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Open Access Publications from the University of California


The fourth bi-annual Adaptive Optics for Extremely Large Telescopes meeting took place in October 2015 at the UCLA Conference Center in Southern California. The theme of the meeting was AO systems and related instrumentation and the special challenges they face on extremely large aperture telescopes. The conference gathered specialists to review and discuss the latest developments of the ELT’s current design in terms of AO systems, related instruments and science goals. The conference also reported on pathfinder projects planned or implemented on existing telescopes, including solar telescopes, which provide relevant results for the next ELT’s design phase. Special attention is given to key components and new ideas that have the potential to overcome the limitations of existing systems, in order to increase the scientific impact of the future ELT’s.

Volume 1, Issue 1, 2015


Effects of reconstruction layer profiles on atmospheric tomography in E-ELT AO systems

In this paper, we will present new compression algorithms to determine optimal layer heights and turbulenceweights for the tomographic reconstruction in wide field AO systems. Among other approaches, a new compressionmethod based on discrete optimization of collecting atmospheric layers to subgroups is discussed. Furthermore,studies of the influence of layer heights and c2n-profiles on the reconstruction quality for differentreconstruction algorithms and atmospheric profiles will be shown. Our comparison suggests that reconstructionson fewer atmospheric layers yield comparable quality with lower computational effort, if an appropriatecompression algorithm is used. The numerical results were obtained on the ESO end-to-end simulation toolOCTOPUS.

Dissecting Star-forming regions with the GeMS MCAO instrument: lessons learned for optimal post-processing of WFAO data

The advent of a new generation of Wide Field AO (WFAO) systems marks the beginning of a new era in high spatial resolution imaging. By using multiple Laser Guide Stars, WFAO significantly increases the field of view of the AOcorrected images, and the fraction of the sky that can benefit from such correction. The newly commissioned Gemini South Multi-Conjugate Adaptive Optics System (GeMS) combined with the infrared camera GSAOI is delivering almost di raction-limited images over a field of   2 arc-minutes across. In this paper, we first present recent observations of the young star-forming region N159W located in the Large Magellanic Cloud. We obtained deep JHKs images from the GeMS/ GSAOI instrument and developed reduction tools, in order to photometrically study the properties of the stellar members of the cluster and to bring new elements to our understanding of the process of massive star formation. However, despite the excellent performance of the GeMS/ GSAOI system, some variable residues are still limiting the correction quality over the field. In particular, GSAOI is severely a ected by distortion that can strongly degrade the resolution when combining multiple frames and can consequently reduce the sensitivity. The accuracy of the distortion correction of an instrument is critical for its use for high- precision astrometry and photometry. In a second part of this paper, we investigate an optimal way to correct for the distortion following an inverse problem approach. The formalism as well as first simulation results are presented.


Calibrating the Non-Common Path Aberrations on the MOAO system RAVEN and

Contemporary AO systems, such as the Multi-Object Adaptive Optics system (MOAO) RAVEN currently associated with the Subaru Telescope, can suer from signicant Non-Common Path Aberrations (NCPA). These errors ultimately aect image quality and arise from optical path dierences between the wavefront sensor (WFS) path and the science path. A typical correction of NCPA involves estimating the aberration phase and correcting the system with an oset on the deformable mirror (DM). We summarize two methods used to correct for NCPA on an experimental bench. We also successfully calibrate the NCPA on RAVEN using one of these methods. Finally, we report on some rst science results with RAVEN, obtained after NCPA correction.


Optical calibration of the M4 prototype toward the final unit

The M4DP is the demonstration prototype of the E-ELT adaptive mirror M4. The opticalcalibration and test of the M4DP, held in INAF laboratories during February and March 2015, has beena lesson learned for the forthcoming optical verification of the 5000 actuators, 6 segments final unit.The test procedure was tailored to fit the peculiarities of such 2 segments, 222 actuators prototype. Keyelements are the simultaneous segments control and the measurement and correction of the rigid modesover the segmented pupil; convection noise aecting the phasing was also investigated. In this paper wewill report the results of the optical test and the specific solutions implemented for the phasing controland performance verification.

Precise and deep photometry from the ground: on-sky science performance of MCAO

Multi-conjugate adaptive optics is a central technology for the Extremely Large Telescopes (NFIRAOS on TMTand MAORY on E-ELT). GeMS on the 8-m Gemini South telescope is the rst facility-class MCAO and therst to use laser guide stars. We have observed the Galactic globular cluster NGC 1851 (and 5 other targets)and here we present the results of the prole-tting photometry in the near-infrared. This is the most precisephotometry to date of a cluster taken from the ground, conrmed by our ability to detect the double subgiantbranch, previously observed only from space. The high Strehl ratio of the images pushes the depth of the stellardetections well below the main sequence knee of the colour-magnitude diagram, making this also the deepestnear-infrared CMD yet obtained from ground. The large number of stars allows to evaluate the performanceof the instrument in terms of position-dependent PSF. We demonstrate how the analysis of the spatial andtemporal PSF variations allows us to develop eective photometric techniques for MCAO to be used for the nextgeneration of large telescopes.

Variation around the Pyramid theme: optical recombination and optimal use of photons

We propose a new type of Wave Front Sensor (WFS) derived from the Pyramid WFS (PWFS). This new WFS,called the Flattened Pyramid-WFS (FPWFS), has a reduced Pyramid angle in order to optically overlap the fourpupil images into an unique intensity. This map is then used to derive the phase information. In this paper thisnew WFS is compared to two existing WFSs, namely the PWFS and the Modulated PWFS (MPWFS) followingtests about sensitivity, linearity range and low photon flux behavior. The FPWFS turns out to be more linearthan a modulated pyramid for the high-spatial order aberrations but it provides an improved sensitivity comparedto the non-modulated pyramid. Furthermore, the pixel arrangement being more efficient than for the PWFS,the FPWFS seems particularly well suited for high-contrast applications. A first quick study of the influenceof the angle of the pyramid shows that, it is possible, with a quite constant linear range, to adjust the spatialfrequencies range where the sensitivity is the best. Finally, we also show that replacing the pyramid with aflattened cone also leads to very promising noise propagation properties.

PSF reconstruction for AO photometry and astrometry

Extracting accurate photometry (and astrometry) from images taken with adaptive optics assisted instruments isparticularly challenging. Current post-processing tools are not prepared to achieve high accuracy from AO data,especially in limiting cases of crowded elds and marginally resolved sources. We quantify the limitations of thesetools with synthetic images, and present a proof-of-concept study showing the potential of using reconstructedPSFs from the (GL)AO system telemetry to increase the measured photometric accuracy. We show that thephotometric accuracy is signicantly improved with a good PSF reconstruction in considerably crowded regions.We demonstrate the need for a dedicated post-processing tool that incorporates available information about thePSF, as well as the ability to adjust to the spatial variations of the PSF characteristic of AO data.

Low Wind Effect, the main limitation of the SPHERE instrument

The SPHERE instrument (Beuzit, et al., 2010) is dedicated to the direct imaging of extra-solar planets. This kind of observation allows one to study the photons emitted by the planet’s atmosphere itself, or reflected by its surface. The search for bio-markers is therefore made possible. The SPHERE instrument has been installed and commissioned at VLT Paranal Observatory during 2014 and now routinely delivers high contrast images to the exoplanet community. This paper presents a study of the main actual limitation of the SPHERE instrument, as known as the Low Wind Effect [LWE]. This effect has been discovered on SPHERE during commissioning period. Its effect is a strong degradation of the instrument PSF, preventing instrument to perform high contrast imaging. It happens during particularly low wind conditions (below 1m/s at the telescope level) which happens one night out of five.

Laboratory tests on HeNOS, the MCAO test bench for NFIRAOS

HeNOS is a test bench designed to be a scaled down version of NFIRAOS, the rst lightMCAO instrument for the Thirty Meter Telescope. The system was designed and built in theadaptive optics lab at NRC Herzberg in Victoria. The goal of the test bench is to assess theprediction quality of MAOS, the simulation software for NFIRAOS, to test the robustness ofthe tomographic algorithm under slowly changing conditions and to evaluate the calibrationmethods considered for the real instrument. For these tasks it is important to know the realdimensions of HeNOS with good precision. The goal of the tests presented here is to obtain thesystem parameters from the bench and compare them to the design.

SPHERE extreme AO system On-sky operation, final performance and future improvements

The SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) instrument aims at detecting extremely faintsources (giant extrasolar planets) in the vicinity of bright stars1. Such a challenging goal requires the use of a very-highorderperformance Adaptive Optics [AO] system feeding the scientific instruments with a quasi-perfect flat wave frontcorrected from all the atmospheric turbulence and internal defects. This AO system, called SAXO (Sphere Ao foreXoplanet Observation) is the heart of the instrument, a heart beating 1200 time per second and providing unprecedentedimage quality for a large ground based telescope at optical/near infrared wavelength. We will present the latest resultsobtained on-sky, demonstrating its exceptional performance (in terms of correction quality, stability and robustness) andtremendous potentiality for exoplanet discovery

Estimating the outer scale in altitude - L0(h) - using the GeMS profiler

We analyze the altitude distribution of the turbulence outer scale - L0(h) - at Cerro Pachón from Gemini South MCAO (GeMS) loop data. GeMS turbulence profiler is fed with telemetry from their 5 WFSs and from the voltages applied to the deformable mirrors, providing estimations of r0, Cn2(h), wind profile (speed and direction for every layer), isoplanatic angle and the outer scale distribution L0(h). It is shown that this last parameter ranges from less than 1 meter at the ground to more than 50m (the telescope is insensitive to larger cannot detect differences above this value). The technique is based on cross correlations of the pseudo-open-loop slopes that allow to disentangle the multiple constituents of L0.

An Integrated MASS/DIMM Monitor Based on a Low-Noise CCD Detector


We propose a novel design for a turbulence profiler. Using a single detector, images of the pupil (scintillation) and stars (image motion) are formed in the detector plane. The instrument is called FASS (Full Aperture Scintillation Sensor), as it uses the full aperture of the telescope. Different processing strategies are evaluated, including spatial segmentation and Fourier analysis. The different approaches are tested via simulation and on-sky data from two telescopes and compared to profiles obtained with the Durham Stereo-SCIDAR monitor. Overall, simulations shows that the method is more accurate that the classical MASS configuration, but it is shown that the photon noise plays an important role in the accuracy of the method, imposing stringent requirements on the pixel size, which must be significantly smaller than the speckle size formed from turbulence close to the ground (Fresnel law for speckle size).

Encouraging results have been obtained for on-sky data and compared to contemporaneous profiles obtained with a Stereo-Scidar technique.

