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One of the main challenges for ground-based optical astronomy is to compensate for atmospheric turbulence in near real-time. The goal is to obtain images as close as possible to the diffraction limit of the telescope. This challenge is addressed on the latest generation of giant optical telescopes by deploying multi-conjugate adaptive optics (MCAO) systems performing predictive tomography of the turbulence and multi-layer compensation. Such complex systems require a high fidelity estimate of the turbulence profile above the telescope, to be updated regularly during operations as turbulence conditions evolve. In this paper, we modify the traditional Levenberg-Marquardt (LM) algorithm by considering stochastically chosen subsystems of the full problem to identify the required parameters efficiently, while coping with the real-time challenge. While LM operates on the full set data samples, the resulting Stochastic LM (SLM) method randomly selects subsamples to compute corresponding approximate gradients and Hessians. Hence, SLM reduces the algorithmic complexity per iteration and shortens the overall time to solution, while maintaining LM’s numerical robustness. We present a new convergence analysis for SLM, implement the algorithm with optimized GPU kernels, and deploy it on shared-memory systems with multiple GPU accelerators. We assess SLM in the adaptive optics system configurations in the context of the MCAO-Assisted Visible Imager & Spectrograph (MAVIS) instrument for the Very Large Telescope (VLT). We demonstrate performance superiority of SLM over the traditional LM algorithm and the classical stochastic first-order methods. At the scale of VLT AO, SLM finishes the optimization process and accurately retrieves the parameters (e.g., turbulence strength and wind speed profiles) in less than a second using up to eight NVIDIA A100 GPUs, which permits high acuity real-time throughput over a night of observations.

Accurate astrometry is a key deliverable for the next generation of multi-conjugate adaptive optics (MCAO) systems. The MCAO Visible Imager and Spectrograph (MAVIS) is being designed for the Very Large Telescope Adaptive Optics Facility and must achieve 150 $\mu$as astrometric precision (50 $\mu$as goal). To test this before going on-sky, we have created MAVISIM, a tool to simulate MAVIS images. MAVISIM accounts for three major sources of astrometric error, high- and low-order point spread function (PSF) spatial variability, tip-tilt residual error and static field distortion. When exploring the impact of these three error terms alone, we recover an astrometric accuracy of 50 $\mu$as for all stars brighter than $m=19$ in a 30s integration using PSF-fitting photometry. We also assess the feasibility of MAVIS detecting an intermediate mass black hole (IMBH) in a Milky Way globular cluster. We use an N-body simulation of an NGC 3201-like cluster with a central 1500 M$_{\odot}$ IMBH as input to MAVISIM and recover the velocity dispersion profile from proper motion measurements. Under favourable astrometric conditions, the dynamical signature of the IMBH is detected with a precision of ~0.20 km/s in the inner ~4" of the cluster where HST is confusion-limited. This precision is comparable to measurements made by Gaia, HST and MUSE in the outer ~60" of the cluster. This study is the first step towards building a science-driven astrometric error budget for an MCAO system and a prediction of what MAVIS could do once on sky., Comment: 17 pages, 13 figures, accepted for publication in MNRAS, main result is shown in Figure 12. Fixed typo in introduction

ULTIMATE-Subaru is a next large facility instrument project at Subaru telescope. We will develop a 14x14 sq. arcmin wide-field near-infrared (NIR) imager and a multi-object spectrograph with the aid of a ground- layer adaptive optics system (GLAO), which will uniformly improve the seeing by a factor of 2 over a wide field of view up to ~20 arcmin in diameter. We have developed system modeling of the GLAO and wide-field NIR instruments to define the system level requirements flow down from science cases and derive the system performance budgets based on the GLAO end-to-end numerical simulation and optical system models of the telescope and wide-field NIR science instruments. In this paper, we describe the system performance modeling of ULTIMATE-Subaru and present an overview of the requirements flow down.

"The MCAO Assisted Visible Imager and Spectrograph (MAVIS), is a new instrument for ESO’s Very Large Telescope. The science instruments, namely an imager and a spectrograph observing at VIS wavelengths (370-1000nm), are fed by a MCAO module which performs wide field wavefront sensing and correction by means of both NGS and LGS stars. To maximize sky coverage, tip-tilt sensing is done at NIR wavelengths (1000-1700 nm) by selecting up to three stars in a 2arcmin FoV. In order to maximize the stability between NGS wavefront sensor and scientific instruments, we designed a common-path Atmospheric Dispersion Corrector (ADC) able to efficiently compensate for atmospheric differential refraction in the full wavelength range used by the MAVIS sub-systems. In this paper we present the design of the ADC. A few possible combinations of glasses are proposed and compared in terms of residual chromatic aberration, throughput, exit pupil movement and total thickness of the prism assembly."

