Speakers

Weak gravitational lensing is a cornerstone of precision cosmology, enabling constraints on dark matter, dark energy, and the growth of structure from subtle, percent-level distortions in galaxy images. For Stage-IV surveys such as Rubin LSST and the Roman Space Telescope, the limiting factor is increasingly systematic control: shear estimates must be calibrated to well below the percent level despite realistic observing conditions, complex and chromatic PSFs, correlated noise, detection and selection effects, and ubiquitous blending. In this talk, I will describe a practical approach to the shear calibration challenge based on a perturbative “shear response” formalism. By treating the shear estimator as a measurable function of the image and expanding it to first order in an applied shear, we can compute calibration factors that capture both measurement nonlinearity and selection response, in a way that connects naturally to modern response-based methods. I will then focus on validation—how to stress-test the algorithm with controlled image simulations and how to close the loop on real data using internal consistency checks, null tests, and cross-correlations that are sensitive to residual shear biases. I will conclude by discussing how these end-to-end calibration and validation strategies translate into tighter, more reliable cosmological constraints through improved control of weak-lensing systematics.