Alignment and use of the optical test for the 8.4 m off-axis primary mirrors of the Giant Magellan Telescope
S. C. West, J. H. Burge, B. Cuerden, W. Davison, J. Hagen, H. M. Martin, M. T. Tuell, C. Zhao, T. Zobrist
The Giant Magellan Telescope has a 25 meter f/0.7 near-parabolic primary mirror constructed from seven 8.4 meter diameter segments. Several aspects of the interferometric optical test used to guide polishing of the six off-axis segments go beyond the demonstrated state of the art in optical testing. The null corrector is created from two obliquelyilluminated spherical mirrors combined with a computer-generated hologram (the measurement hologram). The larger mirror is 3.75 m in diameter and is supported at the top of a test tower, 23.5 m above the GMT segment. Its size rules out a direct validation of the wavefront produced by the null corrector. We can, however, use a reference hologram placed at an intermediate focus between the two spherical mirrors to measure the wavefront produced by the measurement hologram and the first mirror. This reference hologram is aligned to match the wavefront and thereby becomes the alignment reference for the rest of the system. The position and orientation of the reference hologram, the 3.75 m mirror and the GMT segment are measured with a dedicated laser tracker, leading to an alignment accuracy of about 100 microns over the 24 m dimensions of the test. In addition to the interferometer that measures the GMT segment, a separate interferometer at the center of curvature of the 3.75 m sphere monitors its figure simultaneously with the GMT measurement, allowing active correction and compensation for residual errors. We describe the details of the design, alignment, and use of this unique off-axis optical test.
Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation
Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation - San Diego, CA, United States
Duration: Jun 27 2010 → Jul 2 2010
Aspheres
Null lens
Optical alignment
Optical testing
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Telescope Mathematics 100%
Hologram Mathematics 91%
Holograms Engineering & Materials Science 91%
Telescopes Engineering & Materials Science 78%
Alignment Mathematics 77%
Polishing Chemical Compounds 77%
Mirror Mathematics 74%
Sphere Chemical Compounds 56%
West, S. C., Burge, J. H., Cuerden, B., Davison, W., Hagen, J., Martin, H. M., Tuell, M. T., Zhao, C., & Zobrist, T. (2010). Alignment and use of the optical test for the 8.4 m off-axis primary mirrors of the Giant Magellan Telescope. In Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation [77390N] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 7739). https://doi.org/10.1117/12.857251
Alignment and use of the optical test for the 8.4 m off-axis primary mirrors of the Giant Magellan Telescope. / West, S. C.; Burge, J. H.; Cuerden, B. et al.
Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation. 2010. 77390N (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 7739).
West, SC, Burge, JH, Cuerden, B, Davison, W, Hagen, J, Martin, HM, Tuell, MT, Zhao, C & Zobrist, T 2010, Alignment and use of the optical test for the 8.4 m off-axis primary mirrors of the Giant Magellan Telescope. in Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation., 77390N, Proceedings of SPIE - The International Society for Optical Engineering, vol. 7739, Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation, San Diego, CA, United States, 6/27/10. https://doi.org/10.1117/12.857251
West SC, Burge JH, Cuerden B, Davison W, Hagen J, Martin HM et al. Alignment and use of the optical test for the 8.4 m off-axis primary mirrors of the Giant Magellan Telescope. In Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation. 2010. 77390N. (Proceedings of SPIE - The International Society for Optical Engineering). doi: 10.1117/12.857251
West, S. C. ; Burge, J. H. ; Cuerden, B. et al. / Alignment and use of the optical test for the 8.4 m off-axis primary mirrors of the Giant Magellan Telescope. Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation. 2010. (Proceedings of SPIE - The International Society for Optical Engineering).
