The European Solar Telescope (EST) is a 4-m class-solar telescope that will become part of the next generation of groundbased facilities. Located at the “Observatorio del Roque de los Muchachos” in La Palma (Spain), it will be aimed to study the magnetic connectivity of the solar atmosphere with high spatial and temporal resolution. The EST optical design has been optimized during the preliminary design phase to maximize throughput, balance the instrumental polarization and to reduce the image rotation due to the change in orientation during operation. The optical system consists of a 4.2m active primary mirror located above the elevation axis to ensure natural air flushing and minimize local seeing degradation and a secondary mirror assembled as an Adaptive Secondary Mirror (ASM). Both arranged in an on-axis Gregorian configuration to deliver an aplanatic secondary focal plane. These are followed by four fold mirrors, which will be upgraded to deformable mirrors and are conjugated to different layers of the atmosphere. These, together with the ASM, M7 and two wavefront sensors, will make up the Multi-Conjugate Adaptive Optics system. Finally, a dioptric system, housed in a vacuum vessel, transfers the light to the science focus, which will be delivered to the Scientific Instrumentation by a dedicated distribution system. EST ultimately provides a diffraction-limited telecentric F/50 science focal plane covering a FOV of 90×90 arcsec2 over a wavelength range from 380nm to 2300nm. Along the contribution, details about the preliminary optical design of EST and its subassemblies will be presented. The expected performance is also discussed.
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 GREGOR Infrared Spectrograph (GRIS) can perform spectropolarimetric observations in the infrared. The spectrograph has a Czerny-Turner design and offered traditional long-slit observations since 2014. Later on, in 2018, it was upgraded with an Integral Field Unit (IFU) based on a slicer mirror, which has slicers of 100-μm width. The latter option makes GRIS a unique instrument in solar physics that, after more than 10 years of operation, is still at the forefront of the field, particularly in the infrared. A third upgrade took place in 2021, where optomechanical, control and software improvements have been conducted to introduce new optical channels that operate below 1 μm. These new spectral channels allow simultaneous observations with the previous infrared camera. Between these improvements, a new diffraction grating was installed to enable multi-wavelength configurations with high scientific potential. This new diffraction grating will be interchangeable with the previous one, offering flexibility between spectral resolution, simultaneity, and spectral coverage. Additionally, two more IFUs will be offered to the community. One IFU with a 70-μm width slicer mirror that has already been manufactured and tested at the telescope, and the second with a 35-μm width slicer mirror that is currently at development status. The three IFUs will be interchangeable and offer three different spatial resolution modes and fields of view. This work presents the final optical configuration of the upgraded GRIS and the installation procedure of the most recent upgrades.
Due to the complexity of scientific instruments, such as spectropolarimeters, managing instrument sequences can be challenging. To address this problem, a Finite-State Machine (FSM) approach has been used to manage solar observation sequences in the GREGOR Infrared Spectrograph (GRIS). FSMs provide a structured and visual representation of control logic, making them well-suited for managing intricate workflows. By using FSMs, both scientists and engineers can clearly define and modify instrument sequences, ensuring the precise coordination of various instrument components. In multiple optical channels spectropolarimeters, such as GRIS, FSMs can effectively synchronize the image acquisition across multiple channels, adjust exposure times, handle errors, and manage the selection of the scanning system. To streamline the implementation process, the CodeDesigner RAD tool was used to create diagrams that illustrate the execution order of the states belonging to a finite-state machine. CodeDesigner’s code generation feature automatically translates these diagrams into C++ code. This approach ensures the precise and reliable operation of the GRIS control software.
One of the main goals of the European Solar Telescope (EST), a 4.2-m telescope, is to clarify the roots of the magnetic processes taking place in the solar atmosphere. This goal has a top-level requirement: perform simultaneous spectropolarimetric measurements in multiple spectral lines. For this purpose, EST will be equipped with a set of instruments working simultaneously in diverse spectral ranges. In this regard, we are designing a Coudé Light Distribution (CLD) responsible for delivering the incoming solar radiation to each instrument. The CLD is formed by a series of optical elements like dichroic and intensity beam splitters, flat mirrors, and optical compensators that will be interchangeable to offer the solar community maximum flexibility for performing observations. In developing the CLD, we are paying great attention to controlling aberration effects generated by the different elements that constitute the light distribution system. Also, we are defining the CLD to reach a balance between throughput, image quality, and a compact distribution of the instruments in the Coudé room. Our aim is to describe in this contribution the current design of the CLD. The present design constitutes the basis of the CLD, with enough flexibility to improve it in the future, if indeed, and adapt it to the evolution of other sub-systems like the instruments, the adaptive optics, or the telescope structure to guarantee that it fulfils the science requirements.
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.
We describe the IR focal plane filters of the MAJIS imaging spectrometer for the JUICE mission to the Jupiter System. The focal plane filters provided by Viavi Solutions are integrated into a filter holder placed above the IR channel focal plane array, enclosed in a baffle and cooled to cryogenic temperatures. The filters comprise two segments bonded together on a sapphire substrate: a broad-band, low-pass filter and a narrow-band linear variable filter (LVF) in the MWIR. We present the justification for using such filters, their architecture, the measurement facilities that were implemented for assessing their performances and the derived optical performances. The filters have been fully qualified and integrated into MAJIS and are within the performance specifications.
