The Giant Magellan Telescope (GMT) Adaptive Optics (AO) systems feature a single conjugate natural guide star based AO system using the 7 deformable secondaries and a post focal wavefront sensor named NGWS (Natural Guide star Wavefront Sensor). The NGWS has two different channels: one featuring a high spatial sampling pyramid sensor dedicated to the fast frame rate correction of atmospheric turbulence and a second dedicated to the correct phasing of the 7 segments of the GMT telescope. The Arcetri AO group in collaboration with the GMT Organization (GMTO) and the University of Arizona (UA) is in charge of providing the design, fabrication and test of a prototype of the NGWS system that shall replicate all aspects of optical sensitivity including optical design, camera selection and data reduction. The prototype design starts from the baseline design for the NGWS that was provided by the Arcetri group in 2013. The prototype project Kick-off Meeting was held on April 16th 2021 and is foreseen to reach completion 34 months later. A first set of performance tests will be performed locally in Arcetri and the final prototype performance verification will happen at UA laboratories after installation of the unit on the High Contrast AO test bench developed by the AO group of UA. This final verification is scheduled for the summer of 2023. The paper reports about the prototype development work summarizing results of numerical simulation that lead to the chosen opto-mechanical design, main features and challenges of optical design for the two sensing channels.
The Giant Magellan Telescope’s primary and deformable secondary mirror are each composed of 7 segments. The Natural Guide Star (NGS) wavefront sensor has the critical task to keep these 7 segments in phase in addition to the classical Adaptive Optics (AO) correction. The baseline defined several years ago has two pyramid wavefront sensors working in the visible. The first one is used to close the AO loop (main channel), but it is not sensitive to differential pistons that are multiples of its central wavelength (λ1), leading to segment ejections. The second pyramid, sensing at a slightly higher wavelength, is then used as a slow ”truth sensor” (2nd channel) to derive the sign of a segment ejection and correct it by steps of λ1. However, the robustness of this solution with respect to noise and turbulence conditions is not satisfying. We are now in a prototyping phase, for which the first step is to improve the baseline or find an alternative design for the 2nd channel in order to gain robustness. One of the potential solutions is LIFT, a focal-plane wavefront sensor. By making use of the sensor at two different wavelengths, it is possible to derive an unambiguous differential piston measurement. In this work, we describe our piston control strategy and show the results of end-to-end simulations comprising the full AO loop and the 2nd channel correction at the faint end of the NGS mode.
Multiconjugate adaptive Optic Relay For ELT Observations (MORFEO, formerly known as MAORY) is the multiconjugate adaptive optics system of the ELT, providing a diffraction limited correction over a 60" field to the near infrared spectroimager MICADO; it recently completed the preliminary design phase. MORFEO's tomographic sensing is based on 12 WaveFront Sensors (WFS) working with 6 Laser Guide Stars (LGS) and 3 Natural Guide Star (NGS) and the wavefront correction is realized through the ELT's adaptive M4 and up to 2 post-focal deformable mirrors. Under median conditions, MORFEO will provide about 35% SR in K band with a 50% sky coverage at the galactic pole, and 55% SR in optimal conditions with a SR variation of ≤ 10% over a 60" corrected field. In this work we brie y summarize the key aspects of the AO system, focusing on the analysis that motivates the main design choices for wavefront sensors, deformable mirrors, real-time control and the many auxiliary loops envisaged to maintain an optimal and stable correction during the observation.
The paper presents the current electronics design status of the MORFEO (formerly known as MAORY) Low-Order and Reference (LOR) WFS module. The LOR WFS Module is a subsystem of MORFEO and it implements the NGS WFS capabilities of the MCAO system. The LOR WFS module is hosted in the Green Doughnut: a volume shared with the MICADO SCAO system and embedded into the MICADO envelope. Both the optomechanics and electronics shall take into account the design constraints given by the shared environment. While the LOR devices are placed in the Green Doughnut, the subsystem control electronics modules are hosted inside two cabinets on the MICADO co-rotating platform. In this framework a continuous effort has been carried out to harmonize all the electronics design with the MICADO partners. In this paper we present the tasks of the LOR electronics and the selection of the actuators, cameras and sensors needed to implement the WFS. Moreover, we briefly provide a description of their foreseen positioning inside the two 19” cabinets. Then we focus on the description of the control electronics strategy which follows the ESO design guidelines, i.e. based on Beckhoff PLC and EtherCAT Fieldbus. We detail the analysis of all the hardware modules used to implement functions such as I/O signals, digital communication interfaces, motion control and sensor front-end. Finally, we discuss some preliminary results of the tests performed to evaluate the control strategies. This prototyping activity will be continued and broadened out during the incoming FDR.
