Multi-conjugate Adaptive Optics RelaY Research Articles

Performance of an iterative wavelet reconstructor for the Multi-conjugate Adaptive Optics RelaY of the Extremely Large Telescope

The Multi-conjugate Adaptive Optics RelaY (MAORY) is one of the key adaptive optics (AO) systems on the European Southern Observatory’s Extremely Large Telescope. MAORY aims to achieve good wavefront correction over a large field of view, which involves a tomographic estimation of the three-dimensional atmospheric wavefront disturbance. Mathematically, the reconstruction of turbulent layers in the atmosphere is severely ill-posed, hence, limits the achievable reconstruction accuracy. Moreover, the reconstruction has to be performed in real time at a few hundred to one thousand hertz frame rates. Huge amounts of data have to be processed and thousands of actuators of the deformable mirrors have to be controlled by elaborated algorithms. Even with extensive parallelization and pipelining, direct solvers, such as the matrix vector multiplication method, are extremely demanding. Thus, research in recent years shifted into the direction of iterative methods. We focus on the iterative finite-element wavelet hybrid algorithm (FEWHA). The key feature of FEWHA is a matrix-free representation of all operators involved, which makes the algorithm fast and enables on-the-fly system updates whenever parameters at the telescope or in the atmosphere change. We provide a performance analysis of the method regarding quality and run-time for the MAORY instrument using the AO software package COMPASS.

Structural design of the optical bench and enclosure for MAORY, adaptive optics module for the ELT

This paper outlines an overview of the mechanical design of the optical bench and the enclosure for MAORY (Multi-conjugate Adaptive Optics RelaY) for the Extremely Large Telescope. MAORY will enable high-angular resolution observations in the near infrared by employing real-time compensation of the wave-front distortions due to atmospheric turbulence and other disturbances on the telescope. The main purpose of the optical bench is to provide support to the opto-mechanical mountings and subsystems that will be integrated on it. The design philosophy behind the proposed architecture is a truss spatial structure with the aim of optimizing the mass of the Main Structure. The enclosure has to protect the optomechanical elements and to achieve a uniform temperature distribution in its internal environment. The mechanical design of the bench and the enclosure was supported by a set of structural FE analyses, to verify the design compliance with ESO (European Southern Observatory) requirements.

The MUSE Deep Lensed Field on the Hubble Frontier Field MACS J0416

Context. A census of faint and tiny star forming complexes at high redshift is key to improving our understanding of reionizing sources, galaxy growth, and the formation of globular clusters. Aims. We present the MUSE Deep Lensed Field (MDLF) program, which is aimed at unveiling the very faint population of high redshift sources that are magnified by strong gravitational lensing and to significantly increase the number of constraints for the lens model. Methods. We describe Deep MUSE observations of 17.1 h of integration on a single pointing over the Hubble Frontier Field galaxy cluster MACS J0416, providing line flux limits down to 2 × 10−19 erg s−1 cm−2 within 300 km s−1 and continuum detection down to magnitude 26, both at the three sigma level at λ = 7000 Å. For point sources with a magnification (μ) greater than 2.5 (7.7), the MLDF depth is equivalent to integrating more than 100 (1000) h in blank fields, as well as complementing non-lensed studies of very faint high-z sources. The source-plane effective area of the MDLF with μ > 6.3 is < 50% of the image-plane field of view. Results. We confirm spectroscopic redshifts for all 136 multiple images of 48 source galaxies at 0.9 < z < 6.2. Within those galaxies, we securely identify 182 multiple images of 66 galaxy components that we use to constrain our lens model. This makes MACS J0416 the cluster with the largest number of confirmed constraints for any strong lens model to date. We identify 116 clumps belonging to background high-z galaxies; the majority of them are multiple images and span magnitude, size, and redshift intervals of [ − 18, −10], [ ∼ 400 − 3] parsec and 1 < z < 6.6, respectively, with the faintest or most magnified ones probing possible single gravitationally bound star clusters. The multiplicity introduced by gravitational lensing allows us, in several cases, to triple the effective integration time up to ∼51 h exposure per single family, leading to a detection limit for unresolved emission lines of a few 10−20 erg s−1 cm−2, after correction for lensing magnification. Ultraviolet high-ionization metal lines (and He IIλ1640) are detected with S/N > 10 for individual objects down to de-lensed magnitudes between 28 and 30. The median stacked spectrum of 33 sources with a median MUV ≃ −17 and ⟨z⟩ = 3.2 (1.7 < z < 3.9) shows high-ionization lines, suggesting that they are common in such faint sources. Conclusions. Deep MUSE observations, in combination with existing HST imaging, allowed us to: (1) confirm redshifts for extremely faint high-z sources; (2) peer into their internal structure to unveil clumps down to 100 − 200 pc scale; (3) in some cases, break down such clumps into star-forming complexes matching the scales of bound star clusters (< 20 pc effective radius); (4) double the number of constraints for the lens model, reaching an unprecedented set of 182 bona-fide multiple images and confirming up to 213 galaxy cluster members. These results demonstrate the power of JWST and future adaptive optics facilities mounted on the Extremely Large Telescopes (e.g., European-ELT Multi-conjugate Adaptive Optics RelaY, MAORY, coupled with the Multi-AO Imaging CamerA for Deep Observations, MICADO) or Very Large Telescope (e.g., MCAO Assisted Visible Imager and Spectrograph, MAVIS) when combined in studies with gravitational telescopes.

