Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories
| Autor: | Israel Blanchard, Fernando Selman, Yara L. Jaffé, Pierre-Yves Madec, Frédéric P. A. Vogt, Julien Milli, Pascale Hibon, Wolfgang Hackenberg, Johann Kolb, Ivan Aranda, Marcela Espinoza Contreras, Domenico Bonaccini Calia, Harald Kuntschner, Cyrielle Opitom, Jonathan Smoker, Mauro Comin, Linda Schmidtobreik |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
QC1-999
General Physics and Astronomy FOS: Physical sciences Physics::Optics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences law.invention 010309 optics Telescope Primary mirror Integral field spectrograph law Observatory 0103 physical sciences Extremely Large Telescope Astrophysics::Solar and Stellar Astrophysics 010303 astronomy & astrophysics Spectrograph Instrumentation and Methods for Astrophysics (astro-ph.IM) Astrophysics::Galaxy Astrophysics Physics Very Large Telescope Astrophysics::Instrumentation and Methods for Astrophysics Astronomy Physics - Atmospheric and Oceanic Physics Laser guide star Atmospheric and Oceanic Physics (physics.ao-ph) Astrophysics::Earth and Planetary Astrophysics Astrophysics - Instrumentation and Methods for Astrophysics |
| Zdroj: | Physical Review X, Vol 7, Iss 2, p 021044 (2017) |
| ISSN: | 2160-3308 |
| Popis: | (Abr.) Laser guide stars employed at astronomical observatories provide artificial wavefront reference sources to help correct (in part) the impact of atmospheric turbulence on astrophysical observations. Following the recent commissioning of the 4 Laser Guide Star Facility (4LGSF) on UT4 at the VLT, we characterize the spectral signature of the uplink beams from the 22W lasers to assess the impact of laser scattering from the 4LGSF on science observations. We use the MUSE optical integral field spectrograph to acquire spectra at a resolution of R~3000 of the uplink laser beams over the wavelength range of 4750\AA\ to 9350\AA. We report the first detection of laser-induced Raman scattering by N2, O2, CO2, H2O and (tentatively) CH4 molecules in the atmosphere above the astronomical observatory of Cerro Paranal. In particular, our observations reveal the characteristic spectral signature of laser photons -- but 480\AA\ to 2210\AA\ redder than the original laser wavelength of 5889.959\AA\ -- landing on the 8.2m primary mirror of UT4 after being Raman-scattered on their way up to the sodium layer. Laser-induced Raman scattering is not unique to the observatory of Cerro Paranal, but common to any astronomical telescope employing a laser-guide-star (LGS) system. It is thus essential for any optical spectrograph coupled to a LGS system to handle thoroughly the possibility of a Raman spectral contamination via a proper baffling of the instrument and suitable calibrations procedures. These considerations are particularly applicable for the HARMONI optical spectrograph on the upcoming Extremely Large Telescope. At sites hosting multiple telescopes, laser collision prediction tools also ought to account for the presence of Raman emission from the uplink laser beam(s) to avoid the unintentional contamination of observations acquired with telescopes in the vicinity of a LGS system. Comment: 17 pages, 11 figures, published in Physical Review X. v2: Fixed typo in Eq. 9 and y-labels in Fig. 6 |
| Databáze: | OpenAIRE |
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