4MOST is a versatile spectroscopic facility soon to be installed on the ESO VISTA Telescope at Paranal. Prior to shipment to Chile, our team is conducting a comprehensive characterization of the instrument in a controlled laboratory setting. This preparatory phase is crucial for ensuring the fulfilment of both technical specifications and some key user requirements. The goal of this verification campaign is to obtain characterization data which will benchmark the performance of the spectrographs and the calibration unit against established metrics. The data primarily tests the spectral performance of the three spectrographs, the stability of the system, including the calibration unit, as well as the fiber throughput, which are pivotal for the success of 4MOST’s ambitious science goals. Additionally, the verification contains a selection of user requirements, ensuring the instrument’s readiness for the diverse scientific objectives it aims to enable. The results from these tests inform the observational strategy for future normal science operations. In this paper we outline the undertaken preparatory work, the applied testing procedures, and the anticipated implications of these tests, and their results, in the context of the final verification at the telescope, commissioning and normal science operations. This initial test phase marks a critical juncture in the 4MOST project timeline, setting the stage for a successful commissioning.
4MOST is a wide-field, high-multiplex, fibre-fed spectrograph, which will be mounted on the ESO VISTA telescope. High- and low-redshift surveys, targeting stars, galaxies, and AGN, can be executed in parallel, populating all the available 2436 fibers. Here, we present the 4MOST calibration plan, concentrating on the unique features dictated by the design of the instrument. These include the night-time backillumination of the fibers for precise metrology, simultaneous calibrations by dedicated fibers, attached night-time flatfield and wavelength calibration via a laser driven light source with a Fabry Perot etalon (FPE) on a moving carriage, and the observations of benchmark, telluric, and radial velocity standards for the science cross-calibration between 4MOST and complementary surveys from other telescopes.
4MOST is a new high-multiplex, wide-field spectroscopic survey facility under construction for ESO's 4m-VISTA telescope at Paranal, Chile. Its key specifications are: a large field of view of 4.4 square degrees, a high multiplex fibre positioner based on the tilting spine principle that positions 2436 science fibres in the focal surface of which 1624 fibres go to two low-resolution optical spectrographs (R = λ/Δλ ~ 6500) and 812 fibres transfer light to the high-resolution optical spectrograph (R ~ 20,000). Currently, almost all subsystems are completed and full testing in Europe will be finished in spring 2023, after which 4MOST will be shipped to Chile. An overview is given of instrument construction and capabilities, the planned science of the consortium and the recently selected community programmes, and the unique operational scheme of 4MOST.
The new era of Multi-Object Spectrograph (MOS) Survey projects, in particular WEAVE (on the WHT at the ING) and 4MOST (on VISTA at ESO Paranal), require complex data flow systems. These systems encompass the software development for target selection, fibre configuration and observation at the telescope front-end and spectral processing, spectral analysis and archiving at the back-end. The system must also include quality control procedures, signaling mechanisms and alert reporting to ensure optimal use of telescope time and scientifically robust data products. Key to ensuring a fully functioning data flow system by first light are Operational Rehearsals (OpR) which use simulated data in end-to-end tests of the entire system. The Cambridge Astronomical Survey Unit (CASU) has been integral in defining and coordinating these OpR efforts, in its role of providing the back-end data management and the spectral processing pipelines, for both WEAVE and 4MOST. The WEAVE OpR programme is complete and we await first light. The first two rehearsal stages (OpR1 and OpR2) of the 4MOST OpR programme are complete while the third, and most complex, stage will commence in 2022.
We present an update on the overall integration progress of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), now scheduled for first light in early-2021, with almost all components now arrived at the observatory. We also present a summary of the current planning behind the 5-year initial phase of survey operations, and some detailed end-to-end science simulations that have been implemented to evaluate the final on-sky performance after data processing. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 mini integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000.
A status overview of 4MOST is presented, a new high-multiplex, wide-field spectroscopic survey facility under construction for ESO's VISTA telescope at Paranal. Its key specifications are: a large field of view of 4.4 deg2 and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (R = λ/Δλ ~ 6500), and 812 fibres transferring light to the high-resolution spectrograph (R ~ 20 000). The 4MOST system integration has commenced and the selection process for ESO community survey programmes has been started. This overview presents the expected performance of the instrument, the science the consortium expects to carry out, and the unique operational scheme of 4MOST.
