GREAT4 is the Fourth GRavitational lEnsing accuracy testing project, a cross-survey effort to diagnose and improve systematic effects in weak gravitational lensing. Unlike its successors (STEP1, STEP2, GREAT08, GREAT10, GREAT3), it is currently unclear whether GREAT4 will actually contain a challenge component; the first stage will focus exclusively on simulation software and input datasets that could enable such a challenge.
This repository is primarily for discussion, announcements, and planning (mostly via the Issues tab). We expect most new code to ultimately land in the existing GalSim package, though this may be revisited in the future as more concrete plans develop.
Anyone interested in contributing to GREAT4 or simply tracking its progress is encouraged to "Watch" the repository.