The CTAO’s Technical Specifications

The specifications on this page are supported by the content found on the telescopes and the data and computing pages. To learn more about the testing and findings of the different elements, search the papers library.

Telescope Specifications

Small-Sized Telescope (SST)

The SST relies on a modified Schwarzschild-Couder dual-mirror optical design, providing a good spatial resolution over a large field of view. They are compact telescopes with small focal ratios allowing the use also of compact cameras. Each SST has a primary mirror based on 18 hexagonal segments with a total aperture of 4.3 m and a monolithic secondary mirror of 1.8 m in diameter.  

Medium-Sized Telescope (MST)

The MST is a modified Davies-Cotton telescope with a reflector size of 88 m² and a focal length of 16 m. It will have two different camera designs that use photomultiplier tubes (PMTs). The cameras have a field of view of about 8 degrees, enabling the MSTs to take rapid surveys of the gamma-ray sky.   

Large-Sized Telescope (LST)

The LST is an alt-azimuth telescope. It has a 23 m diameter parabolic reflective surface, which is supported by a tubular structure made of reinforced carbon fibre and steel tubes. A reflective surface of 400 m2 collects and focuses the Cherenkov light into the camera, where photomultiplier tubes convert the light in electrical signals that can be processed by dedicated electronics. Although the LST will stand 45 m tall and weigh around 100 tonnes, it will be extremely nimble, with the ability to re-position between any two points in the sky within 20 seconds.

Software Specifications

The Computing Department software will be responsible for a wide range of duties, from managing the observation proposal lifecycle and controlling the telescopes and array elements on site to the processing and long-term preservation of data and providing the user support and tools for data access and analysis. The below systems are in development to manage these responsibilities.

ACADA – Array Control and Data Acquisition System

The ACADA encompasses all the software responsible for the supervision and control of telescopes and calibration instruments at both CTAO array sites, including the efficient execution of scheduled and dynamically triggered observation. The system will manage the data acquisition and compression of the raw data, as well as the generation of automatic science alerts. The ACADA also provides the user interface for the site operators and astronomers. Its sub-systems are as follows: 

DPPS – Data Processing and Preservation System

The main purpose of the DPPS is to transform raw data products generated by ACADA into science-ready data products appropriate for science analysis, which are delivered to the SUSS for dissemination. It must ensure that all data products are preserved (replicated to at least two off-site data centres), of traceable and reproducible provenance and of the highest scientific quality. The latter is achieved by planning for the periodic re-processing of all data using updated techniques. The DPPS also provides continuous monitoring and quality reporting for its sub-systems and produces high-level science quality metrics and reports related to the services provided. The DPPS will be implemented as a distributed system, deployed as a set of data processing and preservation nodes operated by the SDMC, which will run at the CTAO-North and CTAO-South on-site data centres, as well as at all off-site data centres. The DPPS sub-systems are as follows: 

SUSS – Science User Support System

The SUSS manages the software systems for the high-level science operations workflows, from proposals to data delivery and user support, and is the main access point for the exchange of science-related products with the science users. It also provides the software for the observation planning with long-term to mid-term schedules, for the automatic generation and verification of high-level science data products, the Science Archive, the Science Analysis Tools, the User Support systems, and the Science Portal through which the software applications, services, data and software products are accessible. The SUSS sub-systems are as follows:

SOSS – Science Operations Support System

Hardware Specifications

ICT – Information and Communications Technology

The ICT work packages are responsible for the on-site data centres, networks, the data transfer and the coordination of the off-site data centres. The on-site ICT system ensures that the required computing resources and network capacity are available to support all operations at both array sites. It will provide the interface between all array elements, including the telescopes and the data centres. Monitoring this infrastructure is key to ensuring high performance, of which cyber security is an important feature. The off-site ICT system coordinates with the four off-site data centres, which will operate CTAO software systems and data storage to build a coherent CTAO computing infrastructure. 

Array Clock System

In order to combine the data from the many different and highly distributed CTAO array elements (telescopes, weather stations, etc.), they must be correlated in time. Successful association of these data requires sufficiently accurate and precise timestamping mechanisms, as well as a stable and accurate reference time source at each of the two array sites. Providing such a time source, together with its distribution, is the task of the Array Clock System.