The mission of the SKA Observatory is to build and operate cutting-edge radio telescopes to transform our understanding of the Universe and deliver benefits to society. To fulfill this mission, the SKA radio telescopes have to deal with challenges never faced before. One of the most challenging aspects, especially for the SKA-Low radio telescope, working between 50 and 350 MHz is the calibration, done at different levels, of such a complex telescope in such a harsh environment. Prototyping of the front end, as well as of some of the backend components, is essential in order to evaluate the real behavior of the aperture array and develop and test calibration procedures and propose improvements to make sure that the requirements needed are achieved. This paper presents the latest SKA-Low Aperture Array Verification System version 3 and how this contributes to the risk mitigation and decision making for some fundamental aspects of the SKA-Low radio telescope.

The Square Kilometre Array Observatory mission is to "build and operate cutting-edge radio telescopes to transform our understanding of the Universe and deliver benefits to society through global collaboration and innovation". It will initially realise this through the construction of the world's largest radio telescope facility, composed of a pair of interferometric arrays, SKA-Low (Australia; 50-350 MHz; 74 km max baseline) and SKA-Mid (South Africa; 350 MHz - 15.4 GHz; 150 km max baseline). With the construction approved in July 2021, and permitting access provided to both sites by December 2022, we describe the high-level construction strategy, in particular, to develop the earliest possible working demonstration of the architecture and then maintain a continuously working and expanding facility that demonstrates the full performance capabilities of the SKA design. We report the current status of the infrastructure development, component manufacture, array deployments and system integration on both sites. We highlight the progress to-date against the planning baselines for budget, schedule and performance to indicate the trajectories for community engagement and early science. We also note the challenges encountered and navigated in the execution of global, large research infrastructure construction as well as the broader impacts for such investments, beyond the planned scientific research.

Solaris is a scientific and technological project aimed at the development of a smart Solar monitoring system at high radio frequencies, based on single-dish imaging techniques. It combines the implementation of dedicated and interchangeable high-frequency receivers on existing small single-dish radio telescope systems (1.5/2.6m class) available in our laboratories and in Antarctica, to be adapted for Solar observations. Solaris can perform Solar imaging observations nearly 20h/day during Antarctic summer with optimal sky opacity, and it will be the only Solar facility offering continuous monitoring at 100GHz. In perspective, our system could be implemented also in the Northern hemisphere to offer unprecedented Solar radio monitoring and imaging for the whole year.

Technical leadership is a skill defined in the INCOSE professional competencies. This paper presents reflections on a shared learning journey about technical leadership from the perspective of a group of emerging technical leaders. These reflections provide insights around building awareness, navigating power and influence, benchmarking personal performance, developing capacity for change and establishing critical friends. The final section provides lessons for working as a global team in technical leadership. This paper is of relevance to any technical leader looking to develop this capacity across technical sectors.

The Square Kilometre Array Telescope working at Low Frequencies (SKA-Low, 50-350 MHz) is one of the two interferometric arrays under construction by the SKA Observatory aiming to "build and operate cutting-edge radio telescopes to transform our understanding of the Universe". The SKA-Low telescope architecture is quite complex and consists of 512 stations. These stations are arrays, each made up of 256 dual polarized log-periodic antennas. For this reason, such complex architecture has gone through a comprehensive set of investigations, design decisions and improvements which has led to the latest updates and considerations presented in this paper, as well as results from the latest phased array prototype.

Abstract. Guest Editors Anna Bonaldi, Stefan J. Wijnholds, Luca Stringhetti, and Justin Jonas summarize the Special Section on the SKA Observatory.

We present the main performance aspects of the sensitivity and dynamic range of the Square Kilometre Array (SKA). The sensitivity and dynamic range of a radio astronomy interferometer are affected by different sources of errors and noises. A general description of these effects is given, focusing on the direction-independent effects. (C) 2022 Society of Photo-Optical Instrumentation Engineers (SPIE)

The Square Kilometre Array (SKA) project will build the largest radio telescope in the world with telescope facilities deployed in Australia and South Africa covering a frequency range from 50 MHz to 15 GHz (initial phase). The approval for the start of construction from its governing Council occurred in June 2021. This paper reviews the key science drivers and the outline observatory organization, design summary and site locations. We note the current progress and status of the SKA construction and projected schedule, noting the challenges within the current global climate.

