The Cherenkov Telescope Array (CTA) will be the next generation ground-based very-high energy -ray observatory. CTA will consist of two arrays: one in the Northern hemisphere composed of about 20 telescopes, and the other one in the Southern hemisphere composed of about 100 telescopes, both arrays containing telescopes of different sizes and types and in addition numerous auxiliary devices. In order to provide a test-ground for the CTA array control, the steering software of the 12-m medium size telescope (MST) prototype deployed in Berlin has been implemented using the tools and design concepts under consideration to be used for the control of the CTA array. The prototype control system is implemented based on the Atacama Large Millimeter/submillimeter Array (ALMA) Common Software (ACS) control middleware, with components implemented in Java, C++ and Python. The interfacing to the hardware is standardized via the Object Linking and Embedding for Process Control Unified Architecture (OPC UA). In order to access the OPC UA servers from the ACS framework in a common way, a library has been developed that allows to tie the OPC UA server nodes, methods and events to the equivalents in ACS components. The front-end of the archive system is able to identify the deployed components and to perform the sampling of the monitoring points of each component following time and value change triggers according to the selected configurations. The back-end of the archive system of the prototype is composed by two different databases: MySQL and MongoDB. MySQL has been selected as storage of the system configurations, while MongoDB is used to have an efficient storage of device monitoring data, CCD images, logging and alarm information. In this contribution, the details and conclusions on the implementation of the control software of the MST prototype are presented.
The Cherenkov Telescope Array (CTA) is the next generation Very High Energy (VHE, defined as > 50GeV to several
100TeV) telescope facility, currently in the design and prototyping phase, and expected to come on-line around 2016. The
array would have both a Northern and Southern hemisphere site, together delivering nearly complete sky coverage. The
CTA array is planned to have ~100 telescopes of several different sizes to fulfill the sensitivity and energy coverage needs.
Each telescope has a number of subsystems with varied hardware and control mechanisms; a drive system that gets
commands and inputs via OPC UA (OPC Unified Architecture), mirror alignment systems based on XBee/ZigBee protocol
and/or CAN bus, weather monitor accessed via serial/Ethernet ports, CCD cameras for calibration, Cherenkov camera, and
the data read out electronics, etc. Integrating the control and data-acquisitions of such a distributed heterogeneous system
calls for a framework that can handle such a multi-platform, multi-protocol scenario. The CORBA based ALMA Common
software satisfies these needs very well and is currently being evaluated as the base software for developing the control
system for CTA.
A prototype for a Medium Size Telescope (MST, ~12m) is being developed and will be deployed in Berlin, by end of
2012. We present the development being carried out to integrate and control the various hardware subsystems of this MST
prototype using ACS.
The Cherenkov Telescope Array (CTA) is designed to make a major improvement in the sensitivity of ground based
VHE (Very High Energy, defined as > 20GeV to 100s of TeV) gamma-ray telescopes. Not only will the differential-flux
sensitivity be an order of magnitude better than those of the currently operating Cherenkov telescopes, but there will also be
significant improvements in the energy, spectral and angular resolution. Delivering these features cost-effectively requires
several telescope sizes and designs - a few large size telescopes (23m diameter) are designed for the lowest energies, a
large number of small size telescopes (4-7m diameter) to increase the overall collection area which helps at the highest
energies and a number of Medium Size Telescopes (MST, 9.5m or 12m diameter, depending on the mirror design) to
provide the greatest sensitivity at ∼ 1 TeV. To provide complete sky coverage, CTA will have both a Northern Hemisphere
and a Southern Hemisphere site.
A prototype for an MST design (currently under development) will be build in Berlin by 2012. This MST prototype
has a modified Davies-Cotton design with a tessellated mirror, with individual facets of ∼ 1.2m in diameter. The facets are
three-point mounted on the optical support structure, having two powered actuators for alignment adjustments. In addition
a number of CCD cameras will be mounted at various positions on the dis and will be used for calibration. Here we present
the various optical calibration tasks - optimization of the optical point-spread-function (PSF) and the pointing of this MST
prototype, along with initial results.