5 research outputs found
Extreme Ultraviolet Reflective Grating Characterization and Simulationsfor the Aspera SmallSat Mission
The Aspera SmallSat mission is designed to detect and map the warm-hot gaseous component of the halos of nearby galaxies through long-slit spectroscopy of the ionized O VI emission line (103.2 nm) for the first time. The Aspera Rowland circle type spectrograph uses a toroidal grating coated with a multilayer film consisting of aluminum, lithium fluoride, and magnesium fluoride capping to optimize reflectivity in the extreme ultraviolet (EUV) waveband from 103 to 104nm. We discuss the grating characterization test setup at the University of Arizona (UA), which will validate the multilayer coating and grating efficiency in a UV vacuum chamber. We also simulate the reflectivity of the multilayer thin film coating using IMD IDL software to compare simulated results with measured reflectivity. Additionally, non-sequential ray trace simulations and 3D CAD modeling are used for verification of the test setup. Finally, the implications of the differences between the measured and simulated reflectivity and grating efficiencies are considered, including impact to the mission
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Optical Solutions to Telescope Problems: Stray Light Analysis, Laser-Truss Metrology, and Freeform Optical Design
Astronomical telescopes provide a window into the heavens that far surpasses anything the human eye can see, expanding our scientific understanding by bringing distant objects from the past into the present context. Telescopes, as magnificent as they are, suffer from imperfections which limit their effectiveness. These imperfections include: SNR-degrading stray light contamination from unwanted light which obscures meaningful scientific data in background noise; Misalignment of optics that induce wavefront aberrations and blur science objects; And limitations in the initial optical design of telescopes which prohibit wide-field observations. This dissertation will explore the many imperfections which plague astronomical telescopes and provide possible solutions to overcome these limitations.
First, we examine the effects of stray light on the FIREBall-2 UV balloon telescope, an effort spearheaded by Dr. Erika Hamden of Steward Observatory, and demonstrate a comprehensive system of baffles which effectively mitigate the impact of unwanted light on science observations. Next, we focus on the development of a novel, laser-truss metrology system for improving and maintaining collimation and pointing of the Large Binocular Telescope by a small team led by Dr. Heejoo Choi at the Large Binocular Telescope Observatory in collaboration with the Giant Magellan Telescope Observatory. Finally, we conclude with a discussion on the design of a high-performance, wide-field radio instrument to study the Cosmic Microwave Background at the South Pole Telescope in Antarctica known as the Summertime Line Intensity Mapper, developed in collaboration with Dr. Dan Marrone’s group.
We wrap up with a discourse on the relationship between each of these optical engineering challenges and speak to the impact of this work in benefiting the astronomical community at large and enhancing the science products generated with these astronomical instruments
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Implementation of a laser-truss based telescope metrology system at the Large Binocular Telescope
Large ground-based telescopes are prone to perturbations caused by environmental factors that affect the mechanical structure of the telescope that can cause collimation loss and image quality degradation. The Telescope Metrology System (TMS) is a metrology method under development at the Giant Magellan Telescope (GMT) and prototyped on the Large Binocular Telescope (LBT) to monitor and maintain collimation and pointing. TMS measures the precise position and orientation of a telescope's primary mirror in relation to other telescope elements. Currently, prototyping has progressed to TMS operation at prime focus between LBT's two 8.4m primary mirrors and the Large Binocular Camera (LBC), a pair of prime focus correctors and wide-field detectors. TMS utilizes a multi-channel absolute distance measuring (ADM) interferometer to create a laser truss by determining the distance between fixed points on the primary mirror and the LBC. By performing a kinematic analysis of the ADM data, the relative position and orientation of the primary mirror and LBC can be determined. With knowledge of the position of the telescope, an optical layout model can be created using TMS data as input. This allows for iterative simulation of field aberrations and loss in image quality due to misalignment of the telescope. This will allow for collimation and pointing to be actively monitored and maintained during an observation. This paper will discuss the process of implementing TMS on LBT and the challenges that arose.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]