First light for the sodium laser guide star adaptive optics system on the Lijiang 1.8m telescope

Wei, Kai; Li, Min; Chen, Shan-Qiu; Yang, Bo; Chen, Feng; Zuo, Jun-Wei; Bian, Qi; Yao, Ji; Zhou, Luchun; Lin, Wei Yong; Chen, Donghong; Jin, Kai; Dai, Xiaolin; Fu, Han-Chu; Xu, Chang; Wang, Zhichao; Xue, Xuan; Chen, Xuewu; Qian, Xianmei; Zhou, Yu; Xian, Hao; Peng, Qinjun; Rao, Changhui; Xu, Zuyan; Zhang, Yudong

doi:10.1088/1674-4527/16/12/183

Cited by 7 publications

(5 citation statements)

References 12 publications

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“…LGSAO [6,7] Lijang 1.8-m Telescope LGS-AOS [65] Shane 3-m Telescope ShaneAO [66,67] Subaru AO188 [13,14] VLT (UT4) 4LGSF [16,20] VLT (UT4) PARLA [15] Thirty Meter Telescope…”

Section: Telescopementioning

confidence: 99%

Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories

et al. 2017

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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 the Unit Telescope 4 (UT4) of the Very Large Telescope (VLT), we characterize the spectral signature of the uplink beams from the 22 W lasers to assess the impact of laser scattering from the 4LGSF on science observations. We use the Multi-Unit Spectroscopic Explorer (MUSE) optical integral field spectrograph mounted on the Nasmyth B focus of UT4 to acquire spectra at a resolution of R ∼ =3000 of the uplink laser beams over the wavelength range of 4750Å → 9350Å. 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 480Å to 2210Å redder than the original laser wavelength of 5889.959Å -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, a phenomenon not usually discussed in the astronomical context, 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 (ELT). 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.Popular summary: Atmospheric turbulence strongly affects the sharpness of astronomical observations from the ground. Specially-equipped telescopes (and their associated instruments) can reduce this effect by directing lasers up into the sky, causing sodium atoms in the upper atmosphere to glow. Deformable mirrors can then use these "artificial guide stars" to help correct for the impact of turbulence on observations.Four such lasers were recently installed at the Very Large Telescope (VLT) at Cerro Paranal in Chile. For the first time, we characterized the astronomical consequences of laser-induced inelastic Raman scattering, a process through which the laser photons lose energy by exciting air molecules. This isa possible source of contamination for astrophysical observations, appearing in the data as complex groups of emission lines.We used the Multi-Unit Spectroscopic Explorer (MUSE) integral field spectrograph -an instrument that obtains a spectrum for each pixel of an image in a...

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“…LGSAO [6,7] Lijang 1.8-m Telescope LGS-AOS [65] Shane 3-m Telescope ShaneAO [66,67] Subaru AO188 [13,14] VLT (UT4) 4LGSF [16,20] VLT (UT4) PARLA [15] Thirty Meter Telescope…”

Section: Telescopementioning

confidence: 99%

Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories

et al. 2017

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“…The LLT has a field of view of ±2 5 and focuses the laser beam at 90 km ∼ 210 km. The total throughput of the LLT is about 90% (Wei et al 2016). The piezoelectric ceramic actuator is used to precisely change the placement angle and position of the high-reflection mirrors HR7, HR8, HR9, and HR10, to optimize the included angle and separation distance between the optical axes of the four laser beams, and to project them into the sky to form a laser guide star constellation.…”

Section: Laser Guide Star Facilitymentioning

confidence: 99%

First Sodium Laser Guide Star Asterism Launching Platform in China on the 1.8 m Telescope at Gaomeigu Observatory

Li¹,

Lu²,

Li³

et al. 2023

PASP

Self Cite

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The application of a sodium laser guide star is the key difference between a modern adaptive optics system and traditional adaptive optics system. Especially in system such as multiconjugate adaptive optics, a sodium laser guide star asterism that is formed by several laser guide stars in a certain pattern is required to probe more atmospheric turbulence in different directions. To achieve this, a sodium laser guide star asterism launching platform is required. In this paper, we introduce the sodium laser guide star asterism launching platform built and tested on the 1.8 m telescope of Gaomeigu Observatory. The platform has two functions: one function is to compare the performance of sodium laser guide stars generated by different lasers at the same place, and the other function is to generate a sodium laser guide star asterism with an adjustable shape. The field test results at the beginning of 2021 verified the important role of the platform, which is also the first time that a sodium laser guide star asterism was realized in China.

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“…and the sodium layer density, for simplicity, we will use photons subaperture -1 frame -1 as the measurement of LGS power. For further study of the LGS system, the laser power requirement for different types of laser guide stars can be calculated with their individual models, different in situ sodium densities (Wei et al 2016;Feng et al 2016) and the simulation results discussed in this paper.…”

Section: Lgs Power Requirementsmentioning

confidence: 99%

OUP accepted manuscript

Jia

Basden

Osborn

2018

MNRAS

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First light for the sodium laser guide star adaptive optics system on the Lijiang 1.8m telescope

Cited by 7 publications

References 12 publications

Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories

Detection and Implications of Laser-Induced Raman Scattering at Astronomical Observatories

First Sodium Laser Guide Star Asterism Launching Platform in China on the 1.8 m Telescope at Gaomeigu Observatory

OUP accepted manuscript

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