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Following the arrival of MATISSE, the second-generation of VLTI instrumentation is now complete and was simultaneously enhanced by a major facility upgrade including the NAOMI Adaptive Optics on the Auxiliary Telescopes. On the Unit Telescopes, significant efforts were also made to improve the injection stability into VLTI instruments. On top of GRAVITY's own evolution, its fringe tracker is now being used to allow coherent integrations on MATISSE (the so-called GRA4MAT project). Meanwhile, operations also evolved to be more flexible and make the most of an extended observing parameter space. In this context, we present an overview of the current VLTI performances. Finally, we will report on on-going improvements such as the extension of the longest baselines.

The near-infrared GRAVITY instrument has become a fully operational spectro-imager, while expanding its capability to support astrometry of the key Galactic Centre science. The mid-infrared MATISSE instrument has just arrived on Paranal and is starting its commissioning phase. NAOMI, the new adaptive optics for the Auxiliary Telescopes, is about to leave Europe for an installation in the fall of 2018. Meanwhile, the interferometer infrastructure has continuously improved in performance, in term of transmission and vibrations, when used with both the Unit Telescopes and Auxiliary Telescopes. These are the highlights of the last two years of the VLTI 2nd generation upgrade started in 2015.

The New Adaptive Optics Module for Interferometry (NAOMI) is ready to be installed at the 1.8-metre Auxiliary Telescopes (ATs) at ESO Paranal. NAOMI will make the existing interferometer performance less dependent on the seeing conditions. Fed with higher and more stable Strehl, the fringe tracker will achieve the fringe stability necessary to reach the full performance of the second-generation instruments GRAVITY and MATISSE. All four ATs will be equipped between September and November 2018 with a Deformable mirror (ALPAO DM-241), a 4*4 Shack– Hartmann adaptive optics system operating in the visible and an RTC based on SPARTA Light. During the last 6 months thorough system test has been made in laboratory to demonstrate the Adaptive Optics and chopping capability of NAOMI.

The New Adaptive Optics Module for Interferometry (NAOMI) will be developed for and installed at the 1.8-metre Auxiliary Telescopes (ATs) at ESO Paranal. The goal of the project is to equip all four ATs with a low-order Shack– Hartmann adaptive optics system operating in the visible. By improving the wavefront quality delivered by the ATs for guide stars brighter than R = 13 mag, NAOMI will make the existing interferometer performance less dependent on the seeing conditions. Fed with higher and more stable Strehl, the fringe tracker(s) will achieve the fringe stability necessary to reach the full performance of the second-generation instruments GRAVITY and MATISSE.

For two years starting in February 2014, the AO modules GRAAL for HAWK-I and GALACSI for MUSE of the Adaptive Optics Facility project have undergone System Testing at ESO's Headquarters. They offer four different modes: NGS SCAO, LGS GLAO in the IR, LGS GLAO and LTAO in the visible. A detailed characterization of those modes was made possible by the existence of ASSIST, a test bench emulating an adaptive VLT including the Deformable Secondary Mirror, a star simulator and turbulence generator and a VLT focal plane re-imager. This phase aimed at validating all the possible components and loops of the AO modules before installation at the actual VLT that comprises the added complexity of real LGSs, a harsher non-reproducible environment and the adaptive telescope control. In this paper we present some of the major results obtained and challenges encountered during the phase of System Tests, like the preparation of the Acquisition sequence, the testing of the Jitter loop, the performance optimization in GLAO and the offload of low-order modes from the DSM to the telescope (restricted to the M2 hexapod). The System Tests concluded with the successful acceptance, shipping, installation and first commissioning of GRAAL in 2015 as well as the acceptance and shipping of GALACSI, ready for installation and commissioning early 2017.

