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The development of the alignment techniques for small instruments is well validated throughout the history of the Optomechanical and astronomical instrumentation, nevertheless those techniques cannot be applied on large ones. This thesis proposes a procedure that allows to evaluate the position of optical elements in large volume very precisely. This enables the achievement of the scientific goals by minimizing the alignment procedure duration the costs.
In this work it is evaluated the possibility to use a laser tracker as essential embedded tool for the alignment and for the monitoring of the instrument, or better, evaluate if the uncertainty of the tracker measuring the optical elements stay within the alignment requirements.
The case study presented here is MORFEO which is a first-light instrument for the European Extremely Large Telescope. The study consists in the realization of a software that optimizes the position of the tracker inside the instrument considering the nominal position of the targets measured (SMRs) and the possible vignetting based on the prediction of the accuracy and repeatability of the measurements. This analysis is made by steps: the first one considers the error model gave from the manufacture of the tracker. The second one is based on a series of tests and characterizations performed in laboratory to determine more accurately the performances. The results obtained have been validated using a dummy version of an optomechanical element measured by using a Coordinate Measurement Machine (CMM).
MAORY stands for Multi-conjugate Adaptive Optics RelaY (the name has been recently changed to MORFEO, which stands for Multiconjugate adaptive Optics For ELT Observations, thus in this article we will use MORFEO), and it is one of the instruments of the European Extremely Large Telescope (ELT). The main function of MORFEO is to relay the light beam from the ELT focal plane to the client instrument (initially MICADO) while compensating, through a multiconjugate adaptive optics system, the effects of the atmospheric turbulence and other disturbances affecting the wavefronts coming from the scientific sources of interest.
The MORFEO instrument is designed and developed by a European consortium composed of INAF (Istituto Nazionale di AstroFisica, Italy), CNRS/INSU (Centre National de la Recherche Scientifique/ Institut National des Sciences de l’Univers, France), NUIG (National University of Ireland Galway, Ireland) and ESO (European Southern Observatory, Europe).
The opto-mechanical design of MORFEO has been developed in 3 dimensions, using the volume between the ELT output focal plane and the Nasmyth floor. The design uses the available volume in a very efficient way, but this poses constraints on the orientation of the optical elements and adds complexity to the AIT operations. In this paper we describe the strategy of the AIT process which will be performed at INAF-OAS Bologna (Italy), which is conceived to maximize knowledge of the instrument and thereby optimize (and, possibly, minimize) the time requested at Armazones for the AIV operations.
SHARK-NIR is an instrument which provides direct imaging, coronagraphic imaging, dual band imaging and low resolution spectroscopy in Y, J and H bands, taking advantage of the outstanding performance of the Large Binocular Telescope AO systems. Binocular observations will be provided used in combination with SHARK-VIS (operating in V band) and LMIRCam of LBTI (operating from K to M bands), in a way to exploit coronagraphic simultaneous observations in three different wavelengths.
A wide variety of coronagraphic techniques have been implemented in SHARK-NIR, ranging from conventional ones such as the Gaussian Lyot, to others quite robust to misalignments such as the Shaped Pupil, to eventually techniques more demanding in term of stability during the observation, as the Four Quadrant; the latter is giving in theory and simulations outstanding contrast, and it is supported in term of stability by the SHARK-NIR internal fast tip-tilt loop and local NCPA correction, which should ensure the necessary stability allowing this technique to operate at its best.
The main science case is of course exoplanets search and characterization and young stellar systems, jets and disks characterization, although the LBT AO extreme performance, allowing to reach excellent correction even at very faint magnitudes, may open to science previously difficult to be achieved, as for example AGN and QSO morphological studies.
The institutes participating to the SHARK-NIR consortium which designed and built the instrument are Istituto Nazionale di Astro Fisica (INAF, Italy), the Max Planck Institute for Astronomy (MPIA, Heidelberg, Germany) and University of Arizona/Steward Observatory (UoA/SO, Tucson, Az, USA). We report here about the SHARK-NIR status, that should achieve first light at LBT before the end of 2022.
The Multi-conjugate adaptive Optics Relay For ELT Observations (MORFEO), formerly MAORY, is the Multi-conjugate Adaptive Optics (MCAO) relay for the Extremely Large Telescope (ELT). The instrument provides the MCAO correction to two instruments at the ELT Nasmyth platform. One first light instrument fed by MORFEO is the Multi-AO Imaging Camera for Deep Observations (MICADO) that will provide imaging, astrometric, spectroscopic and coronographic observing modes. A second generation instrument, still to be defined, will occupy the other port of MORFEO. The delivered MCAO-corrected Field of View (FoV) of MORFEO is 2 arcmin. In this paper we present the possible fine optical alignment and recollimation strategies to bring the relay optics within the diffraction-limited performances.
