The Cherenkov Telescope Array Observatory: top level use cases

Abstract

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.

The Cherenkov Telescope array on-site integral sensitivity: observing the Crab

“…Short exposures, from 1000 seconds to 10 hours, are used to evaluate the OSA and in particular the RTA performance in the detection of Crab-like sources: even for a 1000 second long observation, a significant Crab detection is ensured up to about 10 TeV. We plan the computation of the integral sensitivity, using short exposures, for each RTA science use case [20], using the most accurate models available from literature to characterize each science target class.…”

Software architecture and development approach for the ASTRI Mini-Array project at the Teide Observatory

“…The requirement inception is the first step to collect the requirements from users and other stakeholders to 1. understand the workflow, starting with user expectations; 2. maintain costs within a chosen envelope, deciding what to build, what the system must do, how it must behave, the properties it must exhibit, the qualities it must possess, and the constraints that the system and its development must satisfy; 3. maps the functionalities to the science requirements. A requirement inception process is a challenge because there are many different problems during this phase: 21 (i) problem of scope: the user specifies technical details, and the boundary of the system is not well defined; (ii) problem of understanding: the users do not have a complete understanding of the problem domain, have trouble communicating needs to the system/software engineers, omit information that is believed to be "obvious," specify requirements that conflict with the needs of other customers/users, and have a glossary with terms with different meanings; (iii) requirements volatility: the requirements change over time.…”

The Transient program of the Cherenkov Telescope Array

“…After the definition of the KSPs, the details of the future operation and observations with CTA were defined as use cases. These were produced at different levels, ranging from the individual subsystems to the full operation of the observatory and then combined in a high-level layer, the Top Level Use Cases [3]. Partially based on the experience with current IACTs, detailed observation scenarios ranging from the reception of the alerts, their analysis, the reaction of the CTA infrastructure, the data taking, and the final physics analyses have been outlined.…”