The European Solar Telescope

The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope, the German Vacuum Tower Telescope and GREGOR, the French Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires, and the Dutch Open Telescope. With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems

Update on the characterisation of the pGCT, a prototype of 4m dual-mirror Cherenkov Telescope

International audienceThe Gamma-ray Cherenkov Telescope prototype (pGCT) is a prototype of an Imaging Atmospheric Cherenkov Telescope, developed as Small-Sized Telescope (SST) of 4m during the preparation of the Cherenkov Telescope Array (CTA). Based on a Schwarzschild-Couder dual-mirror optical design aiming to provide an optimised Point Spread Function (PSF) on a wide field, it had its first Cherenkov light on the Meudon site of the Observatoire de Paris in 2015. Since the decision of CTA to harmonize its future SSTs, the pGCT instrument and the experience gained with its development are now used by the Observatoire de Paris team to provide a test bench for Cherenkov astronomy and a pedagogical tool for educational purposes in Meudon. This paper briefly describes the design of the pGCT and presents the latest advances in the optics of the prototype and its characterisation, directly related to the implementation of new high-quality metallic mirrors carried out since 2020

Assessment of the GCT Prototypes Optical System Implementation and Other Key Performances for the Cherenkov Telescope Array

International audienceThe Cherenkov Telescope Array (CTA) project, led by an international collaborationof institutes, aims to create the world's largest next generation observatory for Very HighEnergy (VHE) gamma-ray astronomy. It will be devoted to observations in a wide band ofenergy, from a few tens of GeV to a few hundreds of TeV with Large, Medium and Small-sizedtelescopes.The Small-Size Telescopes (SSTs) are dedicated to the highest energy range above afew TeV and up to 300 TeV. GCT is an imaging atmospheric Cherenkov telescope (IACT)proposed for the subarray of about 70 SSTs to be installed on the Southern site of CTA inChile. The Observatory of Paris and the National Institute for Earth Sciences and Astronomy(INSU/CNRS) have developed the mechanical structure, mirrors (aspherical lightweightaluminium segments) and control system of the GCT. The GCT is based on a Schwarzschild-Couder (S-C) dual-mirror optical design which has the advantages, compared to the currentIACTs, to offer a wide field of view (~ 9°) while decreasing the cost and volume (~ 9 m x 4 mx 6 m for ~ 11 tons) of the telescope structure, as well as the camera. The prototype (pGCT)has been installed at the Meudon's site of the Observatory of Paris and was the first S-Ctelescope and the first CTA prototype to record VHE events on-sky in November 2015.After three years of intensive testing, pGCT has now been commissioned. This paperis a status report on the complete GCT telescope optical system and the performance it canprovide for CTA

Operating performance of the gamma-ray Cherenkov telescope: An end-to-end Schwarzschild–Couder telescope prototype for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) consortium aims to build the next-generation ground-based very-high-energy gamma-ray observatory. The array will feature different sizes of telescopes allowing it to cover a wide gamma-ray energy band from about 20 GeV to above 100 TeV. The highest energies, above 5 TeV, will be covered by a large number of Small-Sized Telescopes (SSTs) with a field-of-view of around 9°. The Gamma-ray Cherenkov Telescope (GCT), based on Schwarzschild–Couder dual-mirror optics, is one of the three proposed SST designs. The GCT is described in this contribution and the first images of Cherenkov showers obtained using the telescope and its camera are presented. These were obtained in November 2015 in Meudon, France

Operating performance of the gamma-ray Cherenkov telescope: An end-to-end Schwarzschild-Couder telescope prototype for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) consortium aims to build the next-generation ground-based very-high-energy gamma-ray observatory. The array will feature different sizes of telescopes allowing it to cover a wide gamma-ray energy band from about 20 GeV to above 100 TeV. The highest energies, above 5 TeV, will be covered by a large number of Small-Sized Telescopes (SSTs) with a field-of-view of around 9°. The Gamma-ray Cherenkov Telescope (GCT), based on Schwarzschild–Couder dual-mirror optics, is one of the three proposed SST designs. The GCT is described in this contribution and the first images of Cherenkov showers obtained using the telescope and its camera are presented. These were obtained in November 2015 in Meudon, France

The GCT camera for the Cherenkov Telescope Array

The Gamma Cherenkov Telescope (GCT) is one of the designs proposed for the Small Sized Telescope (SST) section of the Cherenkov Telescope Array (CTA). The GCT uses dual-mirror optics, resulting in a compact telescope with good image quality and a large field of view with a smaller, more economical, camera than is achievable with conventional single mirror solutions. The photon counting GCT camera is designed to record the flashes of atmospheric Cherenkov light from gamma and cosmic ray initiated cascades, which last only a few tens of nanoseconds. The GCT optics require that the camera detectors follow a convex surface with a radius of curvature of 1 m and a diameter of ~35 cm, which is approximated by tiling the focal plane with 32 modules. The first camera prototype is equipped with multi-anode photomultipliers, each comprising an 8×8 array of 6×6 mm2 pixels to provide the required angular scale, adding up to 2048 pixels in total. Detector signals are shaped, amplified and digitised by electronics based on custom ASICs that provide digitisation at 1 GSample/s. The camera is self-triggering, retaining images where the focal plane light distribution matches predefined spatial and temporal criteria. The electronics are housed in the liquid-cooled, sealed camera enclosure. LED flashers at the corners of the focal plane provide a calibration source via reflection from the secondary mirror. The first GCT camera prototype underwent preliminary laboratory tests last year. In November 2015, the camera was installed on a prototype GCT telescope (SST-GATE) in Paris and was used to successfully record the first Cherenkov light of any CTA prototype, and the first Cherenkov light seen with such a dual-mirror optical system. A second full-camera prototype based on Silicon Photomultipliers is under construction. Up to 35 GCTs are envisaged for CTA

The small size telescope projects for the Cherenkov Telescope Array

International audienc

The small size telescope projects for the Cherenkov Telescope Array

International audienc

Galactic transient sources with the Cherenkov Telescope Array

International audienceA wide variety of Galactic sources show transient emission at soft and hard X-ray energies: low-mass and high-mass X-ray binaries containing compact objects (e.g., novae, microquasars, transitional millisecond pulsars, supergiant fast X-ray transients), isolated neutron stars exhibiting extreme variability as magnetars as well as pulsar wind nebulae. Although most of them can show emission up to MeV and/or GeV energies, many have not yet been detected in the TeV domain by Imaging Atmospheric Cherenkov Telescopes. In this paper, we explore the feasibility of detecting new Galactic transients with the Cherenkov Telescope Array (CTA) and the prospects for studying them with Target of Opportunity observations. We show that CTA will likely detect new sources in the TeV regime, such as the massive microquasars in the Cygnus region, low-mass X-ray binaries with low-viewing angle, flaring emission from the Crab pulsar-wind nebula or other novae explosions, among others. We also discuss the multi-wavelength synergies with other instruments and large astronomical facilities