Rolled edges and phasing of segmented telescopes presentation (original) (raw)

AI-generated Abstract

This work investigates the impact of rolled edges in the polishing process on the performance of segmented telescopes. It presents models for edge profiles influenced by polishing techniques, aiming to optimize image formation by managing edge behaviors. The findings suggest that controlled adjustments to edge profiles are critical in enhancing the operational efficiency of segmented telescopes.

Manufacture of 8.4-m off-axis segments: a 1/5-scale demonstration

Optical Fabrication, Metrology, and Material Advancements for Telescopes, 2004

We describe the requirements for manufacturing and maintaining alignment of the 8.4 m off-axis segments of the Giant Magellan Telescope's primary mirror, and a demonstration of the manufacturing techniques on the 1.7 m off-axis primary mirror of the New Solar Telescope. This mirror is approximately a 1/5 scale model of a GMT segment. We show that the stressed lap polishing system developed for highly aspheric primary and secondary mirrors is capable of figuring the GMT segments and the NST mirror. We describe an optical test with a null corrector consisting of a tilted spherical mirror and a computer-generated hologram, and derive accuracy requirements for the test. The criterion for accuracy of low-order aberrations is that the active support system can correct any figure errors due to the laboratory measurement, with acceptably small forces and residual errors.

New results from the Precessions polishing process scaled to larger sizes

Optical Fabrication, Metrology, and Material Advancements for Telescopes, 2004

The Precessions process uses an inflated membrane-tool that delivers near-Gaussian polishing spots. The tool-motion over the part can be constructed to preserve an aspheric form whilst removing damage from preceding processes, or control the form through a tool-path prescribed by numerical optimization. The process has previously been validated on surfaces up to 200mm diameter and used extensively in industrial environments. In this paper we report the first trials on a substantially larger part -a 500mm diameter f/1 ellipsoidal mirror -as part of the UK's technology-development for Extremely Large Telescopes. We draw attention to subtle problems that have arisen along the way. We also report on developing the process for free-form surfaces, in contrast to the axially-symmetric parts worked hitherto. The paper concludes with an assessment of the lessons learnt from the experiments, as they may impact on realization in a practical ELT segment fabrication facility.

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