Abstract
Gemini Observatory has been awarded from the National Science Foundation a major fund to build a new state-of-the-art Multi Conjugate Adaptive Optics facility for Gemini North on Maunakea called GNAO. The current baseline system will use two lasers each split in two to create an artificial constellation of four laser guide star to measure the distortions caused by the atmosphere. At least two deformable mirror conjugated to 0km and the main altitude layer above Maunakea will be used to correct these distortions. The facility will be designed to feed future instrumentation, initially a near infrared imager and potentially a visiting 4-arm multi object adaptive optics IFU spectrograph.1 In this paper I will present the main characteristics of this exciting facility, its promises and its challenges. I will also present its conceptual design and results of trade studies conducted within the team and the Gemini Adaptive Optics Working Group. The expected first light is for October 2024.

Abstract
We present PEPITO as a new low-cost and low-complexity concept for profiling the vertical distribution of atmospheric turbulence. PEPITO utilizes post facto tip-tilt (TT) corrected short-exposure images to reproduce the anisokinetism effect and then produces the profile estimation using a model-fitting algorithm. We present in this proceedings the methodology we use to estimate the profile and simulation results, that show that PEPITO can reach potentially 1% of accuracy on a 0.5 m telescope by using 5 stars of magnitude mV=15 mag and distributed over a field of 10, arcmin. We present the sensitivity of PEPITO as well as a sky coverage analysis.

Abstract
The development and study of new, more robust and powerful wavefront sensors plays an important role in the improvement of the wavefront sensing capabilities of adaptive optics systems. The LAM-ONERA On-sky Pyramid Sensor is a R&D bench dedicated to study and characterize these new wavefront sensors. In this paper, we give a glance at the current status of the bench in terms of hardware and at the most recent results obtained using new flavours of Fourier filtering wavefront sensors.

Abstract
Laser Guide Star [LGS] wave-front sensing is a key element of the Laser Tomographic AO system and mainly drives the final performance of any ground based high resolution instrument. In that framework, HARMONI the first light spectro-imager of the ELT [1,2], will use 6 Laser focused around 90km(@Zenith) with a circular geometry in order to sense, reconstruct and correct for the turbulence volume located above the telescope. LGS wave-front sensing suffers from several well-known limitations [3] which are exacerbated by the giant size of the Extremely Large Telescopes. In that context, the presentation is threefold: (1) we will describe, quantify and analyse the various effects (bias and noise) induced by the LGS WFS in the context of ELT. Among other points, we will focus on the spurious low order signal generated by the spatially and temporally variable sodium layer. (2) we will propose a global design trade-off for the LGS WFS and Tomographic reconstruction process in the HARMONI context. We will show that, under strong technical constraints (especially concerning the detectors characteristics), a mix of opto-mechanic and numerical optimisations will allow to get rid of WFS bias induce by spot elongation without degrading the ultimate system performance (3) beyond HARMONI baseline, we will briefly present alternative strategies (from components, concepts and algorithms point of view) that could solve the LGS spot elongation issues at lower costs and better robustness.

Abstract
Model-based matrix-free wavefront reconstruction algorithms have proven to provide highly accurate results for both Shack-Hartmann and pyramid wavefront sensors in various simulation environments (OCTOPUS, YAO, COMPASS, OOMAO). Previously, test bench as well as on-sky tests were performed with the CuReD for the Shack-Hartmann sensor providing a convincing performance level together with highly reduced computational efforts. The P-CuReD is a method with linear complexity for wavefront reconstruction from pyramid sensor data which employs the CuReD algorithm and a data preprocessing step converting pyramid signals into Shack-Hartmann-like data. Here we present experimental results for the pyramid sensor being controlled with the P-CuReD on the LOOPS test bench of the Laboratoire d’Astrophysique de Marseille. Through the example of the P-CuReD a comparison of control using matrix-free Fourier domain based methods to standard interaction-matrix-based approaches is provided.

Abstract
Some coronagraph masks can be turned into wave front sensing masks thanks to minor modification. For instance, one only has to divide by two the depth of the central well to convert the Roddier & Roddier coronograph into the Zernike wave front sensor (WFS). Physically, the opposition of phase in coronagrapy becomes a quadrature phase in wave front sensing. Here, we replicate this idea to the Four Quadrant Phase Mask (FQPM) coronagraph by introducing a sensor that we call the iQuad WFS, generated by a mask which has the same geometrical structure as the FQPM but with a modified differential piston. An optical and mathematical description of this new WFS is firstly provided showing its great elegance and the central role played by the Hilbert transform in its understanding. We then compare its performance criteria with two classical wave front sensors. We finally show the iQuad sensor has major similarities to the Pyramid sensor making it a wonderful theoretical object to improve our understanding of this sensor.