One of the greatest technical challenges of the doubly-segmented Giant Magellan Telescope is the accurate and stable control of segment piston in the diffraction limited observation mode. To address this challenge, in collaboration with the University of Arizona, Smithsonian Astrophysical Observatory and the Istituto Nazionale di Astrofisica, GMTO is executing a project to optimize and validate segment piston control strategies and algorithms using a pair of testbeds. The testbeds provide disturbances to simulate atmospheric turbulence and differential atmospheric dispersion. In addition to the phasing demonstration, the testbeds offer the opportunity to validate hardware designs for the Acquisition & Guiding Wavefront Sensor (AGWS) and the Natural Guide Star Wavefront Sensor (NGWS) and to mitigate their fabrication and assembly risks. Significant progress is reported in the design of the AGWS and NGWS prototypes as well as preliminary test results from the testbeds.
The paper describes the design of the NGS WFS sub-module of MAVIS, an instrument for the VLT UT4 that aims to provide diffraction limited imaging and spectroscopy at visible wavelengths. In this framework the NGS WFS provides means for the tomographic measurement of the lower-orders of the atmospheric turbulence allowing MAVIS to reach the required performances in terms of sky coverage and resolution. We present the optical design and performance of the NGS WFS probes and acquisition camera, the actuators embedded in the subsystem and their control hardware. Finally, we show the mechanical arrangement of the submodule.
MORFEO (formerly known as MAORY) is a post-focal adaptive optics module that forms part of the first light instrument suite for the Extreme Large Telescope (ELT). The project passed the Preliminary Design Review in two stages in April and July 2021 and is now entering the Final Design Phase. In this paper we report the status of the project.
MORFEO/MAORY is the post-focal adaptive optics instrument of the ELT. It is designed to provide the 53×53 arcsec field of view of MICADO with MCAO correction based on split-tomography, where the Low-Order modes are sensed by three NGS-based WFS. To maximize the sky-coverage the LO-WFS are 2×2 subapertures Shack- Hartmann sensors working in the H band, making use of the FREDA detectors. MAORY also implements 3 dedicated NGS-based truth sensors to measure at slow rate the true higher order atmospheric aberrations and to de-trend the LGS WFS measurements. These WFS work with the visible light of the NGS to feed a 10 × 10 SH sensor that makes use of the ALICE detector. Each unit of LOR WFS is provided with a couple of orthogonal linear stages to allow for the NGS acquisition in a 80 arcsec radius. The 3 LOR WFS are arranged at 120° geometry on a common support structure that rigidly connects them to MICADO and its rotator.
In this paper we present the status of the LOR WFS Module at the output of the MORFEO preliminary design review. We focus on the optomechanical arrangement of the subsystem highlighting the design choices and the analyses we carried out to verify its compliance to the requirements.
This paper provides a description of the Instrument Control Hardware design for MORFEO (Multiconjugate adaptive Optics Relay For ELT Observations), an adaptive optics module for ESO ELT. The MORFEO Instrument Control Hardware is in charge of the control electronics of the entire system. The architecture of the control system is thus based on the paradigm of decentralized functions, connected via EtherCAT fieldbus, allowing for easy communication between components that are not physically near each other. The use of industrial standards and COTS elements also leads to rapid development, easier update of the components, lower cost for spare parts and a widespread understanding of architecture among specialized firms. The Instrument Control Hardware design described in this paper is an updated version of the configuration presented for the Preliminary Design Review in the first half of 2021.
MAVIS (MCAO Assisted Visible Imager and Spectrograph) is a new instrument that will operate on the UT4 of the ESO Very Large Telescope (VLT), delivering comparable angular resolution in the optical to that delivered by ELTs in the infrared. The MAVIS core is represented by a multi-conjugate Adaptive Optics Module (AOM) designed to feed an Imager, a Spectrograph and a visiting instrument, all operating in the visible range. The project is now in the preliminary design phase and will be commissioned in 2027 according to the current plan. We present the current status of the MAVIS AOM instrument control electronics that will manage all the motorized functions and auxiliary sensors, focusing on the main design concepts and the preliminary prototyping activities. The design includes ESO standards and Commercial Off-The-Shelf (COTS) industrial components organized in a modular architecture to simplify the AOM preliminary integration activities, planned simultaneously in different sites. Important guidelines to the design are the attention to the overall reliability and maintainability and the minimization of risks. Almost all the motorized functions are implemented adopting preassembled industrial motorized stages. For the tracking axes, a prototyping activity has been envisaged during the design phases, in order to assess the adopted solutions are compatible with the positioning and tracking requirements.
MORFEO (formerly known as MORFEO) 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. We will discuss the evolution of the architecture 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…). We will also make a brief description of way in which we implemented Model Based System Engineering and the tools adopted in order to manage requirements, use cases and interfaces.
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