The telescope main mirror (M1) of the Ariel Space Mission is a lightweight elliptical mirror with a parabolic surface, supported by three flexure hinges designed to mitigate deformation effects. Since these hinges must meet stringent planarity tolerances of 2 μm on their interface pads, they were manufactured using Single Point Diamond Turning (SPDT). However, initial manufacturing attempts failed in obtaining a component within the tolerance, revealing significant deformations of the flexure hinge during machining. This paper presents a simulation-based approach developed to address this issue. The component deformations were predicted considering the effects of centrifugal forces, gravity, and clamping. However, such simulation showed deformations significantly lower than the experimental results, suggesting unaccounted effects from coupling surface tolerances. Based on CMM measurements of the interfaces, a revised clamping configuration was proposed to minimize the influence of coupling tolerances. This approach significantly improved planarity, achieving a final flatness of 1.5 μm, well within the required tolerance. The proposed simulation-based procedure reduced trial-and-error iterations, improving manufacturing efficiency and precision in the production of the flexure hinges. Although not accounting for all factors, the simulations provided valuable insights into the causes of errors and guided the development of a successful fixturing strategy.

The assessment of slippage in cryogenic space missions is fundamental from a mechanical point of view as it is one of the main failure modes of a bolt in a mechanical interface. It is usually performed on the basis of temperature maps obtained from the worst-case thermal design cases, with particular interest in the transient case during the cooldown. Traditionally, the thermal mapping has to be transferred to the detailed FEM model. This process requires a lot of interaction between the thermal and structural disciplines, which is often not easy. Moreover, the thermal mapping usually corresponds to the instant of maximum gradient between the clamped parts along the transient case. In this paper, a new methodology is proposed to speed up the evaluation of the temperature effect on the slippage from an analytical model correlated with the FEM model. Then, the interactions between the structural and the thermal responsible may be reduced. In addition, the proposed methodology evaluates the entire temperature curve of the transient case, rather than a single instant. In this way, the thermal effect on slippage can be evaluated in a robust and agile process, facilitating the definition of requirements in terms of the maximum allowable temperature gradient as a function of preload or vice versa. This methodology has been validated with the primary mirror of the ARIEL mission, which is a cryogenic European mission that aims to study exoplanets by making observations from a thermally stable orbit at L2 point of the Sun-Earth system. Therefore, the correct design of the primary mirror is essential for the successful science observations of the mission.

The increasing digitalization in the manufacturing industry, the development of digital models (Digital Twins) representing products, processes, resources, and systems, as well as the adoption of AI to support classification and automatic reasoning approaches, are paving the way for the raise of platform-based business approaches for manufacturing very shortly. The PLAT4M project aims at defining a general modelling framework, and supporting methodologies, enabling a platform-based quotation approach for mechanical components. Within this framework, customers will be able to submit technical specifications of the requested products and receive a quotation in terms of costs and delivery date. In this work the ongoing activities related to the developing of the AI-based approach for generating process plans and characterizing process steps for turned parts is presented.

Dot-by-dot is an emerging Wire and Arc Additive Manufacturing (WAAM) technology, allowing for the precise deposition of tiny spheres of molten material, to form slender bars that could be used to manufacture complex lattice structures. Dots' geometry plays a key role in determining both the welding torch optimal toolpath and the mechanical properties of the final product. In this paper an analytical physics-based geometrical model is presented, capable of predicting the geometric characteristics of dot-by-dot additively manufactured bars from the properties of the feedstock material, the welding process parameters and interpass temperature. The proposed model is based on heat transfer and mass conservation and can be applied to different scenarios and materials, being more general with respect to experimental-regressive approaches. A preliminary experimental validation on ER70S-6 steel bars was performed on different case studies, showing fair accuracy in predicting bars diameter and height.

