Thermal Design and Analysis of a Passively Cooled, Low Temperature Cryogenic Astrophysical Observatory in Low Earth Orbit
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| 出版年: | ProQuest Dissertations and Theses (2025) |
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ProQuest Dissertations & Theses
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| オンライン･アクセス: | Citation/Abstract Full Text - PDF |
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| 245 | 1 | |a Thermal Design and Analysis of a Passively Cooled, Low Temperature Cryogenic Astrophysical Observatory in Low Earth Orbit | |
| 260 | |b ProQuest Dissertations & Theses |c 2025 | ||
| 513 | |a Dissertation/Thesis | ||
| 520 | 3 | |a The Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) is a NASA Medium-class Explorer mission conducting a 26-month all-sky survey from low Earth orbit. This dissertation documents the development, correlation, and on-orbit performance of SPHEREx’s passive cryogenic thermal system. The work begins with detailed modelling of key thermophysical and thermo-optical properties of the payload, including honeycomb photon shields, V-grooves, and detector harnessing. Temperature- and wavelength-dependent emissivity, ice contamination effects, and optical constants of coatings are incorporated through a combination of literature data, first-principles derivations, and custom MATLAB tools. Ground testing of subcomponents, composite conductance, paint emissivity, and detector power dissipation provide anchor points for model calibration.A comprehensive Thermal Desktop® model was developed with Monte-Carlo radiation analysis, environmental load estimators, and sensitivity studies covering emissivity, specularity, transmissivity, tip-over angle, and structural support geometry. Novel tools were created to translate spacecraft attitude into environmental heat-load predictions, enabling rapid assessment of seasonal trends and pointing maneuvers. On-orbit telemetry collected since the successful launch in March 2025 demonstrates that the MWIR and SWIR focal plane assemblies reached their 45 K and 62 K setpoints faster than predicted (13 days versus 13.7 days) and have maintained stable control with margins exceeding 150 % relative to requirement temperatures. Model correlation with in-flight data reduced discrepancies in stage loads to below 5–10 %, validated contamination-control strategies, and identified likely mechanisms for gradual emissivity changes such as UV darkening and ice accumulation.Beyond verifying SPHEREx’s thermal performance, the methods employed in this work are transferable to future cryogenic missions, including fundamental optical properties and ice emissivity, contamination management, and automated environmental-load mapping from flight telemetry. Together these techniques expand what is considered feasible for entirely passive cryogenic cooling in low Earth orbit and provide a roadmap for designing, testing, and correlating next-generation space observatories. | |
| 653 | |a Aerospace engineering | ||
| 653 | |a Thermodynamics | ||
| 653 | |a Mechanical engineering | ||
| 773 | 0 | |t ProQuest Dissertations and Theses |g (2025) | |
| 786 | 0 | |d ProQuest |t ProQuest Dissertations & Theses Global | |
| 856 | 4 | 1 | |3 Citation/Abstract |u https://www.proquest.com/docview/3262144422/abstract/embedded/7BTGNMKEMPT1V9Z2?source=fedsrch |
| 856 | 4 | 0 | |3 Full Text - PDF |u https://www.proquest.com/docview/3262144422/fulltextPDF/embedded/7BTGNMKEMPT1V9Z2?source=fedsrch |