Presently TNO/Demcon are manufacturing nine Laser Projection Systems (LPS). TNO is responsible for the design and manufacturing of the Optical Tube Assembly (OTA), the baseplate and the LPS cover. Demcon designed and manufactured the Beam Conditioning and Diagnostic System (BCDS). TNO is also responsible for the system performance and its verification tests. Six units will be used on the ELT. The other three are destined for the VLT. That will allow the operation of the adaptive mirrors enabling unprecedented image quality of the telescopes. The design of this system is based on the four laser guide stars units as used on the VLT. The system has been upgraded considerably compared to the units used for the VLT. Its FOV has increased to 7 arcmin (half cone). The laser power goes up to 50W and the BCDS has been completely redesigned. The BCDS is located between the laser source and the OTA that produces the O300 mm output beam. Maintainability and accessibility of the system have also been much improved. Prime qualities are its insensitivity to temperature changes (static and dynamic), its accuracy and its FOV. Assembly of the first unit is finished and in January the acceptance testing of the system started. The first unit is expected to be delivered to ESO in autumn 2024.

Tight relationships exist in the local universe between the central stellar properties of galaxies and the mass of their supermassive black hole. These suggest galaxies and black holes co-evolve, with the main regulation mechanism being energetic feedback from accretion onto the black hole during its quasar phase. A crucial question is how the relationship between black holes and galaxies evolves with time; a key epoch to probe this relationship is at the peaks of star formation and black hole growth 8-12 billion years ago (redshifts 1-3). Here we report a dynamical measurement of the mass of the black hole in a luminous quasar at a redshift of 2, with a look back time of 11 billion years, by spatially resolving the broad line region. We detect a 40 micro-arcsecond (0.31 pc) spatial offset between the red and blue photocenters of the H$\alpha$ line that traces the velocity gradient of a rotating broad line region. The flux and differential phase spectra are well reproduced by a thick, moderately inclined disk of gas clouds within the sphere of influence of a central black hole with a mass of 3.2x10$^{8}$ solar masses. Molecular gas data reveal a dynamical mass for the host galaxy of 6x10$^{11}$ solar masses, which indicates an under-massive black hole accreting at a super-Eddington rate. This suggests a host galaxy that grew faster than the supermassive black hole, indicating a delay between galaxy and black hole formation for some systems.

The GRAVITY+ project includes the upgrade of the Very Large Telescope Interferometer infrastructure and of the instrument GRAVITY to improve sky coverage, high contrast capabilities, and faint science. The improved sky coverage is obtained via the implementation of one Laser Guide Star (LGS) on each Unit Telescope (UT). This first requires an upgrade of the infrastructure of each of the UTs, which was made over 18 months in 2022 and 2023. The addition of the LGS system requires the implementation of multiple components on several areas of the telescope. These areas include the top ring, the centerpiece, a new platform under the Nasmyth platform, and in the basement. The system includes pointing and aircraft avoidance cameras, the laser projector, laser and electronics cabinets, a heat exchanger, and pumps. As none of the UTs were developed with the infrastructure needed to carry such a system, the same upgrade is made for each of the three UTs. This upgrade consists of a full adaptation of the centerpiece, an upgrade of one of the altitude cable wraps, the installation of a platform under the Nasmyth platform, and the implementation of a cooling circuit running from the basement to the new sub-Nasmyth platform via the azimuth cable wrap. This upgrade requires two missions per telescope, for a total of 30 nights out of operation per telescope. The centerpiece activity also requires the removal of the M1 mirror and cell. The activities were therefore coordinated with the regular recoating of the M1 to minimize the number of nights out of operation. The upgrade required approximately 7.5 staff years of work and 36 missions from Europe to Chile, with around 60 people participating in at least one of the seven missions.

The GRAVITY instrument has been revolutionary for near-infrared interferometry by pushing sensitivity and precision to previously unknown limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer (VLTI) in GRAVITY+, these limits will be pushed even further, with vastly improved sky coverage, as well as faint-science and high-contrast capabilities. This upgrade includes the implementation of wide-field off-axis fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser guide stars in an upgraded facility. GRAVITY+ will open up the sky to the measurement of black hole masses across cosmic time in hundreds of active galactic nuclei, use the faint stars in the Galactic centre to probe General Relativity, and enable the characterisation of dozens of young exoplanets to study their formation, bearing the promise of another scientific revolution to come at the VLTI.

