  High quality, repeatable point-spread functions are important for science
cases like direct exoplanet imaging, high-precision astrometry, and
high-resolution spectroscopy of exoplanets. For such demanding applications,
the initial on-sky point-spread function delivered by the adaptive optics
system can require further optimization to correct unsensed static aberrations
and calibration biases. We investigated using the Fast and Furious focal-plane
wavefront sensing algorithm as a potential solution. This algorithm uses a
simple model of the optical system and focal plane information to measure and
correct the point-spread function phase, without using defocused images,
meaning it can run concurrently with science. On-sky testing demonstrated
significantly improved PSF quality in only a few iterations, with both narrow
and broadband filters. These results suggest this algorithm is a useful path
forward for creating and maintaining high-quality, repeatable on-sky adaptive
optics point-spread functions.
