MORFEO is a post-focal adaptive optics module that forms part of the first light instrument suite for the Extreme Large Telescope (ELT). The project is now in the Final Design Phase. In this paper, we report the status of the project.
The field curvature has been a long-term problem optical designers had to deal with, to propose flat corrected field instruments. Combinations of highly aspherical optics, TMA configurations, achromatic doublets or field flatteners are often used to reach good optical quality across the image.
Allowing designers to play with the parameters of the field’s shape is offering them a brand-new game field. The possibility of curving the CMOS sensors to fit curved/aspherical/freeform shapes of focal surfaces has been studied for the last 20 years and led today to different applications and prototypes.
We present in this article 1/ the parameter studies we performed over a large set of optical designs showing the gain offered by this approach, 2/ the CMOS sensors curving process and performance over a large set of prototypes, 3/ Optical systems that have been produced with this technology and 4/ the roadmap related to the development of curved-sensors based instrumentation for astronomy with the CASTLE telescope project and physical sciences through the Auroral UV Imager program led by ESA.
Morfeo (Multi-conjugate adaptive Optics Relay For ELT Observations) is an adaptive optics module able to compensate the wavefront disturbances affective the scientific observation. It will be installed on the straight-through port of the telescope Nasmyth platform to serve the first-light instrument MICADO and with the provision for a future second instrument. The module underwent the Preliminary Design Review in 2021 and is expected to be commissioned in 2029. In this paper we present a synthesis of the System Engineering approach adopted to manage the development of the instrument assessing the criticalities of phase B (preliminary design) and preliminary phase C (final design). We will discuss the evolution of the system engineering approach, identifying within the MBSE framework the evolution of the various modelling artefacts. towards the requirements. We will detail the criticalities of the system engineering with a particular focus onto the management of the interfaces between subsystems and external systems (Telescope, other instruments…).
The field curvature has been a long-term problem optical designers had to deal with, to propose flat corrected field instruments. Combinations of highly aspherical optics, TMA configurations, achromatic doublets or field flatteners are often used to reach good optical quality across the image.
Allowing designers to play with the parameters of the field’s shape is offering them a brand-new game field. The possibility of curving the CMOS sensors to fit curved/aspherical/freeform shapes of focal surfaces has been studied for the last 20 years and led today to different applications and prototypes.
We present in this article 1/ the parameter studies we performed over a large set of optical designs showing the gain offered by this approach, 2/ the CMOS sensors curving process and performance over a large set of prototypes, 3/ Optical systems that have been produced with this technology and 4/ the roadmap related to the development of curved-sensors based instrumentation for astronomy with the CASTLE telescope project and physical sciences through the Auroral UV Imager program led by ESA, and the IMANCES project led by the Neurosciences Institute INT.
A new step was taken in the development of the Chemical-Mechanical mirror polishing (CMP) manufacturing process for so-called “hyper-polished” optics. The main objective was to explore the limits of hyper polishing with the synthesis of Silica oxide and Cerium oxide nanoparticle slurries. Better control of the size and morphology of the synthesized SiO2 and CeO2 nanoparticles in the slurries will give us information on the surface chemistry and the interaction that happens while polishing but it will also allow us to take a step forward to meet the challenge of reducing the surface roughness below the Angstrom.
A freeform-curved sensor is presented here to demonstrate its highlights in off-axis optical system design. First, we take the extremely demanding TMA telescope as an example, the introduction of the freeform sensor makes the imaging performance reach the diffraction limit, and the PV sag departure of the mirror surface is reduced by 71% compared with the traditional design using flat sensor. Next, we performed finite element analysis on the silicon die with freeform shape to ensure that the stress distribution of the curved sensor is within a safe range when bending. Finally, the prototype of freeform-curved sensor will be manufactured, and its surface shape will be tested in the laboratory.
Innovative optical designs combing freeform optics and curved freeform sensors will be key elements to improve the optical performance and reduce the overall manufacturing and testing pressure of optical complex systems. In this paper, three version of unobscured all-reflective TMA-type telescopes (D=10cm, FOV=7°×7°) will be designed separately with flat sensor, spherical sensor and freeform sensor. Then, we will analyze and compare their imaging quality (RMS spot radius) and surface complexity (PV sag departure and Max slope departure) to demonstrate the advantage of freeform sensor applied in the off-axis optical system. Finally, we make comparison on sensitivity analysis of surface error between mirror surfaces and freeform sensor surfaces to prove that the manufacturing pressure of the sensor did not increase even though its surface complexity increased. We expect that such a design has a great potential to be applied in the space weather monitoring and solar system planetary exploration drones.
This conference presentation was prepared for the Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V conference at SPIE Astronomical Telescopes + Instrumentation, 2022.
KEYWORDS: Adaptive optics, Wavefronts, Device simulation, Computer simulations, Large telescopes, Telescopes, Digital signal processing, Optical simulations, Control systems, Wavefront sensors
The control of AO systems dedicated to ELT is a difficult problem related to the large number of degrees of freedom. The
standard and most used adaptive optics AO control starting from the integrator to the LQG are not useful in such a case.
In fact, for future Extremely Large Telescope (ELT's) the number of degrees of freedom is very large related to the large
diameter of the ELT's and the emergence of new architectures for the AO systems. So that the necessary computational
power for real time control RTC on such systems is currently unattainable when using these control methods.
In this paper we present an Adaptive Optics E2E simulator which includes a very fast wave front reconstruction which is
dedicated for the Extremely Large Telescope. This code takes advantages of the SOY library, where we build the interaction
and reconstruction matrix in a sparse format. Based on a script for solving linear systems by conjugate gradient with Jacobi
preconditioner , our reconstruction matrix is computed very fast.
Moreover, we present the reconstruction results for a 42 m and so the characterization time of the code.
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