Ariel ( Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is ESA's M4 mission within the "Cosmic Vision" program, set to launch in 2029. Its goal is to survey the atmospheres of known exoplanets using transit spectroscopy. The mission employs a 1-meter-class telescope that is optimized for spectroscopy in the 1.95 to 7.8 mu m wavelength range, operating at cryogenic temperatures between 40 and 50 K. The Ariel Telescope features an off-axis, unobscured Cassegrain configuration, incorporating a parabolic recollimating tertiary mirror and a flat folding mirror that directs the output beam parallel to the optical bench. Additionally, the secondary mirror is mounted on a roto-translating stage to allow for adjustments during the mission. All mirrors and supporting structures are made from an aerospace-grade aluminium alloy, 6061-T651, chosen for its ease of manufacturing and thermalization. However, the material's low stiffness presents unique challenges for integration and alignment. A series of simulations were conducted to analyse the telescope ' s alignment, with a specific focus on mechanical tolerances and their impact on the optical performance. The paper thoroughly describes the simulation setup, the methodology used to assess tolerance effects, and presents the resulting data, offering valuable guidance for optimizing telescope alignment and ensuring robust optical performance.

In machining, tool vibrations are one of the main causes of process inaccuracies and poor finishing. To tackle these phenomena, the identification of the tool tip frequency response function (FRF) is essential, since it allows to determine the most suitable cutting conditions for an accurate and stable cut. Nonetheless, the identification of the tool tip FRF is usually achieved through experimental modal methods whose set up and testing phases require specific expertise as well as sensors and devices to be mounted on the machine tool. This paper investigates a methodology to identify tool tip FRF starting from the surface location error (SLE) without the need of additional equipment for the machine tool. The method exploits on-machine sensors (i.e., measuring probe), and it identifies tool tip FRF using a frequency domain cutting force model and the SLEs measured in different cutting tests. The method was experimentally tested to verify its effectiveness and limitations.

The Atmospheric Remote-sensing Infrared Exoplanet Large-survey (Ariel), selected as ESA's fourth medium-class mission in the Cosmic Vision program, is set to launch in 2029. The objective of the study is to conduct spectroscopic observations of approximately one thousand exoplanetary atmospheres for better understanding the planetary system formation and evolution and identifying a clear link between the characteristics of an exoplanet and those of its parent star. The realization of the Ariel's telescope is a challenging task that is still ongoing. It is an off-axis Cassegrain telescope (M1 parabola, M2 hyperbola) followed by a re-collimating off-axis p arabola ( M3) a nd a p lane fold mirror (M4). It is made of Al 6061 and designed to operate at visible and infrared wavelengths. The mirrors of the telescope will be coated with protected silver, qualified to operate at cryogenic temperatures. The qualification of the coating was performed according to the ECSS Q-ST-70-17C standard, on a set of samples that have been stored in ISO 6 cleanroom conditions and are subjected to periodic inspection and reflectance measurements to detect any potential performance degradation. The samples consist of a set of Aluminum alloy Al 6061-T651 disks coated with protected silver. This paper presents the results of the morphological characterization of the samples based on Atomic Force Microscopy (AFM) and the reflectivity measurement in the infrared by Fourier Transform Infrared (FTIR) spectroscopy.

Aluminum is the material of choice for the majority of aerospace components, and, in the past few years, its application has been extended also to the mirrors of space telescopes because of the improved thermal behavior and the possibility to build the entire telescope with the same material. However, the low elastic modulus of such material, combined with the extremely tight tolerances of optical applications, make the production of these components very challenging and, usually, based on a trial-and-error approach. This paper presents a structured methodology for the prediction of the results of manufacturing in Single Point Diamond Turning of optical components, both in terms of absolute deformation as well as optical aberrations (via Zernike polynomials). All the most significant parameters acting on the workpiece have been simulated and combined. The proposed approach has been experimental validated on an actual aluminum mirror, proving its good accuracy (<5 % rms error). While some improvement can be performed to better match the experimental data in terms of Zernike coefficients, especially for non-symmetric aberrations, this paper forms the basis for an off-machine optimization of the SPDT process, drastically reducing the trial-and-error efforts.

