Predictive thermal control (PTC) technology to enable thermally stable telescopes: first two year status

The Predictive Thermal Control Technology (PTCT) development project is a multiyear effort initiated in Fiscal Year (FY) 2017, to mature the Technology Readiness Level (TRL) of critical technologies required to enable ultra-thermallystable ultraviolet/optical/infrared (UVOIR) space telescope primary-mirror assemblies for ultra-high-contrast observations of exoplanets. Key accomplishments of 2017 to 2019 include: creating a high-fidelity STOP model of the AMTD-2 1.5-m Ultra-Low Expansion (ULE®) mirror (manufactured by Harris Corp) by merging 3D X-Ray computed tomography data of the ‘as-built’ mirror and coefficient of thermal expansion (CTE) data maps for each of the 18 core elements; partially validating this model by measuring the mirror’s response to bulk temperature changes and lateral thermal gradients; designed and built (with PTC partner Harris Corp) a 1.5-m enclosure with 26 actively-control thermal zones; and defined specifications for a potential 4-m primary mirror thermal enclosure for the Habitable Exoplanet (HabEx) Imager mission.

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