221 research outputs found
Simulations of ELT-GMCAO performance for deep field observations
No full textThe Global-Multi Conjugated Adaptive Optics (GMCAO) approach offers an alternative way to correct an adequate scientific Field of View (FoV) using only natural guide stars (NGSs) to extremely large ground-based telescopes. Thus, even in the absence of laser guide stars, a GMCAO-equipped ELT-like telescope can achieve optimal performance in terms of Strehl Ratio (SR), retrieving impressive results in studying star-poor fields, as in the cases of the deep field observations. The benefits and usability of GMCAO have been demonstrated by studying 6000 mock high redshift galaxies in the Chandra Deep Field South region. However, a systematic study simulating observations in several portions of the sky is mandatory to have a robust statistic of the GMCAO performance. Technical, tomographic and astrophysical parameters, discussed here, are given as inputs to GIUSTO, an IDL-based code that estimates the SR over the considered field, and the results are analyzed with statistical considerations. The best performance is obtained using stars that are relatively close to the Scientific FoV; therefore, the SR correlates with the mean off-axis position of NGSs, as expected, while their magnitude plays a secondary role. This study concludes that the SRs correlate linearly with the galactic latitude, as also expected. Because of the lack of natural guide stars needed for low-order aberration sensing, the GMCAO confirms as a promising technique to observe regions that can not be studied without the use of laser beacons. It represents a robust alternative way or a risk mitigation strategy for laser approaches on the ELTs
PLATO-INAF-PL-LI-0058 TOU NCRs, RFAs, RFDs and RFWs Status List
No full textPLATO-INAF-PL-LI-0058 TOU NCRs, RFAs, RFDs and RFWs Status Lis
TOU Prototype Test Report
No full textThe PLATO mission, as part of the Cosmic Vision Programme, aims to detect and characterize terrestrial exoplanets within the habitable zones of solar-type stars, utilizing a multi-camera approach to monitor a wide field of view with high precision. The TOU prototype, designed to test assembly and alignment procedures under varying thermal conditions, underscores the mission's innovative approach to observing the cosmos, blending technical rigor with groundbreaking optical technology to advance our understanding of distant worlds
A Holographic Diffuser Generalised Optical Differentiation Wavefront Sensor
No full textThe wavefront sensors used today at the biggest World’s telescopes have either a high dynamic range or a high
sensitivity, and they are subject to a linear trade off between these two parameters. A new class of wavefront sensors, the Generalised Optical Differentiation Wavefront Sensors, has been devised, in a way not to undergo this linear trade off and to decouple the dynamic range from the sensitivity. This new class of WFSs is based on the light filtering in the focal plane from a dedicated amplitude filter, which is a hybrid between a linear filter, whose physical dimension is related to the dynamic range, and a step in the amplitude, whose size is related to the sensitivity.
We propose here a possible technical implementation of this kind of WFS, making use of a simple holographic diffuser to diffract part of the light in a ring shape around the pin of a pyramid wavefront sensor. In this way, the undiffracted light reaches the pin of the pyramid, contributing to the high sensitivity regime of the WFS, while the diffused light is giving a sort of static modulation of the pyramid, allowing to have some signal even in high turbulence conditions. The holographic diffuser zeroth order efficiency is strictly related to the sensitivity of the WFS, while the diffusing angle of the diffracted light gives the amount of modulation and thus the dynamic range. By properly choosing these two parameters it is possible to build a WFS with high sensitivity and high dynamic range in a static fashion. Introducing dynamic parts in the setup allows to have a set of different diffuser that can be alternated in front of the pyramid, if the change in the seeing conditions requires it
Aligning the demonstration model of CHEOPS
No full textCHEOPS (CHaracterizing ExOPlanets Satellite) is an ESA Small Mission, planned to be launched in mid-2018 and whose main goal is the photometric precise characterization of radii of exoplanets orbiting bright stars (V<12) already known to host planets. Given the fast-track nature of this mission, we developed a non-flying Demonstration Model, whose optics are flight representative and whose mechanics provides the same interfaces of the flight model, but is not thermally representative. In this paper, we describe CHEOPS Demonstration Model handling, integration, tests, alignment and characterization, emphasizing the verification of the uncertainties in the optical quality measurements introduced by the starlight simulator and the way the alignment and optical surfaces are measured
TOU Prototype Design and AIV Concept
