WM Keck Observatory's Hydrostatic Bearing System Controls Replacement Project - Zero Loss of Observing, Remote Operations, Enhanced Troubleshooting, and Improved Energy Efficiency

The W.M. Keck Observatory's (WMKO) Hydrostatic Bearing System (HBS) is a critical system that supplies the Keck I and Keck II telescopes with filtered, cooled, and pressurized oil. This system lifts the telescopes up allowing them to float on a thin film of oil and rotate with ease. The pressurized oil supplied by this system is also required to release the brakes, allowing telescope motion in both azimuth and elevation. Each telescope has its own independent HBS as well as its own HBS control system. Since its design in the late 1980's, WMKO's HBS had been running using the original relay logic control system. However, in the late summer and early fall of 2023 the HBS control systems for both telescopes were replaced. Replacing and modernizing control systems is nothing out of the ordinary, however both Keck I and Keck II HBS control systems were replaced without any downtime to nighttime operations. This was one of the key requirements of this project. In addition to the installation resulting in no loss of observing, we now have much greater capacity for monitoring, troubleshooting and improved energy efficiency as well as remote operations. In this paper, we will describe the equipment and methods used to replace the control system while maintaining nighttime operations. The benefits of modernized controls and results of the energy efficiency improvements will also be discussed.