The manufacturing and assembly of the CTAO Medium-Sized Telescopes (MST) is a complex process that involves a geographically dispersed engineering collaboration. This collaboration must integrate all stakeholders, provide effective decision-making procedures, and establish reliable and efficient material and information flow. One of the key challenges in mastering this process is the digitalisation of manufacturing planning, coordination and progress tracking processes based on a Product Lifecycle Management (PLM) system. The PLM system provides comprehensive engineering data and digital workflow for activities such as reviews and sign-offs, as well as for managing changes and non-conformities. The digitalisation of the manufacturing process enables the optimisation of logistics and the automation of workflow. It facilitates the creation of shared vision among all involved parties and ensures the prompt and effective implementation of decisions. This paper presents an overview of the current status of the MST project and the implementation of the PLM system.
The Cherenkov Telescope Array Observatory (CTAO) will be the world-wide largest and most sensitive ground-based gamma-ray observatory. CTAO consists of three telescope types: Large, Medium, and Small Sized Telescopes (LST, MST, SST). The observatory construction period is expected to commence in 2023 and will last for five years. The Medium-Sized Telescopes (MSTs) of CTA are dominating the sensitivity in the core energy range from 100 GeV to 5 TeV. Covering an about 8 degrees field of view, the modified Davis-Cotton telescopes will have a tiled reflector of 12-m diameter and 16-m focal length. This contribution will detail the construction plans of the MSTs on both observatory sites and present in detail the design and expected performance of the telescopes and cameras.
The prototype Schwarzschild-Couder Telescope (pSCT) is a candidate for a medium-sized telescope in the Cherenkov Telescope Array. The pSCT is based on a dual-mirror optics design that reduces the plate scale and allows for the use of silicon photomultipliers as photodetectors. The prototype pSCT camera currently has only the central sector instrumented with 25 camera modules (1600 pixels), providing a 2.68-deg field of view (FoV). The camera electronics are based on custom TARGET (TeV array readout with GSa/s sampling and event trigger) application-specific integrated circuits. Field programmable gate arrays sample incoming signals at a gigasample per second. A single backplane provides camera-wide triggers. An upgrade of the pSCT camera that will fully populate the focal plane is in progress. This will increase the number of pixels to 11,328, the number of backplanes to 9, and the FoV to 8.04 deg. Here, we give a detailed description of the pSCT camera, including the basic concept, mechanical design, detectors, electronics, current status, and first light.
The Cherenkov Telescope Array (CTA) is the next ground-based gamma-ray observatory in the TeV γ-ray spectral region operating with the Imaging Atmospheric Cherenkov Technique. It is based on almost 70 telescopes of different class diameters—Large-Sized Telescope, Medium-Sized Telescope (MST), and Small-Sized Telescope (SST) of 23, 12, and 4 m, respectively—to be installed in two sites in the two hemispheres (at La Palma, Canary Islands, and near Paranal, Chile). Several thousands of reflecting mirror tiles larger than 1 m2 will be produced for realizing the segmented primary mirrors of a so large number of telescopes. Almost in parallel, the ASTRI mini-array (MA) is being implemented in Tenerife (Canary Islands), composed of nine 4-m diameter dual-mirror Cherenkov telescopes (very similar to the SSTs). We completed the mirror production for all nine telescopes of the ASTRI MA and two MSTs (400 segments in total) using the cold glass slumping replication technology. The results related to the quality achieved with a large-scale production are presented, also discussing the adopted testing methods and approaches. They will be very useful for the adoption and optimization of the quality assurance process for the huge production (almost 3000 m2 of reflecting surface) of the MST and SST CTA telescopes.
The novel 9.7m Schwarzschild-Couder Telescope (SCT), utilizing aspheric dual-mirror optical system, has been constructed as a prototype medium size x-ray telescope for the Cherenkov Telescope Array (CTA) observatory. The prototype SCT (pSCT) is designed to achieve simultaneously the wide (≥ 8°) field of view and the superior imaging resolution (0.067 per pixel) to significantly improve scientific capabilities of the observatory in conducting the sky surveys, the follow-up observations of multi-messenger transients with poorly known initial localization and the morphology studies of x-ray sources with angular extent. In this submission, we describe the hardware and software implementations of the telescope optical system as well as the methods specifically developed to align its complex optical system, in which both primary and secondary mirrors are segmented. The pSCT has detected Crab Nebula in June 2020 during ongoing commissioning, which was delayed due to worldwide pandemic and is not yet completed. Verification of pSCT performance is continuing and further improvement of optical alignment is anticipated.
The Cherenkov Telescope Array (CTA) is the next generation of ground-based gamma-ray observatory. The observatory will consist of two arrays, one located in the southern hemisphere (Paranal, Chile) and the other in the northern hemisphere (Canary Island, Spain), covering the whole sky in the range of observation. More than 100 telescopes are planned to be in operation for as long as 30 years, which motivated the development of a continuous condition monitoring of the individual telescopes. The main goal of the monitoring is to detect degradation and failures before critical damages occur. Two approaches are considered: the structure monitoring system, in which the Eigenfrequencies of the telescope and their damping rates are measured and monitored; and the drive monitoring, in which the power spectra of rotating components are measured during telescope movements. The structure monitoring concept system was applied to the prototype Medium Size telescope (MST) prototype of CTA in Berlin during late 2018 and in 2019, and the first results are presented here. The system showed reasonable stability during periods, in which the telescope structure was unchanged. The system was also capable to detect mechanical changes, e.g. varying tension in the steel ropes of the camera support structure. The successful implementation of the structure monitoring system supports the decision of implementing the system in all future MSTs.
For the first time in the history of ground-based y-ray astronomy, the on-axis performance of the dual mirror, aspheric, aplanatic Schwarzschild-Couder optical system has been demonstrated in a 9:7-m aperture imaging atmospheric Cherenkov telescope. The novel design of the prototype Schwarzschild-Couder Telescope (pSCT) is motivated by the need of the next-generation Cherenkov Telescope Array (CTA) observatory to have the ability to perform wide (≥8°) field-of-view observations simultaneously with superior imaging of atmospheric cascades (resolution of 0:067 per pixel or better). The pSCT design, if implemented in the CTA installation, has the potential to improve significantly both the x-ray angular resolution and the off-axis sensitivity of the observatory, reaching nearly the theoretical limit of the technique and thereby making a major impact on the CTA observatory sky survey programs, follow-up observations of multi-messenger transients with poorly known initial localization, as well as on the spatially resolved spectroscopic studies of extended x-ray sources. This contribution reports on the initial alignment procedures and point-spread-function results for the challenging segmented aspheric primary and secondary mirrors of the pSCT.
The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for gamma-ray astronomy at very-high energies. It will consist of over a hundred telescopes of different sizes (small, medium, and large) located in the northern and southern hemispheres. The Italian National Institute of Astrophysics (INAF) contributes to CTA through the ASTRI project (Astrofisica con Specchi a Tecnologia Replicante Italiana), whose main aim is to provide a series of dual-mirror small-sized telescopes (SST-2M ASTRI) and the mirrors for the single-mirror design of the medium-sized telescopes (MST). Both the primary mirror of the SST-2M ASTRI and the mirror of the MST are segmented, and such segments are realized with cold-slumping technology already used for the mirror facets of MAGIC, a system of two Cherenkov telescopes operating on the Canary Island of La Palma. On the other hand, the secondary mirror of the SST-2M ASTRI is monolithic and is realized with hot-slumping technology. Currently, we have completed the mirror production for nine SST-2M ASTRI telescopes, which will form the so-called ASTRI Mini-Array. Moreover, we have almost completed also the production of mirrors for two MSTs. In this paper, we present the mirror designs and describe the qualification activities that were performed to assess and consolidate the production process. Moreover, we report on the quality assurance approach we adopted to monitor and verify the production reliability. Finally, we present the performance of the produced mirrors and discuss their compliance with the CTA requirements.