The exoplanetary science through direct imaging and spectroscopy will largely expand with the forthcoming development of new instruments at the VLT (SPHERE), Gemini (GPI), Subaru (HiCIAO), and Palomar (Project 1640) observatories. All these ground-based adaptive optics instruments combine extremely high performance adaptive optics (XAO) systems correcting for the atmospheric turbulence with advanced starlight-cancellation techniques such as coronagraphy to deliver contrast ratios of about 10-6 to 10-7. While the past fifteen years have seen intensive research and the development of high-contrast coronagraph concepts, very few concepts have been tested under dynamical seeing conditions (either during sky observation or in a realistic laboratory environment). In this paper, we discuss the results obtained with four different coronagraphs -- phase and amplitude types -- on the High-Order Testbench (HOT), the adaptive optics facility developed at ESO. This facility emphasizes realistic conditions encountered at a telescope (e.g., VLT), including a turbulence generator and a high-order adaptive optics system. It enables to evaluate the performance of high-contrast coronagraphs in the near-IR operating with an AO-corrected PSF of 90% Strehl ratio under 0.5 arcsec dynamical seeing.

The New Adaptive Optics Module for Interferometry (NAOMI)1 is the future low order adaptive optics system to be developed for and installed at the ESO 1.8 m Auxiliary Telescopes (ATs). The four ATs2 are designed for interferometry which they are essentially dedicated for. Currently the AT’s are equipped with a fast, visible tip-tilt sensor called STRAP3 (System for Tip/tilt Removal with Avalanche Photodiodes), and the corrections are applied through a tip-tilt mirror. The goal is to equip all four ATs with a low-order Shack-Hartmann system operating in the visible for the VLTI dual feed light beams in place of the current tip-tilt correction. Because of the limited size of the ATs (1.8m diameter), a low-order system will be sufficient. The goal is to concentrate the energy into a coherent core and to make the encircled energy (into the single mode fibers) stable and less dependent on the atmospheric conditions in order to increase the sensitivity of the interferometric instruments. The system will use the ESO real time computer platform Sparta-light as the baseline. This paper presents the preliminary design concept and outlines the benefits to current and future VLTI instruments.

The New Adaptive Optics Module for Interferometry (NAOMI) is the future low order Adaptive optics system to be developed for and installed at the ESO 1.8 m Auxiliary Telescopes (ATs). The four ATs are designed for interferometry which they are essentially dedicated for. The project goal is to equip the telescopes with a low-order Shack-Hartmann system operating in the visible in place of the current tip-tilt correction. The deformable mirror (DM) for NAOMI is rotating with the AT azimuth axis whereas the wavefront sensor (WFS), which signals are used to control the DM, has a fixed position in the telescope basement. It is not co-rotating with the DM. The result is that the projection of the actuator pattern is rotating with respect to the WFS when the telescope is tracking an object on sky. In order to avoid the use of an optical de-rotator we developed an algorithm to de-rotate the commands to the DM in software. This paper outlines the concept of the software de-rotation as well as the performance obtained from end-to-end simulations.

We present the latest update of the European Southern Observatory's Very Large Telescope interferometer (VLTI). The operations of VLTI have greatly improved in the past years: reduction of the execution time; better offering of telescopes configurations; improvements on AMBER limiting magnitudes; study of polarization effects and control for single mode fibres; fringe tracking real time data, etc. We present some of these improvements and also quantify the operational improvements using a performance metric. We take the opportunity of the first decade of operations to reflect on the VLTI community which is analyzed quantitatively and qualitatively. Finally, we present briefly the preparatory work for the arrival of the second generation instruments GRAVITY and MATISSE., Comment: 10 pages, 7 figures, Proceedings of the SPIE, 9146-19

In an AO system the correction to be applied to the Deformable Mirror is computed at each loop cycle from the residual slopes on the Wavefront Sensor and the Interaction Matrix of the system DM/WFS. But the a posteriori analysis of the DM commands and WFS slopes can also provide a wealth of information on the closed loop behavior. In this paper we present a non-exhaustive list of what can be learned from such data. We base our analysis on simulated data, on data recorded on ESO’s PEACE test bench, and on data recorded on the NAOS instrument at the VLT during technical nights in 2010 and 2011, in the framework of the preparation of the algorithms for the AO Facility. The topics presented include the reconstruction of the input turbulence in the WFS domain (pseudo open-loop slopes), the estimation of the seeing, turbulence profile, coherence time, wind speed and direction, the measurement of LGS spot size, the detection of vibrations via modal transfer functions, the identification of DM/WFS mis-registration and the optimal loop gain computation.

