arXiv subjects

Malak Galal

Publications and source records attributed to Malak Galal.

14 recordsLinked to original sources

arXiv2026

WST, the wide-field spectroscopic telescope: progress on the design of the instruments

WST, the Wide-field Spectroscopic Telescope is a proposed new facility that will provide a transformational gain in spectroscopic survey capability over existing facilities. The WST is a 12 metre class telescope equipped with instrumentation to provide simultaneous observations in both multiple-object spectroscopy and integral field spectroscopy modes. This paper will describe the status of the instruments being designed for the WST, the fibre positioner module, the low and high-resolution multiple object spectrographs, the integral field spectrograph, disperser technology, sustainable detector and cryostat technology, and the calibration system. An overview of the overall layout of the instruments within the WST facility will be provided.

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arXiv2026

ESO-VLT BlueMUSE instrument - Conceptual Design for Phase A

BlueMUSE is a blue-optimised, medium spectral resolution, panoramic integral field spectrograph under development for the ESO's Very Large Telescope (VLT). The project is now entering preliminary design phase. With an optimised transmission down to 350 nm, spectral resolution of R $\sim$ 3500 on average across the wavelength range, and a large FoV (1 arcmin2), BlueMUSE will open up a new range of galactic and extragalactic science cases facilitated by its specific capabilities. BlueMUSE consists of several subsystems arranged along the light path. A calibration unit reproduces the VLT's optical conditions, while the fore optics reshape the telescope's focal image. The splitting and relay optics divide the field of view into 16 channels, each feeding an integral field unit that contains an image slicer, a spectrograph, and a detector vessel. The image slicer converts the 2D sub-field into a 1D pseudo-slit, which the spectrograph disperses into spectra recorded by a 4k x 4k CCD in each detector vessel. A vacuum and cryogenic system cools the detectors, and the data reduction software processes the raw data into data cubes which are subsequently processed by a data analysis software system. All subsystems are supported by the instrument main structure and enclosed in a thermal housing for stability. The whole instrument is managed by an integrated control system combining electronics and software. This paper summarizes the baseline architecture, interfaces, and functional descriptions of the BlueMUSE instrument at the start of Design Phase. This architecture is derived from the top-level requirements and the experience acquired from MUSE. It presents the global concepts along with their preliminary performance estimates.

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arXiv2026

MOSAIC at ELT: Design and First Prototyping of Novel Robotic Optical-Relay Positioners

The Extremely Large Telescope (ELT) is, to date, the most ambitious ground-based telescope under construction. MOSAIC is a multi-objects spectrograph (MOS) that aims to make full use of the largest telescope in the world. At its heart, about 300 robotic positioners will pick-off skylight from the focal surface of the ELT to feed it to its Near Infrared (NIR) and visible (VIS) spectrographs. The gigantic scale of the ELT presents three main challenges for MOSAIC positioners: (1) the light beams on the focal surface cannot be focused in a single fiber, similarly to other MOS instruments, involving a design with relay mirrors patrolling the field of view, and reimaging the sub-field on 2 fixed fiber bundles located 600 mm behind the ELT focal plane (2) The positioner needs to adapt to the local telecentricity, which means it has to point at the ELT pupil center located 37.868 m away from the focal plane (3) The Atmospheric Dispersion Corrector (ADC) needed to cover the whole focal surface of the ELT is impossible to build to this scale; hence each positioner needs its own ADC. EPFL is responsible for designing and supervising the mass manufacturing of the positioners. This paper aims to present its initial design and prototypes.