We describe the IR focal plane unit of the MAJIS imaging spectrometer for the JUICE mission to the Jupiter Sys tem. Optical light from the telescope and spectrometer is focalized on the IR Focal plane unit which compris es a Teledyne Imaging Sensors H1RG detector overlain by a Viavi Solutions filter assembly. Both components are baffled and work at cryogenic temperatures. We describe the IR focal plane architecture, the measurement facilities and the main performance-critical specifications. The IR channel of MAJIS offers strong versatility with the capability to acquire high resolution spectra from the Jupiter atmosphere to organic matter on icy moon surfaces, over a wide spectral and dynamical range.
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.
PLATO is an ESA mission to hunt for Earth-sized exoplanets in the habitable zone of their host star. The heart of the payload consists of 26 wide-field cameras. We develop a Common Electrical Ground Support Equipment (EGSE) framework for the testing and verification of these cameras. The focal planes are aligned to the telescope optics at ambient temperature and the performance verification is done at operational temperature in thermal-vacuum conditions in different facilities. The Common-EGSE system will guarantee that tests are executed via the same procedures and are analyzed identically, by providing a software framework that can be tuned for site-specific hardware and avoids duplicate developments. The Common EGSE provides commanding for the camera and the Ground Support Equipment (GSE), telemetry monitoring, logging, data storage, and data analysis. In addition, the design allows for sharing commanding and analysis scripts. We present the design of the system and the generic commanding scheme for test setup hardware.
The understanding of the solar outer atmosphere requires a simultaneous combination of imaging and spectral observations concerning the far UV lines that arise from the high chromospheres up to the corona. These observations must be performed with enough spectral, spatial and temporal resolution to reveal the small atmospheric structures and to resolve the solar dynamics. An Imaging Fourier Transform Spectrometer working in the far-UV (IFTSUV, Figure 1) is an attractive instrumental solution to fulfill these requirements. However, due to the short wavelength, to preserve IFTSUV spectral precision and Signal to Noise Ratio (SNR) requires a high optical surface quality and a very accurate (linear and angular) metrology to maintain the optical path difference (OPD) during the entire scanning process by: optical path difference sampling trigger; and dynamic alignment for tip/tilt compensation (Figure 2).
The Polarimetric and Helioseismic Imager (PHI) on board of Solar Orbiter will observe the Sun to measure the photospheric vector magnetic field and the line-of-sight velocity. It will employ a narrowband filtergraph (FG) to scan the FeI 6173 Å absorption line. At different spectral positions, the polarization state of the incoming light will be analyzed. The FG will provide a tuning range to scan the line, the continuum, and to compensate for the spacecraft radial velocity, as it will approach to the Sun down to 0.28 AU. The FG includes a Fabry-Perot etalon and two narrowband prefilters. The bandpass of the narrowest one has a nominal Full Width at Half Maximum (FWHM) of 2.7 Å. The measurement of the prefilters characteristics is essential for the instrument calibration. Here we present the results of the breadboard prefilters characterization, which is an important milestone in the development of the instrument.
The spectroscopy of the far UV emission lines of the solar spectrum combined with an imaging capability is essential to
understand the physics of the outer solar atmosphere. An imaging Fourier transform spectrometer (IFTSUV) is an
attractive instrumental solution to perform such far-UV solar observations. Working in the far UV involves high
precision metrology to maintain the optical path difference (OPD) during the entire scanning process of the
interferogram. It also involves a compact all-reflection design for UV applications. We present the specification of a
servo-system that enables dynamic tip/tilt alignment compensation and OPD sampling measurement of the IFTSUV
scanning mirror. We also discuss the first experimental results of a breadboard as well as the preliminary design of a
space-based device.
Imaging Fourier Transform Spectrometer working in the far UV (IFTSUV) may be the technical solution to
answer many unsolved problems concerning the physics of the solar outer atmosphere. The VUV domain
highly constrains the instruments design and performances as it demands a high optics surface quality and an
accurate metrology to preserve IFTSUV spectral precision and Signal to Noise Ratio (SNR). We present the
advancements on the specification of a metrology system, meeting the predicted performance requirements of
an IFTSUV.
The study of the outer solar atmosphere requires combining imaging and spectroscopy in the UV lines formed
in the high chromosphere, the transition region and the corona. We start from the science requirements and we
define the instrumental specifications in terms of field-of-view (FOV), spatial, temporal and spectral resolution
and bandpass. We propose two different all-reflection optical architectures based on interferometric techniques:
Spatial Heterodyne Spectroscopy (SHS); and Imaging Transform Spectrometer (IFTS). We describe the different
set-ups and compare the potential performances of the two types of solutions, and discuss their feasibility. We
conclude that IFTS appears to be the best solution, meeting the needs of UV solar physics. However, we point
out the many difficulties to be encountered, especially as far as metrology is concerned.
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