GeMS: first on-sky results

GeMS, the Gemini Laser Guide Star Multi-Conjugate Adaptive Optics facility system, has seen first light in December 2011, and has already produced images with H band Strehl ratio in excess of 35% over fields of view of 85x85 arcsec, fulfilling the MCAO promise. In this paper, we report on these early results, analyze trends in performance, and concentrate on key or novel aspects of the system, like centroid gain estimation, on-sky non­ common path aberration estimation. We also present the first astrometric analysis, showing very encouraging results

Comparison of multiconjugate adaptive optics configurations and control algorithms for the Gemini South 8-m telescope

This paper focuses on two main categories of the multiconjugate adaptive optics (MCAO) parameter space for performance optimization: the geometrical configuration of guide stars and deformable mirrors (DMs), and the wavefront reconstructors. From the first category it is shown how, for a fixed reconstructor and imaging wavelength, the performance metrics with a few important exceptions improve with an increasing number of (1) DMs, (2) actuators per DM and (3) guide stars. The metrics are seen to degrade with (1) an increasing field of compensation and (2) DM conjugation altitude mismatch with the significant turbulent atmospheric layers. In the second category, this study also compares the performance with a fixed MCAO configuration using the least- square estimator (LSE) and the maximum a posteriori estimator (MAP) for wavefront reconstruction. The MAP is shown to perform significantly better than the LSE at low or intermediate signal-to-noise ratios (SNRs), and somewhat better even in the absence of noise due to its a priori knowledge of the phase statistics

Gemini multiconjugate adaptive optics system review – I. Design, trade-offs and integration

The Gemini multiconjugate adaptive optics system (GeMS) at the Gemini South telescope in Cerro Pachón is the first sodium-based multilaser guide star (LGS) adaptive optics system. It uses five LGSs and two deformable mirrors to measure and compensate for atmospheric distortions. The GeMS project started in 1999, and saw first light in 2011. It is now in regular operation, producing images close to the diffraction limit in the near-infrared, with uniform quality over a field of view of two square arcminutes. This paper is the first one in a two-paper review of GeMS. It describes the system, explains why and how it was built, discusses the design choices and trade-offs, and presents the main issues encountered during the course of the project. Finally, we briefly present the results of the system first light

Principles, limitations, and performance of multiconjugate adaptive optics

Multi-Conjugate Adaptive Optics (MCAO) holds the promise of moderate to large adaptively compensated field of view with uniform image quality. This paper is a first effort to analyze the fundamental limitations of such systems, and that are mainly related to the finite number of deformable mirrors and guide stars. We demonstrate that the ultimate limitation is due to the vertical discretization of the correction. This effect becomes more severe quite rapidly with increasing compensated field of view or decreasing wavelength, but does not depend at first order on the telescope aperture. We also discuss limitations associated with the use of laser guide stars and ELT related issues

GeMS: first on-sky results

GeMS, the Gemini Laser Guide Star Multi-Conjugate Adaptive Optics facility system, has seen first light in December 2011, and has already produced images with H band Strehl ratio in excess of 35% over fields of view of 85x85 arcsec, fulfilling the MCAO promise. In this paper, we report on these early results, analyze trends in performance, and concentrate on key or novel aspects of the system, like centroid gain estimation, on-sky non­ common path aberration estimation. We also present the first astrometric analysis, showing very encouraging results

Comparison of multiconjugate adaptive optics configurations and control algorithms for the Gemini South 8-m telescope

This paper focuses on two main categories of the multiconjugate adaptive optics (MCAO) parameter space for performance optimization: the geometrical configuration of guide stars and deformable mirrors (DMs), and the wavefront reconstructors. From the first category it is shown how, for a fixed reconstructor and imaging wavelength, the performance metrics with a few important exceptions improve with an increasing number of (1) DMs, (2) actuators per DM and (3) guide stars. The metrics are seen to degrade with (1) an increasing field of compensation and (2) DM conjugation altitude mismatch with the significant turbulent atmospheric layers. In the second category, this study also compares the performance with a fixed MCAO configuration using the least- square estimator (LSE) and the maximum a posteriori estimator (MAP) for wavefront reconstruction. The MAP is shown to perform significantly better than the LSE at low or intermediate signal-to-noise ratios (SNRs), and somewhat better even in the absence of noise due to its a priori knowledge of the phase statistics

Curvature-based laser guide star adaptive optics system for Gemini South

The Gemini Observatory and University of Hawaii are planning to install an 85-element curvature adaptive optics system with a laser guide star system on its Cerro Pachon telescope in 2001. This paper discusses the motivation, issues on implementing a laser guide star with a curvature-based system, the implementation of a laser guide star based on a commercially available 2W ring-dye laser, and the expected performance of the system. Detailed simulations show very promising results for system performance down to natural guide star magnitudes of 19 - 20th magnitude. The performance cross- over point between NGS and LGS is between 13 - 16th magnitude depending on the performance parameter of interest (e.g. Strehl, energy through a slit, etc.)