Presently, dedicated instruments at large telescopes (SPHERE for the VLT, GPI for Gemini) are about to discover and explore self-luminous giant planets by direct imaging and spectroscopy. The next generation of 30m-40m ground-based telescopes, the Extremely Large Telescopes (ELTs), have the potential to dramatically enlarge the discovery space towards older giant planets seen in reflected light and ultimately even a small number of rocky planets. EPICS is a proposed instrument for the European ELT, dedicated to the detection and characterization of Exoplanets by direct imaging, spectroscopy and polarimetry. ESO completed a phase-A study for EPICS with a large European consortium which - by simulations and demonstration experiments - investigated state-of-the-art diffraction and speckle suppression techniques to deliver highest contrasts. The paper presents the instrument concept and analysis as well as its main innovations and science capabilities. EPICS is capable of discovering hundreds of giant planets, and dozens of lower mass planets down to the rocky planets domain. © 2010 Copyright SPIE - The International Society for Optical Engineering.

The purpose of FFREE - the new optical bench devoted to experiments on high-contrast imaging at LAOG - consists in the validation of algorithms based on off-line calibration techniques and adaptive optics (AO) respectively for the wavefront measurement and its compensation. The aim is the rejection of the static speckles pattern arising in a focal plane after a diffraction suppression system (based on apodization or coronagraphy) by wavefront pre-compensation. To this aim, FFREE has been optimized to minimize Fresnel propagation over a large near infrared (NIR) bandwidth in a way allowing efficient rejection up to the AO control radius, it stands then as a demonstrator for the future implementation of the optics that will be common to the scientific instrumentation installed on EPICS., 12 pages, 15 figures, Proceeding 7736120 of the SPIE Conference "Adaptive Optics Systems II", monday 28 June 2010, San Diego, California, USA

Extreme adaptive optics systems (XAO) dedicated to the search for extrasolar planets are currently being developed for 8-10 meter telescopes. The High-Order Test bench (HOT) is a high-contrast imaging adaptive optics bench developed at the European Southern Observatory to test and optimize different techniques and technologies (e.g. wavefront sensors, coronagraphs, speckle calibration methods, image post-processing). It reproduces realistic conditions at a telescope (e.g. Very Large Telescope, VLT), including a turbulence generator, a high-order adaptive optics system, a near-IR coronagraph, and sequential differential imaging modes (spectral and polarimetric). We discuss the results of XAO coronagraphy obtained in the laboratory in the context of imminent planet-finder instruments (e.g. SPHERE1, GPI2, and HiCIAO3). In particular, results obtained with HOT will be discussed and compared with contrast goals of the near-IR camera of SPHERE.

E cient suppression of the residual stellar light is paramount to the success of exoplanet imaging e orts. We present a new approach to di raction suppression on extremely large telescopes. The method is based on the realization that by obscuring part of the wavefront in the Lyot stop we can change the shape of the cor- responding PSF. This obscuration is then modulated leading to modulated Airy pattern, while image of a planet - if present - is only slightly a ected. The modulation could then be removed from the set of images, leading to better SNR of the possible planets. Simulation of the European Extremely Large Telescope has been used to test this approach.

The segmented primary mirror of the E-ELT imposes particular requirements on an Extreme Adap- tive Optics (XAO) system. At present, there are already several AO systems working on segmented telescopes but the achieved performances are too low to draw conclusions for XAO systems aiming at some 90% Strehl ratio in the NIR. On other hand, several analytical studies and simulations were done, but laboratory studies are required to confirm the corrections expected. The goal of the present study is to determina the capability of XAO systems to deal with segmentation piston errors. In particular, the e ffects on the AO performance and the ability of the AO system to correct the segmentation piston errors were studied. The experiments were carried out on the High Order Test Bench at ESO (Munich) using a Shack-Hartmann wave front sensor and under most realistic condi- tions with phase screens simulating atmospheric turbulence and segmentation piston errors. Segment geometry was chosen such that about 6 actuators of the XAO DM cover one segment representing the design of EPICS at the EELT. Extreme Adaptive Optics (XAO) at the E-ELT requires dealing with a primary segmented mirror. The wave front control of the ELT includes three main units: adaptive optics, active optics and phasing camera. Each wave front control is affected to some extend by the total wavefront, but, on the other hand the different control units can "help" each other. The wavefront sensor of the AO unit will see the telescope aberrations and segments misalignments; hence the AO deformable mirror will try to compensate for them. The goal of the present study is to determina the capability of the adaptive optics to deal with and correct for the segmentation piston errors. At present, there are several segmented telescope working with AO systems but the experience from them could not be use for extrapolation to a XAO system. Several analytical studies and simulations were done (2). From these studies, the ability of the AO system to correct for the segmentation errors strictly depends on the design of the DM and the wave front sensor. The density of the actuators, the coupling factor and the geometry of actuators distribution have directly impact on the performance. The ELT primary mirror will be composed by around 1000 hexagonal segments of 1.5 m with a gap of 10 mm. 5-7 actuators per segment are expected considering a deformable mirror of 200x200 actuators. The experiments were carried out on the HOT Bench using a Shack-Hartman WFS and taking into account the ELT geometry and the requirements for a XAO instrument. They will also be run under realistic atmospheric conditions.

