We propose to use HRPD to determine the detailed structures of a series of cobalt oxysulfides containing Co in square planar coordination. Two compositions Sr2CoO2Cu2-deltaS2 with delta ~ 0.2 prepared using low temperature chemical methods will be examined. The aim is to correlate the detailed structure, including the possibility of a small structural distortion found when delta < 0.1, with the composition. This accompanies companion experiments on OSIRIS and POLARIS which will enable the magnetic structures of these and related materials to be determined and the size of the ordered moment to be correlated with composition and the fine details of the crystal structure.