Reducing adaptive optics latency using many-core processors

The high control frequency required of planned E-ELT adaptive optics modules (from several hundreds of Hz tothousands and typically in the region of 500 Hz for first light E-ELT instruments such as HARMONI), along withthe high number of actuators, leads to very demanding computational needs for the real-time AO control (RTC)systems. The number of actuators, proportional the total area of the telescope primary mirror, will range fromseveral thousands to tens of thousands (typically 4-6 thousand for first light E-ELT instruments). TraditionalRTC architectures based on CPU only technologies are typically unable to achieve the required performancein a cost-effective and maintainable manner. Alternative hardware such as many-core hardware acceleratorsneed to be considered to deliver the computational power. These many-core processors offering a highly parallelenvironment, have the potential of coping with the high computational load and of accelerating parts of the AOcontrol loop. AO systems for the E-ELT however, also put heavy constrains on acceptable levels of jitter andlatency.In this paper, we investigate novel hardware that has the potential to accelerate wavefront reconstruction andwavefront pre-processing, respectively the Intel Xeon Phi and the TILERA TILE-Gx processors. We present adetailed performance analysis putting an emphasis on execution time, jitter (i.e. variation in execution time)and outliers (i.e. results significantly apart from mean). Results are explored both for specific first light E-ELTinstruments and, to stay as general as possible and fully appreciate scalability issues, for a much wider range ofAO system sizes. The paper also addresses anticipated near future hardware developments and examines theirsuitability for the E-ELT.

Progress with the 4m high-order AO demonstrator, CHOUGH

We report the progress of the Canary High-Order Upgrade (CHOUGH) addition to the CANARY AO experimentat the 4.2m WHT telescope, ORM, La Palma. While CANARY has been developed to investigate severaltomographic congurations relevant to the E-ELT, it also has the ability to host guest AO instruments andprovide them with relevant infrastructure. CHOUGH is a self-contained AO bench that integrates into CANARY,via an external feed of light, to provide a Strehl 0:5 in the visible. Within CANARY, CHOUGH picks o lightafter a 240-actuator deformable mirror and delivers the on-axis beam into the internal relay which feeds varioussub-systems. These are include pick-o optics, a ADC, and 1k-actuator DM, all of which are part of an internalrelay to three instruments: a spatially-ltered SH WFS, a calibration interferometer, and a narrow-eld imagingcamera. As CHOUGH is constructed on a separate breadboard, the components are self-contained and can beintegrated and operated separately from CANARY. In this paper the progress on the design, procurement, andperformance of the CHOUGH sub-systems and the experiment as a whole is given. Attention is given to thealgorithms that will be used and the control methods that will be utilized on-sky. The modular nature of thedesign leads to potential upgrade paths and a brief discussion is made of new directions of on-sky research thatcould be carried out with replacement sub-systems and new instrumentation.

MCAO numerical simulations for EST: analysis and parameter optimization

The European Solar Telescope (EST) will be a new generation Solar telescope with the challenge of achieving a corrected field of view (FOV) of 1 arcminute with a minimum Strehl of 40% in the whole range of elevation angles of observation. For this purpose the EST will be equipped with a MCAO (Multi- conjugate Adaptive Optics) system. The proposed MCAO system for Solar telescopes combines a narrow and a wide extended Shack Hartman (SH) wavefront sensors (WFS) taking as references the spot or granulation of the sun. The number and position of deformable mirrors (DMs), the wavefront field of view (FOV), and asterism geometry have to be correctly settled as a function of the site turbulence conditions. We have performed numerical simulations using real turbulence profiles obtained at Observatorio del Teide in order to optimize the MCAO parameters for EST.

OCAM2S: an integral shutter ultrafast and low noise wavefront sensor camera for laser guide stars adaptive optics systems


To date, the OCAM2 system has demonstrated to be the fastest and lowest noise production ready wavefront sensor, achieving 2067 full frames per second with subelectron readout noise. This makes OCAM2 the ideal system for natural as well as continuous wave laser guide star wavefront sensing. In this paper we present the new gated version of OCAM2 named OCAM2-S, using E2V’s CCD219 sensor with integral shutter. This new camera offers the same superb characteristics than OCAM2 both in terms of speed and readout noise but also offers a shutter function that makes the sensor only sensitive to light for very short periods, at will. We will report on gating time and extinction ratio performances of this new camera. This device opens new possibilities for Rayleigh pulsed lasers adaptive optics systems. With a shutter time constant well below 1 microsecond, this camera opens new solutions for pulsed sodium lasers with backscatter suppression or even spot elongation minimization for ELT LGS. This camera has been successfully used for the first time on the CANARY instrument on the William Herschel Telescope. The final phase of CANARY is a demonstrator of a single MOAO channel for the proposed EAGLE instrument on the future European ELT. We will report on-sky performance with this instrument.

Deformable Mirrors developments at ESO

Already several deformable mirrors are in use at Paranal and more will come in the next years. With the next generation and telescope and associated instruments, adaptive optics become an integrated part of the telescope and provide as such the first layer of image correction. The M4 E-ELT has been specified to provide a good image quality under average seeing but it is also clear that going to larger field of view or when looking for higher performance additional deformable mirrors need to be implemented in the instruments. We present here how the needs in term of performance have evolved in the last decade. After a description of the performance for the future ELT M4, a review of the parameter space will be outlined and the development plan presented.

Analytical study of high altitude turbulence wide-field wavefront sensing: impact on the design and reconstruction quality of future solar AO systems

The European Solar Telescope is a 4-m planned facility designed to have high spatial resolution capabilities tounderstand the mechanisms of magnetic coupling in the chromosphere and the photosphere. It will feature both aconventional and a multi-conjugate adaptive optics (AO) of similar complexity than the systems for night-timeExtremely Large Telescopes. A particularity of solar AO is that it uses the solar granulation as a reference; therefore thewavefront sensing is performed using correlations on images with a field of view of ~10”. A sensor collecting such awide field of view averages wavefront information from different sky directions, affecting the sensing of high altitudeturbulence, the sampling of which does not depend anymore on the size of the subapertures only, but rather on the size ofthe projection of the extended field of view. Understanding this effect is crucial for the design of future solar facilities,i.e. to choose the adequate height of the DMs on MCAO systems, and also to predict the quality of the reconstructionthat such system would be able to achieve. For that reason, we have studied wide field sensing and found the analyticalequations that describe the process, in order to use this information as an input to improved designs of solar AO systems.

Experimental implementation of a Pyramid WFS: Towards the

Investigations into the Pyramid wavefront sensor (P-WFS) have experimentally demonstrated the ability toachieve a better performance than with a standard Shack-Hartmann sensor (SH-WFS). Implementation on theLarge Binocular Telescope (LBT) provided the rst operational demonstration on a facility-class instrument ofa P-WFS on sky. The desire to implement a Pyramid on an Extremely Large Telescope (ELT) requires furthercharacterisation in order to optimise the performance and match our knowledge and understanding of otherwave-front sensors (WFSs).Within the framework of the European Extremely Large Telescope (E-ELT), the Laboratoire d'Astrophysiquede Marseille (LAM) is involved in the preparation of the Single Conjugate Adaptive Optics (SCAO) system ofHARMONI, E-ELT's 1st light integral eld spectrograph (IFU). The current baseline WFS for this adaptiveoptics system is a Pyramid WFS using a high speed and sensitive OCAM2 camera. At LAM we are currentlycarrying out laboratory demonstrations of a Pyramid-WFS, with the aim to fully characterise the behaviour ofthe Pyramid in terms of sensitivity and linear range. This will lead to a full operational procedure for the use ofthe Pyramid on-sky, assisting with current designs and future implementations. The nal goal is to provide anon sky comparison between the Pyramid and Shack-Hartmann at Observatoire de la C^ote d'Azur (OCA). Herewe present our experimental setup and preliminary results.

Coupling of WFS with a segmented DM “Test of different concepts: SH, Pyramid, Zernike phase sensor”

LAM is developing several R&D activities for E-ELT instrumentation, in particular, different WFS concepts areinvestigated (Pyramid, ZELDA, a Zernike phase mask sensor, Phase diversity or still NL Curvature) and an ESO-EELTM1 mirror segment (1.5 m) has been demonstrated. Segmented mirrors are not only the solution for the problem of ELTsmonolithic size but also for other questions related to fabrication, optics replacement and transport. And, they are widelyused today for other applications: fiber coupling, LGS beam shaping, etc. Their only problem is how to assure thecophasing of segments to take advantage of the full optimum size. In the present work, we study the sensitivity todifferent WFS (Sack-Hartmann, Pyramid and ZELDA) to pupil phase discontinuity using a PTT mirror from Iris AO.Various test such as segment phasing, stability, saturation, flat, or still the addressing mode are then performed andcompared.

Anti-aliasing wave-front reconstruction with Shack-Hartmann sensors

The discrete sampling of a wave-front using a Shack-Hartmann sensor limits the maximum spatial frequencywe can measure and impacts sensitivity to frequencies at the high end of the correction band due to aliasing.Here we present Wiener lters for wave-front reconstruction in the spatial-frequency domain, ideally suited forsystems with a high number of degrees of freedom. We develop a theoretical anti-aliasing (AA) Wiener lterthat optimally takes into account high-order wave-front terms folded in-band during the sensing (i.e., discretesampling) process. We present Monte-Carlo simulation results for residual wave- fronts and propagated noise andcompare to standard reconstruction techniques (in the spatial domain). To cope with nite telescope aperturewe've developed and optimised a Gerchberg-Saxton like iterative-algorithm that provides superior performance.

State of the art IR cameras for wavefront sensing using e-APD MCT arrays

The recent discovery of electron initiated avalanche photodiodes (e-APDs) using mercury cadmium telluridesemiconductor materials has permitted a significant advance in short-wave infrared imaging. In the visible spectrum,electron-multiplying charge-coupled devices (EMCCDs) improved imaging techniques—especially in the life sciences.And yet, no significant breakthroughs have been made in infrared imagery since the hybridization of III-V or II-VIsemiconductors with low bandgap on complementary metal-oxide semiconductor (CMOS) read-out integrated circuits(ROICs).In 2012, Philippe Feautrier et al.[1] and Gert Finger et al. [2] of the European Southern Observatory (ESO; Garching,Germany) reported successful hybridization of HgCdTe e-APDs on CMOS ROICs with a significant number of pixels(320 × 256). Feautrier et al. [3] also reported the use of a Sofradir/CEA-LETI APD array on the ESO Very Large TelescopeInterferometer (VLTI), called RAPID, demonstrating for the first time the successful operation of this technology in arepresentative environment.First Light Imaging [4] is the first commercial company to make e-APD infrared array technology available in its C-REDOne camera. Using a 320 × 256, 2.5 μm cutoff wavelength HgCdTe e-APD array deeply cooled to 80 K with a highreliabilitypulse-tube cryocooler (mean-time between failure or MTBF of approximately 90,000 hours), the camera has ahigh readout speed of 3500 frames/s (full frame) while exhibiting a readout noise below one electron—thanks to the APDgain in the range of 1 to 60.This paper reports on the results of the Sofradir/CEA-LETI RAPID program [5] and on the development of the C-REDone infrared camera from First Light Imaging based of the SELEX SAPHIRA detector [6]. The interest of ShortWavelengths InfrRed (SWIR) e-APD versus more classical HgCdTe arrays as infrared tilt sensors or pyramid wavefrontsensor like what is currently developed at Keck Observatory is also discussed in this paper.