ESO and a large European consortium completed the phase-A study of EPICS, an instrument dedicated to exoplanets direct imaging for the EELT. The very ambitious science goals of EPICS, the imaging of reflected light of mature gas giant exoplanets around bright stars, sets extremely strong requirements in terms of instrumental contrast achievable. The segmented nature of an ELT appears as a very large source of quasi-static high order speckles that can impair the detection of faint sources with small brightness contrast with respect to their parent star. The paper shows how the overall system has been designed in order to maximize the efficiency of quasi-static speckles rejection by calibration and post-processing using the spectral and polarization dependency of light waves. The trade-offs that led to the choice of the concepts for common path and diffraction suppression system is presented. The performance of the instrument is predicted using simulations of the extreme Adaptive Optics system and polychromatic wave-front propagation through the various optical elements. © 2010 SPIE.

We present a new class of algorithms for the detection of faint companions to stars. The new approach was tested on astronomical observations and on high-contrast coronagraphic data recorded in a laboratory experiment.

The High Order Testbench (HOT) is a joint experiment of ESO, Durham University and Arcetri Observatory to built and test in laboratory the performance of Shack-Hartmann and pyramid sensor in a high-order correction loop using a 32x32 actuators MEMS DM. This paper will describe the pyramid wavefront sensor unit developed in Arcetri and now installed in the HOT bench at ESO premises. In the first part of this paper we will describe the pyramid wavefront sensor opto-mechanics and its real-time computer realized with a commercial Linux-PC. In the second part we will show the sensor integration and alignment in the HOT bench and the experimental results obtained at ESO labs. Particular attention will be paid to the implementation of the modal control strategy, like modal basis definition, orthogonalization on the real pupil, and control of edge actuators. A stable closed loop controlling up to 667 modes has been achieved obtaining a Strehl ratio of 90 -- 93% in H band.

High-contrast imagers dedicated to the search for extrasolar planets are currently being developed for the VLT (SPHERE) and Gemini (GPI) observatories. A vital part of such a high-contrast imager is the extreme adaptive optics (XAO) system that very efficiently removes effects of atmospheric turbulence and instrument aberrations. The high order test bench (HOT) implements an XAO system under realistic telescope conditions reproduced by star and turbulence generators. New technological developments (32x32 actuator micro deformable mirror, read-noise free electron multiplying CCD60, SPARTA real time computer) are used to study and compare two potential XAO wave front sensors: The Pyramid- and the Shack-Hartmann wave front sensors. We will describe the overall design of HOT including the sub-systems. We will present the closed loop study results of the behavior of the Shack-Hartmann wave front sensor in terms of linearity, sensitivity to calibration errors, performance and other specific issues.

We report laboratory development of coronagraphic devices to be implemented on the High Order Testbench (HOT) to assess intensity reduction between them at a high Strehl ratio regime. The high order test bench implements extreme adaptive optics with realistic telescope conditions reproduced by star and turbulence generators. A 32×32 actuator micro deformable mirror, one pyramid wave front sensor, one Shack-Hartmann wave front sensor and the ESO SPARTA realtime computer. This will enable characterization and comparative study of different types of coronagraphs in realistic conditions. We have developed several prototypes of promising coronagraphs concepts: Four Quadrants Phase Mask 1