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.

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.

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.

The Thirty Meter Telescope (TMT) first light instrument IRIS (Infrared Imaging Spectrograph) will complete its preliminary design phase in 2016. The IRIS instrument design includes a near-infrared (0.85-2.4 micron) integral field spectrograph (IFS) and imager that are able to conduct simultaneous diffraction-limited observations behind the advanced adaptive optics system NFIRAOS. The IRIS science cases have continued to be developed and new science studies have been investigated to aid in technical performance and design requirements. In this development phase, the IRIS science team has paid particular attention to the selection of filters, gratings, sensitivities of the entire system, and science cases that will benefit from the parallel mode of the IFS and imaging camera. We present new science cases for IRIS using the latest end-To-end data simulator on the following topics: Solar System bodies, the Galactic center, active galactic nuclei (AGN), and distant gravitationally-lensed galaxies. We then briefly discuss the necessity of an advanced data management system and data reduction pipeline.