ESO adaptive optics facility

Arsenault, Robin; Madec, Pierre-Yves; Hubin, N.; Paufique, J.; Stroebele, Stefan; Soenke, C.; Donaldson, Robert H.; Fedrigo, Enrico; Oberti, Sylvain; Tordo, Sebastien; Downing, Mark; Kiekebusch, M.; Conzelmann, Ralf; Duchateau, M.; Jost, A.; Calia, Domenico Bonaccini; Delabre, B.; Stuik, Remko; Biasi, Roberto; Gallieni, Daniele; Lazzarini, Paolo; Lelouarn, M.; Glindeman, A.

doi:10.1117/12.790359

Cited by 33 publications

(12 citation statements)

References 2 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%

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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%

“…We thank the AOF Builders [20] for the construction and installation of the AOF on UT4 at the VLT. We are grateful to Alain Smette for stimulating discussions over the course of the commissioning tests, to George Hau, Julien Girard, Thomas Pfrommer, Steffen…”

Section: Acknowledgmentsmentioning

confidence: 99%

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

et al. 2017

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“…Deformable secondaries have been constructed for the Large Binocular Telescope (LBT) and the Magellan Telescope 11 and are being completed for the Very Large Telescope (VLT). 12 Recent work with one of the Large Binocular Telescope's deformable secondary mirrors has demonstrated the exquisite image sharpness obtainable with these mirrors. The PSFs obtained, with > 80% Strehl in H-band, are among the highest quality images ever taken from the ground at this wavelength.…”

Section: Science With Deformable Secondary Adaptive Optics Systemsmentioning

confidence: 99%

Demonstration of 17 cm robust carbon fiber deformable mirror for adaptive optics

et al. 2011

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Carbon-fiber reinforced polymer (CFRP) composite is an attractive material for fabrication of optics due to its high stiffness-to-weight ratio, robustness, zero coefficient of thermal expansion (CTE), and the ability to replicate multiple optics from the same mandrel. We use 8 and 17 cm prototype CFRP thin-shell deformable mirrors to show that residual CTE variation may be addressed with mounted actuators for a variety of mirror sizes. We present measurements of surface quality at a range of temperatures characteristic of mountaintop observatories. For the 8 cm piece, the figure error of the Al-coated reflective surface under best actuator correction is ~43 nm RMS. The 8 cm mirror has a low surface error internal to the outer ring of actuators (17 nm RMS at 20°C and 33 nm RMS at -5°C). Surface roughness is low (< 3 nm P-V) at a variety of temperatures. We present new figure quality measurements of the larger 17 cm mirror, showing that the intra-actuator figure error internal to the outer ring of actuators (38 nm RMS surface with one-third the actuator density of the 8 cm mirror) does not scale sharply with mirror diameter.

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“…The first activities to prepare the unit telescope#4 (UT4) to receive the AOF have taken place in last April and were successful. The facility has been described previously in various papers; see [1], [2], [3].…”

Section: Introductionmentioning

confidence: 99%

ESO adaptive optics facility progress report

et al. 2012

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The ESO Adaptive Optics Facility (AOF) consists in an evolution of one of the ESO VLT unit telescopes to a laser driven adaptive telescope with a deformable mirror in its optical train.The project has completed the procurement phase and several large structures have been delivered to Garching (Germany) and are being integrated (the AO modules GRAAL and GALACSI and the ASSIST test bench). The 4LGSF Laser (TOPTICA) has undergone final design review and a pre-production unit has been built and successfully tested. The Deformable Secondary Mirror is fully integrated and system tests have started with the first science grade thin shell mirror delivered by SAGEM. The integrated modules will be tested in stand-alone mode in 2012 and upon delivery of the DSM in late 2012, the system test phase will start. A commissioning strategy has been developed and will be updated before delivery to Paranal. A substantial effort has been spent in 2011-2012 to prepare the unit telescope to receive the AOF by preparing the mechanical interfaces and upgrading the cooling and electrical network. This preparation will also simplify the final installation of the facility on the telescope.A lot of attention is given to the system calibration, how to record and correct any misalignment and control the whole facility. A plan is being developed to efficiently operate the AOF after commissioning. This includes monitoring a relevant set of atmospheric parameters for scheduling and a Laser Traffic control system to assist the operator during the night and help/support the observing block preparation.

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ESO adaptive optics facility

Cited by 33 publications

References 2 publications

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

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

Demonstration of 17 cm robust carbon fiber deformable mirror for adaptive optics

ESO adaptive optics facility progress report

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