We present an update on the overall construction progress of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), now that all the major fabrication contracts are in place. We also present a summary of the current planning behind the 5-year initial phase of survey operations, and some detailed end-to-end science simulations that have been effected to evaluate the final on-sky performance after data processing. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project has experienced some delays in procurement and now has first light expected for the middle of 2019.
We present an overview and status update of the 4MOST project at the Final Design Review. 4MOST is a major new wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope at the Paranal Observatory of ESO. Starting in 2022, 4MOST will deploy 2436 optical fibres in a 4.1 square degree field-of-view using a fibre positioner based on the tilting spine principle. The fibres will feed one high-resolution (R~20,000) and two low-resolution (R~5000) spectrographs that all have fixed configuration, 3-channel designs with identical 6k x 6k CCD detectors. Updated performance estimates will be presented based on components already manufactured and pre-production prototypes of critical subsystems.
The 4MOST science goals are mostly driven by a number of large area, space-based observatories of prime European interest: Gaia and PLATO (Galactic Archeology and Stellar Physics), eROSITA (High-Energy Sky), and Euclid (Cosmology and Galaxy Evolution). Science cases based on these observatories, along with wide-area ground-based facilities such as LSST, VISTA and VST drive the ten Consortium Surveys covering a large fraction of the Southern sky, with bright time mostly devoted to the Milky Way disk and bulge areas and the Magellanic Clouds, and the dark/gray time largely devoted to extra-galactic targets. In addition there will be a significant fraction of the fibre-hours devoted to Community Surveys, making 4MOST a true general-purpose survey facility, capable of delivering spectra of samples of objects that are spread over a large fraction of the sky.
The 4MOST Facility Simulator was created to show the feasibility of the innovative operations scheme of 4MOST with all surveys operating in parallel. The simulator uses the mock catalogues created by the science teams, simulates the spectral throughput and detection of the objects, assigns the fibres at each telescope pointing, creates pointing distributions across the sky and simulates a 5-year survey (including overhead, calibration and weather losses), and finally does data quality analyses and computes the science Figure-of-Merits to assess the quality of science produced. The simulations prove the full feasibility of running different surveys in parallel.
The United Kingdom Infrared Telescope (UKIRT) observatory has been transferred to the ownership of the University of Hawaii (UH) and is now being managed by UH. We have established partnerships with several organizations to utilize the UKIRT for science projects and to support its operation. Our main partners are the U.S. Naval Observatory (USNO), the East Asian Observatory (EAO), and the UKIRT microlensing team (JPL/IPAC/OSU/Vanderbilt). The USNO is working on deep northern hemisphere surveys in the H and K bands and the UKIRT microlensing team is running a monitoring campaign of the Galactic bulge. EAO, UH, and USNO have individual P.I. research programs. Most of the observations are using the Wide Field Camera (WFCAM), but the older suite of cassegrain instruments are still fully operational. Data processing and archiving continue to be done CASU and WSA in the UK. We are working on a concept to upgrade the WFCAM with new larger infrared detector arrays for substantially improved survey efficiency.
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.
WEAVE is the next-generation spectroscopic facility for the William Herschel Telescope (WHT), offering multi-object (1000 fibres) and integral-field spectroscopy at two resolutions (R ~ 5000, 20000) over a 2-deg field of view at prime focus. WEAVE will (mainly) provide optical follow up of ground-based (LOFAR) and space-based (GAIA) surveys. First light is expected in mid 2018. Here, we describe the calibration unit, which will be adapted from an existing unit for the AF2+WYFFOS spectrograph (WEAVE's precursor) at the WHT. We summarise the results from a thorough characterisation of current performance (e.g. intensity, stability and focal-plane coverage of illumination as a function of lamp type and wavelength). We then set out our plans for upgrading the unit and its control systems to meet the WEAVE science and operational requirements. We conclude from this assessment that the upgraded AF2+WYFFOS calibration unit will meet the requirements for WEAVE. The design of the WEAVE calibration unit is now complete.
