MICADO is the Multi-AO Imaging Camera for Deep Observations, a first light instrument for the Extremely Large Telescope (ELT). The instrument will be assisted by a Single-Conjugate Adaptive Optics (SCAO) system and the Multiconjugate adaptive Optics Relay For ELT Observations (MORFEO). MICADO can operate in the so-called standalone mode in the absence of MORFEO with the SCAO correction alone. The Relay Optics (RO), is the optical system relaying the ELT focal plane to an appropriate position inside the MICADO cryostat for that SCAO-only stand-alone observing mode. After successfully passing the Final Design Review (FDR), the manufacturing of the RO is in full swing. We present here the current status of the ongoing assembly, integration and verification campaign (AIV), together with its upcoming challenges. The RO consists of an optical bench made of carbon fiber reinforced plastic (CFRP), an optical assembly made of three flat, motorized tip-tilt-piston mirrors (M1, M5 and M6) and three powered mirrors (M2, M3 and M4) of up to ~500 mm in diameter, the MICADO calibration assembly (MCA) including its deployable unit with a flat mirror (MDU) and a cover to protect all opto-mechanical components on top of the bench. The fabrication of the mirrors has started, while the machining of the mirror mounts is well ahead. The optical bench, as well as all other CFRP parts have been ordered and the manufacturing is completed. In order to get optimum performance and minimal wavefront error (WFE), the mirrors are tested in their mounts before carrying out the final polishing operations. Therefore, all mirror mounts are scheduled to be delivered to the mirror vendor QED Optics by the end of 2024.
MICADO is the Multi-AO Imaging Camera for Deep Observations, a first light instrument for the Extremely Large Telescope (ELT). The instrument will be assisted by a Single-Conjugate Adaptive Optics (SCAO) system and the Multi conjugate Adaptive Optics RelaY (MAORY). MICADO can operate in the so-called stand-alone mode in the absence of MAORY with the SCAO correction alone. Here, we present the opto-mechanical final design of the Relay Optics (RO), the optical system relaying the ELT focal plane to an accessible position of MICADO for that SCAO-only stand-alone observing mode. The RO consists of an optical bench made of carbon fiber reinforced plastic (CFRP), an optical assembly made of three flat, motorized tip-tilt-piston mirrors and three powered mirrors of up to ~500 mm in diameter, the MICADO calibration assembly and a cover to protect all opto-mechanical components on top of the bench. A 9-point whiffletree support, combined with a thermal compensation system is implemented for the critical flat mirror (M6), while a more simple 3- point support is employed for the other two flat mirror M1 and M5. The powered mirrors (M2, M3, M4) comprising the relay's three mirror anastigmat (TMA) are supported by V-shape mounts. The static and the dynamic performance of the MICADO RO are investigated through a detailed Finite Element Analysis (FEA), whose results are combined with a Zernike basis representation of the surface deformations performed in Zemax for assessing the optical performance. The variation of the mirror position due to the operational temperature drift Delta T and other disturbances, is also considered in an end-to-end simulation. The required overall wavefront error of 100 nm rms is fulfilled with the current design proposal. Additionally, the results of a motorized tip-tilt-piston mirror mount prototype are presented as well..
MICADO is the Multi-AO Imaging Camera for Deep Observations, a first light instrument for the Extremely Large Telescope (ELT). The instrument provides imaging, astrometric, spectroscopic and coronographic observing modes. MICADO will be assisted by a Single-Conjugate Adaptive Optics (SCAO) system and the Multi-conjugate Adaptive Optics RelaY (MAORY). The instrument will provide a narrow (19′′) and a wide (51”) Field of View. MICADO can operate in the so-called stand-alone mode in the absence of MAORY with the SCAO correction alone. Here, we present the opto-mechanical design of the Relay Optics (RO), the optical system relaying the ELT focal plane to an accessible position for MICADO using the SCAO-only stand-alone observing mode. The RO consists of an optical bench made of carbon fiber reinforced plastic (CFRP), an optical assembly made of three flat mirrors with motorized piston-tip-tilt mounts and three additional powered mirrors of up to ~500 mm in diameter, the MICADO calibration assembly, and a cover to protect all opto-mechanical components on top of the bench. A 9-point whiffletree support, combined with a thermal compensation system is implemented for the critical mirrors. The static and the dynamic performance of the MICADO RO are investigated through a detailed Finite Element Model (FEM), the results are combined with a Zernike basis representation of the mirror surface deformations performed in Zemax for assessing the optical performance.
MICADO is the Multi-AO Imaging Camera for Deep Observations, a first light instrument for the Extremely Large Telescope (ELT). It will provide the ELT with diffraction limited imaging capacity over a ~53-arcsec field of view, while operating with the Multi-Conjugate Adaptive Optics (MCAO) module MAORY (0.8-2.5 μm). Here, we present the design status of the MICADO derotator, which at the same time serves (i) as crucial mechanical interface between the cryo-opto-mechanical camera assembly and the instrument support structure and (ii) as high-precision image and wavefront sensor derotator to allow for 50 µas astrometry over the entire MCAO corrected field. Additionally, first test results are presented which were obtained with a derotator prototype based on a scaled 1:2 test bearing. The derotator test stand is essential to explore the limitations of the preferred bearing type in the context of the given requirements. The technical difficulties addressed by the design include: (i) design of adequate mechanical interfaces to minimize mass, deformation and the effect of the warping moment on the bearing and (ii) analysis of the friction-related stick-slip effects at low tracking velocities for the implementation of a suitable position-velocity closed-loop control system. Furthermore, our prototype setup is used to develop and test the required control concept of this high-precision application.
This paper describes the development of a Carbon Fiber-Reinforced Plastics (CFRP) structure for the interferometric instrument LINC-NIRVANA (LN) at the Large Binocular Telescope (LBT) Arizona, USA. This structure carries all components between the two "bent" Gregorian foci of the individual telescopes necessary to combine the light of the two arms coherently.
Especially developed for aerospace and defence, CFRP materials now find widespread use across a number of other applications where their special properties are beneficial. We will profit in LN from the good rigidity, high strength, low thermal expansion, low mass and high damping properties of CFRP.
An extended Finite Element Analysis was performed to simulate the properties of the structure for different telescope positions and different temperatures.
We built a 560 mm x 550 mm x 385 mm test piece of the LN optical bench for flexure tests to confirm the results of the Finite Element Analysis.
The complete LN instrument with a mass of 7.5 tons will be mounted at a tilting unit to simulate the different telescope positions.
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