The European Southern Observatory (ESO) has made a considerable progress in the implementation of a new software framework, the Instrument Control System Framework (IFW) tailored to facilitate the development of upcoming astronomical instruments at the Extremely Large Telescope (ELT). This framework offers a complete, scalable, and adaptable infrastructure to support the diverse needs of instrument control. The framework’s architecture is strongly based on ESO's extensive experience in operating and maintaining VLT instruments while integrating the technological innovations specified by the ELT project. It presents a unified approach to instrument control, fostering the coordination of various heterogenous instruments subsystems and tasks, ranging from the control of instrument hardware functions and data visualization to the execution of science observations and instrument calibrations. The framework is primarily targeted to instrument developers from ESO partner institutes who are currently working on the first-generation ELT instruments. ESO extended the framework's application in 2019 to all new instruments within its optical telescopes. This strategy aims to reduce maintenance costs and promote ELT-VLT integrated operations, embracing future VLT instruments. The framework is being elaborated following the ELT Development Process, a sort of scrum like process supported by the tools Jenkins, Gitlab and Jira. This paper provides an overview of the design principles, key features, as well as details of the development process and main technologies employed in its construction.
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 Enhanced Resolution Imager and Spectrograph (ERIS) is a next-generation, adaptive optics assisted, near-IR imager and integral field spectrograph (IFS) for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4. It will make use of the Adaptive Optics Facility (AOF), comprising the Deformable Secondary Mirror (DSM) and the UT4 Laser Guide Star Facility (4LGSF). It is a rather complex instrument, with its state of the art AO system and two science channels. It is also meant to be a "workhorse" instrument and offers many observation modes. ERIS is being built by a Consortium of European Institutes comprising MPE Garching (D), ATC (UK), ETH Zürich (CH), Leiden University (NL) and INAF (I) in collaboration with ESO. The instrument passed Final Design Review in mid-2017 and is now in the MAIT phase. In this paper we describe the design of the ERIS Instrument Software (INS), which is in charge of controlling all instrument functions and implementing observation, calibration and maintenance procedures. The complexity of the instrument is reflected in the architecture of its control software and the number of templates required for operations. After a brief overview of the Instrument, we describe the general architecture of the ERIS control network and software. We then discuss some of the most interesting aspects of ERIS INS, like the wavefront sensors function control, AO secondary loops, IFS quick-look processing and the on-line processing for high-contrast imaging observations. Finally, we provide some information about our development process, including software quality assurance activities.
MUSE Instrumentation Software is the software devoted to the control of the Multi-Unit Spectroscopic Explorer
(MUSE), a second-generation VLT panoramic integral-field spectrograph instrument, installed at Paranal in January
2014. It includes an advanced and user-friendly GUI to display the raw data of the 24 detectors, as well as the on-line
reconstructed images of the field of view allowing users to assess the quality of the data in quasi-real
time. Furthermore, it implements the slow guiding system used to remove effects of possible differential drifts between
the telescope guide probe and the instrument, and reach high image stability (<0.03 arcsec RMS stability).
In this paper we report about the software design and describe the developed tools that efficiently support astronomers
while operating this complex instrument at the telescope.
ESO is currently in the final phase of the standardization process for PC-based Programmable Logical Controllers (PLCs) as the new platform for the development of control systems for future VLT/VLTI instruments. The standard solution used until now consists of a Local Control Unit (LCU), a VME-based system having a CPU and commercial and proprietary boards. This system includes several layers of software and many thousands of lines of code developed and maintained in house. LCUs have been used for several years as the interface to control instrument functions but now are being replaced by commercial off-the-shelf (COTS) systems based on BECKHOFF Embedded PCs and the EtherCAT fieldbus. ESO is working on the completion of the software framework that enables a seamless integration into the VLT control system in order to be ready to support upcoming instruments like ESPRESSO and ERIS, that will be the first fully VLT compliant instruments using the new standard. The technology evaluation and standardization process has been a long and combined effort of various engineering disciplines like electronics, control and software, working together to define a solution that meets the requirements and minimizes the impact on the observatory operations and maintenance. This paper presents the challenges of the standardization process and the steps involved in such a change. It provides a technical overview of how industrial standards like EtherCAT, OPC-UA, PLCOpen MC and TwinCAT can be used to replace LCU features in various areas like software engineering and programming languages, motion control, time synchronization and astronomical tracking.
Recent improvements in industrial vision technology and products together with the increasing need for high
performance, cost efficient technical detectors for astronomical instrumentation have led ESO with the contribution of
INAF to evaluate this trend and elaborate ad-hoc solutions which are interoperable and compatible with the evolution of
VLT standards. The ESPRESSO spectrograph shall be the first instrument deploying this technology.
