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Optical alignment of contamination-sensitive Far-Ultraviolet spectrographs for Aspera SmallSat mission
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Optical alignment of contamination-sensitive Far-Ultraviolet spectrographs for Aspera SmallSat mission

Aafaque R Khan, Erika Hamden, Haeun Chung, Heejoo Choi, Daewook Kim, Nicole Melso, Keri Hoadley, Carlos J Vargas, Daniel Truong, Elijah Garcia, …
arXiv.org
07/22/2024
DOI: 10.48550/arxiv.2407.15391
url
https://doi.org/10.48550/arxiv.2407.15391View
Preprint (Author's original)This preprint has not been evaluated by subject experts through peer review. Preprints may undergo extensive changes and/or become peer-reviewed journal articles. Open Access

Abstract

Aspera is a NASA Astrophysics Pioneers SmallSat mission designed to study diffuse OVI emission from the warm-hot phase gas in the halos of nearby galaxies. Its payload consists of two identical Rowland Circle-type long-slit spectrographs, sharing a single MicroChannel plate detector. Each spectrograph channel consists of an off-axis parabola primary mirror and a toroidal diffraction grating optimized for the 1013-1057 Angstroms bandpass. Despite the simple configuration, the optical alignment/integration process for Aspera is challenging due to tight optical alignment tolerances, driven by the compact form factor, and the contamination sensitivity of the Far-Ultraviolet optics and detectors. In this paper, we discuss implementing a novel multi-phase approach to meet these requirements using state-of-the-art optical metrology tools. For coarsely positioning the optics we use a blue-laser 3D scanner while the fine alignment is done with a Zygo interferometer and a custom computer-generated hologram. The detector focus requires iterative in-vacuum alignment using a Vacuum UV collimator. The alignment is done in a controlled cleanroom facility at the University of Arizona.
Physics - Instrumentation and Detectors Physics - Instrumentation and Methods for Astrophysics Physics - Optics

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