AO for MOSAIC, the E-ELT Multiple Object Spectrograph

MOSAIC is the proposed multiple object spectrograph for the E-ELT that will eventually combine two AO observing modes within a single instrument. MOSAIC will contain up to 20 open-loop multiple object AO channels feeding NIR IFUs in addition to up to 200 seeing-limited (or GLAO corrected) VIS – NIR fibre pickoffs. Wavefront tomography will be implemented using a combination of LGS and a few high-order NGS distributed across the field with the wavefront correction applied in a split open/closed loop configuration. MOSAIC will be the only E-ELT instrument planned that can utilize the full 10 arcminute diameter field of view, enabling highly efficient observing modes for this workhorse instrument. Use of the full E-ELT field inevitably requires a closer integration between the telescope control system and the instrument AO systems, however this can bring several potential benefits to overall system performance. Here we present the initial design concept and baseline performance of the MOSAIC instrument and AO system(s) taking advantage of the CANARY on-sky results and inheriting from the previous Phase A study of EAGLE. Finally, we will highlight areas of system performance and calibration that will require further analysis and trade-off during the course of the upcoming Phase A study.

Measuring Segment Piston with a Dispersed Fringe Sensor on the Giant Magellan Telescope

The Giant Magellan Telescope (GMT) consists of seven 8.365 m segments with a separation of 0.345 m. A uniquechallenge for GMT lies in phasing these segments and, in particular, how to measure segment piston optically.Making segment piston measurements is relatively straight-forward when using diffraction-limited light, such aswavefront-corrected light at near infrared wavelengths. Unfortunately, we don’t have that luxury, since all of thatlight is passed to the science instrument. Instead, we must use stars 6’-10’ from the optical axis when guidingwith laser guide stars. The segment piston measurement can be made in two different ways using subaperturesthat span adjacent segments with dispersed broadband light. The Dispersed Hartmann Sensor takes the averagesthe Fourier phase of the dispersed fringes over baselines spanning the segment gap, while the Dispersed FringeSensor works by measuring the angle of the dispersed fringes. We explore the properties of the two approaches,discuss their relative advantages, and evaluate their performance using end-to-end simulations in YAO.

Measuring Segment Piston with a Non-Redundant Pupil Mask on the Giant Magellan Telescope

The Giant Magellan Telescope (GMT) consists of seven 8.365 m segments with a separation of 0.345 m. A uniquechallenge for GMT lies in phasing these segments and, in particular, how to measure segment piston optically.In this paper, we present a results of a phasing strategy using a non-redundant pupil mask. We show how thismethod can be extended to measure segment piston differences of more than half a wave by using broadbandlight.

The use of CPU, GPU and FPGA in real-time control of adaptive optics systems

The use of deformable mirrors for the compensation of the effect of the atmospheric turbulence in Adaptive Optics (AO) systems requires a very fast computation of the adequate commands with the information provided by wavefront sensors. Providing accurate results with minimum latency is vital to achieve optimum performance. Conventional CPUs, GPUs and also FPGAs have been successfully used in real-time control for AO at IAC for a number of projects (EDIFISE, AOLI, AOconFPGA, GTCAO). Based in this experience, a comparative description is made in this paper, pointing out advantages and drawbacks of each solution as seen by each of the projects.

Selex infrared sensors for astronomy – present and future

Many branches of science require infrared detectors sensitive to individual photons.Applications range from low background astronomy to high speed imaging. Selex-ES Ltd inSouthampton, UK, has been developing HgCdTe avalanche photodiode (APD) sensors forastronomy in collaboration with ESO since 2008 and more recently the University of Hawaii.The devices utilise MOVPE grown on low-cost GaAs substrates and in combination with amesa device structure achieve very low dark current and near-ideal MTF. MOVPE providesthe ability to grow complex HgCdTe heterostructures which have proved crucial to suppressbreakdown currents and allow high avalanche gain in low background situations. A customdevice called Saphira (320x256/24μm) has been developed for wavefront sensors,interferometry and transient event imaging. This device has achieved read noise as low as0.26 electrons rms and single photon imaging with avalanche gains up to x100. It is used inthe ESO Gravity program for adaptive optics and fringe tracking and has been successfullytrialled on the 3m NASA IRTF, 8.2m Subaru and 60 inch Mt Palomar for lucky imaging andwavefront sensing. In future the technology offers much shorter observation times for readnoiselimited instruments, particularly spectroscopy. The paper will describe the MOVPEAPD technology and current performance achievements.

Near-infrared tip-tilt sensing at Keck: System architecture and on-sky performance

The sky coverage and performance of laser guide star (LGS) adaptive optics (AO) systems is limited by the natural guidestar (NGS) used for low order correction. This limitation can be reduced by measuring image motion of the NGS in thenear-infrared where it is partially corrected by the LGS AO system and where stars are generally several magnitudesbrighter than at visible wavelengths. We have integrated a near-infrared tip-tilt sensor with the Keck I telescope’s LGSAO system and recently began offering it for science use. The implementation involved modifications to the AO bench,real-time control system, higher-level controls and operations software. The tip-tilt sensor is a H2RG-based near-infraredcamera with 0.05 arcsecond pixels. Low noise at high sample rates is achieved by only reading a small region of interest,from 2x2 to 16x16 pixels, centered on an NGS anywhere in an 100 arc second diameter field. The sensor operates ateither Ks or H-band using light reflected by a choice of dichroic beam-splitters located in front of the OSIRIS integralfield spectrograph. This work presents an overview of the completed system along with on-sky performance results.Lessons learned and efforts to extend the capabilities and further optimize the system are also discussed.

Prototyping the GMT phasing camera with the Magellan AO system

The future diffraction-limited performance of the 25.4 meter Giant Magellan Telescope (GMT) will rely on the activeand adaptive wavefront sensing measurements made by the Acquisition, Guiding, and Wavefront Sensor (AGWS)currently being designed by SAO. One subsystem of the AGWS, the phasing camera, will be responsible for measuringthe piston phase difference between the seven GMT primary/secondary segment pairs to 50 nm accuracy with full skycoverage using natural guide stars that are 6-10 arcmin off-axis while the on-axis light is used for science operations.The phasing camera will use a dispersed fringe sensor to measure the phase difference in rectangular subaperturesspanning the gaps between adjacent mirror segments. The large gap between segments (>295 mm, compared to 3 mmfor the Keck telescope) reduces the coherence of light across the subapertures, making this problem particularlychallenging. In support of the AGWS phasing camera technical goals, SAO has undertaken a series of prototypingefforts at the Magellan 6.5 meter Clay telescope to demonstrate the dispersed fringe sensor technology and validateatmospheric models. Our latest on-sky test, completed in December 2015, employs a dual-band (I and J) dispersedfringe sensor. This prototype uses an adaptive optics corrected beam from the Magellan AO adaptive secondary system.The system operates both on-axis and 6 arcmin off-axis from the natural guide star feeding the MagAO wavefrontsensor. This on-sky data will inform the development of the AGWS phasing camera design towards the GMT first light.

Filtering the interaction matrix in an adaptive optics system

We present a method to reduce the noise in the interaction matrix by calibration of the adaptive optics system.The method utilizes a matching between the actuators on the deformable mirror and the sub-apertures on thewavefront sensor to dene a lter matrix. Then, the lter matrix is applied to the sparse interaction matrix toremove the elements that should be zero. This method is useful for high-order systems and/or noise calibrationissues. The latter case is illustrated in the problem of on-sky calibration of an adaptive secondary system on atelescope, with a natural guide star, in which the noise in the interaction matrix is increased by the eects ofthe turbulent atmosphere.

Pyramid versus Shack-Hartmann: Trade Study Results for the NFIRAOS NGS WFS

NFIRAOS, the first light AO system for the Thirty Meter Telescope, will include a natural guide star (NGS) pyramidwave-front sensor (PWFS). This WFS will have two functions: (i) when there is a bright enough NGS within the sciencefield and the lasers are turned off, the PWFS will act as the fast high order WFS driving the SCAO loop (e.g. for highcontrastimaging); and (ii) when the lasers are in use and the system operates in MCAO mode, the PWFS will act as aslow truth WFS (e.g. to measure drifts in the structure of the sodium layer). The decision to select a PWFS instead of amore conventional Shack-Hartmann WFS (SHWFS) is the outcome of a detailed trade study. In this paper, wesummarize the results of this trade study. These include extensive simulation work, which shows that, in the expectedoperating conditions of NFIRAOS, the PWFS will bring significant performance improvements, including higher Strehlratio, higher limiting magnitude and lower residual speckle levels for high contrast imaging, even when the system hasto correct for significant levels of non-common path aberrations. Our simulation results also provides new insights onthe properties of the PWFSs. We also report on opto-mechanical design work, which shows that, with the PWFS, the twofunctions (i) and (ii) can actually be combined into a single optical path, thus reducing the complexity in terms ofnumber of mechanisms and optical elements. Finally, we discuss the impacts of switching to a PWFS on the otheralready designed NFIRAOS sub-systems (e.g. the real-time computer), which we have found to be very modest.

Dark Wavefront Sensing

The concepts and considerations that could leads to the development of a novel kind of classes of wavefront sensors inwhich the information is retrieved by the absence of photons rather than from their presence are shown. In quantumoptics the concept of ”sensing” an object without actually having photons interacting with it is already known. Thepotentiality in terms of sensitivity has been already pointed out. Under the conditions that background counts are smallenough (something that evolved with time with respect to a couple of decades ago, as today close to zero RON detectorsare available, although sky background would continue to impose some limit to this approach) detecting ”no photons”can be made with an SNR larger than detecting a ”given amount of photons” in a number of practical situations. Whilewe review the case of the coronograph coupled with a conventional WFS -a case already proposed in the literature- weexplore variations on the theme of the Smartt wavefront sensor and in particular we explore the case of a double channelWFS where two images of the pupil are exploited and the flat wavefront is perceived as no photons on the pupils. Thepresence of a signal on subapertures on one pupil or the other indicates the sign of the wavefront perturbation. Thesystem can be tuned in its sensitivity and -potentially- adjusted in order to have the two detectors working with close tozero flux on them while in closed loop operations. As the ”signal” is coming from the condition of no photons Idescribed these as a ”Dark” WFS.

