The Gran Telescopio de Canarias Adaptive Optic System (GTCAO) is designed to provide nearly diffraction-limited images to GTC. GRANCAIN (GRAN CAmara INfrarroja) is a first light imaging instrument in J, H, and K infrared bands, and it will be integrated into the Nasmyth focus of GTCAO, contributing to carry out his acceptance tests. The instrument aims to capture NIR (Near-Infrared) diffraction limit images for a field of view of 22x22 arcsec operating up to seeing conditions of 1.5 arcsec and zenithal distances up to 60deg. The instrument has a telecentric optical design based on a collimator-camera with a 2:1 magnification, with a cold stop and the filters located in the collimated beam. The detector is a 4Mpx Hawaii-2 PACE Teledyne (H2P), which operates at 77K. The instrument is composed of a rectangular aluminum 6061-T6 cryostat cooled by a closed Gifford-McMahon helium cycle cryocooler with an optical bench where the entire optical train is mounted. The opto-mechanical system consists of two filter wheels, containing three wide and three narrowband filters in the J, H, and K bands in charge of selecting the wavelengths of the science images. Thanks to a wide background knowledge built up at the Instituto de Astrofísica de Canarias (IAC) and the use of commercial elements, the instrument development plan has been reduced to one year and a half. The article contains a general description of the design, fabrication, integration, and testing of the opto-mechanical elements, cryostat, cooling, and anti-vibration systems.
HARMONI is the Extremely Large Telescope visible and near infrared integral field spectrograph and will be one of the first light instruments. The instrument supports four operational modes called No Adaptive Optics (NOAO), Single Conjugated Adaptive Optics (SCAO), High Contrast Adaptive Optics (HCAO), and Laser Tomography Adaptive Optics (LTAO). These operational modes are closely related to the wavefront correction topology used to support the performance required for each of the science cases. By following a novel function model-based systems engineering (FBSE) methodology in conjunction with observing the software computer system golden rule of design; namely having tight cohesion within software modules and loose coupling between modules, a system architecture has emerged. In this paper, we present the design of the HARMONI Control System (HCS). Although this is not the first time (for example NACO on VLT and NIRC2 on Keck) that the adaptive optics required to correct the atmospheric turbulence is part of a general instrument design, and not tailored for a very specific science case, this will be the first instrument of this size and complexity in the era of extremely large ground-based telescopes. The instrument control design must be compatible with the ELT instrument control system framework while there is also an expectation that the adaptive optics (AO) real-time computer toolkit (RTC-TK) should be used for the realization of the AO real-time control software and hardware. The HCS is composed of the instrument control electronics (ICE), the Instrument Control System (ICS), and the AO Control Sub-system (AOCS). The operation concept of the instrument is also novel in that for each mode the instrument creates an instantiation of a virtual system composed of only the system blocks required to provide the selected mode of operation. Therefore, each mode supports a unique system composition in terms of hardware, software, and the sequencing of activities.
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.
WEAVE is a new wide-field multi-object spectroscopy (MOS) facility proposed for the prime focus of the 4.2m William Herschel Telescope. The facility comprises a new 2-degree field-of-view Prime Focus Corrector (PFC) with a 1000-multiplex fibre positioner, a small number of individually deployable integral field units, and a large single integral field unit (IFU). The IFUs and the MOS fibres can be used to feed a dual-beam spectrograph that will provide full coverage of the majority of the visible spectrum in a single exposure at a spectral resolution of ~5000 or modest wavelength coverage in both arms at a resolution ~20000. In order to compensate the field rotation, the Prime Focus Rotator (PFR) is assembled in between the WEAVE Fiber Positioner (system that positions the fibers in the focal plane) and with the Central Can (contains the Prime Focus corrector optics) on the William Herschel Telescope (WHT). The Prime Focus Rotator must provide a rotation degree of freedom for the Fibre Positioner with a high bending stiffness (causing a deflection smaller than 0.008° between interface flanges) adding the minimum mass possible to the system (less than 700kg). This is easily identified as the main design driver to be considered. The Prime Focus Rotator positions the Fibre Positioner to an accuracy of 5 arcsec when tracking and guides all the fibres and other power and control lines through a cable wrap, for which the available space is limited. IDOM proposal to comply with these coupled requirements consists of an optimized structural system with a slightly preloaded cross roller bearing providing the highest possible stiffness to weight ratio. The rotation is driven by means of a direct drive motor powered by a servo drive. For the Cable Wrap, a compact design based on a concept previously developed by IDOM for the Folded Cassegrain Sets the GTC was proposed.
