Status and plans for the Array Control and Data Acquisition System of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is the next-generation atmospheric Cherenkov gamma-ray observatory. CTA will consist of two installations, one in the northern, and the other in the southern hemisphere, containing tens of telescopes of different sizes. The CTA performance requirements and the inherent complexity associated with the operation, control and monitoring of such a large distributed multi-telescope array leads to new challenges in the field of the gamma-ray astronomy. The ACTL (array control and data acquisition) system will consist of the hardware and software that is necessary to control and monitor the CTA arrays, as well as to time-stamp, read-out, filter and store -at aggregated rates of few GB/s- the scientific data. The ACTL system must be flexible enough to permit the simultaneous automatic operation of multiple sub-arrays of telescopes with a minimum personnel effort on site. One of the challenges of the system is to provide a reliable integration of the control of a large and heterogeneous set of devices. Moreover, the system is required to be ready to adapt the observation schedule, on timescales of a few tens of seconds, to account for changing environmental conditions or to prioritize incoming scientific alerts from time-critical transient phenomena such as gamma ray bursts. This contribution provides a summary of the main design choices and plans for building the ACTL system

Optimisation of the Drive Software for the Medium-Sized Telescopes of the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is the next-generation ground-based observatoryfor gamma-ray astronomy at very high energies. In its initial Alpha Configuration, itwill consist of 64 imaging atmospheric Cherenkov telescopes (IACTs) of different size anddesign, which will be deployed in the form of two large arrays in the northern hemisphereat the Roque de Los Muchachos Observatory on La Palma (Canary Islands, Spain) andin the southern hemisphere at the Paranal Observatory in the Atacama Desert (Chile),respectively. The core energy range of CTA (approximately 100 GeV to several TeV) willbe covered by the Medium-Sized Telescopes (MSTs), which are planned to be built atboth sites.Observations of astronomical targets with MSTs are facilitated by the drive system, mov-ing the telescope in elevation and in azimuth direction, respectively. It is steered and con-trolled by the drive software, which uses the OPC Unified Architecture (OPC UA) stan-dard to communicate with the programmable logic controller (PLC) operating the drivemotors, and is implemented on top of the ALMA Common Software (ACS) framework(except for the PLC). In this contribution, the architecture of the MST drive software willbe presented. A particular focus will be on the description of the newly-developed softwarelibrary of the MST drive system and its algorithms for the generation and optimisationof the time-dependent trajectories which the telescope follows during the observation ofastronomical targets

Control, Readout and Monitoring for the Medium-Sized Telesopes in the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is the next-generation ground-based gamma-ray observatory. Its design comprises close to 100 imaging atmospheric Cherenkov telescopes deployed at a southern (Paranal, Chile) and a northern (La Palma, Canary Islands, Spain) site. The inclusion of various array elements, like Large-Sized, Medium-Sized and Small-Sized Telescopes, instruments for atmosphere monitoring, etc, into the Array Control and Data Acquisition System (ACADA) poses a particular challenge which is met by an appropriate software architecture and a well-defined interface for array elements. This conference contribution describes exemplarily how the interface is implemented for the Medium-Sized Telescopes (MSTs, 12m diameter). The implementation uses the ALMA Common Software (ACS) as a framework for software applications facilitating the readout and control of telescope subsystems like the drive system or the pointing camera; the communication with subsystems takes advantage of the OPC UA protocol. It is also discussed what technologies (e.g. data bases) are used for the acquisition and storage of telescope-specific monitoring data