The Square Kilometre Array (SKA) is a next-generation radio astronomy facility that will revolutionize our understanding of the Universe and the laws of fundamental physics. To achieve the intended objectives, it needs a stable reference frequency and accurate timing signals at each digitizer. These references are used for digitizing astronomical signals received from the receptors. The stability and accuracy of these references are highly important for coherently sampling the astronomical data. They are distributed using long-distance fibers that are susceptible to environmental perturbations, which makes meeting the requirements a challenge. The system overcomes these perturbations by actively stabilizing the noise during fiber transmission to achieve the required reference signal stability and sub-nanosecond level of timing accuracy. We collect together summary descriptions of the sub-systems designed for distributing the reference frequency and timing signals for each telescope, to provide an overview of the whole timing and frequency system for the SKA. (C) 2022 Society of Photo-Optical Instrumentation Engineers (SPIE)

The Square Kilometre Array is a global research infrastructure project to construct and operate a radio telescope observatory of unprecedented scale. The first stage of the project’s implementation (SKA1) has concluded its design phase and is about to begin construction in 2021. Composed of two interferometric arrays covering a frequency range of 50-350 MHz in Australia (SKA-LOW) and 350 MHz to 15.4 GHz in South Africa (SKA-MID), the observatory provides sensitivity and resolution which advance the currently available research infrastructure capabilities across a range of scientific frontiers. We describe the design development process for the SKA1, the antenna design and specifications, and the current construction planning and schedule.

We report on the first detection of very high-energy gamma-ray emission from the Crab Nebula by a Cherenkov telescope in dual-mirror Schwarzschild-Couder (SC) configuration. This result has been achieved by means of the 4 m ASTRI-Horn telescope, operated on Mt. Etna, Italy, and developed in the context of the Cherenkov Telescope Array Observatory preparatory phase. The dual-mirror SC design is aplanatic and characterized by a small plate scale, which allows us to implement large cameras with a large field of view, with small-size pixel sensors and a high level of compactness. The curved focal plane of the ASTRI camera is covered by silicon photo-multipliers, managed by an unconventional front-end electronic system that is based on a customized peak-sensing detector mode. The system includes internal and external calibration systems, hardware and software for control and acquisition, and the complete data archiving and processing chain. These observations of the Crab Nebula were carried out in December 2018 during the telescope verification phase for a total observation time (after data selection) of 24.4 h, equally divided between on- and off-axis source exposure. The camera system was still under commission and its functionality was not yet completely exploited. Furthermore, due to recent eruptions of the Etna Volcano, the mirror reflection efficiency was reduced. Nevertheless, the observations led to the detection of the source with a statistical significance of 5.4σ above an energy threshold of ∼3 TeV. This result provides an important step toward the use of dual-mirror systems in Cherenkov gamma-ray astronomy. A pathfinder mini-array based on nine ASTRI-like telescopes with a large field-of-view is in the course of implementation.

Lean Product Development (LPD) is suggested as an approach that can reduce waste in projects aimed at developing technically complex items, which typically present substantial uncertainty about their output, as well as higher costs and longer development times. However, how can LPD be implemented in complex projects, where some redundancies in the development process are considered necessary in order to guarantee the quality of the final outcome? This paper answers this question, through a survey conducted at INAF, the Italian Institute of Astrophysics, that runs complex projects. The evidence shows that complex projects can actually be affected by the types of waste reported in LPD literature. Still, researchers may fail to determine the real priorities of intervention as they have trouble distinguishing between value-adding and value-destroying activities. Furthermore, they do not perceive the relevance of addressing the wastes generated by their own work; on the contrary, they place considerable attention on inefficiencies that are beyond the scope of their direct responsibilities. Recommendations to overcome this problem are proposed.

This paper will describe the progress of the SKA-1 Telescope during the period from Preliminary Design Review to Critical Design Review. In addition to this, it will provide information on the management of the project with respect to managing cost and scope whilst working within a fixed cost cap. The paper will consider the balance between the technical choices made with the risk of delivering a large, distributed observatory across several continents. In addition, it will consider the challenges of carrying this out whilst developing the organisation towards an Inter-Governmental Organisation. It will consider, briefly, the key management tools used and the lessons learned.

The focus of this paper is to describe the front-end of the SKA1-LOW Telescope and the next steps in its design towards the critical design review.

ASTRI SST-2M is an end-to-end telescope prototype developed by the Italian National Institute of Astrophysics (INAF) in the framework of the Cherenkov Telescope Array (CTA). The CTA observatory, with a combination of large-, medium-, and small-sized telescopes (LST, MST and SST, respectively), will represent the next generation of imaging atmospheric Cherenkov telescopes. It will explore the very high-energy domain from a few tens of GeV up to few hundreds of TeV.The ASTRI SST-2M telescope structure and mirrors have been installed at the INAF observing station at Serra La Nave, on Mt. Etna (Sicily, Italy) in September 2014. Its performance verification phase began in autumn 2015. Part of the scheduled activities foresees the study and characterization of the optical and opto-mechanical performance of the telescope prototype.In this contribution we report the results achieved in terms of kinematic model analysis, mirrors reflectivity evolution, telescopes positioning, flexures and pointing model and the thermal behavior.

