Wavefront Sensor for High Speed Adaptive Optics based Astronomy

As previously mentioned in Introduction to Astronomical Adaptive Optics, the Adaptive optic approach is a powerful tool for minimising the distortions caused by Atmospheric turbulence.

The Shack-Hartmann based Wavefront sensor approach can be seen at The Center for High Angular Resolution Astronomy (CHARA) Array, [2, 3] at the Mount Wilson Observatory. See Figure 1 & 2. The Chara Array is a IR and Near Infrared telescope system comprising of 6 optically connected telescopes, each fitted with an EMCCD (Andor iXon Ultra) based AO system which operates at 1000 frames per second (set up using a 90 x 90 pixel ROI).

Figure 1. Shack Hartmann Adaptive Optic setup at the Chara Array [4]

And alternative AO implementations can be found at The Large Binocular Telescope which utilises a Laser based guide Star, adaptive secondary mirror with 672 actuators and Andor Zyla sCMOS camera operating at 1 kHz (200 x 200 Pixels). [5,6]

The Raven AO system utilises 5 EMCCD cameras and used multiple objects in a field of view to perform Multi-object correction over a very large image plane.[8,9]

Table 1 Shows a broad range of Adaptive Optic systems and the telescopes where they are based.

Figure 2. Top left: short exposure (1 ms) PSF of GLIESE 777. Top right: long exposure (5 s) PSF of GLIESE 777. Bottom: radial profile of both short (dashed line) and long (blue continuous line) exposure PSFs. [7]

Table 1, A list of Innovative Adaptive Optic systems.
1 Chara Array Mt Wilson Observatory, CA iXon 897 EMCCD
2 Large Binocular Telescope Mt Graham International Observatory, AZ Zyla sCMOS
3 Multi-Object Adaptive Optics (MOAO) Subaru Telescope, Hawaii 5 x Zyla
4 The portable adaptive optics System Various iXon 897 EMCCD
5 The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument - VAMPIRES Subaru Telescope, Hawaii iXon 897 EMCCD
6 Robo AO Palomar Observatory, CA iXon 888 EMCCD
7 Fastcam William Herschel Telescope, Canary Islands, Spain iXon 897 EMCCD
8 Anglo Australian Telescope AO Siding Spring Observatory, Australia Zyla sCMOS
9 Canary Moao William Herschel Telescope, Canary Islands, Spain iXon EMCCD
  1. 12 October 2009 / Vol. 17, No. 21 / OPTICS EXPRESS 18970
  2. T. A. ten Brummelaar, H. A. McAlister, S. T. Ridgway, W. G. Bagnuolo Jr., N. H. Turner, L. Sturmann, J. Sturmann, First results from the CHARA Array. II. A description of the instrument, Astrophys. J. 628, p. 453-465, 2005
  3. T. A. ten Brummelaar, H. A. McAlister, S. Ridgway, D. R. Gies, J. Sturmann, L. Sturmann, N. H. Turner, An update on the CHARA Array, Proc. SPIE 7013, p. 701308, 2008. doi:10.1117/12.788008
  4. http://www.physics.usyd.edu.au/~bnorris/QAstro2015_Talks/2015_08_Quantum_Talk_Theo.pdf
  5. F. Pedichini et al 2017 Astronomical Journal 154 74
  6. Astronomical Adaptive Optics Systems and Applications IV. Edited by Tyson, Robert K.; Hart, Michael. Proceedings of the SPIE, Volume 8149, pp. 814902-814902-10 (2011)
  7. http://iopscience.iop.org/article/10.3847/1538-3881/aa7ff3/meta
  8. http://web.uvic.ca/~ravenmoa/Docs/Andersen_AO4ELT2_2012.pdf
  9. http://web.uvic.ca/~ravenmoa/

Date: November 2018

Author: Dr Andrew Dennis

Category: Solution Note

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