For more than ten years, the Gregor Infrared Spectrograph (GRIS) has been the infrared spectropolarimeter on the Gregor telescope since its inauguration in 2012. The instrument mainly performs polarimetric observations of the wavelength regions at 1083 and 1565nm, which have high scientific potential. There, observers can find spectral lines that provide information on the atmospheric parameters over a vast range of atmospheric layers and with high sensitivity to the magnetic field. Due to the high demand for GRIS and the versatility of the Gregor environment, we decided to upgrade the system once more, allowing it to become one of the instruments with the highest potential in any ground-based solar observatory. This time, the upgrades add two spectral channels for performing multi-wavelength observations in long-slit or IFU mode.
The Gregor Infrared Spectrograph (GRIS) is installed at the Gregor telescope at Observatorio del Teide, Spain. The instrument started observations in 2012 and underwent several upgrades in the following years. Currently, it is experiencing the most significant upgrade so far, which includes, among other things, adding two optical channels to perform simultaneous multi-wavelength observations. One of the elements we need to modify to optimise the performance of the instrument on all the new spectral channels is the Polarisation Module Unit (PMU). In this contribution, we want to present our theoretical analysis, laboratory experiments, and first-light results related to the new version of the PMU. This new version and many of the improved capabilities of the instrument will be offered to the community gradually during 2024.
The European Solar Telescope (EST) is a 4.2-metre telescope that will be equipped with a multi-conjugate adaptive optics (MCAO) system to provide a high spatial resolution over a circular field of view with 60” diameter. The EST-MCAO testbed is a downscaled demonstrator of solar MCAO with similar requirements to those defined for EST. It has been designed and developed to identify and better understand the capabilities of this system. Before MCAO implementation, different AO configurations must be first evaluated in the testbed. Single conjugate adaptive optics for point-like sources has been identified as the first step towards MCAO for the EST. This configuration is based on the use of a deformable mirror with 820 actuators and a Shack-Hartmann wavefront sensor with 33x33 subapertures. The main objective of this paper is to present the results obtained in the EST-MCAO testbed when testing different phase reconstruction algorithms and closed-loop schemes to deal with SCAO for point-like sources. Center of gravity technique was proposed for local slope computation when using point-like sources. Both zonal and modal approaches, including SVD and their regularized least-squares versions, were evaluated and tested for the reconstruction. A closed-loop strategy based on a proportional-integral controller was initially proposed. The benefits of pseudo open-loop control were also evaluated. The performance of the algorithms was tested considering different seeing conditions. Finally, a comparison based on RMS wavefront error and Strehl Ratio was conducted.
Once the design phase of the Multi-Conjugated Adaptive Optics (MCAO) testbed for the European Solar Telescope (EST) is completed, the system has been assembled and integrated at the Instituto de Astrofísica de Canarias (IAC). The aim of this highly configurable optical testbed is to study different solar adaptive optics solutions, including Single Conjugated Adaptive Optics (SCAO), Ground Layer Adaptive Optics (GLAO), and MCAO. The testbed will be used to evaluate the performance of different wavefront sensing and correction strategies. It consists of different subsystems that are being integrated with high precision by using optomechanical elements mostly developed at IAC. The testbed emulates a 4-m telescope with a Field of View (FoV) of 70 arcseconds. It currently operates as a SCAO configuration consisting of: an illumination system with point-like and extended source capability coupled with a configurable turbulence simulator based on Phase Screens (PS); a pupil-conjugated Deformable Mirror (DM) with 820 actuators; a high order Shack-Hartmann Wavefront Sensor (SH-WFS) with 33 subapertures across the pupil, which measures on-axis aberrations with a FoV of 10 arcseconds; and the science detector. The next steps include the integration of the elements that will provide GLAO and MCAO capabilities, such as two SH-WFSs with a FoV of 70 arcseconds, and two DMs conjugated to different atmospheric layers. This contribution describes the optomechanical components designed and the alignment procedure carried out to set up each subsystem and configuration to be studied.
The GREGOR Infrared Spectrograph (GRIS) can perform spectropolarimetric observations in 1.0-1.8 μm and pure spectroscopic in the band 2.0-2.3 μm. The spectrograph has a Czerny-Turner design and has allowed the operation in the traditional long-slit mode since 2014. And also, in IFU mode since was upgraded in 2018. A third upgrade took place in 2021, where optomechanical, control and software improvements have been conducted to introduce a new spectral channel that receives light below 900 nm. This new spectral channel allows simultaneous observations with the previous infrared camera. Additional improvements include replacing the old diffraction grating with a new one and acquiring a sensor for the new spectral channel. The new grating allows having different order separation and maximising the combination of spectral bands of interest between both channels. Also, a dichroic was placed after the focal plane of the spectrograph, and a reimaging system was introduced in the new spectral channel to match the spatial scale (arcsec/px) in the old and new detectors. The feasibility of operating both cameras simultaneously, and synchronised with the polarisation modulation package, has been already tested. This work describes the optical design for all the spectral channels. We also examine its optical performance, as well as discussing future upgrades in terms of additional spectral channels that are already in progress.
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.
For more than ten years, the GREGOR Infrared Spectrograph (GRIS) has been the main spectropolarimeter on the GREGOR telescope since its inauguration in 2012. The instrument mainly performs polarimetric observations of the wavelength regions at 1083 and 1565 nm, with high scientific potential. There, observers can find spectral lines that provide information on the atmospheric parameters over a vast range of atmospheric layers and with high sensitivity to the magnetic field. Due to the high demand for GRIS and the versatility of the GREGOR environment, we decided to upgrade the system once more, allowing it to become one of the instruments with the highest potential in any ground-based solar observatory. This time, the upgrades add two spectral channels for performing multi-wavelength observations, either in long-slit or IFU mode.
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.
Jose M. Gonzalez-Cava, Mahy Soler, Francisco González, Juan Cózar-Castellano, Angel Mato, Marta Belío-Asin, Jorge Sánchez-Capuchino, Miguel Núñez Cagigal, Mary Barreto
The European Solar Telescope (EST) is a 4-m class solar telescope that will include a multi-conjugate adaptive optics system (MCAO) integrated in the telescope optical path. Currently, the EST is in its preliminary design phase, in which different alternatives for the main telescope subsystems must be proposed and evaluated to meet the main scientific requirements. The availability of models to predict the performance in this phase is therefore essential. A global end-to-end model including the main telescope structure control, the active optics system and adaptive optics strategy is planned for the EST. This document presents the in-house model developed to evaluate the dynamic requirements defined for the telescope structure during tracking operation. First, those requirements specified for the EST during tracking operation are presented. Then, the whole process to obtain and validate the dynamic representation of the telescope structure from the mechanical model is explained. Main dynamic loads likely to affect the tracking performance such as wind buffeting initially characterized for the EST are described. A controller is tuned for closed-loop axes control to ensure trajectory tracking while rejecting the wind effects. Finally, a Simulink model for the evaluation of the tracking performance including the main elements identified for the EST is proposed. Preliminary results based on simulations and their effects on the final telescope structure design are presented. In addition, possible implications on the tip-tilt control strategy to reduce residual image motion for an accurate image stability are analyzed.
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