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Torben Anderssen. Profile picture.

Torben Andersen

Professor emeritus (Leave of Absence)

Torben Anderssen. Profile picture.

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

Author

  • Jacques M. Beckers
  • Mette Owner-Petersen
  • Torben Andersen

Editor

  • Arne L. Ardeberg
  • Torben Andersen

Summary, in English

To obtain full sky coverage, astronomical adaptive optics systemsrequire Na Sodium Beacons (SBs) (also referred to as Laser Guide Starsor LGSs) located at heights extending from 85 to 100 km. When viewed atthe edge of large telescopes these SBs appear elongated. For the Euro5050 meter aperture telecopes this elongation amounts to 6 to 9 arcsecondswhen the laser is launched from a point on the telescope axis. This issubstantially larger than the -0.6 arcsec FWHM SB when viewed near thetelescope center. This so-called "perspective elongation" substantiallydecreases the sensitivity of SB aided adaptive optics. We describe a wayof removing this elongation when using pulsed lasers. It uses rapid(microsecond) refocusing of the telescope with the aid of birefringentlenses and polarization modulators. We present an outline of the SBwavefront sensor for the Euro50.

Department/s

  • Lund Observatory - Has been reorganised

Publishing year

2004

Language

English

Pages

510-519

Publication/Series

Proceedings of the SPIE

Volume

5382

Document type

Conference paper

Publisher

SPIE

Topic

  • Astronomy, Astrophysics and Cosmology

Conference name

Second Backaskog Workshop on Extremely Large Telescopes

Conference date

0001-01-02

Status

Published

ISBN/ISSN/Other

  • ISBN: 0-8194-5299-8