The Extremely Large Telescope (ELT) is a 39 meters optical telescope under construction in the Chilean Atacama Desert. The control software is under advanced development and the system is slowly taking shape for first light in 2028. ESO is directly responsible for coordination functions and control strategies requiring astronomical domain knowledge. Industrial contractors are instead developing the low-level control of individual subsystems. We are now implementing the coordination recipes and integrating the local control systems being delivered by contractors. System tests are performed in the ELT Control Model in Garching, while waiting for the availability of individual subsystems at the telescope. This paper describes the status of development for individual subsystems, of the high-level coordination software and of the system integration on the ELT Control Model (ECM), focusing on testing and integration challenges.
KEYWORDS: Photonic integrated circuits, Large telescopes, Control systems, Commercial off the shelf technology, Standards development, Telecommunications, Optical proximity correction, Licensing
In the last ten years the European Southern Observatory's (ESO) Very Large Telescope (VLT) Instrumentation Framework has begun moving its low level interface to instrument functions away from VME-based Local Control Units (LCU's) to Commercial Off The Shelf (COTS) components connected with industry standard fieldbuses. This move has resulted in the adoption of PC-based Programmable Logical Controllers (PLC's) that directly control the instrument devices, connected via Ethernet to Linux workstations that provide high level coordination and user-interfaces. To enable this shift to COTS components, a new "fieldbus-aware" Instrument Control System Base (IC0FB) was developed which utilizes, among others, the Open Platform Communications Unified Architecture (OPC UA) standard for communication between the workstations and the PLC's. The initial implementation of IC0FB used closed source libraries for this OPC-UA-based communication, however, licensing restrictions made compiling and distributing difficult throughout the VLT project. This has prompted the recent re-implementation of the OPC UA IC0FB Communication Interface using the open source library open625411 and the adoption of open62541 for ESO's new Extreme Large Telescope. In this paper, we discuss the lessons learned in moving to open source implementation of an industry standard. We compare the performance of the open62541 implementation and the implementation based on the commercially licensed Softing Automation SDK2 and show that the performance of the open source solution is comparable to the closed source implementation.
The paper describes the introduction of a new automatized build and test infrastructure, based on the open-source software Jenkins1, into the ESO Very Large Telescope control software to replace the preexisting in-house solution. A brief introduction to software quality practices is given, a description of the previous solution, the limitations of it and new upcoming requirements. Modifications required to adapt the new system are described, how these were implemented to current software and the results obtained. An overview on how the new system may be used in future projects is also presented.
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