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.
At the core of the AGILE scientific instrument, designed to operate on a satellite, there is the Gamma Ray
Imaging Detector (GRID) consisting of a Silicon Tracker (ST), a Cesium Iodide Mini-Calorimeter and an
Anti-Coincidence system of plastic scintillator bars. The ST needs an on-ground calibration with a γ-ray beam to
validate the simulation used to calculate the energy response function and the effective area versus the energy and
the direction of the γ rays. A tagged γ-ray beam line was designed at the Beam Test Facility (BTF) of the INFN
Laboratori Nazionali of Frascati (LNF), based on an electron beam generating γ rays through bremsstrahlung in
a position-sensitive target. The γ-ray energy is deduced by the difference with the post-bremsstrahlung electron
energy<sup>1-.2</sup> The electron energy is measured by a spectrometer consisting of a dipole magnet and an array of
position sensitive silicon strip detectors, the Photon Tagging System (PTS). The use of the combined BTF-PTS
system as tagged photon beam requires understanding the efficiency of γ-ray tagging, the probability of fake
tagging, the energy resolution and the relation of the PTS hit position versus the γ-ray energy. This paper
describes this study comparing data taken during the AGILE calibration occurred in 2005 with simulation.
AGILE is a γ/X-ray telescope which has been in orbit since 23 April 2007. The
γ-ray detector, AGILE-GRID,
has observed Galactic and extragalactic sources, many of which were collected in the first AGILE Catalog.
We present the calibration of the AGILE-GRID using in-flight data and updated Monte Carlo simulations,
producing response matrices for the effective area, energy dispersion, and point spread dispersion as a function
of pointing direction in instrument coordinates and energy.
We performed Monte Carlo simulations in GEANT3 at different
γ-ray photon energies and incident angles,
using Kalman filter-based photon reconstruction and on-board and on-ground filters. Long integrations of in-flight observations of the Vela, Crab and Geminga sources in broad and narrow energy bands were used to validate