ARIEL is ESA's fourth medium-class mission in the Cosmic Vision program, is scheduled for launch in 2029. The telescope aims to conduct an expansive, unbiased spectroscopic survey, unraveling the complexities of exoplanet atmospheres and interiors to better comprehend the key factors influencing planetary system formation and evolution. The baseline payload features an off-axis Cassegrain telescope (M1-M2), a collimating off-axis parabola (M3), and a plane folding mirror (M4) channeling the collimated beam into two instrument modules. ARIEL's capabilities span primary and secondary transit spectroscopy (1.10 to 7.80 mu m), broad-band photometry in the Optical (0.50 - 0.80 mu m) and Near IR (0.80 - 1.10 mu m) ranges, and a Fine Guidance System. This work will focus on M1, an aluminum mirror with an unobscured elliptical shape of size 1100 x 730mm. The Surface Error budget for M1 covers low and mid spatial frequencies. The work describes the manufacturing process of the mirror, the method used to quantify surface roughness, the characterization of MSF errors, and the study of the degradation of the system performance due to MSF errors.

The ARIEL mission is a European space project that aims to detect exoplanets with a spacecraft orbiting around the L2 point of the Sun-Earth system. The main payload consists of a Cassegrain telescope composed of mirrors that reflect and concentrate the incoming light from the deep space observations to finally guide it to the detectors. As in many other space missions, a dedicated complex assessment is established during the design phase to evaluate the impact on the optical performance caused by thermoelastic effects, which involves the coordinated work of the thermal, structural, and optical engineers. Despite that well-known and standardized processes and tools are established separately in each involved area, there is a lack of standardization about the way of exchanging the data between them, where additional calculations are required in some cases. This work focuses on the temperature mapping, which is the intermediate step between thermal and structural analyses, where temperatures are transferred to the structural model. The main difficulty of this process is related to the differences in modelling methods and approaches between both models, being necessary the development of an adequate algorithm to find the most accurate transfer of temperatures. This paper shows two different options for temperature mapping, detailing the proposed flowcharts. One of these methods requires the performance of an additional thermal conductive analysis, where a new improved procedure has been implemented in this work to solve some computational issues that made its application for large models difficult or even unfeasible. Both temperature mapping methods have been applied to the payload module of the ARIEL spacecraft, comparing the output results in terms of temperatures, stresses, forces, and displacements to evaluate their differences.

Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is ESA's M4 mission of the "Cosmic Vision" program, with launch scheduled for 2029. Its purpose is to conduct a survey of the atmospheres of known exoplanets through transit spectroscopy. Ariel is based on a 1 m class telescope optimized for spectroscopy in the waveband between 1.95 and 7.8 mu m, operating at cryogenic temperatures in the range 40-50 K. The Ariel Telescope is an off-axis, unobscured Cassegrain design, with a parabolic recollimating tertiary mirror and a flat folding mirror directing the output beam parallel to the optical bench. The secondary mirror is mounted on a rototranslating stage for adjustments during the mission. The mirrors and supporting structures are all realized in an aerospace-grade aluminum alloy T6061 for ease of manufacturing and thermalization. The low stiffness of the material, however, poses unique challenges to integration and alignment. Care must be therefore employed when designing and planning the assembly and alignment procedures, necessarily performed at room temperature and with gravity, and the optical performance tests at cryogenic temperatures. This paper provides a high-level description of the Assembly, Integration and Test (AIT) plan for the Ariel telescope and gives an overview of the analyses and reasoning that led to the specific choices and solutions adopted.

Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is the fourth medium-class mission (M4) of the ESA's Cosmic Vision Program. Its launch is planned for 2029. Ariel will observe a large and well selected sample of transiting gas giants, neptunes and super-earths around a wide range of host star types, with the objective to study planetary atmospheres and to understand composition and evolving processes of the planetary systems. A Structural, Thermal, and Optical Performance (STOP) analysis is conducted at Payload level to estimate the thermo-elastic induced degradation of the system performance for a number of selected environmental load cases. In particular, this document presents the general approach followed and the results of the optical design analysis performed to predict the performance of the Ariel Telescope Assembly for the in-flight operational cases during Cycle C-1.

Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is the adopted M4 mission of ESA "Cosmic Vision" program. Its purpose is to conduct a survey of the atmospheres of known exoplanets through transit spectroscopy. Launch is scheduled for 2029. Ariel scientific payload consists of an off-axis, unobscured Cassegrain telescope feeding a set of photometers and spectrometers in the waveband between 0.5 and 7.8 mu m, and operating at cryogenic temperatures. The Ariel Telescope consists of a primary parabolic mirror with an elliptical aperture of 1.1 m of major axis, followed by a hyperbolic secondary, a parabolic recollimating tertiary and a flat folding mirror. The Primary mirror is a very innovative device made of lightened aluminum. Aluminum mirrors for cryogenic instruments and for space application are already in use, but never before now it has been attempted the creation of such a large mirror made entirely of aluminum: this means that the production process must be completely revised and fine-tuned, finding new solutions, studying the thermal processes and paying a great care to the quality check. By the way, the advantages are many: thermal stabilization is simpler than with mirrors made of other materials based on glass or composite materials, the cost of the material is negligeable, the shape may be free and the possibility of making all parts of the telescope, from optical surfaces to the structural parts, of the same material guarantees a perfect alignment at whichever temperature. The results and expectations for the flight model are discussed in this paper.

The Atmospheric Remote-Sensing Infrared Exoplanet Large Survey (Ariel) is the M4 mission adopted by ESA's "Cosmic Vision" program. Its launch is scheduled for 2029. The mission aims to study exoplanetary atmospheres on a target of similar to 1000 exoplanets. Ariel's scientific payload consists of an off-axis, unobscured Cassegrain telescope. The light is directed towards a set of photometers and spectrometers with wavebands between 0.5 and 7.8 mu m and operating at cryogenic temperatures. The Ariel Space Telescope consists of a primary parabolic mirror with an elliptical aperture of 1.1 center dot 0.7 m, all bare aluminum. To date, aluminum mirrors the size of Ariel's primary have never been made. In fact, a disadvantage of making mirrors in this material is its low density, which facilitates deformation under thermal and mechanical stress of the optical surface, reducing the performance of the telescope. For this reason, studying each connection component between the primary mirror and the payload is essential. This paper describes, in particular, the development, manufacturing, and testing of the Flexure Hinges to connect Ariel's primary Structural Model mirror and its optical bench. The Flexure Hinges are components already widely used for space telescopes, but redesigning from scratch was a must in the case of Ariel, where the entire mirror and structures are made of aluminum. In fact, these flexures, as well as reducing the stress due to the connecting elements and the launch vibrations and maintaining the alignment of all the parts preventing plastic deformations, amplified for aluminum, must also have resonance frequencies different from those usually used, and must guarantee maximum contact (tolerance in the order of a micron) for the thermal conduction of heat. The entire work required approximately a year of work by the Ariel mechanical team in collaboration with the industry.

Turning slender components is a critical task since workpiece flexibility entails relevant deformations during the process, leading to potential loss of accuracy, lower machining efficiency, and higher manufacturing costs. In this paper, a compensation strategy for diametral error in turning of slender workpieces is presented. The proposed method computes a toolpath that compensate diametral error based on the prediction of such error performed by a finite element-based approach. The developed algorithm automatically generates the compensated toolpath based on few inputs: nominal toolpath, workpiece material, tool geometry, stock dimensions, and fixturing system. First, nominal toolpath is analyzed and discretized, then at each step, workpiece deflection is estimated by coupling the FE model of the workpiece (automatically generated using Timoshenko beam elements) and the cutting forces model. Material removal is considered in the process by updating the geometry of the stock at each step of the machining cycle. Using the predicted deformation of the workpiece the compensated toolpath is generated and the toolpath ISO-standard file is updated. The proposed algorithm was experimentally validated on four case studies: three single diameter bars and a multi-diameter shaft. The results demonstrate the accuracy of the proposed predictive approach, with small deviations in estimating average diametral error (less than 6 μm). Furthermore, it has been demonstrated that the compensated toolpath is successful in reducing the diametral errors by at least 50