The European Solar Telescope (EST) is a 4.2-m telescope which has been redesigned with a fully integrated Multi-Conjugate Adaptive Optics (MCAO) into the optical path right after the EST primary mirror. The current baseline configuration considers four altitude Deformable Mirrors (DM) conjugated to 5, 9, 12 and 20 km above the telescope entrance pupil and an Adaptive Secondary Mirror (ASM) conjugated to the entrance pupil. The wavefront sensing will be performed by a set of correlation-based Shack Hartmann wavefront sensors (WFS) combining an on-axis High-Order WFS (HOWFS) to be used either in Single Conjugate AO (SCAO) to drive the ASM as well as operating simultaneously with a Multi-Directional WFS (MDWFS) to drive the MCAO. Beyond the current baseline configuration, different alternatives are currently being investigated both in the wavefront sensing strategy by evolving from a HOWFS+MDWFS into possibly a single High Order Multi Directional WFS (HOMDWFS) and/or wavefront sensors operating at different observing bands.
This paper describes the preliminary design of the Adaptive Secondary Mirror (ASM) for the European Solar Telescope (EST), as designed by TNO. This ASM will contain 1950 actuators over an optical aperture of Ø80cm. The mirror-shell of this ASM is concave with a radius of 2.156m and has a thickness of 2.5mm. To cope with the high optical heat-load, the mirror shell will be cooled actively by means of conduction through a small (0.3mm) airgap between the mirror shell and the cooled SiC supporting structure. One of the unique characteristics of this ASM are the highly efficient actuators by TNO, delivering 30N Peak-to-Valley of linear force range within a packaging of Ø15x40mm. These actuators are based on the proven electromagnetic actuation principle by TNO but have been significantly redesigned to improve manufacturability and integration. The actuators are interfaced to the mirror shell via a stiff carbon fiber strut assembly and are designed to be replaceable during off-telescope maintenance. For overall alignment of the ASM a hexapod is used, while a faster tip-tilt stage is used to compensate for tip-tilt disturbances up to 20Hz bandwidth. The optical performance of the ASM under various environmental conditions has been extensively studied with Finite-Element-Analysis. To verify the performances of the actuator and the cooling systems, an actuator and thermal- breadboard are being constructed.
The European Solar Telescope (EST) is a 4-m class solar telescope that will be installed at the Observatorio del Roque de los Muchachos in La Palma (Spain). Two important factors make EST different from other similar size telescopes: high thermal load due to solar radiation and open dome configuration during observation. Therefore, the entire telescope will be exposed to direct and indirect solar radiation, which requires a very demanding thermal management in order to minimize local seeing. In addition, the complete telescope will be exposed to wind, which has an important impact both in image stability and image quality. The EST M1 Assembly (primary mirror and cell) will have to cope with these critical issues, apart from other aspects common to primary mirrors of similar size. In 2020, in the scope of the EST Preliminary Design Phase, the development of the M1 Assembly was granted to the company SENER-Aeroespacial. The first step, before starting the design, was to evaluate different technologies and configurations for the following critical aspects: mirror (lightweight or not), number and type of axial actuators, cooling system, and number of interfaces with the elevation tube. A comparative study was carried out in order to define the baseline configuration for the M1 Assembly. This baseline configuration was then fully developed up to preliminary design level. This paper addresses the comparative study performed for selecting the most promising baseline configuration for the EST M1 Assembly.
The European Solar Telescope (EST) is a 4-meter class solar telescope led by the Instituto Astrofísico de Canarias that will be erected in La Palma Island. The design process is now approaching the Preliminary Design Review. The EST, as solar telescope, will have singularities that make its design differ from other telescopes. Telescope configuration, high solar radiation, absence of dome during observation, besides other elements, will have a strongly impact to the system design. One of the telescope critical elements is the primary mirror and its support. Along the last months, the preliminary design of these items has been performed. Critical aspects as mirror heat rejection, surface temperature and homogeneity, shape error, wind perturbations, etc., have had strong influence in the design solutions, pushing to use, for example, the thinner solid meniscus mirror never manufactured supported by 80 tripods over electromechanical actuators. This paper presents the design of the primary mirror and its support, presenting the adopted design solutions to cope with the different difficulties as well as the results of some protypes manufactured to reduce the project risk.
