The GRavitational lEnsing Accuracy Testing 2008 (GREA T08) Challenge focuses on a problem that is of crucial importance for future observations in cosmology. The shapes of distant galaxies can be used to determine the properties of dark energy and the nature of gravity, because ligh t from those galaxies is bent by gravity from the intervening dark matter. The observed galaxy images appear distorted, although only slightly, and their shapes must be precisely disentangled from the effects of pixelisation,con volution and noise. The worldwide gravitational lensing community has made signi fficant progress in techniques to measure these distortions via the ShearTEsting Program (STEP). Via STEP, we have run
Challenges within our own community, and come to recognise that this particular image analysis problem is ideally matched to experts in statistical inference, inverse problems and computational learning. Thus, in order to continue the progress seen in recent years, we are seeking an infusion of few ideas from these communities.