High contrast imaging upgrades for the Keck adaptive optics imager

The Keck II adaptive optics (AO) system is being upgraded with a near-infrared Pyramid Wavefront Sensor (PWS) as part of the Keck Planet Imager and Characterizer (KPIC) upgrade. The overview of the KPIC project and the PWS development are presented elsewhere in this conference. This paper focuses on improvements made to the NIRC2 science instrument, referred to as the NIRC2 upgrade, aimed at enhancing its high contrast imaging capabilities. The NIRC2 upgrade incorporates new coronagraphic elements that reach their maximum performance when operated in combination with the new near-infrared PWS and polarimetric elements that would add polarimetric capability when fully implemented. The key elements to the NIRC2 upgrade are the installation of two next-generation Vector Vortex Coronographic (VVC) masks, one optimized for the L and M band, and the other one optimized for the K band. Also key to the upgrade is the incorporation of a new Lyot stop optimized to minimize diffraction and residual nutation of the Keck-II telescope pupil. These new elements provide improved coronographic performance when operated with the new PWS and the existing Shack Hartmann wavefront sensor (SH WFS). The upgrade implementation and preliminary on-sky results are discussed. © 2019 AO4ELT 2019 - Proceedings 6th Adaptive Optics for Extremely Large Telescopes. All rights reserved.