The works described in the current paper correspond to some exploratory advances that were performed by ESTEYCO in close collaboration with IAC on the European Solar Telescope (EST) main structure beyond the conceptual design activities conducted up to 2011, which were taken as the starting point. The works to develop this advanced conceptual design of the EST telescope structure were conducted within a collaboration agreement between ESTEYCO and IAC. The paper presents a brief summary of the main design modification activities that are proposed for the telescope structure, the different methodologies involved including structural, mechanical and aerodynamic performance, the rationale behind the different design change proposals and, finally, a quantitative assessment of the effectiveness of the different design alternatives and modifications in order to provide a consistent methodology to judge the improvement between the different alternatives. In order to have a clear and consistent comparison, it was decided to generate independent Finite Element models from the reference conceptual design. After this assessment, the elevation structure is proposed to undergo several modifications (mainly oriented at the suppression of the rocking-chair like wheels) to improve its structural and mechanical performance. The load transfer path is also changed by modifying the azimuthal radial guides radii in order to have a more direct transfer from the elevation structure to the ground. Some of these modifications are conducted by means of a newly developed in-house program that enables automatizing a series of constrained numerical optimization to improve the structural response.
The European Solar Telescope (EST) aims to become the most ambitious ground-based solar telescope in Europe. Its roots lie in the knowledge and expertise gained from building and running previous infrastructures like, among others, the Vacuum Tower Telescope, Swedish Solar Telescope, or the GREGOR telescope. They are installed in the Canary Islands observatories, the selected EST site. Furthermore, the telescope has a novel optical design, including an adaptive secondary mirror (ASM) that allows reducing the number of optical surfaces to 6 mirrors (plus two lenses) before the instruments’ focal plane. The latter, combined with a configuration of mirrors that are located orthogonally oriented to compensate for the instrumental polarisation induced by each surface, makes EST a reference telescope in terms of throughput and polarimetric accuracy. In its main core design, EST also includes a Multi-Conjugated Adaptive Optics (MCAO) system where the ASM compensates for the ground layer turbulence. The rest of the mirrors on the optical train correct for the atmospheric turbulence at different layers of the atmosphere. The MCAO guarantees that the large theoretical spatial resolution of the 4-metre EST primary mirror is achieved over a circular FOV of 60 arcsec. Those main elements, combined with a set of instruments with capabilities for spectropolarimetry, make EST the next frontier in solar ground-based astronomy. In this contribution, we will cover the main properties and status of all the mentioned sub-systems and the following steps that will lead to the construction phase.
The European Solar Telescope (EST) is a next generation large-aperture solar telescope, to be located in the Canary Islands. It will be optimized for studies of the magnetic coupling of the solar atmosphere. This will require diagnostics of the thermal, dynamic and magnetic properties of the plasma over many scale heights, by using multi-wavelength imaging, spectroscopy and spectropolarimetry. The optical design of the EST is based on an aplanatic Gregorian telescope, characterized by a 4.2-metre primary mirror, installed above the elevation axis with the aim of enhancing the natural air flushing. The EST works in open configuration, requiring an active/passive thermal control at telescope level to comply with the maximum temperature gradients of ±2°C. The telescope will be placed on the top of a tower to improve the local seeing conditions. The open configuration exposes the telescope to wind disturbances, higher than in other telescopes. The natural frequency of the global modes affecting the position servosystem bandwidth of the telescope are stablished in 12-15 Hz to ensure pointing and tracking accuracy of 2.3 arcsec and 0.8 arsec during 10 mins, respectively. Sophisticated end-to-end control analysis have been carried out to assess in detail the effects of the wind disturbances, but also the impact of non-linear friction, cogging and torque ripple, among others. CFD analyses and wind tunnel test campaigns have been performed to verify the performance of the telescope in operational conditions. The main axes of the telescope must be in parking position before the closure of the retractable enclosure in order to optimize its size. This requires a robust design, including redundancy in azimuth and elevation mechanisms to ensure the protection of the telescope in case of failure. The detailed maintenance strategy has been also established to ensure that every operation can be performed with the closed enclosure.