Ground-based optical astronomical observations supported by or in the vicinity of laser guide-star systems can be contaminated by Raman-scattered laser photons. Anticipating, alleviating, and correcting for the impact of this self-inflicted contamination requires a detailed knowledge of the pure-rotational and rotational-vibrational spectrum of the molecules in our atmosphere. We present a 15.3hr-deep combined spectrum of the 4LGSF's 589nm $\approx$ 509THz sodium laser beams of Paranal observatory, acquired with the ESPRESSO spectrograph at a resolution $\lambda/\Delta\lambda\cong140'000\approx0.12$ cm$^{-1}$ and an altitude of 23 km above mean sea level. We identify 865 Raman lines over the spectral range of [3770; 7900]{\AA}$\approx$[+9540; -4315] cm$^{-1}$, with relative intensities spanning ~5 orders of magnitudes. These lines are associated to the most abundant molecules of dry air, including their isotopes: 14N14N, 14N15N, 16O16O, 16O17O, 16O18O, and 12C16O16O. The signal-to-noise of these observations implies that professional observatories can treat the resulting catalogue of Raman lines as exhaustive (for the detected molecules, over the observed Raman shift range) for the purpose of predicting/correcting/exploiting Raman lines in astronomical data. Our observations also reveal that the four laser units of the 4LGSF do not all lase at the same central wavelength. [...] The [measured] offsets [...] are larger than the observed 4LGSF spectral stability of $\pm$3 MHz over hours. They remain well within the operational requirements for creating artificial laser guide-stars, but hinder the assessment of the radial velocity accuracy of ESPRESSO at the required level of 10 m/s. Altogether, our observations demonstrate how Raman lines can be exploited by professional observatories as highly-accurate, on-sky wavelength references.

We report on the development of a Beam Conditioning and Diagnostics System (BCDS) that will be employed in the Laser Projection System (LPS) of the Extremely Large Telescope (ELT) of ESO. This conference article provides an overview about the detailed design of the BCDS and it summarizes the work of the development phase of this project. To this end, design challenges, concepts and analysis results of the optical layout and the opto-mechanical concept are discussed.

We report on experiments performed with the Swedish Solar Telescope (SST) located in La Palma (Canary Islands) to observe the sodium Laser Guide Star (LGS) during daytime. The ESO Wendelstein Laser Guide Star Unit 20W CW 589nm laser was used to generate an LGS plume at Earth’s Mesosphere, the laser launch telescope being at a distance of 92m from the SST, where a special daytime receiver was installed. The photometry of the LGS plume and the background effects were measured as a function of the angular separation between the plume and the Sun. The ultimate goal is to demonstrate closed-loop LGS Adaptive Optics (AO) during daytime, for Optical Feeder Satellite Communications operating 24/7, as well as for astrophysics of the Sun Coronal Mass Ejections. Other applications of daytime LGS-AO are for thermal imaging of astrophysical objects. This paper presents several system aspects of the daytime LGS-AO setup and discusses the experimental results obtained. We conclude that using an ultra-narrow band magneto-optical filter installed in the daytime SST receiver, the sky background flux is very efficiently suppressed and the LGS flux is well sufficient to drive LGS-AO during daytime for correction at visible wavelengths.

We report on the visible LGS-AO experimental facility which we are building to be installed at the 1m ESA Optical Ground Station at Observatorio del Teide, Tenerife, Canary Islands. We focus on the system aspects related to optics. The instrument will be a novel facility to perform strategic LGS-AO technology R&D in future years, demonstrating a 50+ W CW 589nm laser, uplink laser beam pre-compensation on sodium LGS in pulsed laser operation. The rationale for the LGS-AO facility is to have a synergy between astronomical and space awareness adaptive optics, to technologies for astrophysics and optical communication with satellites (Optical Feeder Links), including daytime LGS-AO, for future OGS systems.

The first observations of laser guide-star photons that are 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 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, which are responsible for a reflectivity loss of ∼8% at 6000 Å, contribute (60 ± 5)% to the laser line fluxes detected by MUSE. The flux of Raman lines, which contaminates scientific observations that are acquired with optical spectrographs, thus provides a new, non-invasive means to monitor the evolving scatter properties of the mirrors of astronomical telescopes that are equipped with laser guide-star systems.

The Adaptive Optics Facility (AOF) is an ESO project, which transformed Yepun, one of the four 8m telescopes in Paranal, into an adaptive telescope. This has been done by replacing the conventional secondary mirror of Yepun by a Deformable Secondary Mirror (DSM) and attaching four Laser Guide Stars (LGS) Units to its centerpiece. Additionally, two Adaptive Optics (AO) modules (GALACSI serving MUSE a 3D spectrograph, and GRAAL, serving Hawk I a wide field infrared imager) have been assembled onto the telescope Nasmyth adapters, each of them incorporating four LGS WaveFront Sensors (WFS) and one tip-tilt sensor used to control the DSM at 1 kHz frame rate. The complete AOF is installed on Yepun for more than one year now, and its commissioning is fully complete. This paper presents the most important and amazing features of the AOF, illustrated by some first science images obtained using MUSE/GALACSI in Ground Layer AO (GLAO) and Laser Tomography AO (LTAO) mode, and HAWK-I/GRAAL in GLAO mode. In the first part of the paper, on-sky performance of GRAAL and GALACSI is presented in terms of gain in image quality and even Strehl Ratio. Efficiency of the on-sky operation of the AOF is described. In the second part, future instruments making use of the AOF capabilities are presented.