HARMONI is the adaptive optics assisted, near-infrared and visible light integral field spectrograph for the Extremely Large Telescope (ELT). A first light instrument, it provides the work-horse spectroscopic capability for the ELT. As the project approaches its Final Design Review milestone, the design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument’s capabilities from a user perspective, provide a summary of the instrument’s design, including plans for operations and calibrations, and provide a brief glimpse of the predicted performance for a specific observing scenario. The paper also provides some details of the consortium composition and its evolution since the project commenced in 2015.
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.
The optical instrument used to measure and characterize sky quality at the IAC observatories is the DIMM (differential image motion measurements). The optical system and its mode of operation are relatively simple. It consists, basically, placing two equal apertures at the entrance of a telescope, in one of them an optical wedge is located. In this way, two beams of the same object are obtained which will lead to two on the focal plane of the telescope but laterally separated a few seconds arc. The complexity of this optical system lies in the "simplicity" of the plate used to separate the beams, it is a flat-faced wedge of a few minutes, and this is where problems arise when manufacturing it.
In this paper we present a new optical system concept to separate the beams. This is done using two optical flats tilted. The optical flats are not placed at the entrance of the telescope, but in the convergent beam. The optical design, manufacture and the test results obtained are presented.
WEAVE is a new wide-field multi-object spectroscopy (MOS) facility proposed for the prime focus of the 4.2m William Herschel Telescope (WHT), situated on the island of La Palma, Canary Islands, Spain. To allow for the compensation of the effects of temperature-induced and gravity-induced image degradation, the WEAVE prime focus assembly will be translated along the telescope optical axis. The assembly comprises the prime focus corrector (PFC), a central mount for the corrector known as FTS[1], an instrument rotator and a twin-focal-plane fibre positioner. SENER, that manufactured and delivered the FTS, is also responsible for the final design, manufacturing, integration, alignment and testing of the PFC and its ancillary equipment. This manuscript describes the final design of the PFC along with the analyses and simulations performed and presents the procedures for the integration and alignment of the lenses in the corrector.
KEYWORDS: Control systems, Spectrographs, Databases, Telescopes, Human-machine interfaces, Data acquisition, Picture Archiving and Communication System, Calibration, Observatories, Sensors
WEAVE is the next-generation spectroscopic facility for the William Herschel Telescope (WHT) 1,2. WEAVE offers multi-object (1000 fibres) and integral-field spectroscopy at two resolutions (R ~ 5000, 20000) over a 2-deg field of view at prime focus and will mainly provide follow up of ground-based (LOFAR) and space-based (GAIA) surveys.
The Observatory Control System (OCS) is responsible for providing the software control and feedback framework through which WEAVE will be operated. This paper summarizes the design of the different OCS subsystems and the interfaces between them and other WEAVE components.
In the remainder of this paper, Section 2 outlines the other WEAVE systems with which the OCS interacts, Section 3 describes the system architecture, Section 4 comments on system-architecture decisions, Section 5 describes the main components of the OCS, Section 6 outlines the life-cycle of an OCS Observing Block and, finally, Section 7 gives an overview of the OCS testing plan.
KEYWORDS: Control systems, Device simulation, Telecommunications, LabVIEW, Telescopes, Interfaces, Systems modeling, Mathematical modeling, Picture Archiving and Communication System, Switches
When an alt-azimuth telescope is tracking at a specific field, it is necessary to use a de-rotator system to compensate the Earth’s rotation of the field of view. In order, to keep the telescope tracking the field of view selected, the instrument will need to a rotation system for compensating it [1]. The new WEAVE [2] two degrees field of view requires a new field de-rotator on the top-end of the telescope. The rotator system has been designed with a direct drive motor which eliminates the need for mechanical transmission elements such as gearboxes, speed reducers, and worm gear drives. This design is a huge advantage for the system performance and lifetime because it eliminates undesirable characteristics such as long-time drift, elasticity, and backlash. The hardware control system has been developed with a Rockwell servo-drive and controller. The rotator has to be controlled by the high-level software which is also responsible for the telescope control. This paper summarizes the model developed for simulating and the software which will be used to accept the rotator system. A performance study is also carried out to test the CIP (Common Industrial Protocol) for communications between the high-level software and the rotator hardware.
