On-sky results with the fast guiding system on the SPIRou spectroplarimeter at CFHT

SPIRou (SpectroPolarimetre Infra-Rouge in French), is a near-infrared, fiber-fed spectropolarimeter at the CanadaFrance-Hawaii Telescope (CFHT) which gives full spectral coverage from 0.98 to 2.35 μm with a resolving power of 70,000. The main science drivers for SPIRou are (i) detecting and characterizing exoplanets around nearby M dwarfs through high-precision (1 m/s) velocimetry, and (ii) investigating the impact of magnetic fields on star/planet formation through spectropolarimetry. One of the requirements for achieving this challenging radial velocity (RV) precision is ensuring that the observed star does not move with respect to the instrument entrance aperture by more than 0.05 arcseconds RMS over the course of the observation. This is complicated by the fact that the guiding uses light from the science target so that only about 13% of the light (10% from the wings and 3% from the core) is available in seeing conditions of 0.65 arc-seconds in H band. To achieve this level of guiding accuracy, a fast guiding system has been implemented in the injection module of the instrument. This paper describes the system, its performance in tests on the sky with the CFHT since the delivery of SPIRou in January 2018, and gives comparisons to laboratory measurements and simulations.