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arXiv2026

Performance Testing of a Trillium-based 21-Positioner Module for Stage-5 Telescopes

Evaluating the performance metrics of theta-phi robotic positioners is crucial to gather insights into the system's behavior and ensure their reliability during operation in Stage-5 telescopes such as the Chinese MUST, the American Spec-S5 and the European WST. With a careful analysis of these metrics, a comprehensive characterization of the system's strengths is obtained, alongside a clear identification of aspects requiring improvement. Thus, providing potential avenues for streamlining and optimizing its design and functionality. In this paper we present the results of the positioning performance and angular tilt tests conducted on 6.2-mm pitch robotic positioner modules developed for high-density fiber positioning in next-generation astronomical systems. The fiber positioners from the tested prototype adopt a mechanical design based on the Trillium open design from the Lawrence Berkeley National Laboratory (LBNL) and were produced by the Japanese company Orbray. The evaluated performance metrics of positioning repeatability, datum repeatability, backlash, non-linearity, and angular tilt were measured and compared to the desired performance for Stage-5 telescopes. The positioners exhibited a generally acceptable performance, although noticeable anomalies affecting several metrics were identified and will require mitigation in subsequent prototypes. Nevertheless, the results indicate promising performance suitable for Stage-5 telescope instrumentation, provided that these issues are successfully resolved.

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arXiv2026

Design and Testing of the Motorized 2-DoF Folding Mirror 1 for the VLT BlueMUSE Instrument

BlueMUSE is a blue-optimized, medium spectral resolution, panoramic integral field spectrograph under development for the Very Large Telescope (VLT). The project is now fully entering the design phase. With an optimized transmission down to 350 nm, spectral resolution of R$\sim$3500 on average across the wavelength range, and a large FoV (1 arcmin), BlueMUSE will open up a new range of galactic and extragalactic science cases facilitated by its specific capabilities. In this paper, we present the design, implementation and evaluation of the motorized mount developed for Folding Mirror 1 (FM1) of the VLT BlueMUSE instrument. The mount provides two degrees of freedom in tip and tilt and is engineered to correct misalignments caused by environmental variations. The preliminary results demonstrate that the motorized FM1 tilt mount achieves the required precision and maintains alignment stability within the tight tolerances defined by the BlueMUSE project.

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arXiv2026

Motorized Mount for the 3-DoF Folding Mirror 2 of the VLT's BlueMUSE Instrument

BlueMUSE is a blue-optimized, medium spectral resolution, panoramic integral field spectrograph under development for the Very Large Telescope (VLT). The project is now fully entering design phase. With an optimized transmission down to 350 nm, spectral resolution of R~3500 on average across the wavelength range, and a large FoV (1 arcmin2), BlueMUSE will open up a new range of galactic and extragalactic science cases facilitated by its specific capabilities. To meet the stability demands required for BlueMUSE, motorized mounts for precise and repeatable positioning of key optics are developed. This paper explores candidate mechanical designs for BlueMUSE's Folding Mirror 2 (FM2), a high-precision mirror mount with three degrees-of-freedom: tip, tilt rotations, and vertical translation. The study includes a comparative performance analysis through theoretical simulations, details the mechanical, software and electronics architecture of the chosen design, as well as the dedicated optical setup design to characterize repeatability, precision, and thermal stability. The resulting performance of the chosen FM2 mount is then evaluated against the specified requirements for BlueMUSE.

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arXiv2026

Testing of a 15-Positioner Module Based on the MPS Design for Stage-5 Telescopes

Assessing the performance metrics of theta-phi micro-robotic positioners is a key step toward understanding their operational behavior and ensuring that they meet the specifications of Stage-5 astronomical facilities, including the Chinese MUST, the American Spec-S5, and the European WST. A detailed examination of these metrics enables a clear evaluation of the system's current capabilities while also revealing aspects that require further refinement, which in turn guides improvements in design and manufacturing. In this work, carried out in collaboration with Micro Precision Systems (MPS) in Switzerland, we present the results of positioning performance and angular tilt characterization conducted on a 6.2-mm-pitch robotic positioner module developed for high-density fiber placement in next-generation spectroscopic instruments. The prototype unit evaluated in this study was produced by MPS. The measured metrics, including positioning repeatability, datum repeatability, backlash, non-linearity, and angular tilt, are compared directly with the nominal performance targets defined for Stage-5 telescope systems.