KEYWORDS: Spectrographs, Control systems, Camera shutters, Picture Archiving and Communication System, Charge-coupled devices, Visualization, Acoustics, Interfaces, Cameras, Power supplies
WEAVE is a wide-field spectroscopy facility for WHT which includes a multi-object dual-beam spectrograph which will operate in the visible wavelength range. The blue beam will cover the range 360-600 nm and the red arm will cover the 580-960 nm range. In these ranges the spectrograph will offer a mid-resolution (~5000), while in three narrower wavelength intervals, two for the blue arm and one for the red one, the instrument will provide a high (~20000) spectrograph resolution. The spectrograph is currently entering the assembly and integration phase and the first light is foreseen in 2019. The entire WEAVE project is managed by an international consortium led by the University of Oxford. The spectrograph is controlled by a coordination process, the so called High-Level Server, which is part of the Observatory Control System (OCS) software suite, and is the single point of access to the embedded control system, the so called Low-Level Control Software, which is based on PAC technology. This paper describes the design of the embedded software for the control of the spectrograph mechanisms. We first describe the interface between high and low level software, then we present the PAC architecture and discuss the low-level state machine. Finally, we provide details on the principal program routines and describe the engineering interface.
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.
WEAVE is a new wide-field spectroscopy facility proposed for the prime focus of the 4.2m William Herschel Telescope (WHT), placed in La Palma, Canary Islands, Spain.
To allow for the compensation of the effects of temperature-induced and gravity-induced image degradation, the WEAVE prime focus assembly will be translated along the telescope optical axis. The assembly comprises the prime focus corrector with integrated ADC, a central mount for the corrector, an instrument rotator and a twin-focal-plane fibre positioner. Translation is accomplished through the use of a set of purpose-built actuators; collectively referred to as the Focus Translation System (FTS), formed by four independently-controlled Focus Translation Units (FTUs), eight vanes connecting the FTUs to a central can, and a central can hosting WEAVE Instrument. Each FTU is capable of providing a maximum stroke of ±4mm with sufficient, combined force to move the five-tonne assembly with a positional accuracy of ±20μm at a resolution of 5μm. The coordinated movement of the four FTUs allows ±3mm WEAVE focus adjustment in the optical axis and ±0.015° tilt correction in one axis. The control of the FTS is accomplished through a PLC-based subsystem that receives positional demands from the higher-level Instrument Control System.
SENER has been responsible for designing, manufacturing and testing the FTS and the equipment required to manipulate and store the FTS together with the instrument.
This manuscript describes the final design of the FTS along with the analyses and simulations that were performed, discusses the manufacturing procedures and the results of early verification prior to integration with the telescope. The plans for mounting the whole system on the telescope are also discussed.
KEYWORDS: Control systems, Spectrographs, Telescopes, Sensors, Picture Archiving and Communication System, Camera shutters, Computer programming, Actuators, Switches, Space telescopes
This work describes the hardware control system of the Prime Focus Corrector (PFC) and the Spectrograph, two of the
main parts of WEAVE, a multi-object fiber spectrograph for the WHT Telescope. The PFC and Spectrograph control
system hardware is based on the Allen Bradley’s Programmable Automation Controller and its modules. Mechanisms,
sensors and actuators of both systems are summarized and their functionality described, showing how they meet the
instrument requirements.
WEAVE is the next-generation optical spectroscopy facility for the William Herschel Telescope and aims at
spectroscopic follow-up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE places in the re-fitted
prime focus either 1000 fibres, 20 fibre-coupled mini-IFUs or a single large 600 fibre IFU. A spectrograph on the
Nasmyth platform analyses the light and supports, in a single exposure, either R~5,000 observations over the full 366-
975 nm wavelength range or simultaneous R~20,000 observations over two out of three pre-specified bands within this
wavelength range. This paper describes the requirements, optical design and mechanical design of the WEAVE
spectrograph.
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.
