We present an overview of the 4MOST project at the Preliminary Design Review. 4MOST is a major new wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of ESO. 4MOST has a broad range of science goals ranging from Galactic Archaeology and stellar physics to the high-energy physics, galaxy evolution, and cosmology. Starting in 2021, 4MOST will deploy 2436 fibres in a 4.1 square degree field-of-view using a positioner based on the tilting spine principle. The fibres will feed one high-resolution (R~20,000) and two medium resolution (R~5000) spectrographs with fixed 3-channel designs and identical 6k x 6k CCD detectors. 4MOST will have a unique operations concept in which 5-year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing concept, showing that we can expect to observe more than 25 million objects in each 5-year survey period and will eventually be used to plan and conduct the actual survey.
4MOST,1 the 4m Multi-Object spectrographic Survey Telescope, is an upcoming optical, fiber-fed, MOS facility for the VISTA telescope at ESO's Cero Paranal Observatory (Chile). The preliminary design of 4MOST features 2,400 fibers split into a low-resolution (1,600 fibers, 390-900 nm, R > 5; 000) and a high-resolution channel (800 fibers, three arms, ~20-25 nm coverage each, R > 18; 000) with an Echidna-style positioner, and covering a hexagonal field of view of ~4.1 sqdeg. 4MOST's main science goals encompass massive (tens of millions of spectra), all-Southern sky (> 18; 000 sqdeg) surveys following up both the Gaia (optical) and eROSITA (X-ray) space missions, plus cosmological science that complements missions such as e.g. Euclid. In a novel approach, observations of these science cases, which are very different from another, are to be carried out in parallel (i.e., simultaneously); thus, from the very different science requirements, key user requirements have to be identified, stringently formulated, and condensed into a coherent set of system specifications. Clearly, identifying common grounds and thereby significantly reducing complexity in both the formulated requirements and the final 4MOST facility, is a very challenging task. In this paper, we will present science and user requirements, and how the latter flow down from the former, and eventually further down to the system-specification level. Special emphasis will be put on the identification of key requirements and their validation and verification protocols, so that significant trade-offs can be done as early on in the design phase as possible, with as little impact as possible on the science capabilities upstream.
The 4MOST instrument is a concept for a wide-field, fibre-fed high multiplex spectroscopic instrument facility on the
ESO VISTA telescope designed to perform a massive (initially >25x106 spectra in 5 years) combined all-sky public
survey. The main science drivers are: Gaia follow up of chemo-dynamical structure of the Milky Way, stellar radial
velocities, parameters and abundances, chemical tagging; eROSITA follow up of cosmology with x-ray clusters of
galaxies, X-ray AGN/galaxy evolution to z~5, Galactic X-ray sources and resolving the Galactic edge;
Euclid/LSST/SKA and other survey follow up of Dark Energy, Galaxy evolution and transients. The surveys will be
undertaken simultaneously requiring: highly advanced targeting and scheduling software, also comprehensive data
reduction and analysis tools to produce high-level data products. The instrument will allow simultaneous observations of
~1600 targets at R~5,000 from 390-900nm and ~800 targets at R<18,000 in three channels between ~395-675nm
(channel bandwidth: 45nm blue, 57nm green and 69nm red) over a hexagonal field of view of ~ 4.1 degrees. The initial
5-year 4MOST survey is currently expect to start in 2020. We provide and overview of the 4MOST systems: optomechanical,
control, data management and operations concepts; and initial performance estimates.
4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large
area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO and from ground-based facilities like VISTA, VST, DES, LSST and SKA. The 4MOST baseline concept features a 2.5 degree diameter field-of-view with ~2400 fibres in the focal surface that are configured by a fibre positioner based on the tilting spine principle. The fibres feed two types of spectrographs; ~1600 fibres go to two spectrographs with resolution R<5000 (λ~390-930 nm) and
~800 fibres to a spectrograph with R>18,000 (λ~392-437 nm and 515-572 nm and 605-675 nm). Both types of spectrographs are fixed-configuration, three-channel spectrographs. 4MOST will have an unique operations concept in which 5 year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the
southern sky. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing
concept. 4MOST has been accepted for implementation by ESO with operations expected to start by the end of 2020.
This paper provides a top-level overview of the 4MOST facility, while other papers in these proceedings provide more
detailed descriptions of the instrument concept, the instrument requirements development, the systems engineering implementation, the instrument model, the fibre positioner concepts, the fibre feed, and the spectrographs.
