arXiv subjects

Younes Chahid

Publications and source records attributed to Younes Chahid.

12 recordsLinked to original sources

arXiv2026

Liquid nitrogen pre-cooling system for ELT instruments utilizing additively manufactured heat exchangers, integrated temperature and liquid level control

Using liquid Nitrogen as the cryogenic fluid for pre-cooling purposes is almost ubiquitous across modern observatories. That method tends to be inefficient since it relies on the evaporation of the fluid afforded by the available surface area within the exchanger without capturing any of its latent heat. An additively manufactured heat exchanger could address that inefficiency by providing an increased evaporation area as well as internal structures that can interact with Nitrogen in its gaseous phase. A miniature pre-cooling system utilizing an existing cryostat was developed so the performance of conventionally and additively manufactured heat exchangers would be compared by recording the time required to cool an instrumented mass. Our findings indicate that there is a clear cost and performance advantage of additively manufactured heat exchangers when compared to conventional units, that could lead to reducing the operating costs of observatories hosting large size instruments such as HARMONI.

astro-ph.IM↗

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.

astro-ph.IM↗

arXiv2026

Exploring generative design AI tools for astronomical instrumentation: a CubeSat chassis case study

Generative design artificial intelligence (AI) tools are currently used in multiple scientific fields, yet their adoption in mechanical engineering computer-aided design (CAD) remains limited due to a lack of disseminated case studies, limited availability of accessible tools, insufficient training in CAD data, the absence of universal editable file formats and more. Mechanical design for astronomical instrumentation faces increasing complexity in thermal, vibrational, and mechanical requirements alongside tight project deadlines. This paper presents a practical evaluation of an AI and FEA based generative design tool applied to chassis design for the Active Deployable Optical Telescope (ADOT) CubeSat mission. Our analysis showcases the workflow steps including the setting of design, manufacturing and objective constraints. This study also shows the clear benefits of these types of tools, especially in the early brainstorming stages of multi-constrained mechanical structures, while also highlighting clear limitations like their black-box nature, the non-manufacturing-ready state of the results, and the time-consuming setup, limiting the tangible gain of these tools to high-value mechanical components.

astro-ph.IM↗

arXiv2026

Laser Remelting for Reduced Porosity on Additively Manufactured Aluminium Mirrors

Additively manufactured (AM) AlSi10Mg mirrors are fabricated through laser powder bed fusion (LPBF), allowing the use of complex geometries such as lattices and organic structures that enable high mass reduction while maintaining mechanical stiffness. Micron-sized pores that cause optical scatter may form during LPBF as a consequence of deviations from the optimal processing window, particularly from laser energy input and scan strategy. This work proposes a laser remelting strategy aimed at reducing porosity; standard LPBF build steps automatically alternate with laser remelting passes, where previously deposited material is remelted during fabrication. Laser remelting is evaluated through fabricating 10 mm proof-of-concept cubes. Following single point diamond turning (SPDT), optical measurements characterised surface roughness and identified surface artefacts. The best-performing AlSi10Mg remelted cube exhibited no pores within sampled regions and achieved 6.4 nm average surface roughness, comparable to a conventionally manufactured RSA 6061 control cube (5.8 nm). Driven by these results, AM 52 mm diameter secondary sandwich mirrors were manufactured using LPBF and laser remelting. These incorporate an optimised diamond TPMS lattice to achieve a 50% mass reduction while accommodating design for AM considerations. Unlike the cube study, the optical surface of the remelted mirror after SPDT exhibited residual porosity and 11.8 nm average surface roughness. These results show that while the proof-of-concept confirmed the viability of laser remelting in reducing porosity within simple geometries, optimisation of the LPBF and SPDT processes are required to translate the benefits of laser remelting to lightweight AlSi10Mg AM mirrors.

physics.optics↗

arXiv2026

WST -- Wide-field Spectroscopic Telescope: The Next Leap in Wide-field Spectroscopy

