3.01 Tesis doctorado

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Browsing 3.01 Tesis doctorado by browse.metadata.categoria "Astronomía"

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    Optical design and prototype of a high resolution near IR spectrograph for astronomy.
    (2019) Rukdee, Surangkhana; Vanzi, Leonardo; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    The search for extraterrestrial planets is an exciting current field of research. One of the most efficient ways to detect exoplanets is through the measurement of the Radial Velocity (RV) detection of Doppler shifts of the host star. Recently, the target of the exoplanet search has moved to cooler and lower mass stars. Although these cool stars are abundant in our galaxy, most of them are too faint to be detected by instruments operating in the visible. Thus, it requires high resolution spectroscopy in the near infrared region. In this work, we will contribute to the field by developing a cost-effective infrared spectrograph which will empower the upcoming generation of telescopes. The Tao Aiuc high Resolution (d) Y band Spectrograph (TARdYS) project is a collaboration between the Center of Astro-Engineering UC-AIUC, Chile and the University of Tokyo, Japan. The instrument is a high resolution near infrared spectrograph for astronomy being developed at the AIUC for installation at the Tokyo Atacama Observatory TAO 6.5 m. telescope. TARdYS is optimized for the precise measurement of radial velocities of cool stars. For this science purpose, the instrument requires high resolution > 60,000 and RV precision of 5 m/s. Moreover, it will also be a powerful tool for the study of astroseismology, star-forming regions, and exoplanet atmosphere. The requirements of the instrument are derived from the science objectives and budget constraint. We select a 1kx1k infrared detector and an R6 echelle disperser. This choice enables high resolution with a small beam diameter. TARdYS can yield a spectral resolution > 60,000 within the spectral coverage from 0.843-1.117 m. We plan to use a cryogenic Dewar in the last part of the objectives to minimize the background radiation reaching the detector. Thus, this will be operated in a semi-cryogenic system as a cost-effective solution. In this work, I created and evaluated the optical design of the two different configurations for a cost-effective high resolution near-infrared spectrograph. This work tests a cost-effective solution with less widely tested spectrograph choices, especially an R6 echelle, and only a semi-cryogenic setup. Optimization with computer-aided simulations yields excellent spectral resolution at the diffraction limit even when taking realistic manufacturing and alignment tolerances into account. I built a prototype of the spectrograph using commercially available components and determined its performance. The measured spectral resolution agrees well with the simulation. With a simple temperature control, I achieved a stability of ±0.1K over several hours. The remaining spectral drift is predominately caused by environmental pressure. Once TARdYS is installed at TAO, it will become available as a exoplanet hunter to the Chilean science community.
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    Wide field astronomical image restoration with convolutional neural networks
    (2023) Bernardi, Rafael Luiz; Torres Torriti, Miguel Attilio; Guzmán Carmine, Christian Dani; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Most image restoration methods in astronomy rely upon probabilistic tools that infer a best solution for a deconvolution problem. They achieve good performances when the Point Spread Function (PSF) is spatially invariable in the image plane. However, this later condition is not always satisfied for real optical systems. PSF angular variations cannot be evaluated directly from the observations, neither be corrected at a pixel resolution. The new method for the restoration of images affected by static and anisotropic aberrations is developed using Deep Neural Networks that can be directly applied to sky images. The network is trained using simulated sky images corresponding to the T80-S Telescope optical model, an 80 cm survey imager at Cerro Tololo (Chile), which are synthesized using a Zernike polynomial representation of the optical system and real observation conditions, like atmospheric turbulence and detector noises. Once trained, the network is used directly on real images from the T80-S telescope, resulting in a prediction that is a corrected version of the image, characterized by a known and constant PSF across the field of view, zero noise and compensation for the effect of atmospheric turbulence. The method tested on real T80-S images was compared to the relative positions of objects in the GAIA survey catalog.