The 4MOST consortium is currently halfway through a Conceptual Design study for ESO with the aim to develop a wide-field ( < 3 square degree, goal < 5 square degree), high-multiplex ( < 1500 fibres, goal 3000 fibres) spectroscopic survey facility for an ESO 4m-class telescope (VISTA). 4MOST will run permanently on the telescope to perform a 5 year public survey yielding more than 20 million spectra at resolution R∼5000 (λ=390–1000 nm) and more than 2 million spectra at R~20,000 (395–456.5 nm and 587–673 nm). The 4MOST design is especially intended to complement three key all-sky, space-based observatories of prime European interest: Gaia, eROSITA and Euclid. Initial design and performance estimates for the wide-field corrector concepts are presented. Two fibre positioner concepts are being considered for 4MOST. The first one is a Phi-Theta system similar to ones used on existing and planned facilities. The second one is a new R-Theta concept with large patrol area. Both positioner concepts effectively address the issues of fibre focus and pupil pointing. The 4MOST spectrographs are fixed configuration two-arm spectrographs, with dedicated spectrographs for the high- and low-resolution fibres. A full facility simulator is being developed to guide trade-off decisions regarding the optimal field-of-view, number of fibres needed, and the relative fraction of high-to-low resolution fibres. The simulator takes mock catalogues with template spectra from Design Reference Surveys as starting point, calculates the output spectra based on a throughput simulator, assigns targets to fibres based on the capabilities of the fibre positioner designs, and calculates the required survey time by tiling the fields on the sky. The 4MOST consortium aims to deliver the full 4MOST facility by the end of 2018 and start delivering high-level data products for both consortium and ESO community targets a year later with yearly increments.
Hundreds of mirror segment, thousands of high precision actuators, highly complex mechanical, hydraulic, electrical and
other technology subsystems, and highly sophisticated control systems: an ELT system consists of millions of individual
parts and components, each of them may fail and lead to a partial or complete system breakdown. The traditional maintenance
concepts characterized by predefined preventive maintenance activities and rigid schedules are not suitable for
handling this large number of potential failures and malfunctions and the extreme maintenance workload. New maintenance
strategies have to be found suitable to increase reliability while reducing the cost of needless maintenance services.
The Reliability Centred Maintenance (RCM) methodology is already used extensively by airlines, and in industrial and
marine facilities and even by scientific institutions like NASA. Its application increases the operational reliability while
reducing the cost of unnecessary maintenance activities and is certainly also a solution for current and future ELT facilities.
RCM is a concept of developing a maintenance scheme based on the reliability of the various components of a system by
using "feedback loops between instrument / system performance monitoring and preventive/corrective maintenance cycles."
Ideally RCM has to be designed within a system and should be located in the requirement definition, the preliminary
and final design phases of new equipment and complicated systems. However, under certain conditions, an implementation
of RCM into the maintenance management strategy of already existing astronomical infrastructure facilities is
This presentation outlines the principles of the RCM methodology, explains the advantages, and highlights necessary
changes in the observatory development, operation and maintenance philosophies. Presently, it is the right time to implement
RCM into current and future ELT projects and to save up to 50% maintenance and operation costs.
Hundreds of mirror segment, thousands of high precision actuators, highly complex mechanical, hydraulic, electrical and other technology subsystems, and extremely sophisticated control systems: an ELT system consists of millions of individual parts and components each of them may fail and lead to a partial or complete system breakdown. Component and system reliability does not only influence the acquisition costs of a product, it also defines the necessary maintenance work and the required logistic support. Taking the long operational life time of an ELT into account, reliability and maintainability are some of the main contributors to the system life cycle costs. Reliability and maintainability are key characteristics of any product and have to be designed into it from the early beginning; they can neither be tested into a product nor introduced by numerous maintenance activities. This presentation explains the interconnections between Reliability, Availability, Maintainability and Safety (RAMS) and outlines the necessary RAMS and Reliability Centered Maintenance (RCM) processes and activities during the entire life cycle of an ELT and an ELT instrument from the initial planning to the eventual disposal phase.
The presentation illustrates the standard life cycles and project phases of a typical large scale astronomical facility acqui-sition and development project and explains the role of Systems Engineering (SE) during the entire project life cycle. The basic SE philosophy and systematic SE approach are described and a road map identifying the main activities of SE during the individual project phases - from the requirement definition to the eventual validation of the erected system- is developed. In addition the presentation describes the methodologies and processes SE can offer to analyse the risks asso-ciated with the definition, development and implementation of large complex scientific infrastructure projects. Risk control methods and approaches which are necessary to systematically reduce the technical, financial and schedule risks to a level acceptable to the scientific / technical project management and to the funding agencies are explained.
