MAVIS: system modelling and performance prediction

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 foru

Rolling shutter-induced aberrations in laser guide star wavefront sensing

Laser guide star (LGS) Shack-Hartmann (SH) wavefront sensors for next-generation Extremely Large Telescopes (ELTs) require low-noise, large format ( 1/41 Mpx), fast detectors to match the need for a large number of subapertures and a good sampling of the very elongated spots. One path envisaged to fulfill this need has been the adoption of complementary metal metal-oxide semiconductor detectors with a rolling shutter read-out scheme that allows low read-out noise and fast readout time at the cost of image distortion due to the detector rows exposed in different moments. Here, we analyze the impact of the rolling shutter read-out scheme when used for LGS SH wavefront sensing; in particular, we focus on the impact on the adaptive optics (AO) correction of the distortion-induced aberrations created by the rolling exposure in the case of fast varying aberrations, like the ones coming from the LGS tilt jitter due to the up-link propagation of laser beams. We show that the LGS jitter-induced aberration for an ELT can be as large as 100-nm root-mean-square, a significant term in the wavefront error budget of a typical AO system on an ELT, and we discuss possible mitigation strategies

Advances in control of a Pyramid Single Conjugate Adaptive Optics system

Adaptive optics systems are an essential technology for the modern astronomy for ground based telescopes. One of the most recent revolution in the field is the introduction of the pyramid wavefront sensor. The higher performance of this device is payed with increased complexity in the control. In this work we report about advances in the AO system control obtained with SOULat the Large Binocular Telescope. The first is an improved Tip/Tilt temporal control able to recover the nominal correction even in presence of high temporal frequency resonances. The second one is a modal gain optimization that has been successfully tested on sky for the first time. Pyramid wavefront sensors are the key technology for the first light AO systems of all ELTs and the reported advances can be relevant contributions for such systems

MAORY AO performances

The Multi-conjugate Adaptive Optics RelaY (MAORY) should provide 30% SR in K band (50% goal) on half of the sky at the South Galactic Pole. Assessing its performance and the sensitivity to parameter variations during the design phase is a fundamental step for the engineering of such a complex system. This step, centered on numerical simulations, is the connection between the performance requirements and the Adaptive Optics system configuration. In this work we present MAORY configuration and performance and we justify theAdaptive Optics system design choices.Comment: 9 pages, 7 figures, 1 table. SPIE conference Astronomical Telescopes and Instrumentation, 14 - 18 December 2020, digital foru

Keck II adaptive optics upgrade: simulations of the near-infrared pyramid sensor

A future upgrade of the Keck II telescope's adaptive optics system will include a near-infrared pyramid wavefront sensor. It will benefit from low-noise infrared detector technology, specifically the avalanche photodiode array SAPHIRA (Leonardo). The system will either operate with a natural guide star in a single conjugated adaptive optics system, or using a laser guide star (LGS), with the pyramid working as a low-order sensor. We present a study of the pyramid sensor's performance via end-to-end simulations, including an analysis of calibration strategies. For LGS operation, we compare the pyramid to LIFT, a focal-plane sensor dedicated to low-order sensing

BRUTE, PSF Reconstruction for the SOUL pyramid-based Single Conjugate Adaptive Optics facility of the LBT

The astronomical applications greatly benefit from the knowledge of the instrument PSF. We describe the PSF Reconstruction algorithm developed for the LBT LUCI instrument assisted by the SOUL SCAO module. The reconstruction procedure considers only synchronous wavefront sensor telemetry data and a few asynchronous calibrations. We do not compute the Optical Transfer Function and corresponding filters. We compute instead a temporal series of wavefront maps and for each of these the corresponding instantaneous PSF. We tested the algorithm both in laboratory arrangement and in the nighttime for different SOUL configurations, adapting it to the guide star magnitudes and seeing conditions. We nick-named it "BRUTE", Blind Reconstruction Using TElemetry, also recalling the one-to-one approach, one slope-to one instantaneous PSF the algorithm applies.Comment: 11 pages, 7 figures, Proceeding of the SPIE Conference 12185, Adaptive Optics Systems VIII, 1218540 (29 August 2022

