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  • Print publication year: 2016
  • Online publication date: December 2016

5 - Active Optics, Adaptive Optics and Other Technical Innovations

from Part 1 - Optical Observatories

Summary

Active Optics

Active optics is usually understood to refer to a low frequency control system applied to the primary mirror of large reflecting telescopes. It corrects for optical aberrations like spherical aberration and astigmatism either detected in the initial set-up of the telescope or caused by flexure of the mirror as the telescope's orientation is changed or its temperature varies. To make the corrections an active optics system detects errors in the mirror's surface shape either directly or via its effect on astronomical images and corrects them using a motorised support system under the mirror. The mirror can be either monolithic, in which case the flexure function has no discontinuities, or segmented where the flexure function is discontinuous.

The first significant step on the road to designing an active optics system appears to have been taken by André Couder in 1931 when he suggested that the astigmatism of inadequately supported mirrors could be corrected by applying appropriate forces to the back of the mirror. Astigmatism left over after mirror manufacture could also be corrected in this way. But he could only measure the astigmatism qualitatively off-line making such corrections cumbersome and slow. As a result his suggested procedure was limited to the initial setting up of the telescope, rather than being applied continuously as in a modern active optics system. Independently Dmitri Maksutov appears to have come up with a broadly similar proposal in 1948, but it had the same limitations.

Technological developments in computer and sensor systems after the Second World War began to make it possible to design much more sophisticated active optics systems. In the event the first major telescope to use a form of active optics was the Multiple Mirror Telescope (MMT) which consisted of six identical 1.8 m telescopes on a common mount. The MMT was designed to bring all six images to a common focus on its central axis. It was planned to continuously monitor the flexure of the structures of the six individual telescopes using an internal laser system, and to correct them in real time to ensure that all six images coincided.

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1. Parker, Barry, Stairway to the Stars; The Story of the World's Largest Observatory, Perseus Publishing, 1994, pp. 79–81.
2. Wilson, R., Progress on the 3.5 m ‘New Technology Telescope’ (NTT), ESO Messenger, No. 29, September 1982, pp. 24–27.
3. Wilson, R. N., et al., Active Optics: the NTT and the Future, ESO Messenger, No. 53, September 1988, pp. 1–7.
4. Noethe, L., Active optics II. Results of an experiment with a thin 1 m test mirror, Journal of Modern Optics, 35, No. 9, 1988, pp. 1427–1457.
5. Babcock, H. W., The Possibility of Compensating Astronomical Seeing, Publications of the Astronomical Society of the Pacific, 65, October 1953, pp. 229–236.
6. Duffner, Robert W., The Adaptive Optics Revolution; A History, University of New Mexico Press, 2009.
7. Zirker, J. B., An Acre of Glass; A History and Forecast of the Telescope, Johns Hopkins University Press, 2005, pp. 202–203.
8. Merkle, F., et al., The Messenger, No. 58, December 1989, pp. 1–4.
9. Rousset, G., et al., First Diffraction-limited Astronomical Images with Adaptive Optics, Astronomy and Astrophysics, 230, 1990, pp. L29–L32.
10. Rigaut, F., et al., Adaptive Optics on a 3.6-m telescope: Results and Performance, Astronomy and Astrophysics, 250, 1991, pp. 280–290.
11. Rigaut, F., et al., Performance of the Canada-France-Hawaii Telescope Adaptive Optics Bonnette, Publications of the Astronomical Society of the Pacific, 110, No. 744, February 1998, pp. 152–164.
12. Foy, R., and Labeyrie, A., Feasibility of Adaptive Telescope with Laser Probe, Astronomy and Astrophysics, 152, 1985, pp. L29–L31.
13. Wilson, R. N., Reflecting Telescope Optics II; Manufacture, Testing, Alignment, Modern Techniques, Springer-Verlag, Corrected Second Printing, 2001, p. 416.
14. McCray, W. Patrick, Giant Telescopes: Astronomical Ambition and the Promise of Technology, Harvard University Press, 2004, p. 158.
15. Beckers, Jacques M., Multiconjugate Adaptive Optics: Experiments in Atmospheric Tomography, Proc. SPIE 4007, 1056, March 2000.
16. Ragazzoni, Roberto, et al., Adaptive-optics Corrections Available for the Whole Sky, Nature, 403, January 2000, pp. 54–56.
17. Langlois, Maud, et al., Solar Multiconjugate Adaptive Optics at the Dunn Solar Telescope: Preliminary Results, Proc. SPIE, 5490, October 2004, p. 59.
18. Berkefeld, Thomas, Soltau, Dirk, and von der Luehe, Oskar, Results of the Multi-conjugate Adaptive Optics System at the German Solar Telescope, Tenerife, Proc. SPIE, 5903, September 2005.
19. Marchetti, Enrico, et al., On-sky Testing of the Multi-Conjugate Adaptive Optics Demonstrator, The Messenger, No. 129, September 2007, pp. 8–13.
20. Neichel, B., et al., The Gemini MCAO System GeMS: Nearing the End of the Lab-story, Proc. SPIE, 7736, July 2010.
21. Neichel, Benoit, et al., Science Readiness of the Gemini MCAO system: GeMS, Proc. SPIE, 8447, September 2012.
22. Brusa, Guido, et al., MMT Adaptive Secondary: First AO Closed-loop Results, Proc. SPIE, 5169, December 2003.
23. Davies, Richard, and Kasper, Markus, Adaptive Optics for Astronomy, Annual Reviews of Astronomy and Astrophysics, 50, 2012, pp. 309–310.
24. Esposito, S., et al., Large Binocular Telescope Adaptive Optics System: New Achievements and Perspectives in Adaptive Optics, Proc. SPIE, 8149, September 2011.
25. Arsenault, Robin, et al., Delivery of the Second Generation VLT Secondary Mirror (M2) Unit to ESO, The Messenger, No. 151, March 2013, pp. 14–19.
26. Ioannisiani, Bagrat K. (Rodman, Richard, B., trans.), The Soviet 6-meter Altazimuth Reflector, Sky and Telescope, November 1977, pp. 356–362.
27. Keel, William C., Galaxies Though a Red Giant, Sky and Telescope, June 1992, pp. 626–627 and 630–632.
28. Learner, Richard, The Legacy of the 200-inch, Sky and Telescope, April 1986, pp. 349–353.
29. Weymann, R. J., and Carlton, N. P., The Multiple-Mirror Telescope Project, Sky and Telescope, September 1972, pp. 159–163.
30. Weekes, T. C. (ed.), The MMT and the Future of Ground-Based Astronomy, Smithsonian Astrophysical Observatory Special Report 385, 1979.
31. Boksenberg, A., The William Herschel Telescope, Vistas in Astronomy, 28, 1985, pp. 531–553.
32. Janesick, James R., Scientific Charge-Coupled Devices, SPIE Publications, 2001.
33. Janesick, James, Sky on a Chip: The Fabulous CCD, Sky and Telescope, September 1987, pp. 238–242.
34. Smith, Robert W., The Space Telescope: A Study of NASA, Science, Technology, and Politics, Cambridge University Press, 1989, p. 251.