Lensing in the Blue: Methods and Prospects for Weak Lensing from the Stratosphere

The Superpressure Balloon-borne Imaging Telescope (SuperBIT) is a diffraction-limited, wide-field, near-infrared to near-ultraviolet observatory designed to exploit the stratosphere's space-like conditions. SuperBIT's 2023 science flight will deliver deep, blue imaging of galaxy clusters for gravitational lensing analysis. In preparation, we have developed a weak lensing measurement pipeline with modern algorithms for PSF characterization, shape measurement, and shear calibration. We validate our pipeline and forecast SuperBIT survey properties with simulated galaxy cluster observations in SuperBIT's near-UV and blue bandpasses. We predict imaging depth, galaxy number density, and redshift distribution for observations in SuperBIT's three bluest filters; the effect of lensing sample selections is also considered. We find that in three hours of on-sky integration, SuperBIT can attain imaging depths competitive with large ground-based surveys. Even with lensing-analysis sample selections, we find galaxy number densities around 28 galaxies per square arcminute at a median redshift of z=1.1. Our results confirm SuperBIT's capability for weak gravitational lensing measurements in the blue.