The ERIS Adaptive Optics System: first on-sky results of the ongoing commissioning at the VLT-UT4

ERIS is a new Adaptive Optics (AO) instrument installed at the Cassegrain focus of VLT-UT4 in January 2022 and led by a Consortium of Max-Planck Institut fuer Extraterrestrische Physik, UK-ATC, ETH-Zurich, NOVA-Leiden, ESO and INAF. The ERIS AO system provides NGS mode to deliver high contrast correction and LGS mode to extend high Strehl performance to large sky coverage. The AO module includes one 40x40 LGS wavefront sensor (WFS), one NGS WFS able to switching between 40x40 and 4x4 configuration, the related optics to relay the telescope beam and a dedicated SPARTA real time computer running the AO loop up to 1kHz. The AO module, with the 1170-actuator Deformable Secondary Mirror and the Laser Facility from VLT-AOF, provides AO correction to the high resolution coronagraphic imager NIX (1-5um) and the IFU spectrograph SPIFFIER (1-2.5um). In this paper we briefly review the ERIS AO system design and we present preliminary AO results of the ongoing commissioning, started in February 2022.