The international environment of the astronomical research and the world wide distribution of astronomical institutes and observatories create a high demand of flexibility from the designers and engineers developing and building the scientific instruments for use in astronomical research programs. In particular, with respect to the safety performance characteristics of the scientific instruments, a harmonization process among the various safety requirements could lead to more safety awareness and understanding of these requirements. Additionally, some kind of standardization in the methods and means used during the acquisition of the instruments would reduce safety risks to an acceptable level
Systems Engineering (SE) is the discipline in a project management team, which transfers the user's operational needs and justifications for an Extremely Large Telescope (ELT) -or any other telescope-- into a set of validated required system performance characteristics. Subsequently transferring these validated required system performance characteris-tics into a validated system configuration, and eventually into the assembled, integrated telescope system with verified performance characteristics and provided it with "objective evidence that the particular requirements for the specified intended use are fulfilled". The latter is the ISO Standard 8402 definition for "Validation".
This presentation describes the verification and validation processes of an ELT Project and outlines the key role System Engineering plays in these processes throughout all project phases. If these processes are implemented correctly into the project execution and are started at the proper time, namely at the very beginning of the project, and if all capabilities of experienced system engineers are used, the project costs and the life-cycle costs of the telescope system can be reduced between 25 and 50 %.
The intention of this article is, to motivate and encourage project managers of astronomical telescopes and scientific instruments to involve the entire spectrum of Systems Engineering capabilities performed by trained and experienced SYSTEM engineers for the benefit of the project by explaining them the importance of Systems Engineering in the AIV and validation processes.
The presentation describes the historical background of systems engineering and its development based on the urgent need for systematic management approaches in highly complex and sophisticated scientific (space) and military projects. Not in every project related to technical equipment for astronomical applications a separate expensive systems engineer or systems engineering team is absolutely necessary. The presentation outlines the typical project constellations and boundary conditions requiring the implementation of systems engineering in a project management organisation and explains the benefits and advantages system engineering offers to the project. Whether a project benefits from the sys-tems engineering function or rather consider it as ballast and wasted money depends to a large degree on the people involved in the systems engineering function. The required characteristics for an efficient systems engineer are discussed as well as the personal and professional experience, which are prerequisites to be or become an ideal systems engineer.
The international environment of astronomical research and the worldwide distribution of astronomical institutes and observatories create a high demand of flexibility on the designers and engineers developing and building scientific instruments for use in astronomical research programs. In particular with respect to the safety performance characteristics of the scientific instruments a harmonization process among the various safety requirements could lead to more safety awareness and understanding of these requirements, and also to some kind of standardization concerning the methods and means used during the acquisition period of the instruments to reduce safety risks to an acceptable level.
Proc. SPIE. 4004, Telescope Structures, Enclosures, Controls, Assembly/Integration/Validation, and Commissioning
KEYWORDS: Telescopes, Manufacturing, Control systems, Space telescopes, Astronomical telescopes, Large telescopes, Systems engineering, Document management, Optical instrument design, Standards development
This presentation describes the verification and validation processes of an Extremely Large Telescope Project and outlines the key role System Engineering plays in these processes throughout all project phases. If these processes are implemented correctly into the project execution and are started at the proper time, namely at the very beginning of the project, and if all capabilities of experienced system engineers are used, the project costs and the life-cycle costs of the telescope system can be reduced between 25 and 50%. The intention of this article is, by explaining the importance of Systems Engineering in the AIV and validation processes, to motivate and encourage project managers of astronomical telescopes and scientific instruments to involve the entire spectrum of Systems Engineering capabilities performed by trained and experienced SYSTEM engineers for the benefit of the project.
The application of computers and software to control continuously or on demand safety critical processes is unavoidable in complex telescopes and associated operation and maintenance support equipment. While the control of the maximum azimuth and elevation movement ranges of a telescope is a rather simple task and hardwired high reliable endstops can be used to practically eliminate any risk associated with the potential exceeding of the range limits, the handling and recoating of a 8 m thin Zerodur mirror is quite a delicate activity. It includes already a number of computer controlled actions which--if no risk reduction measures are established--lead to very high risk. But in complex systems like an 8 m optical telescope, coating facilities or similar the functional control and the control of major safety critical operations have to be performed by computers. Straightforward hardwired interlocks devices are not adequate for the control and monitor of highly complex processes. The still increasing process complexity will also lead to the demand for fast and intelligent risk limitation and reduction devices, and the use of safety related systems based on electrical, electronic and/or programmable electronic technology is unavoidable. But in using computers and software in safety critical applications the applicable standards and norms have to be applied strictly.
Safety, like quality and reliability, has to be designed into a product and respected during all project phases from the concept definition to the operation and maintenance phases. The VLT approach towards occupational safety and health and equipment safety starts with the definition of realistic safety requirements and applicability of ECC directives and national laws of the ESO Member States. The approach continues with preliminary safety analyses during the early project phases, with hazard analysis and safety verifications during the developmental phases, the training for safe operation, maintenance, and later material disposal. System safety is an integral part of the VLT project.