Comment by jdhwosnhw

For point source astrometry, there are a few ways to beat the diffraction limit. For instance, some observers will purposely defocus their optics to spread the target photons over a larger number of pixels, which with sufficient SNR lets you gain a better lower bound (from a Cramer Rao perspective) on precision. I think Gaia actually does something similar to this but “blurs” through time, rather than across space, by purposely not perfectly tracking stars so that they drift at sub-pixel rates across the FPA.