Preliminary design of the MAORY Calibration Unit

MAORY (Multi-conjugate Adaptive Optics RelaY) is one of the first light instruments for the ESO Extremely Large Telescope (ELT). It will be firstly used by MICADO (Multi-AO Imaging CamerA for Deep Observations), a near-infrared high-angular resolution imager, to compensate aberrations and provide high-Strehl images within a (53” × 53”) Field of View (FoV). The complexity of MAORY requires calibration functionalities for both the AIV (Assembly-Integration-Verification) and the operational phase. The function of the Calibration Unit (CU) is keeping the high efficiency of the adaptive correction provided by MAORY during the operational phase, through proper calibration sources, acting as both Natural Guide Stars (NGS) and Laser Guide Stars (LGS) sources. An overview of the system, the status of the current design and the main challenges to face in the future are presented in this work.

The impact of geometric distortions in multiconjugate adaptive optics astrometric observations with future extremely large telescopes

Astrometry is one of the main science case which drives the requirements of the next multiconjugate adaptive optics (MCAO) systems for future extremely large telescopes. The small diffraction limited point-spread function (PSF) and the high Signal-to-Noise Ratio (SNR) of these instruments, promise astrometric precision at the level of micro-arcseconds. However, optical distortions have to be as low as possible to achieve the high demanding astrometry requirements. In addition to static distortions, the opto-mechanical instabilities cause astrometric errors that can be major contributors to the astrometry error budget. The present article describes the analysis, at design level, of the effects of opto-mechanical instabilities when coupled with optical surface irregularities due to the manufacturing process. We analyse the notable example of the Multi-conjugate Adaptive Optics RelaY (MAORY) for the extremely large telescope (ELT). Ray-tracing simulations combined with a Monte Carlo approach are used to estimate the geometrical structure and magnitude of field distortion resulting from the optical design. We consider the effects of distortion on the MCAO correction showing that it is possible achieve the micro-arcseconds astrometric precision once corresponding accuracy is obtained by both optical design and manufacturing. We predict that for single-epoch observations, an astrometric error below 50$\mu$as can be achieved for exposure times up to 2 min, provided about 100 stars are available to remove fifth-order distortions. Such performance could be reproducible for multi-epoch observations despite the time-variable distortion induced by instrument instabilities.

Unveiling the nature of Gemini multiconjugate adaptive optics system distortions

Astrometry was not a science case of the Gemini Multiconjugate adaptive optics System (GeMS) at its design stage. However, since GeMS has been in regular science operation with the Gemini South Adaptive Optics Imager (GSAOI), their astrometric performances have been deeply analysed. The non-linear component of the distortion map model shows a characteristic pattern which is similarly repeated in each detector of GSAOI. The nature of this pattern was unknown and subjected to different hypotheses. This paper describes the origin of the GeMS distortion pattern as well as its multi-epoch variation. At the end, it is showed a comparison with the current design of the Multiconjugate Adaptive Optics RelaY (MAORY) of the Extremely Large Telescope (ELT).

Historic evolution of the optical design of the Multi Conjugate Adaptive Optics RelaY for the Extremely Large Telescope

The optical design of the Multi Conjugate Adaptive Optics Relay for the Extremely Large Telescope experienced many modifications since Phase A conclusion in late 2009. These modifications were due to the evolution of the telescope design, the more and more accurate results of the performance simulations and the variations of the opto-mechanical interfaces with both the telescope and the client instruments. Besides, in light of the optics manufacturing assessment feed-backs, the optical design underwent to a global simplification respect to the former versions. Integration, alignment, accessibility and maintenance issues took also a crucial role in the design tuning during the last phases of its evolution. This paper intends to describe the most important steps in the evolution of the optical design, whose rationale has always been to have a feasible and robust instrument, fulfilling all the requirements and interfaces. Among the wide exploration of possible solutions, all the presented designs are compliant with the high-level scientific requirements, concerning the maximum residual wavefront error and the geometrical distortion at the exit ports. The outcome of this decennial work is the design chosen as baseline at the kick-off of the Phase B in 2016 and subsequently slightly modified, after requests and inputs from alignment and maintenance side.

Prototype of a laser guide star wavefront sensor for the Extremely Large Telescope

The new class of large telescopes, as the future ELT, are designed to work with Laser Guide Star (LGS) tuned to a resonance of atmosphere sodium atoms. This wavefront sensing technique presents complex issues for an application to big telescopes due to many reasons mainly linked to the finite distance of the LGS, the launching angle, Tip-tilt indetermination and focus anisoplanatism. The implementation of a laboratory Prototype for LGS wavefront sensor (WFS) at the beginning of the phase study of MAORY, the Multi-conjugate Adaptive Optics RelaY for the ELT first light, has been indispensable to investigate specific mitigation strategies to the LGS WFS issues. This paper shows the test results of LGS WFS Prototype under different working conditions. The accuracy within which the LGS images are generated on the Shack-Hartmann (SH) WFS has been cross-checked with the MAORY simulation code. The experiments show the effect of noise on the centroiding precision, the impact of LGS image truncation on the wavefront sensing accuracy as well as the temporal evolution of sodium density profile and LGS image under-sampling.