"We present initial results from the Multi-conjugate Adaptive-optics Visible Imager-Spectrograph Image Simulator (MAVISIM) to explore the astrometric capabilities of the next generation instrument MAVIS. A core scientific and operational requirement of MAVIS will be to achieve highly accurate differential astrometry, with accuracies on the order that of the extremely large telescopes. To better understand the impact of known and anticipated astrometric error terms, we have created an initial astrometric budget which we present here to motivate the creation of MAVISIM. In this first version of MAVISIM we include three major astrometric error sources; point spread function (PSF) field variability due to high order aberrations, PSF degradation and field variability due to tip-tilt residual error, and field distortions due to non-common path aberrations in the AO module. An overview of MAVISIM is provided along with initial results from a study using MAVISIM to simulate an image of a Milky Way-like globular cluster. Astrometric accuracies are extracted using PSF-fitting photometry with encouraging results that suggest MAVIS will deliver accuracies of 150µas down to faint magnitudes."

W. M. Keck Observatory (WMKO) has granted in 2018 to Microgate, supported by Swinburne University and Australian National University, the contract for the design, implementation and test of the new Adaptive Optics Real Time Controller. The new system is going to replace the existing Keck Next Generation Wavefront Controller (NGWFC), delivered by the same company 14 years ago and still operational. The new RTC supports, on a smaller scale, most of the operating modii that are planned for the next generation of ELT RTCs, including laser tomography. In addition, the system needs to be interfaced to several wavefront cameras and mirrors, with heterogeneous interfaces. On that base, the system needs to conjugate several aspects, including flexible interfacing, computational throughput with low latency and minimum jitter, large telemetry storage capacity with fast querying capacity, easiness of maintainability, expandability, extreme reliability and environmental challenges to operate at 4,200 meters above the sea level. The proposed architecture comprehends an interface module, physically located close to the various sensors and mirrors, a computational unit based on GPUs and a storage server. The software implementation is based on a modular concept that starts from the COMPASS framework, developed at Observatoire de Paris, and supports easy expandability. The project implementation is almost completed and deployment to the telescope is planned for Q1/2021.

The MCAO Assisted Visible Imager and Spectrograph (MAVIS), is a new instrument for ESO’s Very Large Telescope. The instrument will be installed at the Nasmyth focus of the UT4 telescope and is comprised of an imager and a spectrograph which will take advantage of the unprecedented angular resolution and sky coverage provided by LGS assisted MCAO correction at visible wavelengths. The Adaptive Optics Module (AOM) is the core engine of MAVIS, devoted to multi-conjugate wavefront sensing and correction, and designed to deliver a 30×30 arcsec2 corrected field of view to the scientific instruments. In this paper we focus on the optical design of the AOM, which has been optimized to perform several tasks including field de-rotation, atmospheric dispersion correction, and adaptive optics closed-loop operations. To maximize sky coverage, the system is designed to deliver a 2 arcmin field of view for the selection of up to 3 NGS for measurement of tip-tilt. The AOM module also includes a multiple LGS WFS for high-order wavefront measurements and two post-focal DMs for wide field turbulence compensation. The proposed design is the result of a trade-off study in which particular care has been devoted to satisfy performance and operational requirements, as well as modularity. We present here a complete description of the selected optical configuration with a summary of the performance analyses.

To provide data sharper than JWST and deeper than HST, MAVIS (the MCAO Assisted Visible Imager and Spectrograph) will be driven by a state-of-the-art real-time control (RTC) system leveraging cutting edge technologies both in terms of hardware and software. As an implementation of the COSMIC platform, the MAVIS RTC will host a hard RTC module, fed in quasi real-time with optimized parameters from its companion soft RTC. In order to meet the AO performance requirement in the visible, the overall real-time pipeline latency should be in the range of few hundreds microseconds ; and, considering the several high order wavefront sensors (WFS) of the current optical design, the specifications of the hard RTC module are very close to those contemplated for ELT first light SCAO systems, making it as an at scale pathfinder for these future facilities. In this paper, we will review the hardware and software design and prototyping activities led during phase A of the project.

The Learn and Apply reconstruction scheme uses the knowledge of atmospheric turbulence to generate a tomographic reconstructor, and its performance is enhanced by the real-time identification of the atmosphere and the wind profile. In this paper we propose a turbulence profiling method that is driven by the atmospheric model. The vertical intensity distribution of turbulence, wind speed and wind direction can be simultaneously estimated from the Laser Guide Star measurements. We introduce the implementation of such a method on a GPU accelerated non-linear least-squares solver, which significantly increases the computation efficiency. Finally, we present simulation results to demonstrate the convergence quality from numerically generated telemetry, the end-to-end Adaptive Optics simulation results, and a time-to-solution analysis, all based on the MAVIS system design.

ULTIMATE-Subaru is a next large facility instrument project at Subaru telescope. We will develop a 14x14 arcmin2 wide-field near-infrared (1.0-2.5μm) imager and a multi-object spectrograph with the aid of a ground- layer adaptive optics system (GLAO), which will uniformly improve the seeing by a factor of 2 over a wide field of view up to ~20 arcmin in diameter. The expected spatial resolution by the GLAO correction is about 0.2 arcsec FWHM in K-band under moderate seeing conditions at Subaru telescope. ULTIMATE-Subaru will provide a unique capability to realize wide-field and high spatial resolution survey observations in near infrared in the era of TMT. In this paper, we introduce the project overview including the GLAO and near-infrared instrument conceptual design. We also describe the future wide-field strategy at Subaru telescope with ULTIMATE-Subaru together with HSC and PFS.

This paper presents a preliminary analysis of the first results we have obtained from the adaptive optics systems built for EOS 1.8 m telescope at Mount Stromlo. This presentation focuses on the single-camera stereo-SCIDAR for monitoring the atmospheric seeing. We briefly summarize the system, describe its on-sky performance during commissioning, compare results to numerical simulations and evaluate the remaining challenges going into the future.

The Adaptive Optics Module of MAVIS is a self-contained MCAO module, which delivers a corrected FoV to the postfocal scientific instruments, in the visible. The module aims to exploit the full potential of the ESO VLT UT4 Adaptive Optics Facility, which is composed of the high spatial frequency deformable secondary mirror and the laser guide stars launching and control systems. During the MAVIS Phase A, we evaluated, with the support of simulations and analysis at different levels, the main terms of the error budgets aiming at estimating the realistic AOM performance. After introducing the current opto-mechanical design and AO scheme of the AOM, we here present the standard wavefront error budget and the other budgets, including manufacturing, alignment of the module, thermal behavior and noncommon path aberrations, together with the contribution of the upstream telescope system.

The MCAO Assisted Visible Imager and Spectrograph (MAVIS) Adaptive Optics Module has very demanding goals to support science in the optical: providing 15% SR in V band on a large FoV of 30arcsec diameter in standard atmospheric conditions at Paranal. It will be able to work in closed loop on up to three natural guide stars down to H=19, providing a sky coverage larger than 50% in the south galactic pole. Such goals and the exploration of a large MCAO system parameters space have required a combination of analytical and end- to-end simulations to assess performance, sky coverage and drive the design. In this work we report baseline performance, statistical sky coverage and parameters sensitivity analysis done in the phase-A instrument study., Comment: 12 pages, 9 figures, 7 tables. SPIE conference Astronomical Telescopes and Instrumentation, 14 - 18 December 2020, digital forum

Proliferation of space debris presents an imminent threat to all space assets. The problem is especially severe for the geostationary band of orbits (GEO) because the GEO objects never leave their orbit and, at the same time, are difficult to observe and operate due to large distance from the Earth. Under the influence of tidal forces, even passive GEO objects achieve high local velocities without vacating GEO positions, which may potentially lead to devastating collisions. Our ability to predict collisions in GEO is limited by the scarcity of the accurate orbital data, especially about the small and passive objects. The efforts to address this omission strongly rely on the ground-based optical sensors and, consequently, on the efficient space object detection and tracking techniques. In this paper we propose a passive differential optical debris tracking technique combining adaptive optics and a high accuracy astrometric references resulting in a significant improvement in the GEO object positioning accuracy. The achievable accuracy is estimated via detailed numerical simulations of two telescopes in different locations.

In this paper, we implement and evaluate the performance of multi-rate predictive control for Adaptive Optics systems. The multi-rate strategy yields considerable performance improvements in the case of low-magnitude guide stars and in the presence of wave-front sensor read-out noise, since the wave-front sensor exposure time can be increased to provide useful signal-to-noise ratios without having to limit the temporal bandwidth of the deformable mirror (as is the case in a single-rate control approach). Simulations performed on an end-to-end numerical Adaptive Optics simulation package are presented to demonstrate the advantages of the approach.

High-wind velocity Adaptive Optics (AO) systems depend on functional and identifiable predictive turbulence models. Existing system identification techniques for this specific class of systems is either unnecessarily general (including a large set of impractical solutions), or very specific (not easily scaled to arbitrary wind-velocities). The authors present the motivation and derivation of a system identification method which is solved directly in the parameter space of the predictive estimator, using recent phase estimates of the turbulence.

Adaptive optics is now a fully mature technique to improve the angular resolution of observations taken with ground-based astronomical telescopes. It is available at most of the major optical/IR observatories, and is planned as an integral part of the Extremely Large Telescope next generation facilities. In this mini-review aimed at non-AO specialists, we recall the history, the principle of operation, the major components, the performance, and the future of nighttime astronomical adaptive optics.

Space debris in low Earth orbit (LEO) below 1500 km is becoming an increasing threat to spacecrafts. To manage the threat, we are developing systems to improve the ground-based tracking and imaging of space debris and satellites. We also intend to demonstrate that it is possible to launch a high-power laser that modifies the orbits of the debris. However, atmospheric turbulence makes it necessary to use adaptive optics with such systems. When engaging with objects in LEO, the objects are available only a limited amount of time. During the observation window, the object has to be acquired and performance of all adaptive optics feedback loops optimised. We have implemented a high-level adaptive optics supervision tool to automatise time-consuming tasks related to calibration and performance monitoring. This paper describes in detail the current features of our software.

Adaptive Optics (AO) systems rely on atmospheric turbulence models in order to reduce the effect of wave-front aberrations on image quality. Due to the nature of turbulence, these models can exploit shift-invariant structures without a severe loss in generality. The resulting subset of possible state-matrices is efficiently characterised for identification using Quadratic Programming (QP). Additionally, the initial assumption of shift-invariance is relaxed in order to accommodate for the boundary effect of finite-pupils.

We report the current status of the laser guide star upgrade at Subaru Telescope with a new, more powerful TOPTICA/MPBC laser. While we recycle many of our existing components, such as laser launch telescope, we need to design a new mirror-based laser relay system to replace the current fiber-based relay to accommodate the high power beam. The laser unit has been delivered to Subaru office in March 2018 and installed in a testing lab in June 2018. We describe the preliminary design and its requirements and report future plans. This upgrade will not only improve our current adaptive optics system but also be the first step toward the future laser tomography and ground layer adaptive optics system at Subaru Telescope.

We report on the design and initial laboratory testing of the Adaptive Optics Imaging (AOI) system. AOI has been developed by the Research School of Astronomy and Astrophysics (RSAA) at the Australian National University (ANU), in partnership with the Space Environment Research Centre (SERC), for imaging satellites and debris in low Earth orbit (LEO) and geostationary orbit (GEO). From AO corrected images we will resolve features greater than 50 cm allowing size, shape and orientation characterisation.

CACAO is a generic, low-cost, and portable adaptive optics system which is currently under development at the Australian National University. CACAO is designed to be an adaptive optics system which will be capable of being placed on various small aperture telescopes, under 1m diameter, with only minor modifications and thus leading to a severely reduced deployment time. The entire adaptive optics system, including the control computer, and required electronics and wiring, is designed to fit into a 25cm×20cm × 15cm enclosure. The small footprint of CACAO allows it to be used as a test bed for innovative technologies and techniques with only minor modifications, this will allow for on-sky or in laboratory prototyping and testing in a relatively small time period. We report on the initial development and design of CACAO along with preliminary characterisation results.

We present novel methods for mounting lenses in a pair of instruments that presented challenging optical and mechanical requirements. The first instrument is the replacement Natural Guide Star Sensor (NGS2) for CANOPUS at Gemini South, which incorporates an objective consisting of a stack of six lenses mounted in a common bore. A compliant radial spacer was used to eliminate lens decentre resulting from the additional radial clearance required to accommodate differential thermal strains between the low thermal expansion lenses and a common bore. In the same instrument, tangent contact toroidal spacers were deployed in place of traditional conical spacers to further reduce contact stresses in fragile calcium fluoride lens elements. The toroidal faces were specified with a 10μm profile tolerance to avoid possible edge contact between the spacers and lenses. We investigated milling and turning machining processes for the production of the spacers by comparing their results via Coordinate Measuring Machine (CMM) measurements. In the second instrument, Veloce, built for the Anglo-Australian Telescope, a lens decentre requirement of 40μm led us to develop a simple means of in-situ centring adjustment of the cell mounted lens. Physical testing of the finished instruments verified the performance of each of these methods. NGS2 produced images at the factory acceptance test in which 94% of encircled energy was captured by a single 16um detector pixel, surpassing the specification of 80%. Bench testing of Veloce during assembly showed that the adjustment mechanism allowed centring of the lens over a range of +/- 0.1mm with a precision of 5μm.

As space debris in lower Earth orbits are accumulating, techniques to lower the risk of space debris collisions must be developed. Within the context of the Space Environment Research Centre (SERC), the Australian National University (ANU) is developing an adaptive optics system for tracking and pushing space debris. The strategy is to pre-condition a laser launched from a 1.8 m telescope operated by Electro Optics Systems (EOS) on Mount Stromlo, Canberra and direct it at an object to perturb its orbit. Current progress towards implementing this experiment, which will ensure automated operation between the telescope and the adaptive optics system, will be presented.

This paper presents the overview of on-going and future adaptive optics (AO) activities at the Subaru telescope on the top of Maunakea in Hawaii. Currently, two AO systems are running at the Subaru telescope: AO188, a facility single-conjugate AO system with a bimorph deformable mirror and a curvature wavefront sensor with 188 elements, and SCExAO, an additional extreme AO system operating behind AO188 and specialized for exoplanet sciences. We recently started AO188 upgrade project to improve its performance for the next 5-10 years, which will also help improving SCExAO performance. These upgrades are in line with a development for the ULTIMATE-Subaru ground layer AO system.

A new type of sodium guidestar laser based on semiconductor laser technology is being developed by the astronomy, space, and laser communication communities in Australia and the United States, in partnership with laser manufacturer Arete Associates. Funding has been secured from the Australian Research Council and the Australian National University, with support from academic (UNSW) and industry partners (AAO, GMTO, EOS, Lockheed Martin). The consortium aims to develop a full scale prototype of the Semiconductor Guidestar Laser. The laser, to be delivered in 2019, will be initially installed on the EOS Satellite and Debris Tracking Station 1.8m telescope at Mount Stromlo Observatory where it will be thoroughly tested, on sky and in real operation conditions. This will be the first time that a Laser Guide Star is created in Australian skies. We present the project motivation and objectives, laser development and test plans, and the preliminary test results obtained to date.

We report on the conceptual design study done for the Ground Layer Adaptive Optics system of the ULTIMATE-Subaru project. This is an ambitious instrument project, providing GLAO correction in a square field of view of 14 arcmin on a side, aiming to deliver improved seeing at the near infrared wavelength. Its client instruments are an imager and multi-IFU spectrograph at Cassegrain and a Multi-Object spectrograph at Nasmyth. In this paper, we introduce the ULTIMATE-Subaru project overview and its science case and report the results of the GLAO performance prediction based on the numerical simulation and conceptual design of the wavefront sensor system.

Sodium guide star technologies for Adaptive Optics (AO) have been around for over 20 years. During this time, the technologies for the lasers used to excite the mesospheric sodium have been in constant development, with the goals being not only to excite as much sodium as possible, but to do so efficiently, while producing a round guide star, and while offering a reliable facility. The first lasers in use were dye lasers with a liquid gain medium, while these lasers were able to produce sodium guide stars, the liquid dye used was toxic and flammable. The second generation of guide star lasers used sum-frequency-mixed solid-state lasers. These lasers provided excellent return but were notoriously difficult to calibrate and maintain, requiring a full-time laser engineer on staff. The current third generation of sodium guide star lasers use Raman fiber amplification to generate a laser that is very efficient at exciting sodium with a good spot profile and offer a high degree of reliability. The Gemini South observatory for the last few years has been in the process of obtaining one of these third-generation lasers, a Toptica Sodium Star 20/2 while maintaining its second-generation Lockheed Martin Coherent Technologies (LMCT) 50W CW Mode-locked laser. In October of 2017 successful on-sky commissioning of the Toptica laser was executed while the LMCT laser was still active and in operations. During the course of the commissioning run both lasers were used on sky in close in time in possible. We present a comparative study of the performance of each laser.

Adaptive Optics (AO) systems aim at detecting and correcting for optical distortions induced by atmospheric turbulences. The Gemini Multi Conjugated AO System GeMS is operational and regularly used for science observations since 2013 delivering close to diffraction limit resolution over a large field of view. GeMS entered this year into a new era. The laser system has been upgraded from the old 50W Lockheed Martin Coherent Technologies (LMCT) pulsed laser to the Toptica 20/2W CW SodiumStar laser. The laser has been successfully commissioned and is now used regularly in operation. In this paper we first review the performance obtained with the instrument. I will go then into the details of the commissioning of the Toptica laser and show the improvements obtained in term of acquisition, stability, reliability and performance.

Conference on Adaptive Optics Systems VI -- JUN 10-15, 2018 -- Austin, TX WOS: 000452819300183 Thanks to the availability of high actuator density deformable mirrors (ALPAO 468 DM), the high versatility of the pyramid wavefront sensor and above all, the venue of essentially no noise EMCCD detectors, it becomes possible to fully adapt the degree of correction of an adaptive optics system for a given guide star brightness and atmospheric condition. Indeed, when the conditions are very good, the high actuator density of the DM allows to reach a high Strehl by using all the modes, and when the conditions are less favorable, the spatial sampling, i. the number of modes, and the sensitivity of the detector allows to maximize the Strehl beyond what would be possible with a classical, frozen SH-WFS based system. Beside, oversampling the detector allows to relax the specification on the pupil images given by the pyramid on the detector, which in turn relaxes the pyramid prism manufacturing specifications. We are now designing an AO system for the DAG 4 m telescope that will allow, on the same system, ExAO as well as low order improved seeing observations. This article reports on the AO performance analysis, the final optical design and the design of the double prism achromatic pyramid. SPIE, 4D Technol, Andor Technol Ltd, Astron Consultants & Equipment, Inc, Giant Magellan Telescope, GPixel, Inc, Harris Corp, Mater Corp, Optimax Syst, Inc, Princeton Infrared Technologies, Symetrie, Teledyne Technologies Inc, Thirty Meter Telescope

Turbulence estimation in ground based telescopes as part of the Adaptive Optics (AO) control loop is inherently high-complexity. Even in smaller telescopes such as the EOS 1.8m telescope at Mt Stromlo Observatory, Canberra, closed-loop control systems are required to operate in the order of kHz with hundreds, if not thousands of internal states. Typical Matrix Vector Multiply (MVM) control calculations grow in computational demand to the order of N2. The Distributed Kalman Filter (DKF) proposed by Massioni et al [1] when being performed in the Fourier Domain allows the computational cost to scale as N log N [2], provided that the state space model is shift-invariant in its basis. In this paper we develop a procedure for the modeling and identification of a dynamic shift-invariant turbulence model that does not require prior knowledge of the layers velocities and turbulence profile, while satisfying the structural requirements of the DKF.

Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States of America), The National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Minist´erio de Ciˆencia, Tecnologia e Inova¸c˜ao (Brazil) and Ministerio de Ciencia, Tecnologia e Innovaci´on Productiva (Argentina).

The Gemini Multi-conjugate Adaptive Optics System - GeMS, a facility instrument mounted on the Gemini South telescope, delivers a uniform, near diffraction limited images at near infrared wavelengths (0.95 microns- 2.5 microns) over a field of view of 120 arc seconds. GeMS is the first sodium layer based multi laser guide star adaptive optics system used in astronomy. It uses five laser guide stars distributed on a 60 arc seconds square constellation to measure for atmospheric distortions and two deformable mirrors to compensate for it. In this paper, the second devoted to describe the GeMS project, we present the commissioning, overall performance and operational scheme of GeMS. Performance of each sub-system is derived from the commissioning results. The typical image quality, expressed in full with half maximum, Strehl ratios and variations over the field delivered by the system are then described. A discussion of the main contributor to performance limitation is carried-out. Finally, overheads and future system upgrades are described., 20 pages, 11 figures, accepted for publication in MNRAS

The photometric properties of main sequence (MS) and pre-main sequence (PMS) stars in the young cluster Haffner 16 are examined using images recorded with the Gemini South Adaptive Optics Imager (GSAOI) and corrected for atmospheric blurring by the Gemini Multi-Conjugate Adapative Optics System (GeMS). A rich population of PMS stars is identified, and comparisons with isochrones suggest an age 10 Myr, assuming a distance modulus of 13.5 (D = 5 kpc). This age is consistent with that estimated from the lower cutoff of the MS on the K-band luminosity function and is ~2 Myr younger than the age found from bright MS stars at visible wavelengths. When compared with the solar neighborhood, Haffner 16 is roughly a factor of 2 deficient in objects with subsolar masses. PMS objects in the cluster are also more uniformly distributed on the sky than bright MS stars. It is suggested that Haffner 16 is dynamically evolved and that it is shedding protostars with subsolar masses. Young low mass clusters like Haffner 16 are one possible source of PMS stars in the field. The cluster will probably evolve on time scales of ~100-1000 Myr into a diffuse moving group with a mass function that is very different from that which prevailed early in its life.

Detailed knowledge of the mesopheric sodium layer characteristics is crucial to estimate and optimize the performance of Laser Guide Star (LGS) assisted Adaptive Optics (AO) systems. In this paper, we present an analysis of two sets of data on the mesospheric sodium layer. The first set comes from a laser experiment that was carried out at Cerro Tololo to monitor the abundance and altitude of the mesospheric sodium in 2001, during six runs covering a period of one year. This data is used to derive the mesospheric sodium column density, the sodium layer thickness and the temporal behavior of the sodium layer mean altitude. The second set of data was gathered during the first year of the Gemini MCAO System (GeMS) commissioning and operations. GeMS uses five LGS to measure and compensate for atmospheric distortions. Analysis of the LGS wavefront sensor data provides information about the sodium photon return and the spot elongation seen by the WFS. All these parameters show large variations on a yearly, nightly and hourly basis, affecting the LGS brightness, shape and mean altitude. The sodium photon return varies by a factor of three to four over a year, and can change by a factor of two over a night. In addition, the comparison of the photon returns obtained in 2001 with those measured a decade later using GeMS shows a significant difference in laser format efficiencies. We find that the temporal power spectrum of the sodium mean altitude follows a linear trend, in good agreement with the results reported by Pfrommer & Hickson (2010)., 11pages, 10figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

We present the stellar mass - size relation for 49 galaxies within the $z$ = 1.067 cluster SPT-CL J0546$-$5345, with FWHM $\sim$80-120 mas $K_{\mathrm s}$-band data from the Gemini multi-conjugate adaptive optics system (GeMS/GSAOI). This is the first such measurement in a cluster environment, performed at sub-kpc resolution at rest-frame wavelengths dominated by the light of the underlying old stellar populations. The observed stellar mass - size relation is offset from the local relation by 0.21 dex, corresponding to a size evolution proportional to $(1+z)^{-1.25}$, consistent with the literature. The slope of the stellar mass - size relation $\beta$ = 0.74 $\pm$ 0.06, consistent with the local relation. The absence of slope evolution indicates that the amount of size growth is constant with stellar mass. This suggests that galaxies in massive clusters such as SPT-CL J0546$-$5345 grow via processes that increase the size without significant morphological interference, such as minor mergers and/or adiabatic expansion. The slope of the cluster stellar mass - size relation is significantly shallower if measured in $HST$/ACS imaging at wavelengths blueward of the Balmer break, similar to rest-frame UV relations at $z$ = 1 in the literature. The stellar mass - size relation must be measured at redder wavelengths, which are more sensitive to the old stellar population that dominates the stellar mass of the galaxies. The slope is unchanged when GeMS $K_s$-band imaging is degraded to the resolution of $K$-band HST/NICMOS resolution but dramatically affected when degraded to $K_s$-band Magellan/FourStar resolution. Such measurements must be made with AO in order to accurately characterise the sizes of compact, $z$ = 1 galaxies., Comment: 24 pages, 13 figures, 3 tables. Accepted for publication in MNRAS. Typos corrected, DOI added

Satellite tracking and imaging is conducted by the ANU Research School of Astronomy and Astrophysics (RSAA) and Electro-Optic Systems at Mount Stromlo as part of the Space Environment Management Cooperative Research Centre to support debris tracking. To optimally design adaptive optics systems for those applications, it is important to know the atmospheric profile, i.e. how the turbulence is distributed as a function altitude. We have designed a new stereo-SCIDAR instrument1 to conduct a site characterisation campaign at Mount Stromlo site. This paper summarises our current progress: specifications, design choices and post-processing techniques. In particular, we compare two different post-processing algorithms for stereo-SCIDAR, using simulated data cubes. One of the codes is implemented by the RSAA, the other by the Centre for Advanced Instrumentation, University of Durham. The comparison shows that the current implementations of both codes produce decent results. However, we can see potential for further improvements.

The latency of electro-optical components is of high importance in the design of Adaptive Optics systems, as it limits the performance of the control loop. There exists a need for a latency measurement method that can be constructed with simple components found in most Adaptive Optics labs that still provides a measurement accurate to sub-microseconds. Through a combination of research and experimentation, potential methodologies were investigated with the aim of producing reliable latency measurements. This document will discuss one such method, involving coupling a LED pulse output and detected pulse input signals to the same clock for easy comparison. For this method, a proof-of-concept was developed using MATLAB and small analogue electronics, and the performance characterised. This characterisation showed that although there is some merit to the method, improvements are necessary to increase the precision of the measurement to a level usable in Adaptive Optics systems.

Satellite tracking and imaging is conducted by the ANU Research School of Astronomy and Astrophysics and Electro-Optic Systems (EOS) at Mount Stromlo Observatory, Canberra, Australia, as part of the Space Environment Management Cooperative Research Centre (SERC) to support the development in space situational awareness. Atmospheric turbulence leads to distortions in the measured data. Adaptive optics (AO) systems counteract those distortions and improve the resolution of the tracking and imaging systems. To assist in the design of the AO systems, we need to gather information on the atmosphere at Mount Stromlo: r0, τ 0, and the turbulence Cn2 profile. With the SCIntillation Detection And Ranging (SCIDAR) Technique the scintillation of two stars is measured and their autocorrelation function is computed, providing a measurement of the turbulence profile. This technique usually uses one detector recording the two images of the stars simultaneously. However, the images overlap leading to an underestimation of the Cn2 values. The introduction of stereo-SCIDAR1 over- comes this issue by separating the two stars and imaging them on two separate image sensors. To reduce costs, we introduce a new stereo-SCIDAR system separating the beams from the two stars, but using only one single detector. This has been shown for a Low Layer SCIDAR (LOLAS) system with wide double stars (200 arcsec). We investigate this technique by detecting the scintillation patterns of double stars with separation from 10 to 25 arcsec, allowing some flexibility in the altitude span and resolution, while retaining a simple optical setup. We selected a low noise sCMOS camera as the imager. We show the current design of this system and investigate its feasibility for further development.

GMTIFS requires a deformable mirror (DM) as part of its on-instrument wavefront sensor (OIWFS). The DM facilitates wavefront correction for the off-axis natural guide star, with the objective being to maximize the energy in the diffraction core and improve the signal-to-noise ratio of the guide star position measurement. It is essential that the OIWFS be positionally stable with respect to the science field. The use of J–K to observe the guide star, and thus the need to limit thermal background, essentially requires the DM in the OIWFS to be operated at or below −40°C. This is below the standard operating temperature range of currently available DMs. In cooperation with the manufacturers we are testing the performance of three DMs at temperatures from ambient to −45°C, or cooler. In the context of the OIWFS adequate stroke, open-loop positioning stability, hysteresis, interactuator surface figure and dynamic response are key performance criteria. A test system based around high spatial sampling of the DM aperture with a Shack-Hartmann wavefront sensor has been built. The opto-mechanical design permits a DM to be contained in a cryostat so that it may be cooled in isolation. We describe this test system and the test cases that are applied to the ALPAO DM-69, Boston MicroMachines 492DM and the IrisAO PTT111 deformable mirrors. Preliminary results at ambient temperatures are presented.

GeMS, the Gemini South MCAO System, has now been in operation for 3 years with the near infrared imager GSAOI. We first review the performance obtained by the system, the science cases and the current operational model. In the very near future, GeMS will undergo a profound metamorphosis, as we will integrate a new NGS wavefront sensor, replace the current 50W laser with a more robust one and prepare for a new operational model where operations will shift from the mountain to the base facility. Along this major evolution, we are also presenting several improvements on the loop control, calibrations and automatization of this complex system. We discuss here the progress of the different upgrades and what we expect in terms of performance improvements and operational efficiency.