Text-based requirements management tools are widely used in engineering today. The concept behind it is quite simple, but this simplicity does not mean that these tools are affordable. In most cases, the cost of a requirements management tool license is similar to the cost of a CAD software license, the latter pertaining to a much more complex software tool. At cosmoBots.eu we have developed a plugin for a free and open project management tool (Redmine) that turns it into a powerful requirements management tool, including automatic and instant hierarchy and dependency diagrams, import/export from/to spreadsheets, full interoperability with other tools using the REST API, also including role-based lifecycle management and reporting. Several projects in IAC (EST, MICAL, NRT...) are officially using cosmoSys-Req to manage their requirements, and other projects or institutions (GTC, IACTEC...) are currently evaluating their use.
The European Solar Telescope (EST) is a 4.2-m solar telescope, based on an aplanatic Gregorian configuration with an alt-azimuthal mount. This contribution presents the status of EST and describes the baseline for the preliminary design of the Telescope Structure (Telescope Mount), Enclosure and Pier. It also introduces the systems engineering, model and tools. In addition, it explains the rationale of the main specifications. The optical design has undergone major changes since the conceptual design. The M2 Assembly has become an Adaptive Secondary Mirror, the f-number has been changed and the number of optical surfaces has been reduced to 6 mirrors and 2 lens barrels. Therefore, part of the system has been updated and new assemblies have appeared: The Transfer Optics and Calibration Assembly (TOCA) and the Pier Optical Path (POP). Some requirements make this telescope unique: the primary mirror is above the elevation axis, the multi-conjugated adaptive optics is integrated in the telescope, the telescope instrumental polarization is minimized and the telescope will observe in open enclosure configuration to improve the natural air flushing. The drawback of the open configuration is that the telescope structure, M1 and M2 will be exposed to the wind load and the thermal load by radiation, forcing the development of a stiffer Telescope Structure, a specific thermal control to achieve the pointing and tracking performances and a low local seeing degradation. The Preliminary Design phase of the Telescope Structure, Enclosure and Pier have been developed by IDOM throughout 2021 and 2022, following technical requirements by the EST Project Office.
Here is presented the tests results and the lessons learnt concerning an opto-mechanical device to scan the GREGOR telescope field of view. The scanning is done by means of a set of mirrors and a mechanism which allows to keep the optical path length constant, regardless the portion of the field being scanned. This system is intended to feed a static image slicer used for solar observations. The tight level of tolerances required makes its design and tests a real challenging activity which produces a lot of unexpected lessons to learn. The story after the issues detection, the consequent root cause analysis, the additional tests and tools developed to study the phenomena, and the construction of the solutions and issue mitigation mechanisms provides a good background to elaborate some recommendations for future developments.
We present the commissioning of an IFU based on image-slicers and a 2D-Field-of-View Scanning System (FoV-SS) for the GREGOR Infrared Spectrograph (GRIS). The prototype of the image-slicer has eight slices of 1.8 mm x 0.1 mm in Zerodur, covering an area of 20 arcsec2. The FoV-SS, equipped with three Degrees of Freedom (DoF), allows to scan a region of 1 arcmin2, feeding the image-slicer with different portions of the field of view. A batch of tests was done during the Assembly, Integration and Verification (AIV) at GREGOR telescope.
EMIR is the NIR imager and multi-object spectrograph common user instrument for the GTC and it has recently passed its first light on sky. EMIR was built by a Consortium of Spanish and French institutes led by the IAC. EMIR has finished its AIV phase at IAC facilities and it is now in commissioning on sky at GTC telescope, having completed the first run. During previous cool downs the EMIR subsystems have been integrated in the instrument progressively for verifying its functionality and performance. In order to fulfil the requirements, prepare the instrument to be in the best conditions for installation in the telescope and to solve unexpected electronics drawbacks, some changes in the implementation have been accomplished during AIV. In this paper it is described the adjustments, modifications and lessons learned related to electronics along AIV stages and the commissioning in the GTC. This includes actions in different subsystems: Hawaii2 detector and its controller electronics, Detector translation Unit, Multi object slit, wheels for filters and grisms, automatisms, vacuum, cryogenics and general electronics.
