Innovative Precision Alignment, Stray Light Suppression Solutions for UV Space-Borne and Suborbital Missions

Abstract

This dissertation addresses key optical engineering challenges in modern astronomicalinstruments, focusing on stray light contamination, optical misalignments, and design limitations that affect the performance of space-based and balloon-borne telescopes. These challenges hinder the precision of measurements critical for scientific discovery, and this work presents novel solutions to optimize instrument performance. In Chapter 2, we focus on re-aligning the FIREBall-2 spectrograph, a NASA/CNES balloon-borne telescope designed to study the circumgalactic medium. During its first flight, optical misalignments led to suboptimal resolution, with spatial resolution degrading to 7′′ and spectral resolution to 1300. Post-flight evaluation revealed significant misalignments of optical elements beyond tolerance. We detail a re-alignment procedure that uses Computer-Generated Holograms (CGHs) with a Zygo interferometer to achieve precise alignment of the focal corrector system, resulting in improved performance in the 2023 re-flight. Chapter 3 addresses stray light contamination in the Aspera SmallSat mission, a NASA-funded project aimed at studying galaxy evolution by detecting diffuse O VI emission at 103.2 nm. Stray light degrades the signal-to-noise ratio in spectroscopic observations of galaxy halos. To mitigate this, a two-stage baffle design is proposed, featuring optimized vane geometries and strategically placed shared baffles coated with Acktar Magic Black. Simulation results show that this design effectively meets the mission’s stringent stray light suppression requirements. A third study in Chapter 4 investigates the performance of a dual-ruled grating spectrometer as part of the Spatial Heterodyne Extreme Ultraviolet Interferometer (SHEUVI) project. SHEUVI is a wide-field, all-reflective spatial heterodyne spectrometer that utilizes a single, dual-ruling grating to diffract incoming normal-incidence light into symmetric orders, thereby generating a dispersion-based interference pattern on a detector. Designed to operate at wavelengths below the transmissive optics cutoff (approximately 105 nm), this innovative design minimizes optical path differences by producing both interfering beams from the same grating location. Experimental characterization of the 800 gr/mm ruling, optimized for approximately 590 nm at m = ±1 with a symmetric blaze angle of 13.8, confirms the grating’s effectiveness in isolating and sampling discrete passbands. In conclusion, Chapter 5 of this dissertation presents solutions to common optical challenges including stray light suppression, optical alignment, and diffraction efficiency, that affect astronomical instruments. These contributions enhance the performance of current space missions and provide valuable insights for optimizing the design of future telescopes.