Multi-conjugate Adaptive Optics at Big Bear Solar Observatory

A multi-conjugate adaptive optics (MCAO) system for solar observations has been set up at the 1.6-meter clearaperture New Solar Telescope (NST) in Big Bear Lake, California. Being a pathnder to address fundamentaldesign questions in solar MCAO experimentally, the system is purposely exible. We deploy three deformablemirrors (DMs). One of which is conjugate to the telescope pupil, and the other two to distinct higher altitudes.The pupil DM can be either placed into a pupil image up- or downstream of the high-altitude DMs. Thehigh-altitude DMs can be separately and quickly conjugated to various altitudes between 2 and 8 km. ThreeShack-Hartmann wavefront sensor units are available, one for low-order, multi-directional sensing and two highorderon-axis sensing of which one is used at a time. The exibility of the setup allows us to experimentallystudy the various sequencings of DMs and WFSs, which are hard to simulate conclusively. We report on thepreliminary results and summarize the design and the conguration options of the MCAO system at Big BearSolar Observatory (BBSO).

GMCAO for E-ELT: a feasibility study

In this paper, we discuss the feasibility and the performance assessment of a possible MCAO system for E-ELT, basedon the novel concept of Global MCAO, which takes advantage of a very wide technical FoV to perform adaptive opticscorrection using only natural guide stars, with the aim to increase the sky coverage. The technique envisages thedefinition of Virtual-DMs, as tools for the global reconstruction. This investigation has been carried out during afeasibility study we performed for ESO, in which we combined computations, simulations and literature. The aim of thisanalysis is to identify and review the main parameters and the technical issues, which would act as error sources in a realGMCAO system, evaluating their contribution to the overall performance. The study involves both issues related to thePyramid WFS in general, and to the GMCAO case in particular, including the wavelength and FoV size selection, thenumber of guide stars and reconstructed Virtual-DMs, and actual components parameters.

Statistical and morphological analysis of mock galactic fields in the Global-MCAO perspective

Enabling accurate morphological and photometric analysis across a wide Field of View (FoV) is one of the keyscience requirement for multi-conjugate adaptive optics systems. With this motivation we present a study aimedat the investigation of the performance of Global-MCAO (GMCAO). Such an innovative concept, based onnatural guide stars in a wide technical FoV, addresses the need for an increase of the sky coverage, which is akey ingredient for future MCAO-based VLT instruments and for the forthcoming E-ELT. Using a tomographicsimulation tool, we compute a map of the Strehl Ratio in a 250′′ × 250′′ area, matching the Chandra Deep FieldSouth survey. Mock images of star and galactic fields are then built using such a map and analyzed as if theywere real and observed with the E-ELT instrumentation. We perform the source detection and two-dimensionallight-profile modeling using the IRAF/ELLIPSE code and we then compare the recovered parameters with theintrinsic data. The good match of our results claims that GMCAO is a reliable approach that can rebuild theAO concepts and can provide a frame of reference for a number of science cases.

Non common path aberration correction with non linear WFSs

Non Common Path Aberrations (NCPA) are a usual problem encountered when using an Adaptive Optics System (AO)to produce corrected images in an astronomical instrument. The usual way to correct for such NCPA is to introduce anoffset in the WaveFront Sensor (WFS) signals that corresponds to the aberration to correct. In such a way, when the AOloop is closed, the Deformable Mirror (DM) will converge to the shape required to null the NCPA. The method assumesthat the WFS operation is linear and completely described by some pre-calibrated interaction matrix. This is not the casefor some frequently used wavefront sensors like the Pyramid sensor or a quad-cell Shack-Hartmann sensor. Here wepresent a method to work in closed loop with a Pyramid Wavefront Sensor (PWS), or more generally a non linear WFS,while introducing a static offset on the DM. The DM shape is kept constant even if the AO residuals change over timebecause of variations of seeing, wind speed and so on. Results from numerical simulation and first on sky data from LBTFLAO system and LUCI2 facility instrument are presented.

Use of Laser Guide Star with Pyramid Wavefront Sensor

Laser Guide Star (LGS) reference sources, articially generated at an altitude of 90 km at the atmospheric sodiumlayer, are mandatory to ensure large sky coverage of astronomical Adaptive Optics (AO) systems developed for8m and Extremely Large Telescope (ELT) class telescopes. As a result of the projection eect of an object locatedat a nite distance from the telescope, the AO wavefront sensor (WFS) perceives the LGS as elongated. Thiselongation is a few arcseconds for the 8m class telescopes and can be more than 10 arcseconds for the ELTs. Thiscan pose several challenges when using a Shack-Hartmann wavefront sensor (SHS) such as truncation eects,the requirement for large detectors, and/or the requirement for detectors with geometry that corresponds to thesource shape. In this work, we report the results of numerical simulations focused on the pyramid wavefrontsensor (PWFS) sensitivity when used with a LGS, in this case, a 2D extended object. In addition, the closed-loopperformance of both PWFS and SHS are estimated.

INO Pyramidal Wavefront Sensor Demonstrator: first closed-loop on-sky operation at Mont-Mégantic Telescope

Wavefront sensing is one of the key elements of an Adaptive Optics System. As an alternative to the commonlyencountered, commercially available Shack-Hartmann WFS (SH-WFS), the more recent Pyramid-WFS (P-WFS) isproving to be a very attractive technology, thanks to its high-sensitivity and robustness against aliasing. At INO, centerfor applied research in optics and technology transfer in Quebec City, Canada, we have developed a compact andflexible P-WFS prototype that can be integrated into an AO system. This P-WFS prototype includes a fast piezo-electricmodulation mirror and a high-sensitivity EMCCD camera. Our P-WFS was installed on the experimental AO systemdeveloped by Laval University in Quebec for the 1.6-m Mont-Mégantic telescope, which also includes a commercialhigh-speed SH-WFS. The architecture is such that both WFSs can take measurements simultaneously, and either one canbe used to drive the deformable mirror. Here we present the on-sky results obtained with the INO P-WFS module.

System analysis of the Segmented Pupil Experiment for Exoplanet Detection - SPEED - in view of the ELTs

SPEED is a new experiment in progress at the Lagrange laboratory to study some critical aspects to succeed invery deep high-contrast imaging at close angular separations with the next generation of ELTs. The SPEEDbench will investigate optical, system, and algorithmic approaches to minimize the ELT primary mirrordiscontinuities and achieve the required contrast for targeting low mass exoplanets. The SPEED projectcombines high precision co-phasing architectures, wavefront control and shaping using two sequential high orderdeformable mirrors, and advanced coronagraphy (PIAACMC). In this paper, we describe the overall systemarchitecture and discuss some characteristics to reach 10-7 contrast at roughly 1λ/D.

Non Boltzmann Modeling of Sodium Guidestar Returns and Implications for Guidestar Linewidth

To date, modeling of sodium guidestar mesospheric excitation has assumed that the distribution within the sodium ground states (F = 1 or F = 2) and the distribution between the two ground states was well modeled by a Maxwell-Boltzmann distribution. Recent experimental evidence from Starfire Optical Range and the modeling results of Bhamre et al., show that the Maxwell-Boltzmann distribution is not a good approximation for the velocity distribution within ground states after optical excitation by a narrowband laser (linewidth < 1 MHz). A model is presented to account for the non-Boltzmann effects on the velocity groups of the Doppler profile of the mesospheric sodium atoms. The model is shown to agree fairly well with data provided from the 3.5m telescope and narrowband laser guidestar at Starfire Optical Range. These results challenge the efficacy of reducing the linewidth of sodium laser guidestars below 1 MHz.

A New Slow Focus Sensor for GeMS

The Gemini South 8-meter telescope’s Multi Conjugate Adaptive Optics System GeMS is about to enter a new era ofscience with an entire new upgrade for its Natural Guide Star wave front sensor (NGS2). With NGS2 the limitingmagnitude of the natural guide stars used for tip/tilt sensing is expected to increase from its current limit of 15.4 to 17+in R-band. This will provide a much greater sky coverage over the current system. NGS2 is a complete replacement ofthe current Natural Guide Star wave front sensor (NGS). This presents an interesting challenge as the current NGSincludes a Slow Focus Sensor (SFS) used to compensate for the sodium layer mean altitude variations. With the newNGS2 setup, this SFS will be removed and a suitable replacement must be found. Within the Gemini environment thereexist two facility wave front sensors, Peripheral Wave Front Sensors one and two (PWFS1 and PWFS2), that could actas an SFS. Only one of these (PWFS1) is located optically in front of the GeMS Adaptive Optics (AO) bench (Canopus).We are currently preparing this wave front sensor as the new SFS for GeMS under the NGS2 setup. The results ofseveral nighttime and daytime tests show that PWFS1 will be an adequate SFS for GeMS in the NGS2 setup providingexcellent sky coverage without compromising the GeMS Field of View (FoV).

Implementation of SCAO for ELT-CAM / MICADO-MAORY

ELT-CAM is the E-ELT rst-light instrument that associates MICADO, the near-infrared imager, and MAORY,its multi-conjugate adaptive optics (MCAO) module. ELT-CAM will also come with a single conjugate adaptiveoptics (SCAO) capability motivated by scientic programs for which SCAO provides the best AO performance(e.g. exoplanets, solar system science, bright AGNs, etc).This SCAO capability will be developed within MICADO through a dedicated SCAO module with its naturalguide star (NGS) wavefront sensor (WFS), allowing MICADO to work in a SCAO stand-alone mode withoutMAORY, and inside MAORY with the same dedicated NGS WFS. MICADO and MAORY consortia are workingtogether on the development of this SCAO capability in order to perform a WFS trade-o study between Shack-Hartmann and Pyramid, to optimize the design of the NGS WFS as well as the interfaces between the twoinstruments. We present here the current status of the work done by the two consortia on the implementationof this SCAO capability for MICADO and MAORY.

Laser-only AO, readout noise studies and AO verification and integration for ELTs

We present a concept for visible near-diffraction limited lucky imaging with full-sky laser assisted adaptive optics.Simulation results are given, along with first on-sky measurements taken with the CANARY AO system on theWilliam Herschel Telescope, and extension to ELT scales.We also present a study of readout noise in EMCCD and sCMOS detectors, with findings that are perhapssurprising when compared with naive models of sCMOS noise. We discuss the relative trade-offs of these detectorsfor ELT-scale AO and lucky imaging.Finally we introduce the concept of real-time simulation, necessary for integration and verification of ELT-scale AO systems, and provide details of the system developed for CANARY.

The GMT Dynamic Optical Simulation

The Giant Magellan Telescope (GMT) is a gregorian 25.5-meter diameter primary mirror (M1) made of 7 8.4-meter diameter circular aspheric segments. The secondary mirror (M2) is a 1/8th down-scale model of M1 madeof 7 1- meter diameter segments. Each segments has positionners to adjust its 6 rigid body motions. The gureof M1 segment is controlled with 44 bending modes and M2 segments are deformed using 672 actuators. Inthe active and adaptive operation modes of the GMT, around a dozen wavefront sensors (WFS) are selectivelyused to monitor the optical aberrations building-up into the telescope. A dedicated control system feeds backthe WFS measurements to the mirrors actuators to deliver image quality optimized for the eld of view of eachscientic instrument. This paper describes the GMT Dynamic Optical Simulation (DOS) tool. DOS integratesthe optical and mechanical model of the telescope together with the control system. DOS is a cloud-basedoptical propagation software package with build-in models for both geometric and Fourier optics and a fullcontrol algorithm development environment.