More than one MORFEO fine Optical Alignment (MOA) strategy is currently under study in the development of the instrument towards its final design review. Given the complexity and the size of this new generation instrument diversifying and enlarging the set of possible techniques for the system alignment is an effective and more robust approach. As the Alignment Integration Verification (AIV) phase will develop the different strategies will be deployed and tested to possibly spot the best method (if any) among the others which will then be kept as back-up alternatives. One technique relies on the metrology of out-of-focus PSF images as proxy of the system pupil to detect the main optical aberrations in the instrument. This method has been proposed by Tokovinin & Heathcote [1] for a 2-mirror telescope. The challenge to be faced with MORFEO is given by the large number of optical elements and the related pseudo wavefront sensing limitations. Other techniques under study involve the use of wavefront sensing, phase diversity techniques and aberrations spotting using the MORFEO deformable mirrors. The MOA is meant to be performed both at the first AIV operations and at the periodic recollimations of the system during its nominal operation lifetime. The paper reports the results of a preliminary set of simulations carried out using a OpticStudio-Matlab simulator for the Donut technique.
MORFEO, formerly known with the acronym MAORY, is the Multi-Conjugated Adaptive Optics (MCAO) module for the European Extremely Large Telescope (ELT). MORFEO is designed to feed the Near Infrared (NIR) camera MICADO with both MCAO and Single-Conjugated AO (SCAO) operation modes. The optical configuration provides a one to one imaging of the telescope focal surface on two ports (one feeding MICADO and the other dedicated to a future instrument) and it is equipped with two post-focal deformable mirrors together with the Laser Guide Star (LGS) and Natural Guide Star (NGS) channels for wavefront sensing and tomographic reconstruction.
In this paper, we present the status of the optical configuration at the completion of the Preliminary Design Review (PDR). We will focus our attention on the tolerance analysis of the elements, consisting in both manufacturing and alignment, to provide the expected performances of the instrument after initial integration. We will also present the outcomes of the stability analysis of the instrument, consisting in rigid-body motions and thermoelastic deformations of the structure and optomechanics, used to define the procedures and benchmark to maintain the instrument performances during operation. Details on the integrated modelling, specifically developed for this purpose, will be provided.
Initially proposed as an instrument covering also the K-band, the current design foresees a camera working from Y to H bands, exploiting in this way the synergy with other LBT instruments such as LBTI, which is actually covering wavelengths greater than L' band, and it will be soon upgraded to work also in K band. SHARK-NIR has been undergoing the conceptual design review at the end of 2015 and it has been approved to proceed to the final design phase, receiving the green light for successive construction and installation at LBT.
The current design is significantly more flexible than the previous one, having an additional intermediate pupil plane that will allow the usage of coronagraphic techniques very efficient in term of contrast and vicinity to the star, increasing the instrument coronagraphic performance. The latter is necessary to properly exploit the search of giant exo-planets, which is the main science case and the driver for the technical choices of SHARK-NIR. We also emphasize that the LBT AO SOUL upgrade will further improve the AO performance, making possible to extend the exo-planet search to target fainter than normally achieved by other 8-m class telescopes, and opening in this way to other very interesting scientific scenarios, such as the characterization of AGN and Quasars (normally too faint to be observed) and increasing considerably the sample of disks and jets to be studied.
Finally, we emphasize that SHARK-NIR will offer XAO direct imaging capability on a FoV of about 15"x15", and a simple coronagraphic spectroscopic mode offering spectral resolution ranging from few hundreds to few thousands. This article presents the current instrument design, together with the milestones for its installation at LBT.
This concept was only merely described and functionally tested in the framework of MAD, and subsequently, with a holographic diffuser. The latter produce a sort of random distribution of the light coming out from the pupil plane, leading to sort of inefficient modulation, as most of the rays are focused in the central region of the light diffused by such device. The bi-dimensional original grating is, in contrast, producing a well defined deterministic distribution of the light onto a specifically shaped pattern. A crude option has been already discussed as a possibility, and it is here generalized to holographic plates leading to various distribution of lights, including a circle whose diameter would match the required modulation pattern, or more cost effective approaches like the one of a square pattern. These holographic diffusers would exhibit also zero-th and high order patterns and the actual size of the equivalent modulation would be linearly wavelength dependent, leading to colour effects that requires a careful handling in order to properly choose the right amount of equivalent modulation.
I used this technology to create a 1:1 scale model of the telescope which is the hardware core of the space small mission CHEOPS (CHaracterising ExOPlanets Satellite) by ESA, which aims to characterize EXOplanets via transits observations. The telescope has a Ritchey-Chrétien configuration with a 30cm aperture and the launch is foreseen in 2017. In this paper, I present the different phases for the realization of such a model, focusing onto pros and cons of this kind of technology. For example, because of the finite printable volume (10×10×12 inches in the x, y and z directions respectively), it has been necessary to split the largest parts of the instrument in smaller components to be then reassembled and post-processed. A further issue is the resolution of the printed material, which is expressed in terms of layers thickness, in the Z direction, and in drop-per-inch, in X and Y directions.
3D printing is also an easy and quick production technique, which can become useful in the ad-hoc realization of mechanical components for optical setups to be used in a laboratory for new concept studies and validation, reducing the manufacturing time. With this technique, indeed, it is possible to realize in few hours custom-made mechanical parts, without any specific knowledge and expertise in tool machinery, as long as the resolution and size are compliant with the requirements.
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