The ASTRI mini-array, composed of nine small-size dual-mirror (SST-2M) telescopes, has been proposed to be installed at the southern site of the Cherenkov Telescope Array (CTA), as a set of pre-production units of the CTA observatory. The ASTRI mini-array is a collaborative and international effort carried out by Italy, Brazil and South-Africa and led by the Italian National Institute of Astrophysics, INAF. We present the main features of the current implementation of the Mini-Array Software System (MASS) now in use for the activities of the ASTRI SST-2M telescope prototype located at the INAF observing station on Mt. Etna, Italy and the characteristics that make it a prototype for the CTA control software system. CTA Data Management (CTADATA) and CTA Array Control and Data Acquisition (CTA-ACTL) requirements and guidelines as well as the ASTRI use cases were considered in the MASS design, most of its features are derived from the Atacama Large Millimeter/sub-millimeter Array Control software. The MASS will provide a set of tools to manage all on-site operations of the ASTRI mini-array in order to perform the observations specified in the short-term schedule (including monitoring and controlling all the hardware components of each telescope and calibration device), to analyze the acquired data online and to store/retrieve all the data products to/from the on-site repository.

The ASTRI SST-2M telescope is an end-to-end prototype proposed for the Small Size class of Telescopes (SST) of the future Cherenkov Telescope Array (CTA). The prototype is installed in Italy at the INAF observing station located at Serra La Nave on Mount Etna (Sicily) and it was inaugurated in September 2014. This paper presents the software and hardware architecture and development of the system dedicated to the control of the mount, health, safety and monitoring systems of the ASTRI SST-2M telescope prototype. The mount control system installed on the ASTRI SST-2M telescope prototype makes use of standard and widely deployed industrial hardware and software. State of the art of the control and automation industries was selected in order to fulfill the mount related functional and safety requirements with assembly compactness, high reliability, and reduced maintenance. The software package was implemented with the Beckhoff TwinCAT version 3 environment for the software Programmable Logical Controller (PLC), while the control electronics have been chosen in order to maximize the homogeneity and the real time performance of the system. The integration with the high level controller (Telescope Control System) has been carried out by choosing the open platform communications Unified Architecture (UA) protocol, supporting rich data model while offering compatibility with the PLC platform. In this contribution we show how the ASTRI approach for the design and implementation of the mount control system has made the ASTRI SST-2M prototype a standalone intelligent machine, able to fulfill requirements and easy to be integrated in an array configuration such as the future ASTRI mini-array proposed to be installed at the southern site of the Cherenkov Telescope Array (CTA).

ASTRI SST-2M is an Imaging Atmospheric Cherenkov Telescope (IACT) developed by the Italian National Institute of Astrophysics, INAF. It is the prototype of the ASTRI telescopes proposed to be installed at the southern site of the Cherenkov Telescope Array, CTA. The optical system of the ASTRI telescopes is based on a dual mirror configuration, an innovative solution for IACTs, and the focal plane of the camera is composed of silicon photo-multipliers (SiPM), a recently developed technology for light detection, that exhibit very fast response and an excellent single photoelectron resolution. The ASTRI camera electronics is specifically designed to directly interface the SiPM sensors, detecting the fast pulses produced by the Cherenkov flashes, managing the trigger generation, the digital conversion of the signals and the transmission of the data to an external camera server connected through a LAN. In this contribution we present the general architecture of the camera electronics developed for the ASTRI SST-2M prototype, with special emphasis to some innovative solutions.

Having a solid verification and validation Plan and a clear strategy to implement it plays a crucial role in successfully delivering any project e.g. governative, commercial or scientific. A specific tailoring is required but at the same ti me it is fundamental to share needs, experiences and methods spreading the best practices in the Italian Eco-System and highlighting the commonalities. In this framework the VVT working group of AISE hosted a 1-day workshop held in Bologna at the Area della Ricerca the 26th of May 2016 “Verification Validation and Testing: Passion and Deployment challenges”. This workshop coordinated by AISE and organized by a Research Institute (INAF) and an Industrial partner (Tetra Pak Packaging Solutions) gathered together practitioners for different background (academia, research, industry, software vendors) for a full day discussion and collaborative workshop. This paper presents the outcomes and foresees future steps Keywords—system engineering; verification and validation; best practices.