We present the Final Design of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), together with a status update on the details of manufacturing, integration and the overall project schedule now that all the major fabrication contracts are in place. We also present a summary of the current planning behind the 5-year initial phase of survey operations. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project is now in the manufacturing and integration phase with first light expected for early of 2018.
C. Jakob Walcher, Roelof de Jong, Tom Dwelly, Olga Bellido, Thomas Boller, Cristina Chiappini, Sofia Feltzing, Mike Irwin, Richard McMahon, Andrea Merloni, Olivier Schnurr, Nicholas Walton
The 4MOST instrument is a multi-object spectrograph to be mounted to the VISTA telescope at ESOs La- Silla-Paranal observatory. 4MOST will deliver several 10s of millions of spectra from surveys typically lasting 5 years. 4MOST will address Galactic and extra-galactic science cases simultaneously, i.e. by observing targets from a large number of different surveys within one science exposure. This parallel mode of operations as well as the survey nature of 4MOST require some 4MOST-specific operations features within the overall operations model of ESO. These features are necessary to minimize any changes to the ESO operations model at the La- Silla-Paranal observatory on the one hand, and to enable parallel science observing and thus the most efficient use of the instrument on the other hand. The main feature is that the 4MOST consortium will not only deliver the instrument, but also contractual services to the user community, which is why 4MOST is also described as a 'facility'. We describe the operations model for 4MOST as seen by the consortium building the instrument. Among others this encompasses: 1) A joint science team for all participating surveys (i.e. including community surveys as well as those from the instrument-building consortium). 2) Common centralized tasks in observing preparation and data management provided as service by the consortium. 3) Transparency of all decisions to all stakeholders. 4) Close interaction between science and facility operations. Here we describe our efforts to make parallel observing mode efficient, flexible, and manageable.
The 4MOST[1] 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[1], the instrument requirements development[2], the systems engineering implementation[3], the instrument model[4], the fibre positioner concepts[5], the fibre feed[6], and the spectrographs[7].
WEAVE is an approved massive wide field multi-object optical spectrograph (MOS) currently entering its build phase, destined for use on the 4.2-m William Herschel Telescope (WHT). It will be commissioned and begin survey operations in 2017. This paper describes the core processing system (CPS) system being developed to process the bulk data flow from WEAVE. We describe the processes and techniques to be used in producing the scientifically validated 'Level 1' data products from the WEAVE data. CPS outputs will include calibrated one-d spectra and initial estimates of basic parameters such as radial velocities (for stars) and redshifts (for galaxies).
We present an overview of and status report on the WEAVE next-generation spectroscopy facility for the William
Herschel Telescope (WHT). WEAVE principally targets optical ground-based follow up of upcoming ground-based
(LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree
prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object
(MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single
spectrograph, with a pair of 8k(spectral) x 6k (spatial) pixel cameras, located within the WHT GHRIL enclosure on the
telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single
exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project is now in the final
design and early procurement phase, with commissioning at the telescope expected in 2017.
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.
We present the preliminary design of the WEAVE next generation spectroscopy facility for the William Herschel
Telescope (WHT), principally targeting optical ground-based follow up of upcoming ground-based (LOFAR) and spacebased
(Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2 degree prime focus field of view
at the WHT, with a buffered pick and place positioner system hosting 1000 multi-object (MOS) fibres or up to 30
integral field units for each observation. The fibres are fed to a single spectrograph, with a pair of 8k(spectral) x 6k
(spatial) pixel cameras, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting
observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with
limited coverage in each arm at R~20000.
Data from two IR survey cameras UKIRT's WFCAM and ESO's VISTA can arrive at rates approaching 1.4 TB/night
for of order 10 years. Handling the rate, and volume of survey data accumulated over time, are both challenges. The
UK's VISTA Data Flow System (for WFCAM & VISTA near-IR survey data) removes instrumental artefacts,
astrometrically and photometrically calibrates, extracts catalogues, puts the products in a curated archive, facilitates
production of user-specified data products, and is designed in the context of the Virtual Observatory. The VDFS design
concept is outlined, and experience in handling the first year of WFCAM data described. This work will minimize risk
in meeting the more taxing requirements of VISTA, which will be commissioned in 2007. Tools for preparing survey
observations with VISTA are outlined.