During the last 20 years, many DIMM instruments have been developed to measure astronomical seeing. The IAC has
been involved in several projects to run different campaigns to characterize its observatories. However, the cost in
manpower to maintain and operate these instruments has been too high and it is mandatory to minimize this effort by
constructing a reliable, robust and available seeing monitor.
A review of all sources of errors has been done in order to fit very reliable measurements: acquisition parameters, box
size, signal threshold, SNR threshold, flux, deformations and vibrations for centroid calculations, best pixel scale, jitter
in the images sampling, light bandwidth, CCD noise, as well as the centroid calculation algorithm. Experimental
measurements about the influence of exposure time, number of images for computing the seeing or defocus have been
carried out to identify the practical limits of the instrument.
The IAC automatic DIMM design has been reviewed to improve its robustness and its availability to guarantee the
minimum down-time and to maximize the time between failures. The new design will be shown as part of this work.
We present in this paper the new cute-SCIDAR instrument, entirely developed by the Instituto de Astrofísica de Canarias
(IAC), delivered recently at the European Southern Observatory (ESO) Paranal Observatory (Chile). This instrument,
supported by the European Community (Framework Programme 6, Extremely Large Telescope Design Study), carries
out the generalized SCIntillation Detection And Ranging (g-SCIDAR) technique to obtain the temporal evolution of
turbulence profiles CN
2 with height. A new design was made in order to fit the VLT Auxiliary Telescopes (ATs)
interfaces and control requirements. Also, a new software architecture allows a full remote control, and a data analysis
pipeline provides turbulence profiles in real-time, which is the main achievement of this new cute-SCIDAR. Details of
its design and results of its excellent performance are included.
We have built a hybrid turbulence profiler measuring simultaneously the atmospheric turbulence structure with a Shack-
Hartmann wave front sensor and a G-SCIDAR (scintillation sensor). This is the first instrument combining two different
techniques to measure simultaneously the turbulence structure. The hybrid profiler has been installed at the Carlos
Sánchez Telescope (TCS) at the Teide Observatory (OT), in Tenerife Spain. The G-SCIDAR arm is already working
properly and we are still testing the Shack-Hartmann arm.
We present the statistical results of the optical-turbulence profiles at the Observatorio del Roque de los Muchachos over a period of six consecutive months. The data were obtained using the generalized SCIDAR technique at the 1m Jacobous Kaptein Telescope. In general, most of the turbulence is concentrated close to the observatory level (2400 m above sea level) with no more than two turbulent layers at higher altitudes. The temporal evolution along six consecutive months indicates that the turbulence is concentrated at lower altitude layers during winter. Large isoplanatic angles are also reached in winter compared to the values in spring. For the turbulence profiles measured in February, March and April we have analized the statistical position of demorfable mirrors in an ideal Multi-Conjugate Adaptive Optics system (with two or three deformable mirrors) and the improvements in the isoplanatic angles.
In the planning stage of extremely large telescopes, site testing and study of high performance adaptive optics systems plays very important roles. Site testing is a very time consuming task, therefore, we have built a fully automatic device - the CUTE SCIDAR instrument with a user-friendly interface and real time processing. This instrument is already in operation and now has been installed in the Jacobus Kapteyn Telescope of Roque de los Muchachos Observatory at La Palma for periodical turbulence profiling.
A second version with an additional phase sensor bench contains a motorized field stop, a field lens, a collimator lens, and a Shack-Hartmann sensor. This instrument measures the turbulence from both amplitude and phase variations of the same distorted wave at high frequency bandwidth, with a high resolution and dynamic range. On the one hand, this will solve the calibration problem between different turbulence sensors. On the other hand, it allows investigating the performance of multi-conjugated wavefront sensing using real time information from SCIDAR data and proving validity of the near field assumption. From preliminary Shack-Hartmann measurements we conclude that the instrument should be flexible to change optical layout and detection parameters according to the turbulence conditions. Therefore, the phase sensor branch includes automatically controlled moveable devices, and in the future, fast communication facilities between control computers of both SCIDAR and wavefront sensing are previewed. In this paper, we will present our objectives of building such an instrument, give a detailed state of art design, and considerate the preparation of first observational campaigns, that are the first scientific tasks to do.