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The document details the design and assembly, integration, and verification (AIV) concept of the PLATO Telescope Optical Unit (TOU) prototype. It outlines the optical and mechanical design adaptations for the prototype, aiming to replicate the final TOU structure while addressing cost and schedule constraints. The AIV process emphasizes the precise alignment of lenses and the testing of the prototype's optical performance under varying conditions. This approach facilitates validating the assembly and alignment procedures, ensuring the prototype meets the required specifications for the PLATO space mission, focused on studying exoplanets and stellar oscillation
SHARK-NIR: Challenges and solutions of a high contrast imager alignment
No full textSHARK-NIR is a high contrast camera for the LBT, working in Y, J and H bands. It has been conceived and designed to fully exploit the high Strehl adaptive optics correction delivered by the FLAO module, which is being upgraded to SOUL, and will implement different coronagraphic techniques, with contrast as high as 10-6 up to 65 mas from the star. To maximize the achievable contrast, SHARK-NIR has a couple of peculiar features, namely a fast internal TT loop to minimize the residual jitter and a local NCPA correction, performed through a DM inside the instrument itself. Other than high-contrast imaging, SHARK-NIR also has spectroscopic capabilities, with low and medium resolution, and its relatively wide Field of View (18 x 18 arcsec) makes it accessible to other scientific targets, such as galactic jets and disks, as well as extra-galactic cases. Sharing the focal station with another instrument at LBT (LBTI), the design has been kept very compact. This has been achieved through the use of 4 Off-Axis Parabolic mirrors (OAPs) and three flat folding mirrors able to provide two pupil planes and two focal planes required by the coronagraphic techniques implemented. A mixed optical-mechanical alignment procedure has been identified and extensively simulated using ray-tracing software, demonstrating that the proposed technique converges to the required performance. We report here about the SHARK-NIR lesson learned and status in the frame of the Assembly, Integration & Verification phase (AIV), delayed due to the covid 19 emergency, which is going to finish in first half of 2021 and bringing in this way the first photons to the instrument by the end of 2021
Exploring the impact of mechanical stress in neurodegeneration
No full textMechanical stress has been proposed as a common denominator of different pathological conditions, including chronic inflammation and neurodegenerative disorders such as Alzheimer’s disease. While mechanical signals shape the brain development throughout morphogenesis, a role of mechanical forces in neurodegeneration has been suggested by the observed correlation of traumatic brain injury and cerebrovascular hemodynamic stress with the risk of some neurodegenerative disorders. Furthermore, neurodegenerative diseases and brain injury are associated with changes in composition and properties of the extracellular matrix. Using in vivo models, we provide genetic and molecular evidence that alterations in mechanotransduction could impact on neuronal survival and function in stressful conditions. Our findings help better understand the pathogenesis of neurodegenerative disorders and could lead to the identification of therapeutic targets
TOU Prototype Assembly and Integration Report
No full textThe PLATO mission, part of the Cosmic Vision Programme M3 mission set for launch in 2026, aims to detect and characterize terrestrial exoplanets in habitable zones of solar-type stars. Utilizing a multi-camera approach with 24 Normal Cameras and two Fast Cameras, the mission's payload is designed to monitor a vast field of stars in the extended visible light range. This innovative approach ensures thermal and structural stability, optimizing the observation of numerous targets across varying brightness levels, thereby enhancing the mission's scientific yield
Data processing on simulated data for SHARK-NIR
No full textA robust post processing technique is mandatory to analyse the coronagraphic high contrast imaging data. Angular Differential Imaging (ADI) and Principal Component Analysis (PCA) are the most used approaches to suppress the quasi-static structure in the Point Spread Function (PSF) in order to revealing planets at different separations from the host star. The focus of this work is to apply these two data reduction techniques to obtain the best limit detection for each coronagraphic setting that has been simulated for the SHARK-NIR, a coronagraphic camera that will be implemented at the Large Binocular Telescope (LBT). We investigated different seeing conditions () for stellar magnitude ranging from R=6 to R=14, with particular care in finding the best compromise between quasi-static speckle subtraction and planet detection
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