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Paper: The Camera Server of the ASTRI SST-2M Telescopes Proposed for the Cherenkov Telescope Array
Volume: 512, Astronomical Data Analysis Software and Systems XXV
Page: 635
Authors: Conforti, V.; Trifoglio, M.; Gianotti, F.; Malaguti, G.; Bulgarelli, A.; Fioretti, V.; Zoli, A.; Catalano, O.; Capalbi, M.; Sangiorgi, P.; ASTRI Collaboration; CTA Consortium
Abstract: The Cherenkov Telescope Array (CTA) project is an international initiative to build the next generation of ground-based very high energy gamma-ray instrument. Three classes of telescopes with different mirror size will cover the full energy range from tens of GeV up to hundreds of TeV. The full sky coverage will be assured by two arrays, with one site located in each of the northern and southern hemispheres. In the current design scenario, the southern hemisphere array of CTA will include seventy small size telescopes (SST, 4m diameter) covering the highest energy region. Their implementation includes proposed intermediate steps with the development of mini-arrays of telescope precursors like the ASTRI mini-array, led by the Italian National Institute for Astrophysics (INAF) in synergy with the Universidade de Sao Paulo (Brazil) and the North-West University (South Africa). The ASTRI mini-array will be composed of nine telescope units (ASTRI SST-2M) based on double-mirror configuration whose end-to-end prototype has been installed on Mt. Etna (Italy) and is currently undergoing engineering tests. In the ASTRI SST-2M prototype, operating in single telescope configuration, the basic camera server software is being deployed and tested; it acquires the data sent by the camera back end electronics as a continuous stream of packets. In near real time, the bulk data of a given run are stored in one raw file. In parallel they are sorted by data type, converted to FITS format and stored in one file for data type. Upon closure, each file is transferred to the on-site archive. In addition, the quick look component allows the operator to display the camera data during the acquisition. This contribution presents how the camera server software of the prototype is being upgraded in order to fulfil the mini-array requirements, where it will be deployed on the camera server of each ASTRI SST-2M telescope. Particular emphasis will be devoted to the most challenging requirements that are related to the stereoscopy, when two or more telescopes have triggered simultaneously. To handle stereoscopy, each camera server has also to: (i) get the timestamp information from the clock distribution and trigger time stamping system, and associate it to the related camera event; (ii) get from the software array trigger the timestamp which passed the stereo trigger criteria; and (iii) forward to the array data acquisition system the stereo trigger events, according to the required data format and communication protocol.
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