Adaptive optics with an infrared pyramid wavefront sensor at Keck

The study of cold or obscured, red astrophysical sources can significantly benefit from adaptive optics (AO) systems employing infrared (IR) wavefront sensors. One particular area is the study of exoplanets around M-dwarf stars and planet formation within protoplanetary disks in star-forming regions. Such objects are faint at visible wavelengths but bright enough in the IR to be used as a natural guide star for the AO system. Doing the wavefront sensing at IR wavelengths enables high-resolution AO correction for such science cases, with the potential to reach the contrasts required for direct imaging of exoplanets. To this end, a new near-infrared pyramid wavefront sensor (PyWFS) has been added to the Keck II AO system, extending the performance of the facility AO system for the study of faint red objects. We present the Keck II PyWFS, which represents a number of firsts, including the first PyWFS installed on a segmented telescope and the first use of an IR PyWFS on a 10-m class telescope. We discuss the scientific and technological advantages offered by IR wavefront sensing and present the design and commissioning of the Keck PyWFS. In particular, we report on the performance of the Selex Avalanche Photodiode for HgCdTe InfraRed Array detector used for the PyWFS and highlight the novelty of this wavefront sensor in terms of the performance for faint red objects and the improvement in contrast. The system has been commissioned for science with the vortex coronagraph in the NIRC2 IR science instrument and is being commissioned alongside a new fiber injection unit for NIRSPEC. We present the first science verification of the system—to facilitate the study of exoplanets around M-type stars

Design and status of the NGS WFS of MAORY

MAORY is the first-light multi-conjugate AO facility of the E-ELT, providing a >30% Strehl ratio (evaluated inK band, median seeing conditions) over the MICADO 53 ×53 arcsec FoV and ensuring an overall sky coverageof 50%. MAORY will implement 3 NGS WFS having a double functionality: sensing the atmospheric low-ordermodes (LO-WFS) and de-trending the LGS WFS measurements (Ref-WFS).To maximize the AO sky-coverage the preliminary design of the LO-WFS foresees a 2×2 subapertures Shack-Hartmann sensor working in the H band, where the partial AO-correction regime and the low-noise detectorsbased on APD technology will enhance the WFS sensitivity. The Reference WFS will measure at slow rate(1÷10 s) the first ∼100 modes of the atmospheric aberration and it will correct the LGS measurements that areaffected by the Sodium layer drifts. The Ref-WFS will be a 10×10 SH making use of a CCD220-based detector.Hence it will work at visibile wavelenghts, using the same NGS of the LO-WFS.We present here the results of a study aimed to find the best design solutions for the MAORY NGS WFSin preparation of the project preliminary design review of scheduled in February 2018. We describe first theoutput of numerical simulations to find the best compromise between the working bandwidth and sampling of theLO-WFS and the sky-coverage corresponding to the expected performance. Then we describe the arrangementfor the NGS WFS module, hosted on top of the MICADO cryostat, analyzing the static and dynamic propertiesof the NGS module structure. Finally we present the opto-mechanical layout for the NGS WFS and its degreesof freedom

Adaptive optics with an infrared pyramid wavefront sensor at Keck

The study of cold or obscured, red astrophysical sources can significantly benefit from adaptive optics (AO) systems employing infrared (IR) wavefront sensors. One particular area is the study of exoplanets around M-dwarf stars and planet formation within protoplanetary disks in star-forming regions. Such objects are faint at visible wavelengths but bright enough in the IR to be used as a natural guide star for the AO system. Doing the wavefront sensing at IR wavelengths enables high-resolution AO correction for such science cases, with the potential to reach the contrasts required for direct imaging of exoplanets. To this end, a new near-infrared pyramid wavefront sensor (PyWFS) has been added to the Keck II AO system, extending the performance of the facility AO system for the study of faint red objects. We present the Keck II PyWFS, which represents a number of firsts, including the first PyWFS installed on a segmented telescope and the first use of an IR PyWFS on a 10-m class telescope. We discuss the scientific and technological advantages offered by IR wavefront sensing and present the design and commissioning of the Keck PyWFS. In particular, we report on the performance of the Selex Avalanche Photodiode for HgCdTe InfraRed Array detector used for the PyWFS and highlight the novelty of this wavefront sensor in terms of the performance for faint red objects and the improvement in contrast. The system has been commissioned for science with the vortex coronagraph in the NIRC2 IR science instrument and is being commissioned alongside a new fiber injection unit for NIRSPEC. We present the first science verification of the system—to facilitate the study of exoplanets around M-type stars