This is part of a larger experiment which will investigate three related systems which contain copper deficient anti-fluorite-type copper sulfide layers. The overall aim is to correlate magnetic and structural properties with composition in these systems. On OSIRIS we will probe: 1. The nature of the superstructure and magnetic ordering in the highly copper deficient mixed-valent manganese compound Sr2MnO2Cu1.2S2; 2. The correlation of structures and composition and the possible occurrence of superstructures in the mixed-valent Ce compounds CeCu1-xOS. These long d-spacing measurements will support parallel measurements on HRPD.