A fully data-driven algorithm for accurate shear estimation
  Weak lensing by large-scale structure is a powerful probe of cosmology if the
apparent alignments in the shapes of distant galaxies can be accurately
measured. We study the performance of a fully data-driven approach, based on
MetaDetection, focusing on the more realistic case of observations with an
anisotropic PSF. Under the assumption that PSF anisotropy is the only source of
additive shear bias, we show how unbiased shear estimates can be obtained from
the observed data alone. To do so, we exploit the finding that the
multiplicative shear bias obtained with MetaDetection is nearly insensitive to
the PSF ellipticity. In practice, this assumption can be validated by comparing
the empirical corrections obtained from observations to those from simulated
data. We show that our data-driven approach meets the stringent requirements
for upcoming space and ground-based surveys, although further optimisation is
possible.
