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One of the key noise sources that currently limits high-contrast imagingobservations for exoplanet detection is quasi-static speckles. Quasi-staticspeckles originate from slowly evolving non-common path aberrations (NCPA). Thepurpose of this work is to present a proof-of-concept on-sky demonstration ofspatial Linear Dark Field Control (LDFC). The ultimate goal of LDFC is tostabilize the point spread function (PSF) by addressing NCPA using the scienceimage as additional wavefront sensor. We combined spatial LDFC with theAsymmetric Pupil vector-Apodizing Phase Plate (APvAPP) on the SubaruCoronagraphic Extreme Adaptive Optics system at the Subaru Telescope. In thispaper, we report the results of the first successful proof-of-principle LDFCon-sky tests. We present results from two types of cases: (1) correction ofinstrumental errors and atmospheric residuals plus artificially induced staticaberrations introduced on the deformable mirror and (2) correction of onlyatmospheric residuals and instrumental aberrations. When introducing artificialstatic wavefront aberrations on the DM, we find that LDFC can improve the rawcontrast by a factor of $3$--$7$ over the dark hole. In these tests, theresidual wavefront error decreased by $\sim$50 nm RMS, from $\sim$90 nm to$\sim40$ nm RMS. In the case with only residual atmospheric wavefront errorsand instrumental aberrations, we show that LDFC is able to suppress evolvingaberrations that have timescales of $<0.1$--$0.4$ Hz. We find that the power at$10^{-2}$ Hz is reduced by a factor of $\sim$20, 7, and 4 for spatial frequencybins at 2.5, 5.5, and 8.5 $\lambda/D$, respectively. The results presented inthis work show that LDFC is a promising technique for enabling thehigh-contrast imaging goals of the upcoming generation of extremely largetelescopes.

First on-sky demonstration of spatial Linear Dark Field Control with the vector-Apodizing Phase Plate at Subaru/SCExAO