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arXiv2026

WST Multi-Object Spectrograph Fiber Positioners:Development of a 32,000-Unit Precision Robotic System

The Wide-field Spectroscopic Telescope Multi-Object Spectrograph requires an unprecedented fiber positioning system comprising 30'000 low-resolution and 2'000 high-resolution positioners across a 3.1 deg squared field of view. Each robotic positioner must achieve 5um RMS positioning accuracy in a densely packed focal plane, representing a more than sixfold scale increase over current instruments like 4MOST and DESI. To mitigate risks associated with industrial-scale production of 32'000 precision mechanisms, WST is pursuing a multi-concept development strategy. Four distinct positioner architectures are being prototyped and tested by an international collaboration (EPFL, AIP, UKATC, AAO) using 6.2 mm pitch triangular modules of 63 units each or a new inline modular concept. Performance metrics including positioning accuracy, repeatability, reconfiguration speed, collision avoidance, and manufacturability are being systematically evaluated. Down-selection to one or two concepts is planned for 2026-2027 during the HORIZON Europe-funded conceptual study phase. Current prototype testing demonstrates feasibility of meeting specifications, supporting WST's path toward first light in the early 2040s as ESO's next major spectroscopic facility.

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arXiv2026

Ultra-precise Multi-fiber Optical Connectors for Astronomy

The increasing sensitivity of modern astronomical instruments requires optical fiber connections with high crossmating stability and insertion loss as low as 1% (0.05 dB). Conventional connectors, though suitable for telecommunications, introduce excess attenuation, Fresnel reflections, and alignment instabilities that degrade throughput and calibration accuracy in astronomy. This work presents the design and characterization of ultra-low-loss optical multi-fiber connectors developed for astronomical use. Fabricated using femtosecond-laser 3-D printing, they achieve sub-micron ferrule tolerances. Preliminary metrology shows excellent hole alignment and roundness, and initial throughput tests for three simultaneously connected fibers show losses as low as 0.95% (0.04 dB). Further throughput and FRD characterization to be implemented to assess efficiency, stability, and repeatability under observatory conditions.

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arXiv2026

Comparative Study of Hollow-Core and Standard Optical Fibers for Astronomy

Efficient light transmission in the blue-visible regime remains a major limitation for fiber-fed astronomical spectrographs, where low photon flux and the intrinsic attenuation of conventional silica fibers reduce survey sensitivity and depth. Inhibited-coupling hollow-core fibers (IC-HCFs) with reduced surface roughness offer a promising alternative, providing guidance predominantly in air and enabling significantly lower loss across the visible spectrum. In this study, we present a comparative evaluation of IC-HCFs against standard multi-mode fibers used in current astronomical instrumentation. We assess the throughput loss that occurs due to bending, twisting, or pinching of the optical fibers when moved using one of the robotic fiber-positioner prototypes designed for next-generation telescopes. These measurements quantify the performance gains offered by IC-HCFs for blue-sensitive spectroscopy and assess their suitability for integration into future survey facilities.

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arXiv2026

Thermal Characterization of a 6-Positioner, 6.2-mm-Pitch Module for Stage-5 Telescopes

Ensuring thermal stability of robotic fiber positioners is essential for reliable operation in the real environments of Stage-5 telescopes, where temperature variations can influence mechanical behavior and impact fiber-target accuracy. We present the results of thermal qualification tests conducted on 6.2-mm-pitch robotic positioner modules developed for high-density fiber positioning in next-generation astronomical systems. The positioners were characterized at discrete temperatures spanning negative 20 deg C to positive 30 deg C, representative of expected operational conditions. At each temperature point, key performance metrics, positioning repeatability, hard-stop repeatability, backlash, and non-linearity, were measured and compared to nominal performance. Across the full temperature range, the positioners maintained stable behavior with no measurable degradation in any metric and no evidence of mechanical or electrical damage. These results confirm that the 6.2-mm-pitch architecture provides the necessary thermal resilience for deployment in Stage-5 telescope instrumentation.