The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for gamma-ray astronomy at very high energies in the range from 20 GeV to 300 TeV.1 In order to cover the entire sky an observatory with two telescope arrays is planned, one in the southern hemisphere and one in the northern hemisphere. Each site will combine imaging air Cherenkov telescopes of different sizes and designs to cover the very wide energy range. These sites will complement each other, providing full-sky coverage for galactic and extra-galactic sources. At least three telescope types are required to cover the full CTA energy range in a cost-effective way. The sensitivity in the core energy range between 150 GeV and 5 TeV will be dominated by up to 40 Medium Size Telescopes (MSTs) distributed over both observatory sites. It is intended to equip the MSTs with FlashCam and NectarCAM cameras. This document describes the aspects of the MST design and the status of commissioning and performance validation of the individual assemblies.
The Cherenkov Telescope Array (CTA) will be the next-generation ground-based detector for gamma rays with very high energies. Telescopes will be located at one site each in both the northern and southern hemisphere. The arrays will comprise, in total, more than 100 telescopes of different sizes and designs. The sensitivity of CTA in its central energy range, i.e. between approximately 100 GeV and 1 TeV, will be driven by the performance of the Medium-Sized Telescopes (MSTs). This performance crucially depends on an exact alignment of the facets of the tessellated mirror surface of each telescope. In this contribution, an automated mirror alignment procedure for MSTs is presented. This procedure consists of two steps. First a rough mirror alignment is achieved with the socalled Bokeh method, which is based on the non-focused imaging of an artificial light source onto the Cherenkov camera plane. Afterwards, an optimal mirror alignment is achieved with an alignment procedure based on the focused imaging of stars. Here, the Bokeh method will be described in detail, including the hardware and software setups, devised technologies and pattern recognition with classical and neural network-based methods. Also results from star alignment procedures are given and compared to results from the Bokeh method. The performance of the presented approach is demonstrated with results obtained from measurements at the MST prototype installation in Berlin, Germany.
Today the scientific community is facing an increasing complexity of the scientific projects, from both a technological and a management point of view. The reason for this is in the advance of science itself, where new experiments with unprecedented levels of accuracy, precision and coverage (time and spatial) are realised. Astronomy is one of the fields of the physical sciences where a strong interaction between the scientists, the instrument and software developers is necessary to achieve the goals of any Big Science Project. The Cherenkov Telescope Array (CTA) will be the largest ground-based very high-energy gamma-ray observatory of the next decades. To achieve the full potential of the CTA Observatory, the system must be put into place to enable users to operate the telescopes productively. The software will cover all stages of the CTA system, from the preparation of the observing proposals to the final data reduction, and must also fit into the overall system. Scientists, engineers, operators and others will use the system to operate the Observatory, hence they should be involved in the design process from the beginning. We have organised a workgroup and a workflow for the definition of the CTA Top Level Use Cases in the context of the Requirement Management activities of the CTA Observatory. Scientists, instrument and software developers are collaborating and sharing information to provide a common and general understanding of the Observatory from a functional point of view. Scientists that will use the CTA Observatory will provide mainly Science Driven Use Cases, whereas software engineers will subsequently provide more detailed Use Cases, comments and feedbacks. The main purposes are to define observing modes and strategies, and to provide a framework for the flow down of the Use Cases and requirements to check missing requirements and the already developed Use-Case models at CTA sub-system level. Use Cases will also provide the basis for the definition of the Acceptance Test Plan for the validation of the overall CTA system. In this contribution we present the organisation and the workflow of the Top Level Use Cases workgroup.
The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for gamma-ray astronomy, covering an energy range from a few tens of GeV to a few hundred TeV. The CTA project is currently in the design and prototyping phase, the start of construction is planned for 2016. The planned sensitivity of CTA improves on current ground based Cherenkov telescope experiments by about an order of magnitude. In the core energy range this sensitivity will be dominated by up to 40 Medium-Sized Telescopes (MSTs). These telescopes, of a modified Davies-Cotton mount type with a reflector diameter of 12 m, are currently being prototyped. A full-size mechanical prototype has been operating in Berlin since 2012. Several types of prototype mirrors have been developed and tested, and are mounted on the telescope. CCD cameras with various lenses are mounted on the prototype for studying deformation of the structure, testing alignment techniques, and telescope pointing using astrometry methods. The report will focus on results of optical and structural measurements, commissioning and testing of the MST prototype in Berlin, as well as the final design.
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