Progress report on the ESO 4LGSF

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.

Wavefront control simulations for the Giant Magellan Telescope: Field-dependent segment piston control

We present in this paper preliminary simulation results aimed at validating the GMT piston control strategy. Wewill in particular consider an observing mode in which an Adaptive Optics (AO) system is providing fast on-axisWF correction with the Adaptive Secondary Mirror (ASM), while the phasing system using multiple SegmentPiston Sensors (SPS) makes sure that the seven GMT segments remain phased. Simulations have been performedwith the Dynamic Optical Simulation (DOS) tool developed at the GMT Project Oce, which integrates theoptical and mechanical models of GMT. DOS fast ray-tracing capabilities allows us to properly simulate theeect of eld-dependent aberrations, and in particular, the so-called Field Dependent Segment Piston (FDSP)mode arising when a segment tilt on M1 is compensated on-axis by a segment tilt on M2. We will show thatwhen using an asterism of SPS, our scheme can properly control both segment piston and the FDSP mode.

Processing of external SLODAR turbulence profile measurements to support adaptive optics performance predictions

The Adaptive Optics Facility (AOF) at the Very Large Telescope (VLT) will have two ground layeradaptive optics (GLAO) modes of operation. To make the best use of these modes, informationabout the ground layer turbulence prole up to 500 m will be important. External turbulenceproling support will be provided by a robotic slope detection and ranging (SLODAR) instrumentwith 8 resolution elements and a maximum sensing altitude of 100-500 m. When proling at thehigher end of this range the surface layer of turbulence is not resolved so the fraction observed bythe Unit Telescopes (UTs) is ambiguous. Here we present a method of estimating the surface layercontribution seen by the UTs by assuming an exponential decay model for the surface layer. Older,higher resolution, proles from the prototype surface layer SLODAR instrument (from 2011-2012)have been used to determine the most appropriate scale height for the model. By incorporating themodel, a better estimate of the integrated turbulence strength from the UT dome height upwardscan be achieved.

Development of multi time-step tomographic reconstruction with RAVEN

In this paper, we present a tomographic reconstruction method to reduce a tomographic error, multi time-stepreconstruction, for a wide-eld adaptive optics (WFAO). Based on the frozen ow assumption, we can computethe time evolution of measurements from wave-front sensors (WFS) at previous time-steps with using windinformation. Our idea is to reduce the tomographic error by using the measurements at both the current andprevious time-steps simultaneously. We also develop a method to estimate wind speed and direction at eachaltitude from temporal correlations of phase distortion pattern reconstructed by a classical tomography. Weevaluate the performance of the method by a laboratory experiment with the RAVEN, a multi-object adaptiveoptics (MOAO) technical and science demonstrator. In the laboratory experiment, our wind estimation methodcan estimate wind speeds and directions of multiple layers. By the multi time-step reconstruction method, theensquared energy in a 140 mas box increases about 3{5% compared with a classical tomographic reconstruction.

Resolving the low-mass content of Westerlund 1 using MCAO

We present deep Ks band Gemini GeMS/GSAOI observations of Westerlund 1, the most massive young Galacticstar cluster known. The high spatial resolution combined with a relatively stable point spread function across alarge eld of view provide unique possibilities to resolve the low-mass content of the cluster. We show that theclean point spread function is crucial in handling the source detection in this crowded eld suering extremelyhigh contrast from the brightest hypergiants in the cluster to faint brown dwarfs.

Recent Improvements to the Keck II Laser Guide Star Facility

The laser guide star (LGS) adaptive optics (AO) system on the Keck II telescope has been upgraded with a Center Launch Laser System (CLS) and a next generation laser (NGL; i.e. a TOPTICA/MPBC laser) is being implemented. The purpose of the CLS upgrade is to improve the performance of the existing Keck II LGS AO system by reducing the perspective elongation of the LGS as seen by the AO wavefront sensor and hence the measurement error, one of the largest terms in the current error budget. This performance improvement is achieved by projecting the laser from behind the Keck telescope’s secondary mirror instead of from the side of the Keck telescope. The purpose of the NGL upgrade is to increase the laser return and improve laser operability for science operation. The higher return from the NGL would open up new possibilities for further AO upgrades such as a laser asterism to reduce the focal anisoplanatism, and to increase the wavefront sensor (WFS) sampling rate to reduce the bandwidth error in addition to reducing the measurement error.The CLS transitioned to science operation in June 2015. The NGL with the CLS had first light on Dec. 1, 2015 and is being optimized to support transitioning to science operations in April 2016. This paper provides an overview of the design, implementation and on-sky performance of the new launch system and laser. The results are discussed in the context of AO for extremely large telescopes.

Point spread function determination for Keck adaptive optics: overview

One of the primary scientific limitations of adaptive optics (AO) has been the incomplete knowledge of the point spread function (PSF), which has made it difficult to use AO for accurate photometry and astrometry in both crowded and sparse fields, for extracting intrinsic morphologies and spatially resolved kinematics, and for detecting faint sources in the presence of brighter sources. To address this we initiated a program to determine and demonstrate PSF determination for science observations obtained with Keck AO. This paper aims to give a broad view of the progress achieved in implementing this capability for Keck AO science observations.The concept and the implementation are briefly described. The design and development of prototype operational tools for automated PSF reconstruction is presented in detail. On-sky performance of the technique is discussed by comparing the reconstructed PSFs to the NIRC2 science camera’s PSFs. The PSF algorithm development for this program is presented in this conference in a separate paper (Jolissaint et al. 2016).

Observations of the dynamic turbulence above La Palma using Stereo-SCIDAR

Stereo-SCIDAR is a generalised-SCIDAR instrument which is used to characterise the atmospheric optical turbu- lence in terms of strength (Cn2) and wind velocity profile using the triangulation technique and an optical binary star. Stereo-SCIDAR differs from most other SCIDAR instruments in that, instead of overlapping pupil images on a single detector, the image of each star is recorded on a separate EMCCD. Separating the pupil images in this way leads to several advantages, including better signal to noise ratios, larger useable magnitude difference of the target stars and reliable automated wind velocity measurements. The data is analysed and made available to observatory systems in real-time. Here we review the Stereo-SCIDAR technique and present recent results from the instrument on the Isaac Newton Telescope, La Palma.

Miniaturized Shack-Hartmann Wavefront-Sensors for ELTs

The miniaturization of wavefront sensors overcomes some of the potential barriers faced by ELTs in implementing large- scale multi-object adaptive optics over large focal surfaces. The Australian Astronomical Observatory is prototyping a compact and lightweight Shack-Hartmann wavefront-sensor designed to be positioned by their Starbug parallel fibre positioning robots. Starbugs perform the critical positioning of optical fibers for the MANIFEST instrument for the GMT. Each wavefront sensor uses a set of polymer bundles to relay the image produced by a microlens array near to the focal plane to a re-imaging module. This allows multiple wavefront sensors to be multiplexed to a single low-noise camera for cost efficiencies per wavefront sensor. The ability to have a large number of wavefronts sensors are likely increase the scientific impact of future ELTs. We illustrate our miniature wavefront sensor concept with a potential design for the GMT.

A Fresnel propagation analysis for SPEED (Segmented Pupil Experiment for Exoplanet Detection)

Direct detection and characterization of exoplanets is a major scientific driver of the next decade. Direct imaging requires challenging techniques to observe faint companions around bright stars. The development of future large telescopes will increase the capability to directly image and characterize exoplanets thanks to their high resolution and photon collecting power. The E-ELT will be composed of a segmented ~40 m-diameter primary mirror. High contrast imaging techniques for E-ELT will thus need to deal with amplitude errors due to segmentation (pupil discontinuities between the segments). A promising technique is the wavefront shaping. It consists in the use of deformable(s) mirror(s) to cancel the intensity inside the focal plane region. Algorithm improvements and laboratory demonstrations have been developed since the last 20 years. The use of 2 deformable mirrors (DM) in non-conjugated planes will allow correcting not only for phase aberrations but also for the amplitude errors. Lagrange laboratory has begun in 2013 the development of an instrumental project called SPEED (Segmented Pupil Experiment for Exo-planet Detection). Its goal is to develop and test high-contrast imaging techniques optimized for segmented pupil. In this paper we present a detailed end-to-end simulation for the optimization of the SPEED experiment optical design. In particular, we pay attention to the optimal separation between the two DMs necessary for phase and amplitude correction. The trade-off between various parameters (field of correction, field of view, size constraints,...) is presented and discussed.

Implementation of SLODAR atmospheric turbulence profiling to the ARGOS system

ARGOS is the Ground Layer Adaptive Optics system of the Large Binocular Telescope, on each side it uses three Laser Guide Stars, generated by Rayleigh backscattered light of pulsed lasers. Three Shack-Hartmann WFS are used to measure the wavefront distortion in the Ground Layer. The SLOpe Detection And Ranging (SLODAR) is a technique used to measure the atmospheric turbulence profiles. Cross correlation of wavefronts gradients from multiple stars are used to estimate the relative strength of turbulent layers at different altitudes. We present here the first results obteined on sky of appling the SLODAR technique to ARGOS comparing then with a previous study based on end-to-end simulations.

Optical design of the Post Focal Relay of MAORY

The Multi Conjugate Adaptive Optics Relay (MAORY) for the European Extremely Large Telescope shall re-image the telescope focal plane for the client instruments installed on two exit ports. By means of natural and artificial (laser) reference sources for wavefront sensing, and of deformable mirrors for wavefront correction, MAORY shall be able to compensate the wavefront disturbances affecting the scientific observations, achieving high Strehl ratio and high sky coverage. The optical interfaces to the client instruments must replicate the telescope one while the volume allocation on the Nasmyth platform is under definition at the moment of this writing. We show the latest version of the optical design that matches the current requests and its optical performance. The laser guide stars channel, separated from the science path by means of a dichroic beam-splitter, is also presented.

