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Proceedings Paper

Production of 8.4m segments for the Giant Magellan Telescope
Author(s): H. M. Martin; R. G. Allen; J. H. Burge; D. W. Kim; J. S. Kingsley; K. Law; R. D. Lutz; P. A. Strittmatter; P. Su; M. T. Tuell; S. C. West; P. Zhou
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Paper Abstract

Production of segments for the Giant Magellan Telescope is well underway at the Steward Observatory Mirror Lab. We report on the completion of the first 8.4 m off-axis segment, the casting of the second segment, and preparations for manufacture of the remaining segments. The complete set of infrastructure for serial production is in place, including the casting furnace, two 8.4 m capacity grinding and polishing machines, and a 28 m test tower that incorporates four independent measurement systems. The first segment, with 14 mm p-v aspheric departure, is by some measures the most challenging astronomical mirror ever made. Its manufacture took longer than expected, but the result is an excellent figure and demonstration of valuable new systems that will support both fabrication and measurement of the remaining segments. Polishing was done with a 1.2 m stressed lap for smoothing and large-scale figuring, and a series of smaller passive rigid-conformal laps for deterministic figuring on smaller scales. The interferometric measurement produces a null wavefront with a 3-element asymmetric null corrector including a 3.8 m spherical mirror and a computer-generated hologram. In addition to this test, we relied heavily on the new SCOTS slope test with its high accuracy and dynamic range. Evaluation of the measured figure includes simulated active correction using both the 160-actuator mirror support and the alignment degrees of freedom for the off-axis segment.

Paper Details

Date Published: 13 September 2012
PDF: 15 pages
Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84502D (13 September 2012); doi: 10.1117/12.926347
Show Author Affiliations
H. M. Martin, Steward Observatory, The Univ. of Arizona (United States)
R. G. Allen, Steward Observatory, The Univ. of Arizona (United States)
J. H. Burge, Steward Observatory and College of Optical Sciences, The Univ. of Arizona (United States)
D. W. Kim, College of Optical Sciences, The Univ. of Arizona (United States)
J. S. Kingsley, Steward Observatory, The Univ. of Arizona (United States)
K. Law, Steward Observatory, The Univ. of Arizona (United States)
R. D. Lutz, Steward Observatory, The Univ. of Arizona (United States)
P. A. Strittmatter, Steward Observatory, The Univ. of Arizona (United States)
P. Su, College of Optical Sciences, The Univ. of Arizona (United States)
M. T. Tuell, Steward Observatory, The Univ. of Arizona (United States)
S. C. West, Steward Observatory, The Univ. of Arizona (United States)
P. Zhou, College of Optical Sciences, The Univ. of Arizona (United States)


Published in SPIE Proceedings Vol. 8450:
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II
Ramón Navarro; Colin R. Cunningham; Eric Prieto, Editor(s)

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