ESO's Technical CCD (hereafter TCCD) requirements are extensive and demanding. A lightweight, low maintenance,
rugged and high performance TCCD camera product or family of products is required which can operate in the extreme
environmental conditions present at ESO's observatories with minimum maintenance and minimal downtime. In addition
the camera solution needs to be interchangeable between different technical roles e.g. slit viewing, pupil and field
stabilization, with excellent performance characteristics under a wide range of observing conditions together with ease of
use for the end user. Interoperability is enhanced by conformance to recognized electrical, mechanical and software
standards. Technical requirements and evaluation criteria for the TCCD solution are discussed in more detail.
A software architecture has been adopted which facilitates easy integration with TCCD's from different vendors. The
communication with the devices is implemented by means of dedicated adapters allowing usage of the same core
framework (business logic). The preference has been given to cameras with an Ethernet interface, using standard TCP/IP
based communication. While the preferred protocol is the industrial standard GigE Vision, not all vendors supply
cameras with this interface, hence proprietary socket-based protocols are also acceptable with the provision of a
validated Linux compliant API. A fundamental requirement of the TCCD software is that it shall allow for a seamless
integration with the existing VLT software framework.
ESPRESSO is a fiber-fed, cross-dispersed echelle spectrograph that will be located in the Combined-Coudé Laboratory
of the VLT in the Paranal Observatory in Chile. It will be able to operate either using the light of any of the UT's or
using the incoherently combined light of up to four UT's. The stabilization of the incoming beam is achieved by
dedicated piezo systems controlled via active loops closed on 4 + 4 dedicated TCCD's for the stabilization of the pupil
image and of the field with a frequency goal of 3 Hz on a 2nd to 3rd magnitude star. An additional 9th TCCD system shall
be used as an exposure-meter.
In this paper we will present the technical CCD solution for future VLT instruments.
More than a decade ago, due to obsolescence issues, ESO initiated the design and implementation of a custom-made
CANbus based motion controller (CAN-RMC) to provide, together with a tailor-made software library (motor library),
the motion control capabilities for the VME platform needed for the second generation VLT/VLTI instruments. The
CAN-RMC controller has been successfully used in a number of VLT instruments but it has high production costs
compared to the commercial off-the-shelf (COTS) industrial solutions available on the market today.
In the scope of the selection of a new PLC-based platform for the VLT instrument control systems, ESO has evaluated
motion control solutions from the company Beckhoff. This paper presents the investigation, implementation and testing
of the PLC/TwinCAT/EtherCAT motion controllers for DC and stepper motors and their adaptation and integration into
the VLT instrumentation framework. It reports functional and performance test results for the most typical use cases of
astronomical instruments like initialization sequences, tracking, switch position detections, backslash compensation,
brake handling, etc. In addition, it gives an overview of the main features of TwinCAT NC/PTP, PLCopen MC,
EtherCAT motion control terminals and the engineering tools like TwinCAT Scope that are integrated into the
development environment and simplify software development, testing and commissioning of motorized instrument
functions.
The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics near-IR imager and
spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full
use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable
Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for
construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the Max-
Planck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio
Astrofisico di Arcetri and will offer 1 - 5 μm imaging and 1 - 2.5 μm integral field spectroscopic capabilities with a high
Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or
with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly
sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1’
patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace,
with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by
NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP)
coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be
upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector
replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension
of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on
the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet
detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI
upgrade strategy, which is part of the ERIS development plan and the overall project timeline.
The visitor instrument PIONIER provides VLTI with improved imaging capabilities and sensitivity. The in-
strument started routinely delivering scientic data in November 2010, that is less than 12 months after being
approved by the ESO Science and Technical Committee. We recall the challenges that had to be tackled to design, built and commission PIONIER. We summarize the typical performances and some astrophysical results obtained so far. We conclude this paper by summarizing lessons learned.
PIONIER is a 4-telescope visitor instrument for the VLTI, planned to
see its first fringes in 2010. It combines four ATs or four UTs
using a pairwise ABCD integrated optics combiner that can also be
used in scanning mode. It provides low spectral resolution in H and K band. PIONIER is designed for
imaging with a specific emphasis on fast fringe recording to allow
closure-phases and visibilities to be precisely measured. In
this work we provide the detailed description of the instrument and
present its updated status.
The VLT control system is a large distributed system consisting of Linux Workstations providing the high level
coordination and interfaces to the users, and VME-based Local Control Units (LCU's) running the VxWorks real-time
operating system with commercial and proprietary boards acting as the interface to the instrument functions. After more
than 10 years of VLT operations, some of the applied technologies used by the astronomical instruments are being
discontinued making it difficult to find adequate hardware for future projects. In order to deal with this obsolescence, the
VLT Instrumentation Framework is being extended to adopt well established Commercial Off The Shelf (COTS)
components connected through industry standard fieldbuses. This ensures a flexible state of the art hardware
configuration for the next generation VLT instruments allowing the access to instrument devices via more compact and
simpler control units like PC-based Programmable Logical Controllers (PLC's). It also makes it possible to control
devices directly from the Instrument Workstation through a normal Ethernet connection. This paper outlines the
requirements that motivated this work, as well as the architecture and the design of the framework extension. In addition,
it describes the preliminary results on a use case which is a VLTI visitor instrument used as a pilot project to validate the
concepts and the suitability of some COTS products like a PC-based PLCs, EtherCAT8 and OPC UA6 as solutions for
instrument control.
KEYWORDS: Data archive systems, Databases, Data storage, Data modeling, Local area networks, Computing systems, Observatories, Distributed computing, Control systems, Telescopes
The Data Flow System (DFS) for the ESO VLT provides a global approach to handle the flow of science related data in the VLT environment. It is a distributed system composed of a collection of components for preparation and scheduling of observations, archiving of data, pipeline data reduction and quality control. Although the first version of the system became operational in 1999 together with the first UT, additional developments were necessary to address new operational requirements originating from new and complex instruments which generate large amounts of data. This paper presents the hardware and software changes made to meet those challenges within the back-end infrastructure, including on-line and off-line archive facilities, parallel/distributed pipeline processing and improved association technologies.
KEYWORDS: Data archive systems, Data processing, Observatories, Astronomy, Digital video discs, Telescopes, Information technology, Calibration, Magnetism, Process control
ESO's Science Archive is distributed across four different sites on two continents. With the huge amount of data produced by the various instruments this poses special requirements on the way data is transfered between the sites and distributed to the various subscribers. ESO's latest development, the Next Generation Archive System (NGAS), is based on cheap ATA disks connected to custom PCs running http based servers controlling the archiving process, supporting retrieval and checking the health status of the disks and the data itself. The current deployment of this system covers just a single 8kx8k pixel wide field imager, which is producing about 30 GB of raw data per night. The next generation of wide field telescopes/instruments VISTA/VISTACam and VST/OmegaCam will produce data rates well exceeding 500 GB and 125 GB during a single typical night, respectively. The total data rate of all ESO telescopes/instruments will grow to about 0.75 TB/night once VISTA is operational. The archiving of this data is essential, the next important step is to support not just only retrieval, but also flexible processing schemes of the data within the archive cluster directly.
The VLT Data Flow System (DFS) has been developed to maximize the scientific output from the operation of the ESO observatory facilities. From its original conception in the mid 90s till the system now in production at Paranal, at La Silla, at the ESO HQ and externally at home institutes of astronomers, extensive efforts, iteration and retrofitting have been invested in the DFS to maintain a good level of performance and to keep it up to date. In the end what has been obtained is a robust, efficient and reliable 'science support engine', without which it would be difficult, if not impossible, to operate the VLT in a manner as efficient and with such great success as is the case today. Of course, in the end the symbiosis between the VLT Control System (VCS) and the DFS plus the hard work of dedicated development and operational staff, is what made the success of the VLT possible. Although the basic framework of DFS can be considered as 'completed' and that DFS has been in operation for approximately 3 years by now, the implementation of improvements and enhancements is an ongoing process mostly due to the appearance of new requirements. This article describes the origin of such new requirements towards DFS and discusses the challenges that have been faced adapting the DFS to an ever-changing operational environment. Examples of recent, new concepts designed and implemented to make the base part of DFS more generic and flexible are given. Also the general adaptation of the DFS at system level to reduce maintenance costs and increase robustness and reliability and to some extend to keep it conform with industry standards is mentioned. Finally the general infrastructure needed to cope with a changing system is discussed in depth.
Adaptive Optics as a new tool for astronomical observation has proved a powerful means of investigation in high angular resolution programs. However, in spite of the complexity of the components involved (wavefront sensor, real-time computer), its use must be made as simple as possible in order to make it accessible to the largest audience of observers, and to answer the more demanding needs of modern observatories such as queue scheduling, service observing or remote observing. The Computer Aided Control developed for the Nasmyth Adaptive Optics System of the Very Large Telescope, will provide the astronomer with an extensive support, from the preparation of optimized observations to the automated operation of the instrument at the telescope either for hardware control, real time computing, or even preventive maintenance.
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