We report the results on the EMIR1 (Espectrógrafo Multiobjeto Infra-Rojo) performances after the commissioning period of the instrument at the Gran Telescopio Canarias (GTC). EMIR is one of the first common user instruments for the GTC, the 10 meter telescope operating at the Roque de los Muchachos Observatory (La Palma, Canary Islands, Spain). EMIR is being built by a Consortium of Spanish and French institutes led by the Instituto de Astrofísica de Canarias (IAC). EMIR is primarily designed to be operated as a MOS in the K band, but offers a wide range of observing modes, including imaging and spectroscopy, both long slit and multiobject, in the wavelength range 0.9 to 2.5 μm. The development and fabrication of EMIR is funded by GRANTECAN and the Plan Nacional de Astronomía y Astrofísica (National Plan for Astronomy and Astrophysics, Spain). After an extensive and intensive period of system verification at the IAC, EMIR was shipped to the GTC on May 2016 for its integration at the Nasmyth platform. Once in the observatory, several tests were conducted to ensure the functionality of EMIR at the telescope, in particular that of the ECS (EMIR Control System) which has to be fully embedded into the GCS (GTC Control System) so as to become an integral part of it. During the commissioning, the main capabilities of EMIR and its combined operation with the GTC are tested and the ECS are modified to its final form. This contribution reports on the details of the EMIR operation at the GTC obtained so far, on the first commissioning period.
The European Solar Telescope (EST) is a 4-meter facility to be built in Canary Islands in the near future. Extensive daytime turbulence observation campaigns with the long baseline SHABAR instrument has been carried out in the two candidate sites from 2011 up to the end of 2014. The collected data together with nighttime turbulence data allow the site characterization and the computation of average turbulence profiles. These profiles can be used to feed numerical simulations in order to take important design decisions for the multiconjugate adaptive optics (MCAO) system in the telescope. This paper describes the main tasks developed in this context up to date.
An image slicer has been proposed for the Integral Field Spectrograph [1] of the 4-m European Solar Telescope (EST) [2] The image slicer for EST is called MuSICa (Multi-Slit Image slicer based on collimator-Camera) [3] and it is a telecentric system with diffraction limited optical quality offering the possibility to obtain high resolution Integral Field Solar Spectroscopy or Spectro-polarimetry by coupling a polarimeter after the generated slit (or slits). Considering the technical complexity of the proposed Integral Field Unit (IFU), a prototype has been designed for the GRIS spectrograph at GREGOR telescope at Teide Observatory (Tenerife), composed by the optical elements of the image slicer itself, a scanning system (to cover a larger field of view with sequential adjacent measurements) and an appropriate re-imaging system. All these subsystems are placed in a bench, specially designed to facilitate their alignment, integration and verification, and their easy installation in front of the spectrograph. This communication describes the opto-mechanical solution adopted to upgrade GRIS while ensuring repeatability between the observational modes, IFU and long-slit. Results from several tests which have been performed to validate the opto-mechanical prototypes are also presented.
KEYWORDS: Telescopes, Solar telescopes, Image quality, Turbulence, Thermal modeling, Domes, Temperature metrology, Thermal analysis, Ions, Chemical elements
The European Solar Telescope, EST, ([1], [2]) is a 4-meter solar telescope to be built in the Canary Islands in the near future. In order to select the best configuration for the EST telescope facilities, thermal and CFD analyses have been carried out to evaluate the seeing degradation produced by the telescope environment. The aim of this study is to calculate the values of optical parameters in different configurations and to find out which one causes the lowest image quality degradation. Starting from the determination of seeing degradation along the optical path by CFD techniques, several configurations have been compared making it possible to decide the future development line for the EST.
Integral Field Spectroscopy is an innovative technique that is being implemented in the state-of-the-art instruments of the
largest night-time telescopes, however, it is still a novelty for solar instrumentation. A new concept of image slicer,
called MuSICa (Multi-Slit Image slicer based on collimator-Camera), has been designed for the integral field
spectrograph of the 4-m European Solar Telescope. This communication presents an image slicer prototype of MuSICa
for GRIS, the spectrograph of the 1.5-m GREGOR solar telescope located at the Observatory of El Teide. MuSICa at
GRIS reorganizes a 2-D field of view of 24.5 arcsec into a slit of 0.367 arcsec width by 66.76 arcsec length distributed
horizontally. It will operate together with the TIP-II polarimeter to offer high resolution integral field spectropolarimetry.
It will also have a bidimensional field of view scanning system to cover a field of view up to 1 by 1 arcmin.
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