The XMM Cluster Survey (XCS) is a serendipitous X-ray galaxy cluster survey being conducted using archival data taken by ESA’s XMM-Newton satellite. Galaxy clusters trace the large scale structure of the universe, and their number density evolution with redshift provides a way to measure cosmological parameters, independent of cosmic microwave background experiments or supernovae cosmology projects.[1]
The collaboration is based in the United Kingdom and this is also where the majority of researchers are based. However, there are members of the collaboration across Europe and the Atlantic.