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 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 congruent to 3000 of the uplink laser beams over the wavelength range of 4750 angstrom-9350 angstrom. We report the first detection of laser-induced Raman scattering by N-2, O-2, CO2, H2O, and (tentatively) CH 4 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 angstrom to 2210 angstrom redder than the original laser wavelength of 5889.959 angstrom-landing on the 8.2-m 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 it is 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 thoroughly handle 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-rediction tools should also 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.

We report on the comparison between observations and simulations of a completed 12-month field observation campaign at Observatorio del Teide, Tenerife, using ESO's transportable 20 watt CW Wendelstein laser guide star system. This mission has provided sodium photon return flux measurements of unprecedented detail regarding variation of laser power, polarization and sodium D2b repumping. The Raman fiber laser and projector technology are very similar to that employed in the 4LGSF/AOF laser facility, recently installed and commissioned at the VLT in Paranal. The simulations are based on the open source LGSBloch density matrix simulation package and we find good overall agreement with experimental data.

The Adaptive Optics Facility is an ESO project aiming at converting Yepun, one of the four 8m telescopes in Paranal, into an adaptive telescope. This is done by replacing the current conventional secondary mirror of Yepun by a Deformable Secondary Mirror (DSM) and attaching four Laser Guide Star (LGS) Units to its centerpiece. In the meantime, two Adaptive Optics (AO) modules have been developed incorporating each four LGS WaveFront Sensors (WFS) and one tip-tilt sensor used to control the DSM at 1 kHz frame rate. The four LGS Units and one AO module (GRAAL) have already been assembled on Yepun. Besides the technological challenge itself, one critical area of AOF is the AO control strategy and its link with the telescope control, including Active Optics used to shape M1. Another challenge is the request to minimize the overhead due to AOF during the acquisition phase of the observation. This paper presents the control strategy of the AOF. The current control of the telescope is first recalled, and then the way the AO control makes the link with the Active Optics is detailed. Lab results are used to illustrate the expected performance. Finally, the overall AOF acquisition sequence is presented as well as first results obtained on sky with GRAAL.

The Messenger 164 – June 2016 mounted in that order on the ASSIST (Adaptive Secondary Setup and Instrument Simulator) test bench and tested in realistic conditions. GRAAL tests were completed in early 2015 and GRAAL’s PAE was granted in April 2015. Then the system was prepared for shipment and re-integrated in Paranal in June. This provided a unique opportunity in October 2015 to undertake a combined commissioning run with LGSU#1 and GRAAL, allowing many aspects of the acquisition sequence of the AOF on the telescope to be debugged and tested under real conditions. This evaluation was very instructive and useful to the project and again validated many design choices.

The Four Laser Guide Star Facility (4LGSF) is part of the ESO Adaptive Optics Facility (AOF), in which one of the VLT unit telescopes, UT4, is transformed in an adaptive telescope equipped with a deformable secondary mirror, two adaptive optics systems at the Nasmyth foci and four laser guide star modular units. In this poster we present the key results of the acceptance tests performed on the 4LGSF in Europe and first commissioning results obtained with the Laser Guide Star Unit #1 in stand-alone operation.

The Four Laser Guide Star Facility (4LGSF) is part of the ESO Adaptive Optics Facility (AOF), in which one of the VLT unit telescopes, UT4, is transformed in an adaptive telescope equipped with a deformable secondary mirror, two adaptive optics systems at the Nasmyth foci and four laser guide star modular units. In this poster we present the key results of the acceptance tests performed on the 4LGSF in Europe and first commissioning results obtained with the Laser Guide Star Unit #1 in stand-alone operation.

The Four Laser Guide Star Facility (4LGSF) is part of the ESO Adaptive Optics Facility (AOF), in which one of the VLT unit telescopes, UT4, is transformed in an adaptive telescope - equipped with a deformable secondary mirror, two adaptive optics systems at the Nasmyth foci and four laser guide star modular units. In this poster we present the key results of the acceptance tests performed on the 4LGSF in Europe and first commissioning results obtained with the Laser Guide Star Unit #1 in stand-alone operation.