The Wide-field Spectroscopic Telescope (WST) is a concept for a dedicated 12-m spectroscopic survey facility designed to address some of the most important questions in astrophysics in the 2040s. The WST will provide unprecedented spectroscopic survey capabilities by operating simultaneously over a 2-degree diameter field of view with 54 low-resolution spectrographs fed by 30,000 fibres, 8-16 high-resolution spectrographs fed by 2,000 fibres, and a large panoramic low-resolution integral-field spectrograph. Supported by Horizon Europe, the concept study has refined the science cases, facility architecture, operations model, sustainability strategy, and technology roadmap. The resulting reference design demonstrates that the WST is both scientifically transformative and technically feasible, while identifying the developments required to mitigate the remaining risks. The WST is designed as an ESO flagship facility for the post-ELT construction era and a key spectroscopic complement to the major imaging, time-domain, and multi-messenger facilities of the coming decades.

astro-ph.IM↗

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.

astro-ph.IM↗

arXiv2025

Additive manufacturing in aluminium of a primary mirror for a CubeSat application: manufacture, testing and evaluation

Additive manufacturing (AM; 3D Printing), a process which creates a part layer-by-layer, has the potential to improve upon conventional lightweight mirror manufacturing techniques, including subtractive (milling), formative (casting) and fabricative (bonding) manufacturing. Increased mass reduction whilst maintaining mechanical performance can be achieved through the creation of intricate lattice geometries, which are impossible to manufacture conventionally. Further, part consolidation can be introduced to reduce the number of interfaces and thereby points of failure. AM design optimisation using computational tools has been extensively covered in existing literature. However, additional research, specifically evaluation of the optical surface, is required to qualify these results before these advantages can be realised. This paper outlines the development & metrology of an AM mirror for a CubeSat platform with a targeted mass reduction of 60% compared to an equivalent solid body. This project aims to incorporate recent developments in AM mirror design, with a focus on manufacture, testing & evaluation. This is achieved through a simplified design process of a Cassegrain telescope primary mirror mounted within a 3U CubeSat chassis. The mirror geometry is annular with an external diameter of 84 mm and an internal diameter of 32 mm; the optical prescription is flat for ease of manufacture. Prototypes were printed in AlSi10Mg, a low-cost aluminium alloy commonly used in metal additive manufacturing. They were then machined and single-point diamond turned to achieve a reflective surface. Both quantitative & qualitative evaluations of the optical surface were conducted to assess the effect of hot isostatic pressing (HIP) on the optical surface quality. The results indicated that HIP reduced surface porosity; however, it also increased surface roughness and, consequently, optical scatter.

astro-ph.IM↗

arXiv2024

Investigating Mass Reduction Capabilities of Additive Manufacturing through the Re-Design of a Space-Based Mirror

Additive manufacture (AM) involves creating a part layer by layer and is a rapidly evolving manufacturing process. It has multiple strengths that apply to space-based optics, such as the ability to consolidate multiple parts into one, reducing the number of interfaces. The process also allows for greater mass reduction, making parts more cost-effective to launch, achieved by optimising the shape for intended use or creating intricate geometries like lattices. However, previous studies have highlighted issues associated with the AM process. For example, when trying to achieve high-precision optical surfaces on AM parts, the latticing on the underside of mirrors can provide insufficient support during machining, resulting in the quilting effect. This paper builds on previous work and explores such challenges further. This will be implemented by investigating ways to apply AM to a deployable mirror from a CubeSat project called A-DOT. The reflective surface has a spherical radius of curvature of 682 mm and approximate external dimensions of 106 mm x 83 mm. The aim is to produce two mirrors that will take full advantage of AM design benefits and account for the challenges in printing and machining a near-net shape. The designs will have reduced mass by using selected internal lattice designs and topology-optimised connection points, resulting in two mirrors with mass reduction targets of 50% and 70%. Once printed in aluminium using laser powder bed fusion, the reflective surface will be created using single point diamond turning. Finally, an evaluation of the dimensional accuracy will be conducted, using interferometry, to quantify the performance of the reflective surface.

astro-ph.IM↗

arXiv2024

Additive manufacturing applications in astronomy: a review

Despite the established role of additive manufacturing (AM) in aerospace and medical fields, its adoption in astronomy remains low. Encouraging AM integration in a risk-averse community necessitates documentation and dissemination of previous case studies. The objective of this study is to create the first review of AM in astronomy hardware, answering: where is AM currently being used in astronomy, what is the status of its adoption, and what challenges are preventing its widespread use? The review starts with an introduction to astronomical instruments size/cost challenges, alongside the role of manufacturing innovation. This is followed by highlighting the benefits/challenges of AM and used materials/processes in both space-based and ground-based applications. The review case studies include mirrors, optomechanical structures, compliant mechanisms, brackets and tooling applications that are either in research phase or are implemented.

