fold sphere en · NOUN
Meanings
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A fold mirror that is a "sphere", i.e. a spherical mirror
Center of curvature for the 3.75-m fold sphere is accessible for in situ testing of this mirror.
2006 July, Burge et al., “Design and analysis for interferometric measurements of the GMT primary mirror segments”, in Proceedings of SPIE, volume 6273, →DOI, retrieved 27 Dec 2021, pages 62730M-5: