Multi-object astronomical adaptive-optics (MOAO) is now a mature wide-field observation mode to enlarge the adaptive-optics-corrected field in a few specific locations over tens of arc-minutes. 
The work-scope provided by open-loop tomography and pupil conjugation is amenable to a spatio-angular Linear-Quadratic Gaussian (SA-LQG) formulation aiming to provide enhanced correction across the field with improved performance over static reconstruction methods and less stringent computational complexity scaling laws. 
Starting from our previous work [1], we use stochastic time-progression models coupled to approximate sparse measurement operators to outline a suitable SA-LQG formulation capable of delivering near optimal correction. Under the spatio-angular framework the wave-fronts are never explicitly estimated in the volume,providing considerable computational savings on 10m-class telescopes and beyond. 
We find that for Raven, a 10m-class MOAO system with two science channels, the SA-LQG improves the limiting magnitude by two stellar magnitudes when both Strehl-ratio and Ensquared-energy are used as figures of merit. The sky-coverage is therefore improved by a factor of 5.

Spatio-angular Minimum-variance Tomographic Controller for Multi-Object Adaptive Optics systems

The chemical abundances for five metal-poor stars in and towards the Galactic bulge have been determined from the H-band infrared spectroscopy taken with the RAVEN multi-object adaptive optics science demonstrator and the Infrared Camera and Spectrograph at the Subaru 8.2-m telescope. Three of these stars are in the Galactic bulge and have metallicities between −2.1 < [Fe/H] < −1.5, and high [α/Fe] ∼ +0.3, typical of Galactic disc and bulge stars in this metallicity range; [Al/Fe] and [N/Fe] are also high, whereas [C/Fe] < +0.3. An examination of their orbits suggests that two of these stars may be confined to the Galactic bulge and one is a halo trespasser, though proper motion values used to calculate orbits are quite uncertain. An additional two stars in the globular cluster M22 show [Fe/H] values consistent to within 1σ, although one of these two stars has [Fe/H] = −2.01 ± 0.09, which is on the low end for this cluster. The [α/Fe] and [Ni/Fe] values differ by 2σ, with the most metal-poor star showing significantly higher values for these elements. M22 is known to show element abundance variations, consistent with a multipopulation scenario though our results cannot discriminate this clearly given our abundance uncertainties. This is the first science demonstration of multi-object adaptive optics with high-resolution infrared spectroscopy, and we also discuss the feasibility of this technique for use in the upcoming era of 30-m class telescope facilities.

/pdf/using-the-multi-object-adaptive-optics-demonstrator-raven-to-5162hnd62w.pdf

Using the multi-object adaptive optics demonstrator RAVEN to observe metal-poor stars in and towards the Galactic Centre

Raven is a Multi-Object Adaptive Optics (MOAO) technical and scientific demonstrator which will be used on
the Subaru telescope with the IRCS spectrograph. The optical and mechanical designs are finalised and the
system is now being integrated in the lab at UVic. Raven features three open-loop wavefront sensors (WFS)
patrolling a 3.5' field of regard, one on-axis LGS WFS, two science channels each equipped with a pick-off arm,
an 11x11 actuator deformable mirror, a closed-loop WFS for calibration and performance comparison and an
image rotator. This paper presents in detail the optical design and its performance, as well as the mechanical
design.

Final opto-mechanical design of Raven, a MOAO science demonstrator for Subaru

We present the integration status for 'imaka, the ground-layer adaptive optics (GLAO) system on the University of Hawaii 2.2-meter telescope on Maunakea, Hawaii. This wide-field GLAO pathfinder system exploits Maunakea's highly confined ground layer and weak free-atmosphere to push the corrected field of view to ∼1/3 of a degree, an areal field approaching an order of magnitude larger than any existing or planned GLAO system, with a FWHM ∼ 0.33" in the visible and near infrared. We discuss the unique design aspects of the instrument, the driving science cases and how they impact the system, and how we will demonstrate these cases on the sky.

Imaka: a ground-layer adaptive optics system on Maunakea

`Imaka is a ground layer adaptive optics (GLAO) demonstrator on the University of Hawaii 2.2m telescope with a 24'x18' field-of-view, nearly an order of magnitude larger than previous AO instruments. In 15 nights of observing with natural guide star asterisms ~16' in diameter, we measure median AO-off and AO-on empirical full-widths at half-maximum (FWHM) of 0''95 and 0''64 in R-band, 0''81 and 0''48 in I-band, and 0''76 and 0''44 at 1 micron. This factor of 1.5-1.7 reduction in the size of the point spread function (PSF) results from correcting both the atmosphere and telescope tracking errors. The AO-on PSF is uniform out to field positions ~5' off-axis, with a typical standard deviation in the FWHM of 0''018. Images exhibit variation in FWMM by 4.5% across the field, which has been applied as a correction to the aforementioned quantities. The AO-on PSF is also 10x more stable in time compared to the AO-off PSF. In comparing the delivered image quality to proxy measurements, we find that in both AO-off and AO-on data, delivered image quality is correlated with `imaka's telemetry, with R-band correlation coefficients of 0.68 and 0.70, respectively. At the same wavelength, the data are correlated to DIMM and MASS seeing with coefficients of 0.45 and 0.55. Our results are an essential first step to implementing facility-class, wide-field GLAO on Maunakea telescopes, enabling new opportunities to study extended astronomical sources, such as deep galaxy fields, nearby galaxies or star clusters, at high angular resolution.

https://iopscience.iop.org/article/10.3847/1538-3881/aad1f2/pdf

Improved Image Quality over 10′ Fields with the ʻImaka Ground-layer Adaptive Optics Experiment

This paper discusses static and dynamic tomographic wave-front (WF) reconstructors tailored to Multi-Object Adaptive Optics (MOAO) for Raven, the first MOAO science and technology demonstrator recently installed on an 8m telescope. We show the results of a new minimum mean- square error (MMSE) solution based on spatio-angular (SA) correlation functions, which extends previous work in Correia et al, JOSA-A 2013 1 to adopt a zonal representation of the wave-front and its associated signals. This solution is outlined for the static reconstruction and then extended for the use of stand-alone temporal prediction and as a prediction model in a pupil plane based Linear Quadratic Gaussian (LQG) algorithm. We have fully tested our algorithms in the lab and compared the results to simulations of the Raven system. These simulations have shown that an increase in limiting magnitude of up to one magnitude can be expected when prediction is implemented and up to two magnitudes when the LQG is used.

Tomography and calibration for Raven: from simulations to laboratory results

RAVEN, a Multi-Object Adaptive Optics technology and science demonstrator

Raven is a Multi-Object Adaptive Optics (MOAO) scientific demonstrator which will be used on-sky at the Subaru observatory from 2014. Raven is currently being built and tested at the University of Victoria AO Lab. This paper presents an overview of the optomechanical design and the software architecture of Raven, and gives the current status of this project. Raven includes three open loop wavefront sensors (WFSs), a laser guide star WFS and two figure/truth WFSs. Two science channels containing deformable mirrors (DMs) feed light to the Subaru IRCS spectrograph. Central to the Raven is a Calibration Unit which contains multiple sources, a telescope simulator including two phase screens and a ground layer DM that can be used to calibrate and test Raven in the lab. Preliminary results on calibration and open-loop AO correction using a tomographic reconstructor are presented.

Current status of Raven, a MOAO science demonstrator for Subaru

International Conference on Space Optics—ICSO 2010 Rhodes Island, Greece 4–8 2010 First results of the PERSEE experiment

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