astro-ph.IM↗

arXiv2024

Design, manufacture and metrology of additively manufactured, metal and ceramic lightweight circular mirror prototypes

Spaced-based mirrors are a developing use-case for Additive Manufacturing (AM), the process that builds a part layer-by-layer. The increased geometric freedom results in novel and advantageous designs previously unachievable. Conventionally, mirror fabrication uses subtractive (milling & turning), formative (casting) and fabricative (bonding) manufacturing methods; however, an additive method can simplify an assembly by consolidating individual components into one, and incorporating lattice structures and function optimised geometries to reduce the mass of components, which are beneficial to space-based instrumentation as mass and volume are constrained. Attention must be given to the printability of the design - build orientation and powder/resin removal from lattices and internal cavities are challenges when designing for AM. This paper will describe the design, manufacture and metrology of mirror prototypes from the Active Deployable Optical Telescope (ADOT) 6U CubeSat project. The AM mirror is 52mm in diameter, 10mm deep, with a convex 100mm radius of curvature reflective surface and deploys telescopically on three booms. The objectives of the designs were to combine the boom mounting features into the mirror and to lightweight both prototypes by 50% and 70% using internal, thin-walled lattices. Four final lattice designs were downselected through simulation and prototype validation. Prototypes were printed in the aluminium alloy AlSi10Mg using powder bed fusion and fused silica using stereolithography. Aluminium mirrors were single point diamond turned and had surface roughness measurements taken. Fused silica designs were adapted from the aluminium designs and have completed printing.

astro-ph.IM↗

arXiv2024

Targeting low micro-roughness for 3D printed aluminium mirrors using a hot isostatic press

Additive manufacturing (AM; 3D printing) in aluminium using laser powder bed fusion provides a new design space for lightweight mirror production. Printing layer-by-layer enables the use of intricate lattices for mass reduction, as well as organic shapes generated by topology optimisation, resulting in mirrors optimised for function as opposed to subtractive machining. However, porosity, a common AM defect, is present in printed aluminium and it is a result of the printing environment being either too hot or too cold, or gas entrapped bubbles within the aluminium powder. When present in an AM mirror substrates, porosity manifests as pits on the reflective surface, which increases micro-roughness and therefore scattered light. There are different strategies to reduce the impact of porosity: elimination during printing, coating the aluminium print in nickel phosphorous, or to apply a heat and pressure treatment to close the pores, commonly known as a hot isostatic press (HIP). This paper explores the application of HIP on printed aluminium substrates intended for mirror production using single point diamond turning (SPDT). The objective of the HIP is to reduce porosity whilst targeting a small grain growth within the aluminium, which is important in allowing the SPDT to generate surfaces with low micro-roughness. For this study, three disks, 50 mm diameter by 5 mm, were printed in AlSi10Mg at 0 deg, 45 deg, and 90 deg with respect to the build plate. X-ray computed tomography (XCT) was conducted before and after the HIP cycle to confirm the effectiveness of HIP to close porosity. The disks were SPDT and the micro-roughness evaluated. Mechanical testing and electron backscatter diffraction (EBSD) was used to quantify the mechanical strength and the grain size after HIP.

physics.optics↗

arXiv2024

Additive manufacturing in ceramics: targeting lightweight mirror applications in the visible, ultraviolet and X-ray

Additive manufacturing (AM; 3D printing) has clear benefits in the production of lightweight mirrors for astronomy: it can create optimised lightweight structures and combine multiple components into one. New capabilities in AM ceramics, silicon carbide infiltrated with silicon and fused silica, offer the possibility to combine the design benefits of AM with a material suitable for visible, ultraviolet and X-ray applications. This paper will introduce the printing methods and post-processing steps to convert AM ceramic samples into reflective mirrors. Surface roughness measurements after abrasive polishing of the AM ceramics will be presented.

astro-ph.IM↗