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International audience; The Cherenkov Telescope Array (CTA) is planned as the first ground-based gamma-ray observatory open to the worldwide physics community. The CTA Observatory (CTAO) will consist of arrays of up to 100 telescopes at two sites, one in the Northern and one in the Southern hemisphere, as well as complex and distributed software systems for an efficient operation of the arrays and for the management and scientific exploitation of the CTA data. One of the challenges in the design of such a large installation is to ensure that all the systems that compose the CTAO have well-defined scope and identified interfaces, allowing it to work reliably as a seamless whole. In this contribution, we provide an overview on a methodology for a model-based architecture approach, tailored to the CTA needs, with the main goals to (i) capture the stakeholder interactions with the CTAO, (ii) capture the processes and activities that will be required to successfully operate the CTAO and meet stakeholder expectations, including science operations and maintenance, (iii) agree on a functional decomposition of the CTAO into (sub-)systems and an allocation of the functionality to the (sub-)systems to assign responsibilities and identify interfaces. To accomplish this, we have developed an architecture approach based on process-based system scoping and using a notation based on the SysML and UML formalisms. The different views of the architecture model are presented, each focusing on different aspects of the CTAO. These views contain, among others, stakeholders and project objectives, activity diagrams for describing the CTAO processes, the context and structure of the CTAO system and sub-systems, and their relationships. In this contribution, we will focus on the methodology with a few selected examples.

The Cherenkov Telescope Array (CTA) observatory will be one of the biggest ground-based very-high-energy (VHE) gamma-ray observatory. CTA will achieve a factor of 10 improvement in sensitivity from some tens of GeV to beyond 100 TeV with respect to existing telescopes. The CTA observatory will be capable of issuing alerts on variable and transient sources to maximize the scientific return. To capture these phenomena during their evolution and for effective communication to the astrophysical community, speed is crucial. This requires a system with a reliable automated trigger that can issue alerts immediately upon detection of gamma-ray flares. This will be accomplished by means of a Real-Time Analysis (RTA) pipeline, a key system of the CTA observatory. The latency and sensitivity requirements of the alarm system impose a challenge because of the anticipated large data rate, between 0.5 and 8 GB/s. As a consequence, substantial efforts toward the optimization of high-throughput computing service are envisioned. For these reasons our working group has started the development of a prototype of the Real-Time Analysis pipeline. The main goals of this prototype are to test: (i) a set of frameworks and design patterns useful for the inter-process communication between software processes running on memory; (ii) the sustainability of the foreseen CTA data rate in terms of data throughput with different hardware (e.g. accelerators) and software configurations, (iii) the reuse of non-real-time algorithms or how much we need to simplify algorithms to be compliant with CTA requirements, (iv) interface issues between the different CTA systems. In this work we focus on goals (i) and (ii).

Utilisation des infrastructures de la Grille EGI pour les simulations de CTA