Gaia is an approved ESA cornerstone project, currently scheduled for launch in late 2011. Gaia will provide photometric, positional, spectroscopic and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars in our Galaxy and throughout the Local Group, addressing its core science goals to quantify the formation and assembly history of a large spiral galaxy, the Milky Way. Gaia will achieve this by obtaining a six-dimensional (spatial & kinematic) phase-space map of the Galaxy, complemented by an optimised high-spatial resolution multi-colour photometric survey, and the largest stellar spectroscopic and radial velocity surveys ever made. The Gaia data set will be constructed from 2 × 1012 observations (image CCD transits), whose analysis is a very complex task, involving both real-time (this proposal) and end-of-mission data products. This paper describes the UK Gaia Data Flow System activities as part of the emerging European wide Gaia Data Processing system. We describe the data processing challenges that need to be overcome to meet the heavy demands placed by Gaia. We note the construction processes required to handle the photometric reduction of the data from Gaia's 100+ focal plane CCDs, the pipeline needed to support the 'science alerts' and epoch photometry handling, and the spectroscopic processing system. We note the system software and hardware architecture, and how the data products will be generated to ensure compliance with emerging VO standards.
Data from the two IR survey cameras WFCAM (at UKIRT in the northern hemisphere) and VISTA (at ESO in the southern hemisphere) can arrive at rates approaching 1.4 TB/night for of order 10 years. Handling the data rates on a nightly basis, and the volumes of survey data accumulated over time each present new challenges. The approach adopted by the UK's VISTA Data Flow System (for WFCAM & VISTA data) is outlined, emphasizing how the design will meet the end-to-end requirements of the system, from on-site monitoring of the quality of the data acquired, removal of instrumental artefacts, astrometric and photometric calibration, to accessibility of curated and user-specified data products in the context of the Virtual Observatory. Accompanying papers by Irwin et al and Hambly et al detail the design of the pipeline and science archive aspects of the project.
The UKIRT Wide Field Camera (WFCAM) on Mauna Kea and the VISTA IR mosaic camera at ESO, Paranal, with respectively 4 Rockwell 2kx2k and 16 Raytheon 2kx2k IR arrays on 4m-class telescopes, represent an enormous leap in deep IR survey capability. With combined nightly data-rates of typically 1TB, automated pipeline processing and data management requirements are paramount. Pipeline processing of IR data is far more technically challenging than for optical data. IR detectors are inherently more unstable, while the sky emission is over 100 times brighter than most objects of interest, and varies in a complex spatial and temporal manner. In this presentation we describe the pipeline architecture being developed to deal with the IR imaging data from WFCAM and VISTA, and discuss the primary issues involved in an end-to-end system capable of: robustly removing instrument and night sky signatures; monitoring data quality and system integrity; providing astrometric and photometric calibration; and generating photon noise-limited images and astronomical catalogues. Accompanying papers by Emerson etal and Hambly etal provide an overview of the project and a detailed description of the science archive aspects.
The UKIRT Wide Field Camera (WFCAM) is an IR mosaic camera that represents an enormous leap in deep IR survey capability. It will be used as both an open time facility, and to perform a public IR Deep Sky Survey (the UKIDSS project), starting in early 2004. Here we present current plans for the data archive system, which will be provided as a standard service for all UK WFCAM data whether private or public survey data. The data rate is an order of magnitude larger than any previous survey experiment. WFCAM is therefore a crucial stepping stone between current day surveys such as SuperCOSMOS, APM and SDSS, and future facilities such as VISTA and the LSST. Pipeline processing presents a technical challenge, but the strongest challenges come in operation and curation of such a pipeline and of the rapidly accumulating database. For the public archive, there is little technical challenge in simply storing the data, and the real challenge comes in the rapidly increasing expectations of the user community for the kind of on-line services available with the archive. We describe three levels of archive service and the challenges they present, and discuss the hardware and software solutions we are likely to deploy.
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