The Cherenkov Telescope Array Observatory (CTAO) is the next-generation atmospheric Cherenkov gamma-ray project. CTAO will be deployed at two sites, one in the Northern and the other in the Southern Hemisphere, containing telescopes of three different sizes for covering different energy domains. The commissioning of the first CTAO Large-sized Telescope (LST-1) is being finalized at the CTAO Northern site. Additional calibration and environmental monitoring instruments such as laser imaging detection and ranging (LIDAR) instruments and weather stations will support the telescope operations. The Array Control and Data Acquisition (ACADA) system is the central element for onsite CTAO operations. ACADA controls, supervises, and handles the data generated by the telescopes and the auxiliary instruments. It will drive the efficient planning and execution of observations while handling the several Gb/s camera data generated by each CTAO telescope. The ACADA system contains the CTAO Science Alert Generation Pipeline – a real-time data processing and analysis pipeline, dedicated to the automatic generation of science alert candidates as data are being acquired. These science alerts, together with external alerts arriving from other scientific instruments, will be managed by the Transients Handler (TH) component. The TH informs the Short-term Scheduler of ACADA about interesting science alerts, enabling the modification of ongoing observations at sub-minute timescales. The capacity for such fast reactions – together with the fast movement of CTAO telescopes – makes CTAO an excellent instrument for studying high-impact astronomical transient phenomena. The ACADA software is based on the Alma Common Software (ACS) framework, and written in C++, Java, Python, and Javascript. The first release of the ACADA software, ACADA REL1, was finalized in July 2023, and integrated after a testing campaign with the LST-1 finalized in October 2023. This contribution describes the design and status of the ACADA software system.
The Cherenkov Telescope Array Observatory (CTAO) is a major next-generation instrument in ground-based gamma-ray astronomy that will become operational in the era of multimessenger astronomy. With its unmatched sensitivity and angular resolution, CTAO will play a pivotal role in the study of transient phenomena in the GeV-TeV range. The Transients Handler is the component within the Array Control and Data Acquisition (ACADA) system that enables CTAO to respond swiftly to alerts about transient events with automatically scheduled observations. The Transients Handler’s tasks include (i) filtering thousands of events per night from multiple external and internal alert streams, (ii) matching these events with scientific proposals, (iii) determining the optimal observation strategy, and (iv) scheduling observations within five seconds of receiving an alert. Recently, in October 2023, the first implementation of the Transients Handler was successfully tested during the integration of ACADA with the first CTAO Large-sized Telescope (LST-1). In this contribution, we will present the design of the Transients Handler in detail and preview updates that will be introduced in the next implementation.
The Cherenkov Telescope Array Observatory (CTAO) will be the largest and most advanced ground-based facility for γ-ray astronomy. Several dozens of telescopes will be operated at both the Northern and Southern Hemisphere. With the advent of multi-messenger astronomy, many new large science infrastructures will start science operations and target-of-opportunity observations will play an important role in the operation of the CTAO. The Array Control and Data Acquisition (ACADA) system deployed on each CTAO site will feature a dedicated sub-system to manage external and internal scientific alerts: the Transients Handler. It will receive, validate, and process science alerts in order to determine if target-of-opportunity observations can be triggered or need to be updated. Various tasks defined by proposal-based configurations are processed by the Transients Handler. These tasks include, among others, the evaluation of observability of targets and their correlation with known sources or objects. This contribution will discuss the concepts and design of the Transients Handler and its integration in the ACADA system.
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