99 research outputs found
Status and plans for the Array Control and Data Acquisition System of the Cherenkov Telescope Array
No full textFAIR high level data for Cherenkov astronomy
No full textInternational audienceWe highlight here several solutions developed to make high-level Cherenkov data FAIR: Findable, Accessible, Interoperable and Reusable. The first three FAIR principles may be ensured by properly indexing the data and using community standards, protocols and services, for example provided by the International Virtual Observatory Alliance (IVOA). However, the reusability principle is particularly subtle as the question of trust is raised. Provenance information, that describes the data origin and all transformations performed, is essential to ensure this trust, and it should come with the proper granularity and level of details. We developed a prototype platform to make the first H.E.S.S. public test data findable and accessible through the Virtual Observatory (VO). The exposed high-level data follows the gamma-ray astronomy data format (GADF) proposed as a community standard to ensure wider interoperability. We also designed a provenance management system in connection with the development of pipelines and analysis tools for CTA (ctapipe and gammapy), in order to collect rich and detailed provenance information, as recommended by the FAIR reusability principle. The prototype platform thus implements the main functionalities of a science gateway, including data search and access, online processing, and traceability of the various actions performed by a user
Application of Complex Event Processing Softwareto Error Detection and Recovery for Arrays of Cherenkov Telescopes
No full textData acquisition (DAQ) and control systems for arrays of Cherenkov telescopes comprise hundreds of distributed software processes that implement the readout, control and monitoring of various hardware devices. A multitude of different error conditions (malfunctioning detectorhardware, crashing software, failures of network and computing equipment etc.) can occur and must be dealt with to ensure the speedy continuation of observations and an efficient use of dark time. Flexible, fast and configurable methods for automatic and centralized error detection and recovery are therefore highly desirable for the current generation of ground-based Cherenkovexperiments (H.E.S.S., MAGIC, VERITAS) and will be important for the Cherenkov Telescope Array (CTA), a more complex observatory with O(100) telescopes. This contribution describes a Java-based software demonstrator that was developed for the High Energy Stereoscopic System (H.E.S.S.) and uses the complex event processing engine Esper for error detection and recovery.The software demonstrator analyses streams of error messages in the time domain and aims to apply recovery procedures that reflect the knowledge of DAQ and detector experts
Building a world-wide open source community around a software framework: progress, dos, and don'ts
No full textDetailed spectral and morphological analysis of the shell type supernova remnant RCW 86
No full textAim. We aim for an understanding of the morphological and spectral properties of the supernova remnant RCW 86 and for insights into the production mechanism leading to the RCW 86 very high-energy γ-ray emission.Methods. We analyzed High Energy Spectroscopic System (H.E.S.S.) data that had increased sensitivity compared to the observations presented in the RCW 86 H.E.S.S. discovery publication. Studies of the morphological correlation between the 0.5–1 keV X-ray band, the 2–5 keV X-ray band, radio, and γ-ray emissions have been performed as well as broadband modeling of the spectral energy distribution with two different emission models.Results. We present the first conclusive evidence that the TeV γ-ray emission region is shell-like based on our morphological studies. The comparison with 2–5 keV X-ray data reveals a correlation with the 0.4–50 TeV γ-ray emission. The spectrum of RCW 86 is best described by a power law with an exponential cutoff at Ecut = (3.5 ± 1.2stat) TeV and a spectral index of Γ ≈ 1.6 ± 0.2. A static leptonic one-zone model adequately describes the measured spectral energy distribution of RCW 86, with the resultant total kinetic energy of the electrons above 1 GeV being equivalent to ~0.1% of the initial kinetic energy of a Type Ia supernova explosion (1051 erg). When using a hadronic model, a magnetic field of B ≈ 100 μG is needed to represent the measured data. Although this is comparable to formerly published estimates, a standard E−2 spectrum for the proton distribution cannot describe the γ-ray data. Instead, a spectral index of Γp ≈ 1.7 would be required, which implies that ∼7 × 1049/ncm−3 has been transferred into high-energy protons with the effective density ncm−3 = n/1 cm−3. This is about 10% of the kinetic energy of a typical Type Ia supernova under the assumption of a density of 1 cm−3
Modern Middleware for the Data Acquisition of the Cherenkov Telescope Array
No full textInternational audienceThe data acquisition system (DAQ) of the future Cherenkov Telescope Array (CTA) must be ef- ficient, modular and robust to be able to cope with the very large data rate of up to 550 Gbps coming from many telescopes with different characteristics. The use of modern middleware, namely ZeroMQ and Protocol Buffers, can help to achieve these goals while keeping the development effort to a reasonable level. Protocol Buffers are used as an on-line data for- mat, while ZeroMQ is employed to communicate between processes. The DAQ will be controlled and monitored by the Alma Common Software (ACS). Protocol Buffers from Google are a way to define high-level data structures through an in- terface description language (IDL) and a meta-compiler. ZeroMQ is a middleware that augments the capabilities of TCP/IP sockets. It does not implement very high-level features like those found in CORBA for example, but makes use of sockets easier, more robust and almost as effective as raw TCP. The use of these two middlewares enabled us to rapidly develop a robust prototype of the DAQ including data persistence to compressed FITS files
A prototype for the real-time analysis of the Cherenkov Telescope Array
No full textThe Cherenkov Telescope Array (CTA) observatory will be one of the biggest ground-based very-high-energy (VHE) γ- 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 γ-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 highthroughput 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 nonreal- 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). © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
A system architecture approach for the Cherenkov telescope array (Conference Presentation)
No full textInternational audienceThe 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
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