Commissioned in November 2022 at W. M. Keck Observatory (WMKO), the Keck Planet Finder (KPF) instrument is a fiber-fed high-resolution spectrometer, developed in partnership with California Institute of Technology, University of California Berkeley Space Science Laboratory, and University of California at Santa Cruz. At the heart of object acquisition and tracking is KPF’s guiding system, which uses 100 Hz tip/tilt corrections to maintain the target on the fiber aperture, and coarse telescope corrections to keep the target within the effective range of the tip/tilt mechanism. This paper covers the design of the guider software at the heart of these corrections, emphasizing simplicity for the initial approach, deliberately avoiding potentially unnecessary optimization, while leveraging existing standards and practices at WMKO. The software is implemented in Python with one key component written in C. The paper covers the gradual process of optimization, addressing critical performance bottlenecks in targeted fashion without rewriting the bulk of the code; the bottlenecks include image acquisition, image transmission, command transmission, and image processing. This paper concludes with an analysis of the tip/tilt performance on-sky.
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