@inproceedings{e4678ce6d42b417ab040eff2aded588b,
title = "Alignment and use of the optical test for the 8.4 m off-axis primary mirrors of the Giant Magellan Telescope",
abstract = "The Giant Magellan Telescope has a 25 meter f/0.7 near-parabolic primary mirror constructed from seven 8.4 meter diameter segments. Several aspects of the interferometric optical test used to guide polishing of the six off-axis segments go beyond the demonstrated state of the art in optical testing. The null corrector is created from two obliquelyilluminated spherical mirrors combined with a computer-generated hologram (the measurement hologram). The larger mirror is 3.75 m in diameter and is supported at the top of a test tower, 23.5 m above the GMT segment. Its size rules out a direct validation of the wavefront produced by the null corrector. We can, however, use a reference hologram placed at an intermediate focus between the two spherical mirrors to measure the wavefront produced by the measurement hologram and the first mirror. This reference hologram is aligned to match the wavefront and thereby becomes the alignment reference for the rest of the system. The position and orientation of the reference hologram, the 3.75 m mirror and the GMT segment are measured with a dedicated laser tracker, leading to an alignment accuracy of about 100 microns over the 24 m dimensions of the test. In addition to the interferometer that measures the GMT segment, a separate interferometer at the center of curvature of the 3.75 m sphere monitors its figure simultaneously with the GMT measurement, allowing active correction and compensation for residual errors. We describe the details of the design, alignment, and use of this unique off-axis optical test.",
keywords = "Aspheres, Interferometry, Null lens, Optical alignment, Optical testing, Telescopes",
author = "West, {S. C.} and Burge, {J. H.} and B. Cuerden and W. Davison and J. Hagen and Martin, {H. M.} and Tuell, {M. T.} and C. Zhao and T. Zobrist",
booktitle = "Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation",
note = "Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation ; Conference date: 27-06-2010 Through 02-07-2010",
T1 - Alignment and use of the optical test for the 8.4 m off-axis primary mirrors of the Giant Magellan Telescope
AU - West, S. C.
AU - Burge, J. H.
AU - Cuerden, B.
AU - Davison, W.
AU - Hagen, J.
AU - Martin, H. M.
AU - Tuell, M. T.
AU - Zhao, C.
AU - Zobrist, T.
N2 - The Giant Magellan Telescope has a 25 meter f/0.7 near-parabolic primary mirror constructed from seven 8.4 meter diameter segments. Several aspects of the interferometric optical test used to guide polishing of the six off-axis segments go beyond the demonstrated state of the art in optical testing. The null corrector is created from two obliquelyilluminated spherical mirrors combined with a computer-generated hologram (the measurement hologram). The larger mirror is 3.75 m in diameter and is supported at the top of a test tower, 23.5 m above the GMT segment. Its size rules out a direct validation of the wavefront produced by the null corrector. We can, however, use a reference hologram placed at an intermediate focus between the two spherical mirrors to measure the wavefront produced by the measurement hologram and the first mirror. This reference hologram is aligned to match the wavefront and thereby becomes the alignment reference for the rest of the system. The position and orientation of the reference hologram, the 3.75 m mirror and the GMT segment are measured with a dedicated laser tracker, leading to an alignment accuracy of about 100 microns over the 24 m dimensions of the test. In addition to the interferometer that measures the GMT segment, a separate interferometer at the center of curvature of the 3.75 m sphere monitors its figure simultaneously with the GMT measurement, allowing active correction and compensation for residual errors. We describe the details of the design, alignment, and use of this unique off-axis optical test.
AB - The Giant Magellan Telescope has a 25 meter f/0.7 near-parabolic primary mirror constructed from seven 8.4 meter diameter segments. Several aspects of the interferometric optical test used to guide polishing of the six off-axis segments go beyond the demonstrated state of the art in optical testing. The null corrector is created from two obliquelyilluminated spherical mirrors combined with a computer-generated hologram (the measurement hologram). The larger mirror is 3.75 m in diameter and is supported at the top of a test tower, 23.5 m above the GMT segment. Its size rules out a direct validation of the wavefront produced by the null corrector. We can, however, use a reference hologram placed at an intermediate focus between the two spherical mirrors to measure the wavefront produced by the measurement hologram and the first mirror. This reference hologram is aligned to match the wavefront and thereby becomes the alignment reference for the rest of the system. The position and orientation of the reference hologram, the 3.75 m mirror and the GMT segment are measured with a dedicated laser tracker, leading to an alignment accuracy of about 100 microns over the 24 m dimensions of the test. In addition to the interferometer that measures the GMT segment, a separate interferometer at the center of curvature of the 3.75 m sphere monitors its figure simultaneously with the GMT measurement, allowing active correction and compensation for residual errors. We describe the details of the design, alignment, and use of this unique off-axis optical test.
KW - Aspheres
KW - Interferometry
KW - Null lens
KW - Optical alignment
KW - Optical testing
KW - Telescopes
BT - Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation
T2 - Modern Technologies in Space- and Ground-Based Telescopes and Instrumentation
Y2 - 27 June 2010 through 2 July 2010