Self-Coherent Camera as a focal plane phasing sensor - Overview and early comparison with the Zernike Phase Contrast Sensor

In order to achieve the high performance required for the astronomical science programs with coming Extremely Large Telescopes (ELTs), the errors due to segment misalignment must be reduced to tens of nm. Therefore the development of new co-phasing techniques is of critical importance for ground-based telescopes, and to a large extent for future space-based missions. We propose a new co-phasing method directly exploiting the scientific image delivered by the Self-Coherent Camera (SCC) by adequately combining segment misalignment estimators (piston and tip/tilt) and image processing. The Self-Coherent Camera Phasing Sensor (SCC-PS) is shown to be capable of estimating accurately and simultaneously piston and tip/tilt misalignments and to correct them in close-loop operation in a few iterations. By contrast to several phasing sensor concepts the SCC-PS does not require any a priori on the signal at the segment boundaries, or a dedicated optical path. The SCC-PS is a non-invasive concept that works directly on the scientific image of the instrument, either in a coronagrahic or a non-coronagraphic observing mode. The primary results obtained in this study are very promising and demonstrate that the SCC-PS is a serious candidate for segment co-phasing at the instrument level or at the telescope level for both ground- and space-based applications. Applications of the estimators and algorithm developed for the SCC-PS seem to be possible to other on-segment aberration measurement. Early studies are already in progress to adapt these processes.

XAO at LBT: current performances in the visible and upcoming upgrade

The Extreme Adaptive Optics is one of the new frontiers for astronomical AO and LBT is hosting one of the few XAO systems available on 8m class telescopes. With the 4Runner, a fast visible camera, we measured the AO performances at visible wavelengths. We were able to correct up to 500 modes at 1kHz of framerate, reaching Strehl ratios of about 40% at 630nm of wavelength. We will show the results obtained in daytime with the calibration source and on-sky using natural guidestars. These performances have been obtained at the LBTI-DX focus, one of the 4 LBT focal stations equipped with a SCAO system. All these 4 systems will be upgraded in the framework of the SOUL project. The wavefront sensor detectors will be substituted with low readout noise ones, the adaptive secondary firmware and the AO control both improved. We will briefly describe here SOUL and its performances as estimated via numerical simulations.

Modeling the pyramidal sensor by a ZEMAXTM user defined surface.

After 20 years of wavefront sensors based on pyramid (PWFS), there are no straightforward ways to model such device in standard sequential ray-tracing software: modeling strategies tend to be oriented to the needs of the single user only and, in general, are unsatisfactory due to lack of flexibility. To overcome this problem, we have exploited the possibility of ZEMAXTM – one of the ray- tracing software mostly in use nowadays – to develop a user defined surface (UDS), whose properties are described in a dynamic link library (DLL) written in C language. The pyramid UDS approach greatly improves the versatility during the design and simplifies both quality and tolerance analysis. In order to prove the potentiality of our UDS-DLL surface, referred as PAM2R, we reproduced the optical layout of two PWFS systems already installed at LBT: the single-conjugate system FLAO, and the ground-layer system GWS of LINC-NIRVANA. In this proceeding we will highlight the main characteristics of the PAM2R surface, showing various results we obtained on the above case studies with the aim to establish a common design playground for the PWFS in the AO community.

Development of an ELT XAO testbed using a self referenced Mach-Zehnder wavefront sensor

Extreme adaptive optics (XAO) has severe difficulties meeting the high speed (>1kHz), accuracy and photon efficiency requirements for future extremely large telescopes. An innovative high order adaptive optics system using a self-referenced Mach-Zehnder wavefront sensor (MZWFS) allows counteracting these limitations. In addition to its very high accuracy, this WFS is the most robust alternative to segments gaps and telescope spiders which can result in strong wavefront artifacts. In particular in XAO systems when the size of these gaps in the wavefront measurement is comparable to the sub aperture size, loss in performance can be very high. The MZWFS estimates the wavefront phase by measuring intensity differences between two outputs, with a λ/4 path length difference between its two legs, but is limited in dynamic range. During the past few years, such an XAO system has been studied by our team in the framework of 8-meter class telescopes. In this paper, we report on our latest results with the XAO testbed recently installed in CRAL laboratory, and dedicated to high contrast imaging with 30m-class telescopes (such as the E-ELT or the TMT). A woofer-tweeter architecture is used in order to deliver the required high Strehl ratio (>95%). It consists of a 12x12 deformable mirror (DM) and a 512x512 Spatial Light Modulator (SLM) characterized both using monochromatic and polychromatic light. We present our latest experimental results, including components characterization, close loop performances and sensitivity to calibration errors. This work is carried out in synergy with the validation of fast iterative wavefront reconstruction algorithms and the optimal treatment of phase ambiguities in order to mitigate the dynamical range limitation of such a wavefront sensor.

Durham AO Real-time Controller (DARC) running on Graphics Processing Units (GPUs)

The requirements on the real-time control systems for ELT instruments strongly encourage an investigation of newly emerging hardware and an assessment of its suitability for the job. We have implemented the full AO data processing pipeline on Graphics Processing Units (GPUs), within the framework of Durham AO Real-time Controller (DARC). The pixel data are copied from the CPU memory to the GPU memory. On the GPU, the data are processed and the DM commands are copied back to the CPU. For a system of 80x80 subapertures, the highest rate achieved on a single GPU is 550 frames per second. When running on two or more GPUs, the kernel launching time limits the increase in frame rate. We have also implemented the correlation centroiding algorithm, which - when used - reduces the frame rate by about a factor of two.

Analysis of GeMS tip-tilt on-sky data: LQG implementation for vibration rejections

Adaptive Optics (AO) systems aim at detecting and correcting for optical distortions induced by atmospheric turbulences on ground based telescopes astronomical images. They are also extremely sensitive to extraneous sources of perturbations such as vibrations, which degrade their performance. A new well defined vibration at 37Hz has been detected in January 2015 and is still currently affecting the Gemini South telescope secondary mirror. We show how its existence limits the performance of the operational systems at Gemini South: The Gemini Planet Imager (GPI) and the Gemini Multi-Conjugated AO system (GeMS). We further focus on how these vibrations are affecting GeMS performance and propose to implement the Tip-Tilt control strategy first tested on CANARY and routinely used on SPHERE. It combines identification of a sum of auto-regressive models of order 2 with a Linear Quadratic Gaussian (LQG) control. LQG is now routinely used for Tip-Tilt and focus control for GPI and has been successfully tested on all modes on CANARY. We show that the expected gain in performance brought by this LQG Tip-Tilt control strategy on GeMS compared with an Integral Controller is on the order of 15 to 20mas. The analysis was conducted in ”replay mode” using GeMS Tip-Tilt on-sky data. This allows realistic performance assessment before implementation inside the Real-Time Computer (RTC) of GeMS and on-sky tests during the first semester of 2016.

Performance assessment for the linear control of adaptive optics systems: noise propagation and temporal errors

We propose a detailed study of the temporal and noise propagation errors entering the error budget of Single Conjugate Adaptive Optics (SCAO) systems. A transfer-function oriented method is developed for the compu- tation of these errors, in a general linear control context. We apply this formalism to performance comparison between Linear Quadratic Gaussian (LQG) and Integral action controllers. Simulation results are presented, corresponding to a typical SCAO system, in order to validate some approximations on the perturbation power spectral density. We then apply the formalism to evaluate the tip-tilt error budget on GeMS.

Tip-tilt modelling and control for GeMS: a performance comparison of identification techniques

Perturbation modelling and vibration compensation are key issues to reach better performance in adaptive optics systems for VLTs and future ELTs. In this context, an LQG controller is to be implemented for the tip-tilt loop of the multi-conjugate adaptive optics instrument GeMS. The performance of several models, associated with their identification techniques are considered for tip-tilt disturbance.

Commissioning of ARGOS at LBT: adaptive optics procedures

ARGOS is the laser guide star facility of the Large Binocular Telescope (LBT). It implements a Rayleigh Laser Guide Star system that provides Ground Layer Adaptive Optics (GLAO) correction for the LUCIs, the 2 wide- field near-infrared imagers and multi-object spectrographs installed on the 2 eyes of LBT. In this paper we describe how LBT’s adaptive optics operations have been tailored to ARGOS’s use cases based on the experience developed during over the ARGOS commissioning. We focus on all the aspects that are influenced by the use of the Laser Guide Stars, from collimation to acquisition and LGS guiding and we details the sequences to start, pause and resume the adaptive correction.

Preliminary design of the MICADO calibration unit

MICADO is the Multi-AO Imaging Camera for Deep Observations, which aims to be the first light instrument of E-ELT. Thanks to its robust design with fixed mirrors and a cryogenic environment, MICADO will provide unprecedented astrometric capabilities and image stability in the range 0.8-2.4 μm. The operation of the instrument coupled with a SCAO unit provides diffraction-limited images over a field of view of 27” that will enlarge to 53” after the integration of the Multi-conjugate Adaptive Optics RelaY, MAORY. This work presents some preliminary possible concepts for the MICADO calibration unit, currently under development at MPIA. This subsystem shall provide standard flat-fielding and spectral calibration plus an astrometric calibration performed with an internal calibration mask to measure and compensate instrument distortions, discontinuities between the detectors and telescope instabilities. The goal of the instrument is to deliver an astrometric accuracy of ~50 μas over the whole field of view.

Aligning the LINC-NIRVANA Natural Guide Stars MCAO system

LINC-NIRVANA (LN) is an instrument built to be a Fizeau interferometric imager for the Large Binocular Telescope that will achieve ELT-like spatial resolution. Of course achieving this outstanding resolution requires a very complex instrument, assuring the delivery of plane wavefronts, parallel input beams, homoteticity and zero Optical Path Difference. LN will be one of the most complex ground-based instruments ever built, consisting of a Multi-Conjugate Adaptive Optics (MCAO) system, a fringe tracker, a beam combiner and a Near-InfraRed science camera, for a total of more than 250 indivudual lenses and mirrors.The MCAO sub-unit itself is the state of the art in the sector of wide field adaptive optics. It consists of 4 Wavefront Sensors (WFSs), two for each arm of the telescope, to sense the turbulence at the ground layer and at 7.1 km above the telescope. They operate in a layer oriented, Multiple Field of View mode, using up to 12 Natural Guide Stars (NGSs) for the ground layer correction and up to 8 NGSs for the mid layer correction.The ambitious nature of LN, which compels us to meet very tight requirements, together with the high number of subsystems lead to a challenging alignment procedure of the instrument. Despite of the complexity, the Alignment, Integration and Verification phase of the instrument has been recently completed with success in Heidelberg and LN is currently on its way to the LBT, where it will be re-aligned and finally mounted at one of the bend focal stations of the telescope. In this paper the integration and alignment procedure of the MCAO subsystem to the rest of LN is described and results are presented.

Retrieving tip-tilt information from Tomographic Laser Guide Star Adaptive Optics Systems

Current Laser Guide Star (LGS) Adaptive Optics (AO) systems disregard all tip-tilt wavefront information received from the LGS Wavefront Sensors (WFS), as it is considered irretrievably entangled with the up-link turbulence that the laser encounters as it passes through the atmosphere to form a guide star. Consequently, they must still observe a Natural Guide Star (NGS) in order to correct for tip-tilt aberrations.A method has recently been presented that use the tomographic capabilities of centre-launched, multi-LGS AO systems to predict the LGS uplink turbulence and hence allow correction with a reduced requirement on the NGS, or potentially no NGS requirement at all for some scientific applications. This method is summarised here, and its limitations discussed. Due to the increased separation of the laser beams at higher altitude, the method is more effective for correction of tip-tilt from high altitude turbulence, with performance approaching that of tomographic LGS AO with a tip-tilt NGS. The method is less successful for correcting tip-tilt contributions from low altitudes, though potential mitigation of this is considered.We finally discuss the methods potential for ELT scale operation. Due to the large aperture size, and large LGS separation, it is expected that the method would be more effective for larger telescopes.

SHARK-NIR Channel: a high contrast imager with coronagraphic capabilities for the Large Binocular Telescope

A new coronagraphic instrument for the Large Binocular Telescope (LBT) has successfully passed the conceptual design phase. SHARK-NIR channel will be installed in one arm of the Large Binocular Telescope and it is designed to use different coronagraphic techniques, both to match as much as possible the different requirements of the different science cases and to explore the capabilities of such techniques for the next-generation of ELTs. By exploiting the combination with SHARK-VIS channel mounted at the other LBT arm, the instrument will offer simultaneous coronagraphic observations at different wavelengths, characterized by high contrast, even for relatively faint targets. This will be achievable thanks to the very efficient Adaptive Optics (AO) systems already operating at LBT (First Light AO, FLAO). Furthermore, the latter will be soon upgraded with new detectors, promising even better performance in terms of limiting magnitude. In this paper we present the status of the SHARK-NIR channel design.

GeMS, the path toward AO facility

GeMS, the Gemini South MCAO System, has now been in regular operation since mid-2013 with the imager instrument GSAOI. We review the performance obtained during this past year as well as some of its current limitations. While in operation, GeMS is still evolving to push them back and is currently in the path of receiving two major upgrades which will allow new exciting science cases: a new natural guide star wavefront sensor called NGS2 and a replacement of the current 50W laser. We are also actively moving along the path of further deeper integration with the future AO-fed instruments, we present our first preliminary results of astrometric and spectrometric calibrations with diverse Gemini instruments using an internal calibration source. We finally report our efforts to make GeMS a more robust instrument with the integration of a vibration rejection feature and a more user-friendly AO system as well with advanced gain optimization automatization.

First Results of the Ground Layer Adaptive Optics System ARGOS

We present the first results of Argos, the multiple laser guide star and wavefront sensing facility for the Large Binocular Telescope. This system will deliver an improvement by a factor of two in FWHM over the 4′×4′ field of view of both Luci instruments. Luci 1 and Luci 2 are two near-infrared wide field imagers and multi-object spectrographs which capability and efficiency will be boosted by the increased resolution and encircled energy.The first on-sky ground-layer adaptive optics (GLAO) loop closure with Argos has been achieved in Fall 2014 on the right eye of the telescope. Stable operations in closed-loop have been demonstrated in May 2015 with hour-long integration and repeated good performances over several nights. Since then, the commissioning has been proceeding with the installation of the left system and the beginning of the left on-sky operations in this Fall 2015. The next achievements will be to strengthen the operational aspects and to perform science demonstration in both imaging and spectroscopic modes. We first present the current status of the project and review the operational aspects. Then, we analyze the first combined Luci and Argos observations and discuss the performances and the gains provided by Argos in term of scientific capabilities.

Adaptive Optics Point Spread Function Reconstruction at W. M. Keck Observatory in Laser & Natural Guide Star Modes : Final Developments

We present the final development of our point spread function reconstruction algorithm for the Keck-II telescope adaptive optics system, in laser and natural guide star modes. The method makes use of AO loop teleme- try, nearby CN2 profiler data, and on-sky phase diversity. We describe the fundamental assumptions and the mathematical models for each components of the residual phase structure function. The reconstructed PSF is compared with on-sky single star PSF. We emphasize the importance of access to a good telemetry and the fact that non-common path aberrations also affects PSF-R. The global, statistical quality of the reconstructed PSF demonstrates the validity of the method. The algorithm is now ready for AO science data reduction (see the companion overview paper, Ragland et al.1 - this conference).

Optimizing use of multiple stars for near-infrared tip-tilt compensation at the W. M. Keck Observatory

The implementation of a near-infrared tip-tilt sensor in the Keck I adaptive optics (AO) system is the first of its kind, and represents a substantial step forward in AO technology. Enhanced-TRICK (Tilt Removal with IR Compensation at Keck) is a project built off this implementation which will further improve performance and versatility. Currently the system is capable of using a single star for measuring image motion, but in the off-axis case this may cause elongation in the science image due to tilt anisoplanatism. The near-infrared tip-tilt sensor (NIRTTS) has been designed with the capability of using up to three stars from around the field to correct for elongation. In order for the science object correction to be optimized, the measurements from each star must be weighted based on magnitude and separation from the science object. When weighted optimally the tip-tilt error at the science object will be a minimum. The process for assigning weights is described, and results of performance modeling of the actual systems having multiple tip-tilt stars are presented.

Design and Development Status of MKID Integral Field Spectrographs for High Contrast Imaging

We report on the design and development progress of two Microwave Kinetic Inductance Detector (MKID) integral field spectrographs (IFSs) for high-contrast astronomy applications. DARKNESS is a 10,000 pixel MKID IFS that will integrate with the coronagraphs at Palomar Observatory, as well as directly with the Palm- 3000 (P3K) extreme adaptive optics (AO) system. MEC is a 20,440 pixel MKID IFS that will integrate with the Subaru Coronagraphic Extreme AO (SCExAO) system at the Subaru Telescope. Both IFSs are optimized for 700 to 1400 nm bandpasses to provide low resolution spectroscopy across I and J bands. MKIDs are a promising technology for overcoming the current contrast ceiling in coronagraphic instruments imposed by atmospheric speckles that vary on 1-second timescales. These speckles vary too slowly to average out with long exposures, and too quickly to control in real time with conventional focal plane detectors or to subtract reliably with differential imaging. With these instruments we will demonstrate how the high time resolution of MKIDs allows focal plane speckle nulling at the speed necessary to control atmospheric speckles in real time, and discrimination of speckles from faint companions during post-processing using statistical techniques similar to the “dark speckle” approach. Additionally, the energy resolution of MKIDs allows either form of speckle suppression to be applied as a function of wavelength. First-light for DARKNESS is scheduled for July 2016 and first-light for MEC is targeted for Fall 2016/Winter 2017.

Laser guide star adaptive optics at Lick Observatory

We present an overview of the adaptive optics system at the Shane telescope (ShaneAO) along with research and development efforts on the technology and algorithms for that will advance AO into wider application for astronomy. Diffraction-limited imaging and spectroscopy from ground based large aperture telescopes will open up the opportunity for unprecedented science advancement. The AO challenges we are targeting are correction down to visible science wavelengths, which demands high-order wavefront correction, and dim object viewing over the whole sky, which demands bright artificial laser beacons. We discuss our ongoing development of MEMS based AO correction, woofer-tweeter architecture, wind-predictive wavefront control algorithms and a guide star laser tuned for optical pumping of the sodium layer. We present the latest on-sky results from the new AO system and present status and experimental plans for the optical pumping guide star laser.

On-sky results of Raven, a MOAO science demonstrator at Subaru Telescope

Raven is a Multi-Object Adaptive Optics science demonstrator which has been used on-sky at Subaru telescope from May 2014 to July 2015. Raven has been developed at the University of Victoria AO Lab, in partnership with NRC, NAOJ and Tohoku University. Raven includes three open loop WFSs, a central laser guide star WFS, and two science pick-off arms feeding light to the Subaru IRCS spectrograph. Raven supports different AO modes: SCAO, open-loop GLAO and MOAO. This paper gives an overview of the instrument design, compares the on-sky performance of the different AO modes and presents some of the science results achieved with MOAO.

New Cophasing and AO strategies for an extremely large telescope dedicated to extremely high contrast: The Colossus Project

Detecting an exoplanetary life signal is extremely challenging with current technology because it requires a sensitive telescope and instrument that can measure the planet's reflected optical and infrared light, while distinguishing this from the star's scattered light and the terrestrial thermal noise background. This requires highly accurate adaptive optics, a coronagraph system, and a specially designed and aligned giant telescope. We present here new strategies for building such a telescope with large circular segments using adaptive optics correction independently for each of these segments prior to cophasing the segments. The foreseen cophasing technique uses focal plane images that allow piston measurements and correction between all the segments. In this context we propose to derive the segment phase error using the inverse approach knowing the segment positions and the single aperture Airy function.

SCExAO: the first high contrast exoplanet imager on an ELT?

The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument, currently under development for the Subaru Telescope, optimally combines state-of-the-art technologies to study exoplanets and stellar environments at the diffraction limit, both in visible and infrared light (0.6 to 2.4 μm). The instrument already includes an ultra-fast visible pyramid wavefront sensor operating at 3.5 kHz, a 2k-actuator deformable mirror, a set of optimal coronagraphs that can work as close as 1 l/D, a low-order wavefront sensor, a high-speed speckle control loop, and two visible interferometric modules, VAMPIRES and FIRST. After the integration of the integral field spectrograph CHARIS and a Microwave Kinetic Inductance Detector (MKID) in 2016, SCExAO will be one of the most powerful and effective tools for characterizing exoplanets and disks. None of the ELTs include a high-contrast imager and spectrograph among the first generation of instruments. To address this, we propose to upgrade SCExAO and deliver it as a first light visitor instrument to the Thirty Meter Telescope (TMT), a decade before the second generation instruments come online. SCExAO’s flexibility assures that it will include the latest technologies when it arrives on TMT, achieving the ultimate goal of characterizing the first terrestrial planets in the habitable zones of M-type stars.

Optimizing LGS WFS Pixel Processing in the Context of Evolving Turbulence and Sodium Profile

The time evolution of the sodium profile greatly impact the accuracy of laser guide star (LGS) wavefront sensor (WFS) measurements, for either the traditional thresholded center of gravity or the more advanced constraint matched filter/correlation algorithms. As a result, circularly symmetric wavefront aberrations will be induced in the adaptive optics (AO) corrected science wavefront for center launch LGS. In this paper, we describe our scheme to mitigate this issue by updating pixel processing parameters and employing a truth WFS during LGS AO operation. We also present simulation results using the sodium profiles measured by the UBC lidar. In addition, the time evolution of the turbulence profile will also have an impact on the pixel processing accuracy for the advanced algorithms, as well as the minimum variance wavefront reconstruction. We present simulation results showing how often we have to update the corresponding parameters to minimize the effect.

