Upgrading the Keck AO wavefront controllers

This paper describes the recent upgrade performed on the W. M. Keck Observatory Adaptive Optics (AO) systems, in which the wavefront sensors and wavefront controllers were replaced with components based on new technology. The performance of the upgraded system has yielded an increase in limiting guide star magnitude, an increased Strehl ratio for both Laser Guide Star (LGS) and Natural Guide Star (NGS) modes, and has significantly improved reliability and maintainability compared to the original system. Moreover, the controller is scalable, allowing for future upgrades and improvements as needed. We present an overview of the project; describe the basic architecture of the new wavefront sensor and controller; discuss some of the unique features of the system, including the closed loop mirror positioning system, custom wavefront sensor optics, and full-frame-rate telemetry server; and conclude with results from engineering and science tests of the new controller on the Keck II AO system.