We measure and model the wavelength dependence of the PSF in the Hyper Suprime-Cam ( HSC ) Subaru Strategic Program ( SSP ) survey .
We find that PSF chromaticity is present in that redder stars appear smaller than bluer stars in the g,r, and i -bands at the 1-2 per cent level and in the z and y -bands at the 0.1-0.2 per cent level .
From the color dependence of the PSF , we fit a model between the monochromatic PSF trace radius , R , and wavelength of the form R ( \lambda ) \propto \lambda ^ { b } .
We find values of b between -0.2 and -0.5 , depending on the epoch and filter .
This is consistent with the expectations of a turbulent atmosphere with an outer scale length of \sim 10 - 100 m , indicating that the atmosphere is dominating the chromaticity .
We find evidence in the best seeing data that the optical system and detector also contribute some wavelength dependence . showed that b must be measured to an accuracy of \sim 0.02 not to dominate the systematic error budget of the Large Synoptic Survey Telescope ( LSST ) weak lensing ( WL ) survey .
Using simple image simulations , we find that b can be inferred with this accuracy in the r and i -bands for all positions in the LSST field of view , assuming a stellar density of 1 star arcmin ^ { -2 } and that the optical PSF can be accurately modeled .
Therefore , it is possible to correct for most , if not all , of the bias that the wavelength-dependent PSF will introduce into an LSST-like WL survey .