Simulations of AO for the E-ELT and its instruments

We present an overview of the latest simulation results obtained for the European Extremely Large Telescope's different Adaptive Optics systems. Different areas of the telescope and instruments are covered. Simulations showing how a single conjugated AO system can be used to detect a scalloping error is shown. We show that when the scalloping error modes are entered in the reconstruction modal basis, the DM shape can be used to estimate the scalloping error through a simple matrix vector multiply. Temporal averaging allows to get rid of the atmospheric noise on the scalloping measurement assuming a perfect “scalloping actuator” and to get a measurement accuracy of ~20nm rms. In a second part, we focus on a few results obtained on tomographic AO systems, like for example the sensitivity to the number of Deformable Mirrors and their pitch in multi-conjugate AO, and the impact of the outer scale of turbulence on Laser tomography AO.

Science operation of the SOAR Adaptive Module (SAM)

The adaptive module of the 4-m SOAR telescope (SAM) corrects ground-layer turbulence using a UV laser guide star. It has been commissioned in 2013 and in regular science operation since 2014A. SAM works with the CCD imager covering a 3′ field or with the speckle camera. The instrument operates routinely and stably, delivering in the I band the image quality equal to the free-atmosphere seeing. Preparation of the observing runs and the operational sequence are covered briefly. Observing programs executed so far are presented, ranging from star clusters and binary stars to deep-space objects and gravitational lenses. Emission-line objects were observed with narrow-band filters and Fabry-Perot etalon. Future science use of SAM and its synergy with wide-field optical sky surveys are outlined. New instruments for SAM and its potential upgrades are considered.

Adaptive Optics Program at TMT

The TMT first light Adaptive Optics (AO) facility consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). NFIRAOS is a 60 x 60 laser guide star (LGS) multi-conjugate AO (MCAO) system, which provides uniform, diffraction-limited performance in the J, H, and K bands over 17-30 arc sec diameter fields with 50 per cent sky coverage at the galactic pole, as required to support the TMT science cases. NFIRAOS includes two deformable mirrors, six laser guide star wavefront sensors, and several low-order, infrared, natural guide star wavefront sensors within each client instrument. The first light LGSF system includes six sodium lasers required to generate the NFIRAOS laser guide stars. In this paper, we will provide an update on the progress in designing, modeling and validating the TMT first light AO systems and their components over the last two years. This will include the final design activities for NFIRAOS, preliminary design activities for the LGSF, final design and prototyping activities for the deformable mirrors, final design and fabrication for the visible detectors, preliminary design activities for the NFIRAOS visible cameras, preliminary design activities for the NFIRAOS Real Time Controller (RTC) and development and tests of prototype candidate lasers. Comprehensive and detailed AO modeling is also continuing to support the design and development of the first light AO facility.

Commissioning ShARCS: the Shane Adaptive optics infraRed Camera-Spectrograph for the Lick Observatory 3-m telescope

We describe the design and first-light early science performance of the Shane Adaptive optics infraRed Camera- Spectrograph (ShARCS) on Lick Observatory’s 3-m Shane telescope. Designed to work with the new ShaneAO adaptive optics system, ShARCS is capable of high-efficiency, diffraction-limited imaging and low-dispersion grism spectroscopy in J, H, and K-bands. ShARCS uses a HAWAII-2RG infrared detector, giving high quantum efficiency (>80%) and Nyquist sampling the diffraction limit in all three wavelength bands. The ShARCS instrument is also equipped for linear polarimetry and is sensitive down to 650 nm to support future visible-light adaptive optics capability. We report on the early science data taken during commissioning.

Preliminary performance analysis of a LGS system for GTC

The Gran Telescopio Canarias (GTC) Adaptive Optics (AO) system, designed to work with Natural Guide Stars (NGS), is in its laboratory integration phase. The upgrade for the operation with a Laser Guide Star (LGS) has been approved, and the design of the LGS Facility is going to start. Hereafter we analyse the performance of a LGS AO system taking into account the GTC characteristics and error budget. Two scenarios are studied: launching the laser from the centre of the telescope aperture behind the secondary (on axis) and launching from the side of the primary mirror (off axis). The simulations have been performed using the Fractal Iterative Method (FrIM), a fast-reconstruction algorithm, with the parameters of the GTC for the telescope, the atmospheric profiles of the Observatorio del Roque de Los Muchachos (ORM), and data from the laser star unit developed by ESO.

E-ELT M4 Unit updated design and prototype results

We present the current design of the E-ELT M4 deformable mirror consolidated at the conclusion of the Preliminary Design activity. The most prominent features of this system are the SiC Reference Body now mounted to the positioner by a whiffle-tree and cell structure, actuators bricks, capacitive sensors layout and new cooling concept. All this allowed achieving the challenging stability requirements demanded to the M4U, as proved by analysis and test results measured on the Demonstration Prototype, which has been updated to implement the current design. The final design and construction contract is now on-going: Final Design Review is planned on mid 2017 and delivery to site by late 2022.

Laser Pointing Camera: a valuable tool for the LGS-AO operations

Every observatory using LGS-AO routinely has the experience of the long time needed to bring and acquire the laser guide star in the wavefront sensor field of view. This is mostly due to the difficulty of creating LGS pointing models, because of the opto-mechanical flexures and hysteresis in the launch and receiver telescope structures.The launch telescopes are normally sitting on the mechanical structure of the larger receiver telescope. The LGS acquisition time is even longer in case of multiple LGS systems. In this framework the optimization of the LGS systems absolute pointing accuracy is relevant to boost the time efficiency of both science and technical observations.In this paper we describe the design and functionalities of the Laser Pointing Camera (LPC)3, developed at OAR for the 4LGSF of the ESO Adaptive Optics Facility. The LPC allows to have a fast pointing of the multiple LGS on the AO WFS during the initial acquisition phase of the telescope preset, thus reducing considerably the overheads currently experienced in most LGS-AO systems in operation.By recognizing via astrometric software the field stars as well as the multiple LGS, LPC is insensitive to flexures of the laser launch telescope or of the receiver telescope opto-mechanics. Moreover, LPC gives regularly the photometry and fwhm of the LGS, as well as the scattering of the uplink beams at the height of 10-15km, thus monitoring the presence and evolution of cirrus clouds. We present the first Commissioning results of the Laser Pointing Camera, obtained at the ESO VLT during the 4LGSF first Laser Guide Star Unit Commissioning, and will discuss its possible extension for the ELT operations.

Astrometry with MCAO at Gemini and at ELTs

We present in this study a first analysis of the astrometric error budget of absolute astrometry relative to back- ground galaxies using adaptive optics. We use for this analysis multi-conjugated adaptive optics (MCAO) images obtained with GeMS/GSAOI at Gemini South. We find that it is possible to obtain 0.3 mas reference precision in a random field with 1 hour on source using faint background galaxies. Systematic errors are correctable below that level, such that the overall error is approximately 0.4 mas. Because the reference sources are extended, we find it necessary to correct for the dependency of the PSF centroid on the used aperture size, which would oth- erwise cause an important bias. This effect needs also to be considered for Extremely Large Telescopes (ELTs). When this effect is corrected, ELTs have the potential to measure proper motions of dwarfs galaxies around M31 with 10 km/s accuracy over a baseline of 5 years.

Coupling of WFS with a segmented DM “Test of different concepts: SH, Pyramid, Zernike phase sensor”

LAM is developing several R&D activities for E-ELT instrumentation, in particular, different WFS concepts are investigated (Pyramid, ZELDA, a Zernike phase mask sensor, Phase diversity or still NL Curvature) and an ESO-EELT M1 mirror segment (1.5 m) has been demonstrated. Segmented mirrors are not only the solution for the problem of ELTs monolithic size but also for other questions related to fabrication, optics replacement and transport. And, they are widely used today for other applications: fiber coupling, LGS beam shaping, etc. Their only problem is how to assure the cophasing of segments to take advantage of the full optimum size. In the present work, we study the sensitivity to different WFS (Sack-Hartmann, Pyramid and ZELDA) to pupil phase discontinuity using a PTT mirror from Iris AO. Various test such as segment phasing, stability, saturation, flat, or still the addressing mode are then performed and compared.

Astrometry with MCAO at Gemini and at ELTs

We present in this study a first analysis of the astrometric error budget of absolute astrometry relative to back- ground galaxies using adaptive optics. We use for this analysis multi-conjugated adaptive optics (MCAO) images obtained with GeMS/GSAOI at Gemini South. We find that it is possible to obtain 0.3 mas reference precision in a random field with 1 hour on source using faint background galaxies. Systematic errors are correctable below that level, such that the overall error is approximately 0.4 mas. Because the reference sources are extended, we find it necessary to correct for the dependency of the PSF centroid on the used aperture size, which would oth- erwise cause an important bias. This effect needs also to be considered for Extremely Large Telescopes (ELTs). When this effect is corrected, ELTs have the potential to measure proper motions of dwarfs galaxies around M31 with 10 km/s accuracy over a baseline of 5 years.

SPHERE extreme AO system On-sky operation, final performance and future improvements

The SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) instrument aims at detecting extremely faint1sources (giant extrasolar planets) in the vicinity of bright stars . Such a challenging goal requires the use of a very-high-order performance Adaptive Optics [AO] system feeding the scientific instruments with a quasi-perfect flat wave front corrected from all the atmospheric turbulence and internal defects. This AO system, called SAXO (Sphere Ao for eXoplanet Observation) is the heart of the instrument, a heart beating 1200 time per second and providing unprecedented image quality for a large ground based telescope at optical/near infrared wavelength. We will present the latest results obtained on-sky, demonstrating its exceptional performance (in terms of correction quality, stability and robustness) and tremendous potentiality for exoplanet discovery.

Commissioning of ARGOS at LBT: adaptive optics procedures

ARGOS is the laser guide star facility of the Large Binocular Telescope (LBT). It implements a Rayleigh Laser Guide Star system that provides Ground Layer Adaptive Optics (GLAO) correction for the LUCIs, the 2 wide- field near-infrared imagers and multi-object spectrographs installed on the 2 eyes of LBT. In this paper we describe how LBT’s adaptive optics operations have been tailored to ARGOS’s use cases based on the experience developed during over the ARGOS commissioning. We focus on all the aspects that are influenced by the use of the Laser Guide Stars, from collimation to acquisition and LGS guiding and we details the sequences to start, pause and resume the adaptive correction.

Adaptive Optics Point Spread Function Reconstruction at W. M. Keck Observatory in Laser & Natural Guide Star Modes : Final Developments

We present the final development of our point spread function reconstruction algorithm for the Keck-II telescope adaptive optics system, in laser and natural guide star modes. The method makes use of AO loop teleme- try, nearby CN2 profiler data, and on-sky phase diversity. We describe the fundamental assumptions and the mathematical models for each components of the residual phase structure function. The reconstructed PSF is compared with on-sky single star PSF. We emphasize the importance of access to a good telemetry and the fact that non-common path aberrations also affects PSF-R. The global, statistical quality of the reconstructed PSF demonstrates the validity of the method. The algorithm is now ready for AO science data reduction (see the companion overview paper, Ragland et al.1 - this conference).