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arXiv2026

Prototyping of 6.2-mm-Pitch Fiber Positioner Modules for Stage-V Telescope Instrumentation

Small-pitch populated focal planes are essential enabling technologies for the next generation of highly multiplexed astronomical instruments. As modern astrophysics relies on massive spectroscopic surveys to study dark energy, dark matter, and galactic assembly, the ability to observe thousands of targets simultaneously has become paramount. To achieve these ambitious scientific goals, optical fibers must be packed into the telescope's focal plane with unprecedented density and accuracy. This work reports on comprehensive prototyping activities for novel 6.2 mm-pitch alpha-beta (theta-phi) fiber positioner modules. Achieving reliable operation at this extremely miniaturized scale presents formidable mechanical and control-system challenges. We provide a detailed comparative analysis of two primary architectural approaches: trillium-based mechanisms and independently actuated robotic designs. A rigorous quantitative assessment was conducted for both prototype models. Critical metrics such as XY positioning repeatability, non-linearity, and gear backlash were evaluated, as these directly dictate the targeting accuracy of the fiber on the sky. Furthermore, we analyzed fiber tilt angles, a crucial factor given its severe implications for Focal Ratio Degradation and the subsequent loss of optical throughput to the spectrographs. Our analysis contextualizes these mechanical constraints with their direct implications for overall instrument performance and survey efficiency. Initial results are highly encouraging, indicating that these miniaturized positioners can successfully overcome spatial limitations while maintaining stringent tolerances. These promising metrics demonstrate that 6.2 mm-pitch modules are highly suitable for the next generation telescopes and the massive multi-object spectroscopic facilities.

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arXiv2025

The Spectroscopic Stage-5 Experiment

The existence, properties, and dynamics of the dark sectors of our universe pose fundamental challenges to our current model of physics, and large-scale astronomical surveys may be our only hope to unravel these long-standing mysteries. In this white paper, we describe the science motivation, instrumentation, and survey plan for the next-generation spectroscopic observatory, the Stage-5 Spectroscopic Experiment (Spec-S5). Spec-S5 is a new all-sky spectroscopic instrument optimized to efficiently carry out cosmological surveys of unprecedented scale and precision. The baseline plan for Spec-S5 involves upgrading two existing 4-m telescopes to new 6-m wide-field facilities, each with a highly multiplexed spectroscopic instrument capable of simultaneously measuring the spectra of 13,000 astronomical targets. Spec-S5, which builds and improves on the hardware used for previous cosmology experiments, represents a cost-effective and rapid approach to realizing a more than 10$\times$ gain in spectroscopic capability compared to the current state-of-the-art represented by the Dark Energy Spectroscopic Instrument project (DESI). Spec-S5 will provide a critical scientific capability in the post-Rubin and post-DESI era for advancing cosmology, fundamental physics, and astrophysics in the 2030s.

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arXiv2024

Investigations on assembly and coverage for modular focal planes of multiplexed telescopes

Multiplexed surveys have the ambition to grow larger for the next generation of focal plane instruments. Future projects such as Spec-S5, MUST, and WST have an ever-growing need for multi-object spectroscopy (13,000 - 20,000 simultaneous objects) which demands further investigations of novel focal plane instrumentation. In this paper, we present a rigorous study of focal plane coverage optimization and assembly of triangular modules of alpha-beta fiber positioners with a 6.2 mm pitch. The main focus here is to examine different module arrangements namely, framed, semi-frameless, and fullyframeless assemblies. Framed and semi-frameless describe here the usage of a manufactured focal plate to hold the modules together and provide the correct focus and tilt to the fibers. Work on automatically generating such focal plates for project adaptability and ease of manufacturing will also be presented. On the other hand, the frameless approach proposes a connection method freed from the need of a focal plate. The following paper will also present their capabilities to meet the requirements for focal plane assembly such as focus, tilt and coverage.

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