Engineering topics
Publications and source records attributed to Stephen Cheney.
Gravity-sag (G-sag) for large space-based telescopes is a critical error budget element that must be taken in consideration. Absolute characterization of gravity sag provides necessary information when testing light weighted optics so that true optical performance can be determined. A method is presented for characterizing G-sag to obtain the 0-G optical surface.
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Characterizing Gravity-sag (G-sag) is an essential part of developing a large space-based optic. A method to back out gravity sag of a light-weighted optic using a CGH will be demonstrated. The results from the G-sag CGH determination is compared to the G-sag and Zero-G figure obtained during horizontal G-sag testing. The results from the CGH testing are also compared to the G-sag figure determined from modeling.
Gravity sag is the effect on optical surfaces due to gravity. Additionally, optics manufactured in a gravitational field are made with inherent stresses built in. When these optics are flown in space those stresses release. We call this effect gravity release or “G-release”. To characterize the 0-G shape of optics, theory provides two methods: n-rotation test and face-up/face-down test.
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The Habitable Worlds Observatory (HWO) is NASA’s next large space telescope, selected by the 2020 Decadal Survey in Astronomy and Astrophysics to search for and characterize habitable exoplanets while enabling a broad range of transformative astrophysics. In August 2024, the HWO Technology Maturation Project Office (TMPO) was formed to begin exploring the HWO science, technology, and mission architectures toward a Mission Concept Review (MCR) at the end of the decade. A primary deliverable of this effort is a technology development plan that identifies critical technologies that enable the mission, defines a process for assessing the readiness of those technologies, and outlines a strategy for developing those technologies to a Technology Readiness Level (TRL) of 5 before the MCR. In this paper we summarize the HWO technology development plan which comprises three “tracks”: Coronagraph System technologies, Ultra-stable Telescope System technologies, and High-sensitivity Ultraviolet and Visible Instrumentation technologies. Each track has completed an initial assessment of technology gaps, prioritized the gaps for investment, and laid out development roadmaps to mature candidate technologies to close those gaps.