We present a new generation SCIDAR instrument that is a fully automatically controlled device with a user-friendly interface. Alignment and observation are reduced to easy and rapid handling without the effort operating in the dome. This instrument is installed in the Jacobus Kapteyn Telescope on La Palma. We describe our progress from prototype to second generation instrument, emphasizing the design and the software for Cute SCIDAR, and show profiles from systematic monitoring using the prototype instrument on Tenerife and Cute SCIDAR on La Palma.
The statistics of vertical structure of the turbulence affect the complexity of the design and implementation of Multi-Conjugate Adaptive Optics (MCAO) systems. The operation of these systems could be optimized if the stability of the layers were such as to permit to fix the deformable mirrors (DMs) at specific heights. Moreover, it is desirable to know the effects on the placement of the DMs and the gain of the isoplanatic angle in terms of site characterization.
From the turbulence profiles measured with the G-SCIDAR technique we have analyzed the statistics of the heights of the DMs and the resulting isoplanatic angles. These results are based on the data from a long ongoing campaign at Roque de los Muchachos Observatory (La Palma) and Teide Observatory (Tenerife) with the highest statistical coverage to date. We have used two ideal MCAO systems, consisting of two and three DMs, and, from a specific comparison in simultaneous measurements over two nights, we show the evolution of the position of DMs and isoplanatic angles in both sites, which can sporadically reach values greater than 60" in 500 nm. We also study the effects of the stability of the conjugate planes on the improvements in the isoplanatic angles.
LIRIS is a near-infrared (1-2.5 microns) intermediate resolution spectrograph (R=1000-3000) with added capabilities for multi-slit, imaging, coronography, and polarimetry, built by the IAC to be a common instrument for the WHT (La Palma). Here we report the results of the two commissioning periods. The image quality was checked, obtaining a FWHM of 0".5 in the Ks band over the whole field of view (4'.2 x 4'.2). Zero points and sky brightness were measured, and very low values were found in the latter. The long slit spectra obtained matched the expected spectral resolution (2.6 pixels for a 0".65-wide slit). Flexure tests were carried out with good results. Several science targets were observed, the most note-worthy result being the detection of the CIV 154.9 nm line in the most distant qso at z=6.41.
Knowledge of vertical structure of the turbulence in a site is an essential input for the requirements, performances and operation of Adaptive Optics systems. The statistics of the turbulence intensity and the coherence time of the layers affect the complexity of the design and implementation of a particular MCAO system. On the other hand, the operation of such systems could be optimized if the height and velocity of the layers were available in real time. We present statistical results of the SCIDAR turbulence profiles obtained at the observatories Canary Islands. Statistics of characteristic parameters, of special interest for MCAO, are presented here, together with their temporal evolution. The results have been checked with simultaneous meteorological measurements. We have used the balloon sounding meteorological database of the Instituto Nacional de Meteorologia of the Santa Cruz station (Tenerife) to evaluate the physical conditions related with the behavior of the optical propagation. We have compared this study with the database of indirect measurements from satellites. The reliability of these data has been proved in relation to the balloon meteorological database for all height levels on Tenerife.
SCIDAR has proved to be the most efficient technique to obtain the optical vertical structure of the atmospheric turbulence measured from ground level. However, the common procedure of obtaining the data, as well as its 'a posteriori' treatment, requires a huge number of highly qualified human resources. A systematic monitoring program becomes really onerous. Consequently, the development of a full automatically controlled SCIDAR device seems to be evidently justified. We have recently developed a SCIDAR instrument providing high performances in automatic control and data reduction, presently in test pahse. It has been designed for the Jacobus Kapstein Telescope at the Roque de los Muchachos Observatory, with the goal of monitoring the vertical turbulence with a high temporal coverage. This device is not only restricted to the JKT but can also be used for other telescopes.
LIRIS is a near-infrared (0.9 - 2.4 microns) intermediate resolution spectrograph (R = 1000-3000) conceived as a common user instrument for the (WHT) at the Observatorio del Roque de los Muchachos (ORM) La Palma. LIRIS is now being assembled, integrated and virified at the Instituto Astrofisico de Canarias (IAC). LIRIS will have imaging, long-slit and multi-object spectroscopy working modes. Coronography and polarimetry capabilities will eventually be added. Image capability will allow easy target acquisition.
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