The Cherenkov Telescope Array (CTA) is the major next-generation observa-7 tory for ground-based very-high-energy gamma-ray astronomy. It will improve the sensitivity of current ground-based instruments by a factor of five to twenty, depending on the energy, greatly improving both their angular and energy resolutions over four decades in energy (from 20 GeV to 300 TeV). This achievement will be possible by using tens of imaging Cherenkov telescopes of three successive sizes. They will be arranged into two arrays, one per hemisphere, located on the La Palma island (Spain) and in Paranal (Chile). We present here the optimised and final telescope arrays for both CTA sites, as well as their foreseen performance, resulting from the analysis of three different large-scale Monte Carlo productions.

Diffraction dissociation of both the beam and target particles has been observed in 150-GeV/c .ir--p interactions in the Fermilab 30-in.-bubble-chamber--proportional-wirechambe hybrid spectrometer. The dissociations are observed as recoil systems opposite leading particles, the signals of which are separated from background where appropriate by a variant of the Van Hove sector cut, thus allowing the high-mass portion of the spectrum to be observed. Pion dissociation has a cross section of 1758-t. 105 pb, divided among two-, four., and six-prong events; some p0 production is seen and comes primarily from the n--t2n-.ir + channel. The proton dissociation cross section is 1726, 100 pb, again divided among two-, four-, and six-prong events. The final state contains a neutron more frequently than a proton in the twoand six-prong events, a proton more frequently in the four-prong events. Production of A + + is observed in the p +p.irf T -dissociations. transferring four-momenhim to other particles,

The SST-1M project, run by a Consortium of institutes from Czech Republic, Poland and Switzerland, has been proposed as a solution for implementing the small-size telescope array of the southern site of the Cherenkov Telescope Array. The technology is a pathfinder for efficient production of cost-effective imaging air Cherenkov telescopes. We report on the main system features and recent upgrades, the performances validation and the operation campaign carried out in 2018.

(the SST-1M sub-consortium) for the CTA consortium †. a.

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.