1. Raman-scattered laser guide-star photons to monitor the scatter of astronomical telescope mirrors
- Author
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Frédéric P. A. Vogt, Cyrielle Opitom, Gérard Zins, Ronald Holzlöhner, Harald Kuntschner, Marcela Espinoza Contreras, Cristian Romero, Claudia Cid, Diego Parraguez, Pierre Bourget, George Hau, Linda Schmidtobreick, Jonathan Smoker, Jose Luis Alvarez, Steffen Mieske, Mauro Comin, Ivan Aranda, Wolfgang Hackenberg, Domenico Bonaccini Calia, Israel Blanchard, Pascale Hibon, Yara L. Jaffé, Pierre-Yves Madec, Susana Cerda, Julien Milli, Johann Kolb, Fernando Selman, Sergio Vera Urrutia, and Callum Bellhouse
- Subjects
Photon ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,law.invention ,010309 optics ,Telescope ,symbols.namesake ,Integral field spectrograph ,Optics ,Primary (astronomy) ,law ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Physics ,Very Large Telescope ,business.industry ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Laser ,Laser guide star ,Space and Planetary Science ,symbols ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics ,Raman spectroscopy ,business - Abstract
The first observations of laser guide star photons Raman-scattered by air molecules above the Very Large Telescope (VLT) were reported in June 2017. The initial detection came from the Multi-Unit Spectroscopic Explorer (MUSE) optical integral field spectrograph, following the installation of the 4 Laser Guide Star Facility (4LGSF) on the Unit Telescope 4 (UT4) of the VLT. In this Letter, we delve further into the symbiotic relationship between the 4LGSF laser guide star system, the UT4 telescope, and MUSE by monitoring the spectral contamination of MUSE observations by Raman photons over a 27 month period. This dataset reveals that dust particles deposited on the primary and tertiary mirrors of UT4 -- responsible for a reflectivity loss of ~8% at 6000{\AA} -- contribute (60$\pm5)% to the laser line fluxes detected by MUSE. The flux of Raman lines, contaminating scientific observations acquired with optical spectrographs, thus provides a new, non-invasive means to monitor the evolving scatter properties of the mirrors of astronomical telescopes equipped with laser guide star systems., Comment: 5 pages, 3 figures, 1 table, accepted for publication in A&A Letters
- Published
- 2018
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