AO3k + SCExAO: on-sky wavefront quality and demonstration of novel WFS techniques with the double XAO system

Abstract

The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system, fed by its upstream 3000-actuator "woofer" (AO3k), serves both as a platform for high contrast imaging (HCI) technology maturation and as a science instrument for imaging, spectroscopy, and polarimetry of exoplanets and disks. SCExAO operates in the visible and near-IR and offers a wide choice of instrument configurations. Over the last year, AO3k/SCExAO underwent significant upgrades to bring improved capabilities and support new developments, all while easing science operations. The new configuration features a beam switcher so that light can be shared between several instrument modules. The system is evolving toward a tighter integration between multiple WFSs and AO stages of correction, with the first stage (AO3k) providing visible and nearIR WFSing, as well as laser tomography. AO3k+SCExAO has been fully operational since October 2025, demonstrating very high stability on-sky, even in bad seeing conditions up to 2". Having two XAO in series allows us to deploy advanced wavefront control techniques optimized for high-contrast imaging (e.g. speckle nulling, EFC, Coronagraphic LOWFS, Fast and Furious) on the second-stage XAO loop, as AO3k by itself delivers high-contrast PSFs already. Areas of active ongoing research include use of photonic devices for spectrally dispersed interferometric sensing, PSF reconstruction from WFS telemetry, and non-linear sensors (focal plane and curvature). Recent upgrades to the computer infrastructure are aimed at supporting these R\&D efforts and providing a rich collaborative environment for experimentation. In this paper, we will present on-sky high-contrast performance characterization of AO3k, AO3k+SCExAO, and on-sky demonstrations of novel wavefront control techniques to improve the contrast behind the coronagraph.