, is installed in Italy. It is currently completing the overall commissioning before entering the science verification phase that will performed observing bright TeV sources as Crab Nebula, Mrk421 and Mrk 501 cross-checking the prototype performance with the Monte Carlo predictions. ASTRI telescopes are characterized by a dual-mirror optical design based on the Schwarzschild- Couder (SC) configuration. The focal-plane camera is curved in order to fit the ideal prescription for the SC design and the sensors are small size silicon photomultipliers read-out by a fast front-end electronics. The telescope prototype installed in Italy, has been developed by the Italian National Institute for Astrophysics, INAF, following an end-to-end approach that comprises all aspects from the design, construction and implementation of the entire hardware and software system to the final scientific products. All parts of the system have been designed to comply with the CTA requirements. A collaborative effort, addressed to the implementation of the first ASTRI telescopes for the CTA southern site, is now on-going led by INAF with the Universidade de Sao Paulo (Brazil), the North-West University (South Africa) and the Italian National Institute for Nuclear Physics

The dual-mirror Small Size Telescope for the Cherenkov Telescope Array

In this paper, the development of the dual mirror Small Size Telescopes (SST) for the Cherenkov Telescope Array (CTA) is reviewed. Up to 70 SST, with a primary mirror diameter of 4 m, will be produced and installed at the CTA southern site. These will allow investigation of the gamma-ray sky at the highest energies accessible to CTA, in the range from about 1 TeV to 300 TeV. The telescope presented in this contribution is characterized by two major innovations: the use of a dual mirror Schwarzschild-Couder configuration and of an innovative camera using as sensors either multi-anode photomultipliers (MAPM) or silicon photomultipliers (SiPM). The reduced plate-scale of the telescope, achieved with the dual-mirror optics, allows the camera to be compact (40 cm in diameter), and low-cost. The camera, which has about 2000 pixels of size 6x6 mm^2, covers a field of view of 10{\deg}. The dual mirror telescopes and their cameras are being developed by three consortia, ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana, Italy/INAF), GATE (Gamma-ray Telescope Elements, France/Paris Observ.) and CHEC (Compact High Energy Camera, universities in UK, US and Japan) which are merging their efforts in order to finalize an end-to-end design that will be constructed for CTA. A number of prototype structures and cameras are being developed in order to investigate various alternative designs. In this contribution, these designs are presented, along with the technological solutions under study

The dual-mirror Small Size Telescope for the Cherenkov Telescope Array

International audienceIn this paper, the development of the dual mirror Small Size Telescopes (SST) for the Cherenkov Telescope Array (CTA) is reviewed. Up to 70 SST, with a primary mirror diameter of 4 m, will be produced and installed at the CTA southern site. These will allow investigation of the gamma-ray sky at the highest energies accessible to CTA, in the range from about 1 TeV to 300 TeV. The telescope presented in this contribution is characterized by two major innovations: the use of a dual mirror Schwarzschild-Couder configuration and of an innovative camera using as sensors either multi-anode photomultipliers (MAPM) or silicon photomultipliers (SiPM). The reduced plate-scale of the telescope, achieved with the dual-mirror optics, allows the camera to be compact (40 cm in diameter), and low-cost. The camera, which has about 2000 pixels of size 6x6 mm^2, covers a field of view of 10{\deg}. The dual mirror telescopes and their cameras are being developed by three consortia, ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana, Italy/INAF), GATE (Gamma-ray Telescope Elements, France/Paris Observ.) and CHEC (Compact High Energy Camera, universities in UK, US and Japan) which are merging their efforts in order to finalize an end-to-end design that will be constructed for CTA. A number of prototype structures and cameras are being developed in order to investigate various alternative designs. In this contribution, these designs are presented, along with the technological solutions under study