Sodium beacon wavefront sensing for the Euro50 telescope in the presence of perspective elongation

Jacques Maurice Beckers; Mette Owner-Petersen; Torben E. Andersen

doi:10.1117/12.566229

7 July 2004 Sodium beacon wavefront sensing for the Euro50 telescope in the presence of perspective elongation

Jacques Maurice Beckers, Mette Owner-Petersen, Torben E. Andersen

Proceedings Volume 5382, Second Backaskog Workshop on Extremely Large Telescopes; (2004) https://doi.org/10.1117/12.566229
Event: Second Backaskog Workshop on Extremely Large Telescopes, 2003, Backaskog, Sweden

Abstract

To obtain full sky coverage, astronomical adaptive optics systems require Na Sodium Beacons (SBs) (also referred to as Laser Guide Stars or LGSs) located at heights extending from 85 to 100 km. When viewed at the edge of large telescopes these SBs appear elongated. For the Euro50 50 meter aperture telecopes this elongation amounts to 6 to 9 arcseconds when the laser is launched from a point on the telescope axis. This is substantially larger than the -0.6 arcsec FWHM SB when viewed near the telescope center. This so-called "perspective elongation" substantially decreases the sensitivity of SB aided adaptive optics. We describe a way of removing this elongation when using pulsed lasers. It uses rapid (microsecond) refocusing of the telescope with the aid of birefringent lenses and polarization modulators. We present an outline of the SB wavefront sensor for the Euro50.

Citation Download Citation

Jacques Maurice Beckers, Mette Owner-Petersen, and Torben E. Andersen "Sodium beacon wavefront sensing for the Euro50 telescope in the presence of perspective elongation", Proc. SPIE 5382, Second Backaskog Workshop on Extremely Large Telescopes, (7 July 2004); https://doi.org/10.1117/12.566229

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